From 8dedeb8838895661c931def297cb85da75bbb3b8 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Wed, 4 Aug 2021 01:31:34 -0600 Subject: [PATCH 01/13] FROMLIST: mm: x86, arm64: add arch_has_hw_pte_young() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Some architectures automatically set the accessed bit in PTEs, e.g., x86 and arm64 v8.2. On architectures that do not have this capability, clearing the accessed bit in a PTE usually triggers a page fault following the TLB miss of this PTE (to emulate the accessed bit). Being aware of this capability can help make better decisions, e.g., whether to spread the work out over a period of time to reduce bursty page faults when trying to clear the accessed bit in many PTEs. Note that theoretically this capability can be unreliable, e.g., hotplugged CPUs might be different from builtin ones. Therefore it should not be used in architecture-independent code that involves correctness, e.g., to determine whether TLB flushes are required (in combination with the accessed bit). Link: https://lore.kernel.org/r/20220309021230.721028-2-yuzhao@google.com/ Signed-off-by: Yu Zhao Reviewed-by: Barry Song Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Acked-by: Will Deacon Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: Ie81175d7e0d239f688d31487b298cf9b4fb66707 --- arch/arm64/include/asm/pgtable.h | 8 ++------ arch/x86/include/asm/pgtable.h | 6 +++--- include/linux/pgtable.h | 13 +++++++++++++ mm/memory.c | 14 +------------- 4 files changed, 19 insertions(+), 22 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index ab2443900f4e..dee897bb0c21 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -981,13 +981,9 @@ static inline void update_mmu_cache(struct vm_area_struct *vma, * page after fork() + CoW for pfn mappings. We don't always have a * hardware-managed access flag on arm64. */ -static inline bool arch_faults_on_old_pte(void) -{ - WARN_ON(preemptible()); +#define arch_has_hw_pte_young cpu_has_hw_af - return !cpu_has_hw_af(); -} -#define arch_faults_on_old_pte arch_faults_on_old_pte +#define arch_wants_old_prefaulted_pte cpu_has_hw_af static inline pgprot_t arch_filter_pgprot(pgprot_t prot) { diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 788b3a0120dc..58f01b8e70c5 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1397,10 +1397,10 @@ static inline bool arch_has_pfn_modify_check(void) return boot_cpu_has_bug(X86_BUG_L1TF); } -#define arch_faults_on_old_pte arch_faults_on_old_pte -static inline bool arch_faults_on_old_pte(void) +#define arch_has_hw_pte_young arch_has_hw_pte_young +static inline bool arch_has_hw_pte_young(void) { - return false; + return true; } #endif /* __ASSEMBLY__ */ diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index f924468d84ec..c2b46a765ffb 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -241,6 +241,19 @@ static inline int pmdp_clear_flush_young(struct vm_area_struct *vma, #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif +#ifndef arch_has_hw_pte_young +/* + * Return whether the accessed bit is supported on the local CPU. + * + * This stub assumes accessing through an old PTE triggers a page fault. + * Architectures that automatically set the access bit should overwrite it. + */ +static inline bool arch_has_hw_pte_young(void) +{ + return false; +} +#endif + #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long address, diff --git a/mm/memory.c b/mm/memory.c index 3667ec456ace..2de43adbd9f9 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -122,18 +122,6 @@ int randomize_va_space __read_mostly = 2; #endif -#ifndef arch_faults_on_old_pte -static inline bool arch_faults_on_old_pte(void) -{ - /* - * Those arches which don't have hw access flag feature need to - * implement their own helper. By default, "true" means pagefault - * will be hit on old pte. - */ - return true; -} -#endif - static int __init disable_randmaps(char *s) { randomize_va_space = 0; @@ -2670,7 +2658,7 @@ static inline bool cow_user_page(struct page *dst, struct page *src, * On architectures with software "accessed" bits, we would * take a double page fault, so mark it accessed here. */ - if (arch_faults_on_old_pte() && !pte_young(vmf->orig_pte)) { + if (!arch_has_hw_pte_young() && !pte_young(vmf->orig_pte)) { pte_t entry; vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl); -- Gitee From dffb84c46470f97cb2ac4b8a35848fd2f4cebcf4 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Sat, 26 Sep 2020 21:17:18 -0600 Subject: [PATCH 02/13] FROMLIST: mm: x86: add CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Some architectures support the accessed bit in non-leaf PMD entries, e.g., x86 sets the accessed bit in a non-leaf PMD entry when using it as part of linear address translation [1]. Page table walkers that clear the accessed bit may use this capability to reduce their search space. Note that: 1. Although an inline function is preferable, this capability is added as a configuration option for consistency with the existing macros. 2. Due to the little interest in other varieties, this capability was only tested on Intel and AMD CPUs. [1]: Intel 64 and IA-32 Architectures Software Developer's Manual Volume 3 (June 2021), section 4.8 Link: https://lore.kernel.org/r/20220309021230.721028-3-yuzhao@google.com/ Signed-off-by: Yu Zhao Reviewed-by: Barry Song Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I73f84a21fd315192eaa3e6443334ed1bccb4e99e --- arch/Kconfig | 9 +++++++++ arch/x86/Kconfig | 1 + arch/x86/include/asm/pgtable.h | 3 ++- arch/x86/mm/pgtable.c | 5 ++++- include/linux/pgtable.h | 4 ++-- 5 files changed, 18 insertions(+), 4 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index d2c7203dfaef..ca2d5861ffaa 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -1119,6 +1119,15 @@ config ARCH_SPLIT_ARG64 If a 32-bit architecture requires 64-bit arguments to be split into pairs of 32-bit arguments, select this option. +config ARCH_HAS_NONLEAF_PMD_YOUNG + bool + depends on PGTABLE_LEVELS > 2 + help + Architectures that select this option are capable of setting the + accessed bit in non-leaf PMD entries when using them as part of linear + address translations. Page table walkers that clear the accessed bit + may use this capability to reduce their search space. + config DYNAMIC_SIGFRAME bool diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index e0795d057745..24f597d5c48b 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -77,6 +77,7 @@ config X86 select ARCH_HAS_PMEM_API if X86_64 select ARCH_HAS_PTE_DEVMAP if X86_64 select ARCH_HAS_PTE_SPECIAL + select ARCH_HAS_NONLEAF_PMD_YOUNG select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64 select ARCH_HAS_COPY_MC if X86_64 select ARCH_HAS_SET_MEMORY diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 58f01b8e70c5..769d288926de 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -817,7 +817,8 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd) static inline int pmd_bad(pmd_t pmd) { - return (pmd_flags(pmd) & ~_PAGE_USER) != _KERNPG_TABLE; + return (pmd_flags(pmd) & ~(_PAGE_USER | _PAGE_ACCESSED)) != + (_KERNPG_TABLE & ~_PAGE_ACCESSED); } static inline unsigned long pages_to_mb(unsigned long npg) diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index 3481b35cb4ec..a224193d84bf 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -550,7 +550,7 @@ int ptep_test_and_clear_young(struct vm_area_struct *vma, return ret; } -#ifdef CONFIG_TRANSPARENT_HUGEPAGE +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) int pmdp_test_and_clear_young(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmdp) { @@ -562,6 +562,9 @@ int pmdp_test_and_clear_young(struct vm_area_struct *vma, return ret; } +#endif + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE int pudp_test_and_clear_young(struct vm_area_struct *vma, unsigned long addr, pud_t *pudp) { diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index c2b46a765ffb..dd47fb0cb07a 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -194,7 +194,7 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma, #endif #ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG -#ifdef CONFIG_TRANSPARENT_HUGEPAGE +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, unsigned long address, pmd_t *pmdp) @@ -215,7 +215,7 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, BUILD_BUG(); return 0; } -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ +#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG */ #endif #ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH -- Gitee From 9db2b8660ab14cfe28dfefaf1333632709710d43 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Sun, 27 Sep 2020 20:49:08 -0600 Subject: [PATCH 03/13] FROMLIST: mm/vmscan.c: refactor shrink_node() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This patch refactors shrink_node() to improve readability for the upcoming changes to mm/vmscan.c. Link: https://lore.kernel.org/r/20220309021230.721028-4-yuzhao@google.com/ Signed-off-by: Yu Zhao Reviewed-by: Barry Song Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I186f43f946de0d40d54883fb31114840fc749a57 --- mm/vmscan.c | 186 +++++++++++++++++++++++++++------------------------- 1 file changed, 98 insertions(+), 88 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index c851e5f91842..82ac5cf10e27 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2444,6 +2444,103 @@ enum scan_balance { SCAN_FILE, }; +static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc) +{ + unsigned long file; + struct lruvec *target_lruvec; + + target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat); + + /* + * Determine the scan balance between anon and file LRUs. + */ + spin_lock_irq(&target_lruvec->lru_lock); + sc->anon_cost = target_lruvec->anon_cost; + sc->file_cost = target_lruvec->file_cost; + spin_unlock_irq(&target_lruvec->lru_lock); + + /* + * Target desirable inactive:active list ratios for the anon + * and file LRU lists. + */ + if (!sc->force_deactivate) { + unsigned long refaults; + + refaults = lruvec_page_state(target_lruvec, + WORKINGSET_ACTIVATE_ANON); + if (refaults != target_lruvec->refaults[0] || + inactive_is_low(target_lruvec, LRU_INACTIVE_ANON)) + sc->may_deactivate |= DEACTIVATE_ANON; + else + sc->may_deactivate &= ~DEACTIVATE_ANON; + + /* + * When refaults are being observed, it means a new + * workingset is being established. Deactivate to get + * rid of any stale active pages quickly. + */ + refaults = lruvec_page_state(target_lruvec, + WORKINGSET_ACTIVATE_FILE); + if (refaults != target_lruvec->refaults[1] || + inactive_is_low(target_lruvec, LRU_INACTIVE_FILE)) + sc->may_deactivate |= DEACTIVATE_FILE; + else + sc->may_deactivate &= ~DEACTIVATE_FILE; + } else + sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE; + + /* + * If we have plenty of inactive file pages that aren't + * thrashing, try to reclaim those first before touching + * anonymous pages. + */ + file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE); + if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE)) + sc->cache_trim_mode = 1; + else + sc->cache_trim_mode = 0; + + /* + * Prevent the reclaimer from falling into the cache trap: as + * cache pages start out inactive, every cache fault will tip + * the scan balance towards the file LRU. And as the file LRU + * shrinks, so does the window for rotation from references. + * This means we have a runaway feedback loop where a tiny + * thrashing file LRU becomes infinitely more attractive than + * anon pages. Try to detect this based on file LRU size. + */ + if (!cgroup_reclaim(sc)) { + unsigned long total_high_wmark = 0; + unsigned long free, anon; + int z; + + free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES); + file = node_page_state(pgdat, NR_ACTIVE_FILE) + + node_page_state(pgdat, NR_INACTIVE_FILE); + + for (z = 0; z < MAX_NR_ZONES; z++) { + struct zone *zone = &pgdat->node_zones[z]; + + if (!managed_zone(zone)) + continue; + + total_high_wmark += high_wmark_pages(zone); + } + + /* + * Consider anon: if that's low too, this isn't a + * runaway file reclaim problem, but rather just + * extreme pressure. Reclaim as per usual then. + */ + anon = node_page_state(pgdat, NR_INACTIVE_ANON); + + sc->file_is_tiny = + file + free <= total_high_wmark && + !(sc->may_deactivate & DEACTIVATE_ANON) && + anon >> sc->priority; + } +} + /* * Determine how aggressively the anon and file LRU lists should be * scanned. The relative value of each set of LRU lists is determined @@ -2898,7 +2995,6 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) unsigned long nr_reclaimed, nr_scanned; struct lruvec *target_lruvec; bool reclaimable = false; - unsigned long file; target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat); @@ -2914,93 +3010,7 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) nr_reclaimed = sc->nr_reclaimed; nr_scanned = sc->nr_scanned; - /* - * Determine the scan balance between anon and file LRUs. - */ - spin_lock_irq(&target_lruvec->lru_lock); - sc->anon_cost = target_lruvec->anon_cost; - sc->file_cost = target_lruvec->file_cost; - spin_unlock_irq(&target_lruvec->lru_lock); - - /* - * Target desirable inactive:active list ratios for the anon - * and file LRU lists. - */ - if (!sc->force_deactivate) { - unsigned long refaults; - - refaults = lruvec_page_state(target_lruvec, - WORKINGSET_ACTIVATE_ANON); - if (refaults != target_lruvec->refaults[0] || - inactive_is_low(target_lruvec, LRU_INACTIVE_ANON)) - sc->may_deactivate |= DEACTIVATE_ANON; - else - sc->may_deactivate &= ~DEACTIVATE_ANON; - - /* - * When refaults are being observed, it means a new - * workingset is being established. Deactivate to get - * rid of any stale active pages quickly. - */ - refaults = lruvec_page_state(target_lruvec, - WORKINGSET_ACTIVATE_FILE); - if (refaults != target_lruvec->refaults[1] || - inactive_is_low(target_lruvec, LRU_INACTIVE_FILE)) - sc->may_deactivate |= DEACTIVATE_FILE; - else - sc->may_deactivate &= ~DEACTIVATE_FILE; - } else - sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE; - - /* - * If we have plenty of inactive file pages that aren't - * thrashing, try to reclaim those first before touching - * anonymous pages. - */ - file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE); - if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE)) - sc->cache_trim_mode = 1; - else - sc->cache_trim_mode = 0; - - /* - * Prevent the reclaimer from falling into the cache trap: as - * cache pages start out inactive, every cache fault will tip - * the scan balance towards the file LRU. And as the file LRU - * shrinks, so does the window for rotation from references. - * This means we have a runaway feedback loop where a tiny - * thrashing file LRU becomes infinitely more attractive than - * anon pages. Try to detect this based on file LRU size. - */ - if (!cgroup_reclaim(sc)) { - unsigned long total_high_wmark = 0; - unsigned long free, anon; - int z; - - free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES); - file = node_page_state(pgdat, NR_ACTIVE_FILE) + - node_page_state(pgdat, NR_INACTIVE_FILE); - - for (z = 0; z < MAX_NR_ZONES; z++) { - struct zone *zone = &pgdat->node_zones[z]; - if (!managed_zone(zone)) - continue; - - total_high_wmark += high_wmark_pages(zone); - } - - /* - * Consider anon: if that's low too, this isn't a - * runaway file reclaim problem, but rather just - * extreme pressure. Reclaim as per usual then. - */ - anon = node_page_state(pgdat, NR_INACTIVE_ANON); - - sc->file_is_tiny = - file + free <= total_high_wmark && - !(sc->may_deactivate & DEACTIVATE_ANON) && - anon >> sc->priority; - } + prepare_scan_count(pgdat, sc); shrink_node_memcgs(pgdat, sc); -- Gitee From b307cbf2c94816f54e2c448c6164cf865bd61eeb Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Mon, 25 Jan 2021 21:12:33 -0700 Subject: [PATCH 04/13] FROMLIST: mm: multi-gen LRU: groundwork MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Evictable pages are divided into multiple generations for each lruvec. The youngest generation number is stored in lrugen->max_seq for both anon and file types as they are aged on an equal footing. The oldest generation numbers are stored in lrugen->min_seq[] separately for anon and file types as clean file pages can be evicted regardless of swap constraints. These three variables are monotonically increasing. Generation numbers are truncated into order_base_2(MAX_NR_GENS+1) bits in order to fit into the gen counter in page->flags. Each truncated generation number is an index to lrugen->lists[]. The sliding window technique is used to track at least MIN_NR_GENS and at most MAX_NR_GENS generations. The gen counter stores a value within [1, MAX_NR_GENS] while a page is on one of lrugen->lists[]. Otherwise it stores 0. There are two conceptually independent procedures: "the aging", which produces young generations, and "the eviction", which consumes old generations. They form a closed-loop system, i.e., "the page reclaim". Both procedures can be invoked from userspace for the purposes of working set estimation and proactive reclaim. These features are required to optimize job scheduling (bin packing) in data centers. The variable size of the sliding window is designed for such use cases [1][2]. To avoid confusion, the terms "hot" and "cold" will be applied to the multi-gen LRU, as a new convention; the terms "active" and "inactive" will be applied to the active/inactive LRU, as usual. The protection of hot pages and the selection of cold pages are based on page access channels and patterns. There are two access channels: one through page tables and the other through file descriptors. The protection of the former channel is by design stronger because: 1. The uncertainty in determining the access patterns of the former channel is higher due to the approximation of the accessed bit. 2. The cost of evicting the former channel is higher due to the TLB flushes required and the likelihood of encountering the dirty bit. 3. The penalty of underprotecting the former channel is higher because applications usually do not prepare themselves for major page faults like they do for blocked I/O. E.g., GUI applications commonly use dedicated I/O threads to avoid blocking the rendering threads. There are also two access patterns: one with temporal locality and the other without. For the reasons listed above, the former channel is assumed to follow the former pattern unless VM_SEQ_READ or VM_RAND_READ is present; the latter channel is assumed to follow the latter pattern unless outlying refaults have been observed [3][4]. The next patch will address the "outlying refaults". Three macros, i.e., LRU_REFS_WIDTH, LRU_REFS_PGOFF and LRU_REFS_MASK, used later are added in this patch to make the entire patchset less diffy. A page is added to the youngest generation on faulting. The aging needs to check the accessed bit at least twice before handing this page over to the eviction. The first check takes care of the accessed bit set on the initial fault; the second check makes sure this page has not been used since then. This protocol, AKA second chance, requires a minimum of two generations, hence MIN_NR_GENS. [1] https://dl.acm.org/doi/10.1145/3297858.3304053 [2] https://dl.acm.org/doi/10.1145/3503222.3507731 [3] https://lwn.net/Articles/495543/ [4] https://lwn.net/Articles/815342/ Link: https://lore.kernel.org/r/20220309021230.721028-6-yuzhao@google.com/ Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I333ec6a1d2abfa60d93d6adc190ed3eefe441512 --- fs/fuse/dev.c | 3 +- include/linux/mm.h | 2 + include/linux/mm_inline.h | 217 +++++++++++++++++++++++++++--- include/linux/mmzone.h | 94 +++++++++++++ include/linux/page-flags-layout.h | 11 +- include/linux/page-flags.h | 4 +- include/linux/sched.h | 4 + kernel/bounds.c | 7 + mm/Kconfig | 8 ++ mm/huge_memory.c | 3 +- mm/memcontrol.c | 2 + mm/memory.c | 25 ++++ mm/mm_init.c | 6 +- mm/mmzone.c | 2 + mm/swap.c | 9 +- mm/vmscan.c | 75 +++++++++++ 16 files changed, 438 insertions(+), 34 deletions(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 8ac91ba05d6d..d2e1543a0fec 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -785,7 +785,8 @@ static int fuse_check_page(struct page *page) 1 << PG_active | 1 << PG_workingset | 1 << PG_reclaim | - 1 << PG_waiters))) { + 1 << PG_waiters | + LRU_GEN_MASK | LRU_REFS_MASK))) { dump_page(page, "fuse: trying to steal weird page"); return 1; } diff --git a/include/linux/mm.h b/include/linux/mm.h index 1ae73cc4b806..407f63082763 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1113,6 +1113,8 @@ vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf); #define ZONES_PGOFF (NODES_PGOFF - ZONES_WIDTH) #define LAST_CPUPID_PGOFF (ZONES_PGOFF - LAST_CPUPID_WIDTH) #define KASAN_TAG_PGOFF (LAST_CPUPID_PGOFF - KASAN_TAG_WIDTH) +#define LRU_GEN_PGOFF (KASAN_TAG_PGOFF - LRU_GEN_WIDTH) +#define LRU_REFS_PGOFF (LRU_GEN_PGOFF - LRU_REFS_WIDTH) /* * Define the bit shifts to access each section. For non-existent diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index 8fc71e9d7bb0..ce69f403d559 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -30,6 +30,8 @@ static __always_inline void __update_lru_size(struct lruvec *lruvec, { struct pglist_data *pgdat = lruvec_pgdat(lruvec); + lockdep_assert_held(&lruvec->lru_lock); + __mod_lruvec_state(lruvec, NR_LRU_BASE + lru, nr_pages); __mod_zone_page_state(&pgdat->node_zones[zid], NR_ZONE_LRU_BASE + lru, nr_pages); @@ -45,27 +47,6 @@ static __always_inline void update_lru_size(struct lruvec *lruvec, #endif } -static __always_inline void add_page_to_lru_list(struct page *page, - struct lruvec *lruvec, enum lru_list lru) -{ - update_lru_size(lruvec, lru, page_zonenum(page), thp_nr_pages(page)); - list_add(&page->lru, &lruvec->lists[lru]); -} - -static __always_inline void add_page_to_lru_list_tail(struct page *page, - struct lruvec *lruvec, enum lru_list lru) -{ - update_lru_size(lruvec, lru, page_zonenum(page), thp_nr_pages(page)); - list_add_tail(&page->lru, &lruvec->lists[lru]); -} - -static __always_inline void del_page_from_lru_list(struct page *page, - struct lruvec *lruvec, enum lru_list lru) -{ - list_del(&page->lru); - update_lru_size(lruvec, lru, page_zonenum(page), -thp_nr_pages(page)); -} - /** * page_lru_base_type - which LRU list type should a page be on? * @page: the page to test @@ -125,4 +106,198 @@ static __always_inline enum lru_list page_lru(struct page *page) } return lru; } + +#ifdef CONFIG_LRU_GEN + +static inline bool lru_gen_enabled(void) +{ + return true; +} + +static inline bool lru_gen_in_fault(void) +{ + return current->in_lru_fault; +} + +static inline int lru_gen_from_seq(unsigned long seq) +{ + return seq % MAX_NR_GENS; +} + +static inline bool lru_gen_is_active(struct lruvec *lruvec, int gen) +{ + unsigned long max_seq = lruvec->lrugen.max_seq; + + VM_BUG_ON(gen >= MAX_NR_GENS); + + /* see the comment on MIN_NR_GENS */ + return gen == lru_gen_from_seq(max_seq) || gen == lru_gen_from_seq(max_seq - 1); +} + +static inline void lru_gen_update_size(struct lruvec *lruvec, struct page *page, + int old_gen, int new_gen) +{ + int type = page_is_file_lru(page); + int zone = page_zonenum(page); + int delta = thp_nr_pages(page); + enum lru_list lru = type * LRU_INACTIVE_FILE; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + VM_BUG_ON(old_gen != -1 && old_gen >= MAX_NR_GENS); + VM_BUG_ON(new_gen != -1 && new_gen >= MAX_NR_GENS); + VM_BUG_ON(old_gen == -1 && new_gen == -1); + + if (old_gen >= 0) + WRITE_ONCE(lrugen->nr_pages[old_gen][type][zone], + lrugen->nr_pages[old_gen][type][zone] - delta); + if (new_gen >= 0) + WRITE_ONCE(lrugen->nr_pages[new_gen][type][zone], + lrugen->nr_pages[new_gen][type][zone] + delta); + + /* addition */ + if (old_gen < 0) { + if (lru_gen_is_active(lruvec, new_gen)) + lru += LRU_ACTIVE; + __update_lru_size(lruvec, lru, zone, delta); + return; + } + + /* deletion */ + if (new_gen < 0) { + if (lru_gen_is_active(lruvec, old_gen)) + lru += LRU_ACTIVE; + __update_lru_size(lruvec, lru, zone, -delta); + return; + } +} + +static inline bool lru_gen_add_page(struct lruvec *lruvec, struct page *page, bool reclaiming) +{ + int gen; + unsigned long old_flags, new_flags; + int type = page_is_file_lru(page); + int zone = page_zonenum(page); + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + if (PageUnevictable(page)) + return false; + /* + * There are three common cases for this page: + * 1. If it's hot, e.g., freshly faulted in or previously hot and + * migrated, add it to the youngest generation. + * 2. If it's cold but can't be evicted immediately, i.e., an anon page + * not in swapcache or a dirty page pending writeback, add it to the + * second oldest generation. + * 3. Everything else (clean, cold) is added to the oldest generation. + */ + if (PageActive(page)) + gen = lru_gen_from_seq(lrugen->max_seq); + else if ((type == LRU_GEN_ANON && !PageSwapCache(page)) || + (PageReclaim(page) && (PageDirty(page) || PageWriteback(page)))) + gen = lru_gen_from_seq(lrugen->min_seq[type] + 1); + else + gen = lru_gen_from_seq(lrugen->min_seq[type]); + + do { + new_flags = old_flags = READ_ONCE(page->flags); + VM_BUG_ON_PAGE(new_flags & LRU_GEN_MASK, page); + + /* see the comment on MIN_NR_GENS */ + new_flags &= ~(LRU_GEN_MASK | BIT(PG_active)); + new_flags |= (gen + 1UL) << LRU_GEN_PGOFF; + } while (cmpxchg(&page->flags, old_flags, new_flags) != old_flags); + + lru_gen_update_size(lruvec, page, -1, gen); + /* for rotate_reclaimable_page() */ + if (reclaiming) + list_add_tail(&page->lru, &lrugen->lists[gen][type][zone]); + else + list_add(&page->lru, &lrugen->lists[gen][type][zone]); + + return true; +} + +static inline bool lru_gen_del_page(struct lruvec *lruvec, struct page *page, bool reclaiming) +{ + int gen; + unsigned long old_flags, new_flags; + + do { + new_flags = old_flags = READ_ONCE(page->flags); + if (!(new_flags & LRU_GEN_MASK)) + return false; + + VM_BUG_ON_PAGE(PageActive(page), page); + VM_BUG_ON_PAGE(PageUnevictable(page), page); + + gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; + + new_flags &= ~LRU_GEN_MASK; + /* for shrink_page_list() */ + if (reclaiming) + new_flags &= ~(BIT(PG_referenced) | BIT(PG_reclaim)); + else if (lru_gen_is_active(lruvec, gen)) + new_flags |= BIT(PG_active); + } while (cmpxchg(&page->flags, old_flags, new_flags) != old_flags); + + lru_gen_update_size(lruvec, page, gen, -1); + list_del(&page->lru); + + return true; +} + +#else + +static inline bool lru_gen_enabled(void) +{ + return false; +} + +static inline bool lru_gen_in_fault(void) +{ + return false; +} + +static inline bool lru_gen_add_page(struct lruvec *lruvec, struct page *page, bool reclaiming) +{ + return false; +} + +static inline bool lru_gen_del_page(struct lruvec *lruvec, struct page *page, bool reclaiming) +{ + return false; +} + +#endif /* CONFIG_LRU_GEN */ + +static __always_inline void add_page_to_lru_list(struct page *page, + struct lruvec *lruvec, enum lru_list lru) +{ + if (lru_gen_add_page(lruvec, page, false)) + return; + + update_lru_size(lruvec, lru, page_zonenum(page), thp_nr_pages(page)); + list_add(&page->lru, &lruvec->lists[lru]); +} + +static __always_inline void add_page_to_lru_list_tail(struct page *page, + struct lruvec *lruvec, enum lru_list lru) +{ + if (lru_gen_add_page(lruvec, page, true)) + return; + + update_lru_size(lruvec, lru, page_zonenum(page), thp_nr_pages(page)); + list_add_tail(&page->lru, &lruvec->lists[lru]); +} + +static __always_inline void del_page_from_lru_list(struct page *page, + struct lruvec *lruvec, enum lru_list lru) +{ + if (lru_gen_del_page(lruvec, page, false)) + return; + + list_del(&page->lru); + update_lru_size(lruvec, lru, page_zonenum(page), -thp_nr_pages(page)); +} + #endif diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 8719d891848f..7e965e8e274e 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -274,6 +274,96 @@ enum lruvec_flags { */ }; +#endif /* !__GENERATING_BOUNDS_H */ + +/* + * Evictable pages are divided into multiple generations. The youngest and the + * oldest generation numbers, max_seq and min_seq, are monotonically increasing. + * They form a sliding window of a variable size [MIN_NR_GENS, MAX_NR_GENS]. An + * offset within MAX_NR_GENS, gen, indexes the LRU list of the corresponding + * generation. The gen counter in page->flags stores gen+1 while a page is on + * one of lrugen->lists[]. Otherwise it stores 0. + * + * A page is added to the youngest generation on faulting. The aging needs to + * check the accessed bit at least twice before handing this page over to the + * eviction. The first check takes care of the accessed bit set on the initial + * fault; the second check makes sure this page hasn't been used since then. + * This process, AKA second chance, requires a minimum of two generations, + * hence MIN_NR_GENS. And to maintain ABI compatibility with the active/inactive + * LRU, these two generations are considered active; the rest of generations, if + * they exist, are considered inactive. See lru_gen_is_active(). PG_active is + * always cleared while a page is on one of lrugen->lists[] so that the aging + * needs not to worry about it. And it's set again when a page considered active + * is isolated for non-reclaiming purposes, e.g., migration. See + * lru_gen_add_page() and lru_gen_del_page(). + * + * MAX_NR_GENS is set to 4 so that the multi-gen LRU can support twice of the + * categories of the active/inactive LRU when keeping track of accesses through + * page tables. It requires order_base_2(MAX_NR_GENS+1) bits in page->flags. + */ +#define MIN_NR_GENS 2U +#define MAX_NR_GENS 4U + +#ifndef __GENERATING_BOUNDS_H + +struct lruvec; + +#define LRU_GEN_MASK ((BIT(LRU_GEN_WIDTH) - 1) << LRU_GEN_PGOFF) +#define LRU_REFS_MASK ((BIT(LRU_REFS_WIDTH) - 1) << LRU_REFS_PGOFF) + +#ifdef CONFIG_LRU_GEN + +enum { + LRU_GEN_ANON, + LRU_GEN_FILE, +}; + +/* + * The youngest generation number is stored in max_seq for both anon and file + * types as they are aged on an equal footing. The oldest generation numbers are + * stored in min_seq[] separately for anon and file types as clean file pages + * can be evicted regardless of swap constraints. + * + * Normally anon and file min_seq are in sync. But if swapping is constrained, + * e.g., out of swap space, file min_seq is allowed to advance and leave anon + * min_seq behind. + */ +struct lru_gen_struct { + /* the aging increments the youngest generation number */ + unsigned long max_seq; + /* the eviction increments the oldest generation numbers */ + unsigned long min_seq[ANON_AND_FILE]; + /* the multi-gen LRU lists */ + struct list_head lists[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES]; + /* the sizes of the above lists */ + unsigned long nr_pages[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES]; +}; + +void lru_gen_init_lruvec(struct lruvec *lruvec); + +#ifdef CONFIG_MEMCG +void lru_gen_init_memcg(struct mem_cgroup *memcg); +void lru_gen_exit_memcg(struct mem_cgroup *memcg); +#endif + +#else /* !CONFIG_LRU_GEN */ + +static inline void lru_gen_init_lruvec(struct lruvec *lruvec) +{ +} + +#ifdef CONFIG_MEMCG +static inline void lru_gen_init_memcg(struct mem_cgroup *memcg) +{ +} + +static inline void lru_gen_exit_memcg(struct mem_cgroup *memcg) +{ +} +#endif + +#endif /* CONFIG_LRU_GEN */ + struct lruvec { struct list_head lists[NR_LRU_LISTS]; /* per lruvec lru_lock for memcg */ @@ -291,6 +381,10 @@ struct lruvec { unsigned long refaults[ANON_AND_FILE]; /* Various lruvec state flags (enum lruvec_flags) */ unsigned long flags; +#ifdef CONFIG_LRU_GEN + /* evictable pages divided into generations */ + struct lru_gen_struct lrugen; +#endif #ifdef CONFIG_MEMCG struct pglist_data *pgdat; #endif diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h index e200eef6a7fd..17ebeacdcde2 100644 --- a/include/linux/page-flags-layout.h +++ b/include/linux/page-flags-layout.h @@ -56,7 +56,8 @@ #define ZONES_WIDTH ZONES_SHIFT -#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS +#if ZONES_WIDTH + LRU_GEN_WIDTH + LRU_REFS_WIDTH + SECTIONS_WIDTH + NODES_SHIFT \ + <= BITS_PER_LONG - NR_PAGEFLAGS #define NODES_WIDTH NODES_SHIFT #else #ifdef CONFIG_SPARSEMEM_VMEMMAP @@ -83,15 +84,15 @@ #define KASAN_TAG_WIDTH 0 #endif -#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT+KASAN_TAG_WIDTH \ - <= BITS_PER_LONG - NR_PAGEFLAGS +#if ZONES_WIDTH + LRU_GEN_WIDTH + LRU_REFS_WIDTH + SECTIONS_WIDTH + NODES_WIDTH + \ + KASAN_TAG_WIDTH + LAST_CPUPID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT #else #define LAST_CPUPID_WIDTH 0 #endif -#if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH+LAST_CPUPID_WIDTH+KASAN_TAG_WIDTH \ - > BITS_PER_LONG - NR_PAGEFLAGS +#if ZONES_WIDTH + LRU_GEN_WIDTH + LRU_REFS_WIDTH + SECTIONS_WIDTH + NODES_WIDTH + \ + KASAN_TAG_WIDTH + LAST_CPUPID_WIDTH > BITS_PER_LONG - NR_PAGEFLAGS #error "Not enough bits in page flags" #endif diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 26b36cac9307..5df6404a17a4 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -927,7 +927,7 @@ static inline void ClearPageSlabPfmemalloc(struct page *page) 1UL << PG_private | 1UL << PG_private_2 | \ 1UL << PG_writeback | 1UL << PG_reserved | \ 1UL << PG_slab | 1UL << PG_active | \ - 1UL << PG_unevictable | __PG_MLOCKED) + 1UL << PG_unevictable | __PG_MLOCKED | LRU_GEN_MASK) /* * Flags checked when a page is prepped for return by the page allocator. @@ -938,7 +938,7 @@ static inline void ClearPageSlabPfmemalloc(struct page *page) * alloc-free cycle to prevent from reusing the page. */ #define PAGE_FLAGS_CHECK_AT_PREP \ - (((1UL << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON) + ((((1UL << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON) | LRU_GEN_MASK | LRU_REFS_MASK) #define PAGE_FLAGS_PRIVATE \ (1UL << PG_private | 1UL << PG_private_2) diff --git a/include/linux/sched.h b/include/linux/sched.h index 47f462040f4d..896a2d14879f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -849,6 +849,10 @@ struct task_struct { #ifdef CONFIG_MEMCG unsigned in_user_fault:1; #endif +#ifdef CONFIG_LRU_GEN + /* whether the LRU algorithm may apply to this access */ + unsigned in_lru_fault:1; +#endif #ifdef CONFIG_COMPAT_BRK unsigned brk_randomized:1; #endif diff --git a/kernel/bounds.c b/kernel/bounds.c index 9795d75b09b2..e08fb89f87f4 100644 --- a/kernel/bounds.c +++ b/kernel/bounds.c @@ -22,6 +22,13 @@ int main(void) DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS)); #endif DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t)); +#ifdef CONFIG_LRU_GEN + DEFINE(LRU_GEN_WIDTH, order_base_2(MAX_NR_GENS + 1)); + DEFINE(LRU_REFS_WIDTH, 0); +#else + DEFINE(LRU_GEN_WIDTH, 0); + DEFINE(LRU_REFS_WIDTH, 0); +#endif /* End of constants */ return 0; diff --git a/mm/Kconfig b/mm/Kconfig index 4475bd9f8762..365d8da93abf 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -971,4 +971,12 @@ config MEMORY_RELIABLE source "mm/damon/Kconfig" +config LRU_GEN + bool "Multi-Gen LRU" + depends on MMU + # the following options can use up the spare bits in page flags + depends on !MAXSMP && (64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP) + help + A high performance LRU implementation to overcommit memory. + endmenu diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 79c855b5adad..8219149c4ec0 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2437,7 +2437,8 @@ static void __split_huge_page_tail(struct page *head, int tail, #ifdef CONFIG_64BIT (1L << PG_arch_2) | #endif - (1L << PG_dirty))); + (1L << PG_dirty) | + LRU_GEN_MASK | LRU_REFS_MASK)); /* ->mapping in first tail page is compound_mapcount */ VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e15389aeb641..37dc3ef8f328 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5652,6 +5652,7 @@ static void __mem_cgroup_free(struct mem_cgroup *memcg) static void mem_cgroup_free(struct mem_cgroup *memcg) { + lru_gen_exit_memcg(memcg); memcg_wb_domain_exit(memcg); __mem_cgroup_free(memcg); } @@ -5715,6 +5716,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void) memcg->deferred_split_queue.split_queue_len = 0; #endif idr_replace(&mem_cgroup_idr, memcg, memcg->id.id); + lru_gen_init_memcg(memcg); return memcg; fail: mem_cgroup_id_remove(memcg); diff --git a/mm/memory.c b/mm/memory.c index 2de43adbd9f9..c4838bc3745c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4695,6 +4695,27 @@ static inline void mm_account_fault(struct pt_regs *regs, perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); } +#ifdef CONFIG_LRU_GEN +static void lru_gen_enter_fault(struct vm_area_struct *vma) +{ + /* the LRU algorithm doesn't apply to sequential or random reads */ + current->in_lru_fault = !(vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ)); +} + +static void lru_gen_exit_fault(void) +{ + current->in_lru_fault = false; +} +#else +static void lru_gen_enter_fault(struct vm_area_struct *vma) +{ +} + +static void lru_gen_exit_fault(void) +{ +} +#endif /* CONFIG_LRU_GEN */ + /* * By the time we get here, we already hold the mm semaphore * @@ -4726,11 +4747,15 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, if (flags & FAULT_FLAG_USER) mem_cgroup_enter_user_fault(); + lru_gen_enter_fault(vma); + if (unlikely(is_vm_hugetlb_page(vma))) ret = hugetlb_fault(vma->vm_mm, vma, address, flags); else ret = __handle_mm_fault(vma, address, flags); + lru_gen_exit_fault(); + if (flags & FAULT_FLAG_USER) { mem_cgroup_exit_user_fault(); /* diff --git a/mm/mm_init.c b/mm/mm_init.c index b06a30fbedff..b47a4f497748 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c @@ -69,14 +69,16 @@ void __init mminit_verify_pageflags_layout(void) shift = 8 * sizeof(unsigned long); width = shift - SECTIONS_WIDTH - NODES_WIDTH - ZONES_WIDTH - - LAST_CPUPID_SHIFT - KASAN_TAG_WIDTH; + - LAST_CPUPID_SHIFT - KASAN_TAG_WIDTH - LRU_GEN_WIDTH - LRU_REFS_WIDTH; mminit_dprintk(MMINIT_TRACE, "pageflags_layout_widths", - "Section %d Node %d Zone %d Lastcpupid %d Kasantag %d Flags %d\n", + "Section %d Node %d Zone %d Lastcpupid %d Kasantag %d Gen %d Tier %d Flags %d\n", SECTIONS_WIDTH, NODES_WIDTH, ZONES_WIDTH, LAST_CPUPID_WIDTH, KASAN_TAG_WIDTH, + LRU_GEN_WIDTH, + LRU_REFS_WIDTH, NR_PAGEFLAGS); mminit_dprintk(MMINIT_TRACE, "pageflags_layout_shifts", "Section %d Node %d Zone %d Lastcpupid %d Kasantag %d\n", diff --git a/mm/mmzone.c b/mm/mmzone.c index eb89d6e018e2..2ec0d7793424 100644 --- a/mm/mmzone.c +++ b/mm/mmzone.c @@ -81,6 +81,8 @@ void lruvec_init(struct lruvec *lruvec) for_each_lru(lru) INIT_LIST_HEAD(&lruvec->lists[lru]); + + lru_gen_init_lruvec(lruvec); } #if defined(CONFIG_NUMA_BALANCING) && !defined(LAST_CPUPID_NOT_IN_PAGE_FLAGS) diff --git a/mm/swap.c b/mm/swap.c index c37fac5a73e8..0bdbb460a341 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -458,6 +458,11 @@ void lru_cache_add(struct page *page) VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page); VM_BUG_ON_PAGE(PageLRU(page), page); + /* see the comment in lru_gen_add_page() */ + if (lru_gen_enabled() && !PageUnevictable(page) && + lru_gen_in_fault() && !(current->flags & PF_MEMALLOC)) + SetPageActive(page); + get_page(page); local_lock(&lru_pvecs.lock); pvec = this_cpu_ptr(&lru_pvecs.lru_add); @@ -563,7 +568,7 @@ static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec) static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec) { - if (PageActive(page) && !PageUnevictable(page)) { + if (PageLRU(page) && !PageUnevictable(page) && (PageActive(page) || lru_gen_enabled())) { int lru = page_lru_base_type(page); int nr_pages = thp_nr_pages(page); @@ -680,7 +685,7 @@ void deactivate_file_page(struct page *page) */ void deactivate_page(struct page *page) { - if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) { + if (PageLRU(page) && !PageUnevictable(page) && (PageActive(page) || lru_gen_enabled())) { struct pagevec *pvec; local_lock(&lru_pvecs.lock); diff --git a/mm/vmscan.c b/mm/vmscan.c index 82ac5cf10e27..e8e8552718a3 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2746,6 +2746,81 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, } } +#ifdef CONFIG_LRU_GEN + +/****************************************************************************** + * shorthand helpers + ******************************************************************************/ + +#define for_each_gen_type_zone(gen, type, zone) \ + for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++) \ + for ((type) = 0; (type) < ANON_AND_FILE; (type)++) \ + for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++) + +static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid) +{ + struct pglist_data *pgdat = NODE_DATA(nid); + +#ifdef CONFIG_MEMCG + if (memcg) { + struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec; + + /* for hotadd_new_pgdat() */ + if (!lruvec->pgdat) + lruvec->pgdat = pgdat; + + return lruvec; + } +#endif + VM_BUG_ON(!mem_cgroup_disabled()); + + return pgdat ? &pgdat->__lruvec : NULL; +} + +/****************************************************************************** + * initialization + ******************************************************************************/ + +void lru_gen_init_lruvec(struct lruvec *lruvec) +{ + int gen, type, zone; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + lrugen->max_seq = MIN_NR_GENS + 1; + + for_each_gen_type_zone(gen, type, zone) + INIT_LIST_HEAD(&lrugen->lists[gen][type][zone]); +} + +#ifdef CONFIG_MEMCG +void lru_gen_init_memcg(struct mem_cgroup *memcg) +{ +} + +void lru_gen_exit_memcg(struct mem_cgroup *memcg) +{ + int nid; + + for_each_node(nid) { + struct lruvec *lruvec = get_lruvec(memcg, nid); + + VM_BUG_ON(memchr_inv(lruvec->lrugen.nr_pages, 0, + sizeof(lruvec->lrugen.nr_pages))); + } +} +#endif + +static int __init init_lru_gen(void) +{ + BUILD_BUG_ON(MIN_NR_GENS + 1 >= MAX_NR_GENS); + BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS); + + return 0; +}; +late_initcall(init_lru_gen); + +#endif /* CONFIG_LRU_GEN */ + static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) { unsigned long nr[NR_LRU_LISTS]; -- Gitee From 2a3f20f34e4aa96337adcdf0dbf126b41aa47afc Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Thu, 27 Jan 2022 20:32:37 -0700 Subject: [PATCH 05/13] FROMLIST: mm: multi-gen LRU: minimal implementation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit To avoid confusion, the terms "promotion" and "demotion" will be applied to the multi-gen LRU, as a new convention; the terms "activation" and "deactivation" will be applied to the active/inactive LRU, as usual. The aging produces young generations. Given an lruvec, it increments max_seq when max_seq-min_seq+1 approaches MIN_NR_GENS. The aging promotes hot pages to the youngest generation when it finds them accessed through page tables; the demotion of cold pages happens consequently when it increments max_seq. The aging has the complexity O(nr_hot_pages), since it is only interested in hot pages. Promotion in the aging path does not require any LRU list operations, only the updates of the gen counter and lrugen->nr_pages[]; demotion, unless as the result of the increment of max_seq, requires LRU list operations, e.g., lru_deactivate_fn(). The eviction consumes old generations. Given an lruvec, it increments min_seq when the lists indexed by min_seq%MAX_NR_GENS become empty. A feedback loop modeled after the PID controller monitors refaults over anon and file types and decides which type to evict when both types are available from the same generation. Each generation is divided into multiple tiers. Tiers represent different ranges of numbers of accesses through file descriptors. A page accessed N times through file descriptors is in tier order_base_2(N). Tiers do not have dedicated lrugen->lists[], only bits in page->flags. In contrast to moving across generations, which requires the LRU lock, moving across tiers only involves operations on page->flags. The feedback loop also monitors refaults over all tiers and decides when to protect pages in which tiers (N>1), using the first tier (N=0,1) as a baseline. The first tier contains single-use unmapped clean pages, which are most likely the best choices. The eviction moves a page to the next generation, i.e., min_seq+1, if the feedback loop decides so. This approach has the following advantages: 1. It removes the cost of activation in the buffered access path by inferring whether pages accessed multiple times through file descriptors are statistically hot and thus worth protecting in the eviction path. 2. It takes pages accessed through page tables into account and avoids overprotecting pages accessed multiple times through file descriptors. (Pages accessed through page tables are in the first tier, since N=0.) 3. More tiers provide better protection for pages accessed more than twice through file descriptors, when under heavy buffered I/O workloads. Server benchmark results: Single workload: fio (buffered I/O): +[38, 40]% IOPS BW 5.18-ed4643521e6a: 2547k 9989MiB/s patch1-6: 3540k 13.5GiB/s Single workload: memcached (anon): +[103, 107]% Ops/sec KB/sec 5.18-ed4643521e6a: 469048.66 18243.91 patch1-6: 964656.80 37520.88 Configurations: CPU: two Xeon 6154 Mem: total 256G Node 1 was only used as a ram disk to reduce the variance in the results. patch drivers/block/brd.c < gfp_flags = GFP_NOIO | __GFP_ZERO | __GFP_HIGHMEM | __GFP_THISNODE; > page = alloc_pages_node(1, gfp_flags, 0); EOF cat >>/etc/systemd/system.conf <>/etc/memcached.conf </sys/fs/cgroup/user.slice/test/memory.max echo $$ >/sys/fs/cgroup/user.slice/test/cgroup.procs fio -name=mglru --numjobs=72 --directory=/mnt --size=1408m \ --buffered=1 --ioengine=io_uring --iodepth=128 \ --iodepth_batch_submit=32 --iodepth_batch_complete=32 \ --rw=randread --random_distribution=random --norandommap \ --time_based --ramp_time=10m --runtime=5m --group_reporting cat memcached.sh modprobe brd rd_nr=1 rd_size=113246208 swapoff -a mkswap /dev/ram0 swapon /dev/ram0 memtier_benchmark -S /var/run/memcached/memcached.sock \ -P memcache_binary -n allkeys --key-minimum=1 \ --key-maximum=65000000 --key-pattern=P:P -c 1 -t 36 \ --ratio 1:0 --pipeline 8 -d 2000 memtier_benchmark -S /var/run/memcached/memcached.sock \ -P memcache_binary -n allkeys --key-minimum=1 \ --key-maximum=65000000 --key-pattern=R:R -c 1 -t 36 \ --ratio 0:1 --pipeline 8 --randomize --distinct-client-seed Client benchmark results: kswapd profiles: 5.18-ed4643521e6a 39.56% page_vma_mapped_walk 19.32% lzo1x_1_do_compress (real work) 7.18% do_raw_spin_lock 4.23% _raw_spin_unlock_irq 2.26% vma_interval_tree_subtree_search 2.12% vma_interval_tree_iter_next 2.11% folio_referenced_one 1.90% anon_vma_interval_tree_iter_first 1.47% ptep_clear_flush 0.97% __anon_vma_interval_tree_subtree_search patch1-6 36.13% lzo1x_1_do_compress (real work) 19.16% page_vma_mapped_walk 6.55% _raw_spin_unlock_irq 4.02% do_raw_spin_lock 2.32% anon_vma_interval_tree_iter_first 2.11% ptep_clear_flush 1.76% __zram_bvec_write 1.64% folio_referenced_one 1.40% memmove 1.35% obj_malloc Configurations: CPU: single Snapdragon 7c Mem: total 4G Chrome OS MemoryPressure [1] [1] https://chromium.googlesource.com/chromiumos/platform/tast-tests/ Link: https://lore.kernel.org/r/20220309021230.721028-7-yuzhao@google.com/ Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I3fe4850006d7984cd9f4fd46134b826609dc2f86 --- include/linux/mm_inline.h | 24 ++ include/linux/mmzone.h | 41 ++ kernel/bounds.c | 2 +- mm/Kconfig | 11 + mm/swap.c | 42 ++ mm/vmscan.c | 804 +++++++++++++++++++++++++++++++++++++- mm/workingset.c | 119 +++++- 7 files changed, 1039 insertions(+), 4 deletions(-) diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index ce69f403d559..9a357cf0726c 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -124,6 +124,19 @@ static inline int lru_gen_from_seq(unsigned long seq) return seq % MAX_NR_GENS; } +static inline int lru_hist_from_seq(unsigned long seq) +{ + return seq % NR_HIST_GENS; +} + +static inline int lru_tier_from_refs(int refs) +{ + VM_BUG_ON(refs > BIT(LRU_REFS_WIDTH)); + + /* see the comment on MAX_NR_TIERS */ + return order_base_2(refs + 1); +} + static inline bool lru_gen_is_active(struct lruvec *lruvec, int gen) { unsigned long max_seq = lruvec->lrugen.max_seq; @@ -169,6 +182,15 @@ static inline void lru_gen_update_size(struct lruvec *lruvec, struct page *page, __update_lru_size(lruvec, lru, zone, -delta); return; } + + /* promotion */ + if (!lru_gen_is_active(lruvec, old_gen) && lru_gen_is_active(lruvec, new_gen)) { + __update_lru_size(lruvec, lru, zone, -delta); + __update_lru_size(lruvec, lru + LRU_ACTIVE, zone, delta); + } + + /* demotion requires isolation, e.g., lru_deactivate_fn() */ + VM_BUG_ON(lru_gen_is_active(lruvec, old_gen) && !lru_gen_is_active(lruvec, new_gen)); } static inline bool lru_gen_add_page(struct lruvec *lruvec, struct page *page, bool reclaiming) @@ -233,6 +255,8 @@ static inline bool lru_gen_del_page(struct lruvec *lruvec, struct page *page, bo gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; new_flags &= ~LRU_GEN_MASK; + if (!(new_flags & BIT(PG_referenced))) + new_flags &= ~(LRU_REFS_MASK | LRU_REFS_FLAGS); /* for shrink_page_list() */ if (reclaiming) new_flags &= ~(BIT(PG_referenced) | BIT(PG_reclaim)); diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 7e965e8e274e..45cfbdcd80ee 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -304,12 +304,34 @@ enum lruvec_flags { #define MIN_NR_GENS 2U #define MAX_NR_GENS 4U +/* + * Each generation is divided into multiple tiers. Tiers represent different + * ranges of numbers of accesses through file descriptors. A page accessed N + * times through file descriptors is in tier order_base_2(N). A page in the + * first tier (N=0,1) is marked by PG_referenced unless it was faulted in + * though page tables or read ahead. A page in any other tier (N>1) is marked + * by PG_referenced and PG_workingset. + * + * In contrast to moving across generations which requires the LRU lock, moving + * across tiers only requires operations on page->flags and therefore has a + * negligible cost in the buffered access path. In the eviction path, + * comparisons of refaulted/(evicted+protected) from the first tier and the + * rest infer whether pages accessed multiple times through file descriptors + * are statistically hot and thus worth protecting. + * + * MAX_NR_TIERS is set to 4 so that the multi-gen LRU can support twice of the + * categories of the active/inactive LRU when keeping track of accesses through + * file descriptors. It requires MAX_NR_TIERS-2 additional bits in page->flags. + */ +#define MAX_NR_TIERS 4U + #ifndef __GENERATING_BOUNDS_H struct lruvec; #define LRU_GEN_MASK ((BIT(LRU_GEN_WIDTH) - 1) << LRU_GEN_PGOFF) #define LRU_REFS_MASK ((BIT(LRU_REFS_WIDTH) - 1) << LRU_REFS_PGOFF) +#define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset)) #ifdef CONFIG_LRU_GEN @@ -318,6 +340,16 @@ enum { LRU_GEN_FILE, }; +#define MIN_LRU_BATCH BITS_PER_LONG +#define MAX_LRU_BATCH (MIN_LRU_BATCH * 128) + +/* whether to keep historical stats from evicted generations */ +#ifdef CONFIG_LRU_GEN_STATS +#define NR_HIST_GENS MAX_NR_GENS +#else +#define NR_HIST_GENS 1U +#endif + /* * The youngest generation number is stored in max_seq for both anon and file * types as they are aged on an equal footing. The oldest generation numbers are @@ -337,6 +369,15 @@ struct lru_gen_struct { struct list_head lists[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES]; /* the sizes of the above lists */ unsigned long nr_pages[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES]; + /* the exponential moving average of refaulted */ + unsigned long avg_refaulted[ANON_AND_FILE][MAX_NR_TIERS]; + /* the exponential moving average of evicted+protected */ + unsigned long avg_total[ANON_AND_FILE][MAX_NR_TIERS]; + /* the first tier doesn't need protection, hence the minus one */ + unsigned long protected[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS - 1]; + /* can be modified without holding the LRU lock */ + atomic_long_t evicted[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS]; + atomic_long_t refaulted[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS]; }; void lru_gen_init_lruvec(struct lruvec *lruvec); diff --git a/kernel/bounds.c b/kernel/bounds.c index e08fb89f87f4..10dd9e6b03e5 100644 --- a/kernel/bounds.c +++ b/kernel/bounds.c @@ -24,7 +24,7 @@ int main(void) DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t)); #ifdef CONFIG_LRU_GEN DEFINE(LRU_GEN_WIDTH, order_base_2(MAX_NR_GENS + 1)); - DEFINE(LRU_REFS_WIDTH, 0); + DEFINE(LRU_REFS_WIDTH, MAX_NR_TIERS - 2); #else DEFINE(LRU_GEN_WIDTH, 0); DEFINE(LRU_REFS_WIDTH, 0); diff --git a/mm/Kconfig b/mm/Kconfig index 365d8da93abf..77befc7051d1 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -971,6 +971,7 @@ config MEMORY_RELIABLE source "mm/damon/Kconfig" +# multi-gen LRU { config LRU_GEN bool "Multi-Gen LRU" depends on MMU @@ -979,4 +980,14 @@ config LRU_GEN help A high performance LRU implementation to overcommit memory. +config LRU_GEN_STATS + bool "Full stats for debugging" + depends on LRU_GEN + help + Do not enable this option unless you plan to look at historical stats + from evicted generations for debugging purpose. + + This option has a per-memcg and per-node memory overhead. +# } + endmenu diff --git a/mm/swap.c b/mm/swap.c index 0bdbb460a341..acc56d3658b2 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -401,6 +401,43 @@ static void __lru_cache_activate_page(struct page *page) local_unlock(&lru_pvecs.lock); } +#ifdef CONFIG_LRU_GEN +static void page_inc_refs(struct page *page) +{ + unsigned long refs; + unsigned long old_flags, new_flags; + + if (PageUnevictable(page)) + return; + + /* see the comment on MAX_NR_TIERS */ + do { + new_flags = old_flags = READ_ONCE(page->flags); + + if (!(new_flags & BIT(PG_referenced))) { + new_flags |= BIT(PG_referenced); + continue; + } + + if (!(new_flags & BIT(PG_workingset))) { + new_flags |= BIT(PG_workingset); + continue; + } + + refs = new_flags & LRU_REFS_MASK; + refs = min(refs + BIT(LRU_REFS_PGOFF), LRU_REFS_MASK); + + new_flags &= ~LRU_REFS_MASK; + new_flags |= refs; + } while (new_flags != old_flags && + cmpxchg(&page->flags, old_flags, new_flags) != old_flags); +} +#else +static void page_inc_refs(struct page *page) +{ +} +#endif /* CONFIG_LRU_GEN */ + /* * Mark a page as having seen activity. * @@ -415,6 +452,11 @@ void mark_page_accessed(struct page *page) { page = compound_head(page); + if (lru_gen_enabled()) { + page_inc_refs(page); + return; + } + if (!PageReferenced(page)) { SetPageReferenced(page); } else if (PageUnevictable(page)) { diff --git a/mm/vmscan.c b/mm/vmscan.c index e8e8552718a3..ef0aeae80dd7 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1106,9 +1106,11 @@ static int __remove_mapping(struct address_space *mapping, struct page *page, if (PageSwapCache(page)) { swp_entry_t swap = { .val = page_private(page) }; - mem_cgroup_swapout(page, swap); + + /* get a shadow entry before mem_cgroup_swapout() clears page_memcg() */ if (reclaimed && !mapping_exiting(mapping)) shadow = workingset_eviction(page, target_memcg); + mem_cgroup_swapout(page, swap); __delete_from_swap_cache(page, swap, shadow); xa_unlock_irqrestore(&mapping->i_pages, flags); put_swap_page(page, swap); @@ -2449,6 +2451,9 @@ static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc) unsigned long file; struct lruvec *target_lruvec; + if (lru_gen_enabled()) + return; + target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat); /* @@ -2752,11 +2757,38 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, * shorthand helpers ******************************************************************************/ +#define DEFINE_MAX_SEQ(lruvec) \ + unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq) + +#define DEFINE_MIN_SEQ(lruvec) \ + unsigned long min_seq[ANON_AND_FILE] = { \ + READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]), \ + READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]), \ + } + #define for_each_gen_type_zone(gen, type, zone) \ for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++) \ for ((type) = 0; (type) < ANON_AND_FILE; (type)++) \ for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++) +static int page_lru_gen(struct page *page) +{ + unsigned long flags = READ_ONCE(page->flags); + + return ((flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; +} + +static int page_lru_tier(struct page *page) +{ + int refs; + unsigned long flags = READ_ONCE(page->flags); + + refs = (flags & LRU_REFS_FLAGS) == LRU_REFS_FLAGS ? + ((flags & LRU_REFS_MASK) >> LRU_REFS_PGOFF) + 1 : 0; + + return lru_tier_from_refs(refs); +} + static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid) { struct pglist_data *pgdat = NODE_DATA(nid); @@ -2777,6 +2809,753 @@ static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid) return pgdat ? &pgdat->__lruvec : NULL; } +static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc) +{ + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + + if (mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH) + return 0; + + return mem_cgroup_swappiness(memcg); +} + +static int get_nr_gens(struct lruvec *lruvec, int type) +{ + return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1; +} + +static bool __maybe_unused seq_is_valid(struct lruvec *lruvec) +{ + /* see the comment on lru_gen_struct */ + return get_nr_gens(lruvec, LRU_GEN_FILE) >= MIN_NR_GENS && + get_nr_gens(lruvec, LRU_GEN_FILE) <= get_nr_gens(lruvec, LRU_GEN_ANON) && + get_nr_gens(lruvec, LRU_GEN_ANON) <= MAX_NR_GENS; +} + +/****************************************************************************** + * refault feedback loop + ******************************************************************************/ + +/* + * A feedback loop based on Proportional-Integral-Derivative (PID) controller. + * + * The P term is refaulted/(evicted+protected) from a tier in the generation + * currently being evicted; the I term is the exponential moving average of the + * P term over the generations previously evicted, using the smoothing factor + * 1/2; the D term isn't supported. + * + * The setpoint (SP) is always the first tier of one type; the process variable + * (PV) is either any tier of the other type or any other tier of the same + * type. + * + * The error is the difference between the SP and the PV; the correction is + * turn off protection when SP>PV or turn on protection when SPlrugen; + int hist = lru_hist_from_seq(lrugen->min_seq[type]); + + pos->refaulted = lrugen->avg_refaulted[type][tier] + + atomic_long_read(&lrugen->refaulted[hist][type][tier]); + pos->total = lrugen->avg_total[type][tier] + + atomic_long_read(&lrugen->evicted[hist][type][tier]); + if (tier) + pos->total += lrugen->protected[hist][type][tier - 1]; + pos->gain = gain; +} + +static void reset_ctrl_pos(struct lruvec *lruvec, int type, bool carryover) +{ + int hist, tier; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + bool clear = carryover ? NR_HIST_GENS == 1 : NR_HIST_GENS > 1; + unsigned long seq = carryover ? lrugen->min_seq[type] : lrugen->max_seq + 1; + + lockdep_assert_held(&lruvec->lru_lock); + + if (!carryover && !clear) + return; + + hist = lru_hist_from_seq(seq); + + for (tier = 0; tier < MAX_NR_TIERS; tier++) { + if (carryover) { + unsigned long sum; + + sum = lrugen->avg_refaulted[type][tier] + + atomic_long_read(&lrugen->refaulted[hist][type][tier]); + WRITE_ONCE(lrugen->avg_refaulted[type][tier], sum / 2); + + sum = lrugen->avg_total[type][tier] + + atomic_long_read(&lrugen->evicted[hist][type][tier]); + if (tier) + sum += lrugen->protected[hist][type][tier - 1]; + WRITE_ONCE(lrugen->avg_total[type][tier], sum / 2); + } + + if (clear) { + atomic_long_set(&lrugen->refaulted[hist][type][tier], 0); + atomic_long_set(&lrugen->evicted[hist][type][tier], 0); + if (tier) + WRITE_ONCE(lrugen->protected[hist][type][tier - 1], 0); + } + } +} + +static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv) +{ + /* + * Return true if the PV has a limited number of refaults or a lower + * refaulted/total than the SP. + */ + return pv->refaulted < MIN_LRU_BATCH || + pv->refaulted * (sp->total + MIN_LRU_BATCH) * sp->gain <= + (sp->refaulted + 1) * pv->total * pv->gain; +} + +/****************************************************************************** + * the aging + ******************************************************************************/ + +static int page_inc_gen(struct lruvec *lruvec, struct page *page, bool reclaiming) +{ + unsigned long old_flags, new_flags; + int type = page_is_file_lru(page); + struct lru_gen_struct *lrugen = &lruvec->lrugen; + int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); + + do { + new_flags = old_flags = READ_ONCE(page->flags); + VM_BUG_ON_PAGE(!(new_flags & LRU_GEN_MASK), page); + + new_gen = (old_gen + 1) % MAX_NR_GENS; + + new_flags &= ~LRU_GEN_MASK; + new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF; + new_flags &= ~(LRU_REFS_MASK | LRU_REFS_FLAGS); + /* for end_page_writeback() */ + if (reclaiming) + new_flags |= BIT(PG_reclaim); + } while (cmpxchg(&page->flags, old_flags, new_flags) != old_flags); + + lru_gen_update_size(lruvec, page, old_gen, new_gen); + + return new_gen; +} + +static void inc_min_seq(struct lruvec *lruvec) +{ + int type; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + VM_BUG_ON(!seq_is_valid(lruvec)); + + for (type = 0; type < ANON_AND_FILE; type++) { + if (get_nr_gens(lruvec, type) != MAX_NR_GENS) + continue; + + reset_ctrl_pos(lruvec, type, true); + WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1); + } +} + +static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap) +{ + int gen, type, zone; + bool success = false; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + DEFINE_MIN_SEQ(lruvec); + + VM_BUG_ON(!seq_is_valid(lruvec)); + + for (type = !can_swap; type < ANON_AND_FILE; type++) { + while (min_seq[type] + MIN_NR_GENS <= lrugen->max_seq) { + gen = lru_gen_from_seq(min_seq[type]); + + for (zone = 0; zone < MAX_NR_ZONES; zone++) { + if (!list_empty(&lrugen->lists[gen][type][zone])) + goto next; + } + + min_seq[type]++; + } +next: + ; + } + + /* see the comment on lru_gen_struct */ + if (can_swap) { + min_seq[LRU_GEN_ANON] = min(min_seq[LRU_GEN_ANON], min_seq[LRU_GEN_FILE]); + min_seq[LRU_GEN_FILE] = max(min_seq[LRU_GEN_ANON], lrugen->min_seq[LRU_GEN_FILE]); + } + + for (type = !can_swap; type < ANON_AND_FILE; type++) { + if (min_seq[type] == lrugen->min_seq[type]) + continue; + + reset_ctrl_pos(lruvec, type, true); + WRITE_ONCE(lrugen->min_seq[type], min_seq[type]); + success = true; + } + + return success; +} + +static void inc_max_seq(struct lruvec *lruvec, unsigned long max_seq) +{ + int prev, next; + int type, zone; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + struct pglist_data *pgdat = lruvec_pgdat(lruvec); + + spin_lock_irq(&lruvec->lru_lock); + + VM_BUG_ON(!seq_is_valid(lruvec)); + + if (max_seq != lrugen->max_seq) + goto unlock; + + inc_min_seq(lruvec); + + /* + * Update the active/inactive LRU sizes for compatibility. Both sides of + * the current max_seq need to be covered, since max_seq+1 can overlap + * with min_seq[LRU_GEN_ANON] if swapping is constrained. And if they do + * overlap, cold/hot inversion happens. This can be solved by moving + * pages from min_seq to min_seq+1 but is omitted for simplicity. + */ + prev = lru_gen_from_seq(lrugen->max_seq - 1); + next = lru_gen_from_seq(lrugen->max_seq + 1); + + for (type = 0; type < ANON_AND_FILE; type++) { + for (zone = 0; zone < MAX_NR_ZONES; zone++) { + enum lru_list lru = type * LRU_INACTIVE_FILE; + long delta = lrugen->nr_pages[prev][type][zone] - + lrugen->nr_pages[next][type][zone]; + + if (!delta) + continue; + + WARN_ON_ONCE(delta != (int)delta); + + __update_lru_size(lruvec, lru, zone, delta); + __update_lru_size(lruvec, lru + LRU_ACTIVE, zone, -delta); + } + } + + for (type = 0; type < ANON_AND_FILE; type++) + reset_ctrl_pos(lruvec, type, false); + + /* make sure preceding modifications appear */ + smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1); +unlock: + spin_unlock_irq(&lruvec->lru_lock); +} + +static long get_nr_evictable(struct lruvec *lruvec, unsigned long max_seq, + unsigned long *min_seq, bool can_swap, bool *need_aging) +{ + int gen, type, zone; + long old = 0; + long young = 0; + long total = 0; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + for (type = !can_swap; type < ANON_AND_FILE; type++) { + unsigned long seq; + + for (seq = min_seq[type]; seq <= max_seq; seq++) { + long size = 0; + + gen = lru_gen_from_seq(seq); + + for (zone = 0; zone < MAX_NR_ZONES; zone++) + size += READ_ONCE(lrugen->nr_pages[gen][type][zone]); + + total += size; + if (seq == max_seq) + young += size; + if (seq + MIN_NR_GENS == max_seq) + old += size; + } + } + + /* + * The aging and the eviction is a typical producer-consumer model. The + * aging tries to be lazy to reduce the unnecessary overhead. On the + * other hand, the eviction stalls when the number of generations + * reaches MIN_NR_GENS. So ideally, there should be MIN_NR_GENS+1 + * generations, hence the first two if's. + * + * In addition, it's ideal to spread pages out evenly, meaning + * 1/(MIN_NR_GENS+1) of the total number of pages for each generation. A + * reasonable range for this average portion would [1/MIN_NR_GENS, + * 1/(MIN_NR_GENS+2)]. From the consumer's POV, the eviction only cares + * about the lower bound of cold pages, i.e., 1/(MIN_NR_GENS+2), whereas + * from the producer's POV, the aging only cares about the upper bound + * of hot pages, i.e., 1/MIN_NR_GENS. + */ + if (min_seq[LRU_GEN_FILE] + MIN_NR_GENS > max_seq) + *need_aging = true; + else if (min_seq[LRU_GEN_FILE] + MIN_NR_GENS < max_seq) + *need_aging = false; + else if (young * MIN_NR_GENS > total) + *need_aging = true; + else if (old * (MIN_NR_GENS + 2) < total) + *need_aging = true; + else + *need_aging = false; + + return total > 0 ? total : 0; +} + +static void age_lruvec(struct lruvec *lruvec, struct scan_control *sc) +{ + bool need_aging; + long nr_to_scan; + int swappiness = get_swappiness(lruvec, sc); + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + DEFINE_MAX_SEQ(lruvec); + DEFINE_MIN_SEQ(lruvec); + + mem_cgroup_calculate_protection(NULL, memcg); + + if (mem_cgroup_below_min(memcg)) + return; + + nr_to_scan = get_nr_evictable(lruvec, max_seq, min_seq, swappiness, &need_aging); + if (!nr_to_scan) + return; + + nr_to_scan >>= sc->priority; + + if (!mem_cgroup_online(memcg)) + nr_to_scan++; + + if (nr_to_scan && need_aging && (!mem_cgroup_below_low(memcg) || sc->memcg_low_reclaim)) + inc_max_seq(lruvec, max_seq); +} + +static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) +{ + struct mem_cgroup *memcg; + + VM_BUG_ON(!current_is_kswapd()); + + memcg = mem_cgroup_iter(NULL, NULL, NULL); + do { + struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); + + age_lruvec(lruvec, sc); + + cond_resched(); + } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); +} + +/****************************************************************************** + * the eviction + ******************************************************************************/ + +static bool sort_page(struct lruvec *lruvec, struct page *page, int tier_idx) +{ + bool success; + int gen = page_lru_gen(page); + int type = page_is_file_lru(page); + int zone = page_zonenum(page); + int tier = page_lru_tier(page); + int delta = thp_nr_pages(page); + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + VM_BUG_ON_PAGE(gen >= MAX_NR_GENS, page); + + if (!page_evictable(page)) { + success = lru_gen_del_page(lruvec, page, true); + VM_BUG_ON_PAGE(!success, page); + SetPageUnevictable(page); + add_page_to_lru_list(page, lruvec, page_lru(page)); + __count_vm_events(UNEVICTABLE_PGCULLED, delta); + return true; + } + + if (type == LRU_GEN_FILE && PageAnon(page) && PageDirty(page)) { + success = lru_gen_del_page(lruvec, page, true); + VM_BUG_ON_PAGE(!success, page); + SetPageSwapBacked(page); + add_page_to_lru_list_tail(page, lruvec, page_lru(page)); + return true; + } + + if (tier > tier_idx) { + int hist = lru_hist_from_seq(lrugen->min_seq[type]); + + gen = page_inc_gen(lruvec, page, false); + list_move_tail(&page->lru, &lrugen->lists[gen][type][zone]); + + WRITE_ONCE(lrugen->protected[hist][type][tier - 1], + lrugen->protected[hist][type][tier - 1] + delta); + __mod_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + type, delta); + return true; + } + + if (PageLocked(page) || PageWriteback(page) || + (type == LRU_GEN_FILE && PageDirty(page))) { + gen = page_inc_gen(lruvec, page, true); + list_move(&page->lru, &lrugen->lists[gen][type][zone]); + return true; + } + + return false; +} + +static bool isolate_page(struct lruvec *lruvec, struct page *page, struct scan_control *sc) +{ + bool success; + + if (!sc->may_unmap && page_mapped(page)) + return false; + + if (!(sc->may_writepage && (sc->gfp_mask & __GFP_IO)) && + (PageDirty(page) || (PageAnon(page) && !PageSwapCache(page)))) + return false; + + if (!get_page_unless_zero(page)) + return false; + + ClearPageLRU(page); + + success = lru_gen_del_page(lruvec, page, true); + VM_BUG_ON_PAGE(!success, page); + + return true; +} + +static int scan_pages(struct lruvec *lruvec, struct scan_control *sc, + int type, int tier, struct list_head *list) +{ + int gen, zone; + enum vm_event_item item; + int sorted = 0; + int scanned = 0; + int isolated = 0; + int remaining = MAX_LRU_BATCH; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + + VM_BUG_ON(!list_empty(list)); + + if (get_nr_gens(lruvec, type) == MIN_NR_GENS) + return 0; + + gen = lru_gen_from_seq(lrugen->min_seq[type]); + + for (zone = sc->reclaim_idx; zone >= 0; zone--) { + LIST_HEAD(moved); + int skipped = 0; + struct list_head *head = &lrugen->lists[gen][type][zone]; + + while (!list_empty(head)) { + struct page *page = lru_to_page(head); + int delta = thp_nr_pages(page); + + VM_BUG_ON_PAGE(PageTail(page), page); + VM_BUG_ON_PAGE(PageUnevictable(page), page); + VM_BUG_ON_PAGE(PageActive(page), page); + VM_BUG_ON_PAGE(page_is_file_lru(page) != type, page); + VM_BUG_ON_PAGE(page_zonenum(page) != zone, page); + + prefetchw_prev_lru_page(page, head, flags); + + scanned += delta; + + if (sort_page(lruvec, page, tier)) + sorted += delta; + else if (isolate_page(lruvec, page, sc)) { + list_add(&page->lru, list); + isolated += delta; + } else { + list_move(&page->lru, &moved); + skipped += delta; + } + + if (!--remaining || max(isolated, skipped) >= MIN_LRU_BATCH) + break; + } + + if (skipped) { + list_splice(&moved, head); + __count_zid_vm_events(PGSCAN_SKIP, zone, skipped); + } + + if (!remaining || isolated >= MIN_LRU_BATCH) + break; + } + + item = current_is_kswapd() ? PGSCAN_KSWAPD : PGSCAN_DIRECT; + if (!cgroup_reclaim(sc)) { + __count_vm_events(item, isolated); + __count_vm_events(PGREFILL, sorted); + } + __count_memcg_events(memcg, item, isolated); + __count_memcg_events(memcg, PGREFILL, sorted); + __count_vm_events(PGSCAN_ANON + type, isolated); + + /* + * There might not be eligible pages due to reclaim_idx, may_unmap and + * may_writepage. Check the remaining to prevent livelock if there is no + * progress. + */ + return isolated || !remaining ? scanned : 0; +} + +static int get_tier_idx(struct lruvec *lruvec, int type) +{ + int tier; + struct ctrl_pos sp, pv; + + /* + * To leave a margin for fluctuations, use a larger gain factor (1:2). + * This value is chosen because any other tier would have at least twice + * as many refaults as the first tier. + */ + read_ctrl_pos(lruvec, type, 0, 1, &sp); + for (tier = 1; tier < MAX_NR_TIERS; tier++) { + read_ctrl_pos(lruvec, type, tier, 2, &pv); + if (!positive_ctrl_err(&sp, &pv)) + break; + } + + return tier - 1; +} + +static int get_type_to_scan(struct lruvec *lruvec, int swappiness, int *tier_idx) +{ + int type, tier; + struct ctrl_pos sp, pv; + int gain[ANON_AND_FILE] = { swappiness, 200 - swappiness }; + + /* + * Compare the first tier of anon with that of file to determine which + * type to scan. Also need to compare other tiers of the selected type + * with the first tier of the other type to determine the last tier (of + * the selected type) to evict. + */ + read_ctrl_pos(lruvec, LRU_GEN_ANON, 0, gain[LRU_GEN_ANON], &sp); + read_ctrl_pos(lruvec, LRU_GEN_FILE, 0, gain[LRU_GEN_FILE], &pv); + type = positive_ctrl_err(&sp, &pv); + + read_ctrl_pos(lruvec, !type, 0, gain[!type], &sp); + for (tier = 1; tier < MAX_NR_TIERS; tier++) { + read_ctrl_pos(lruvec, type, tier, gain[type], &pv); + if (!positive_ctrl_err(&sp, &pv)) + break; + } + + *tier_idx = tier - 1; + + return type; +} + +static int isolate_pages(struct lruvec *lruvec, struct scan_control *sc, int swappiness, + int *type_scanned, struct list_head *list) +{ + int i; + int type; + int scanned; + int tier = -1; + DEFINE_MIN_SEQ(lruvec); + + VM_BUG_ON(!seq_is_valid(lruvec)); + + /* + * Try to make the obvious choice first. When anon and file are both + * available from the same generation, interpret swappiness 1 as file + * first and 200 as anon first. + */ + if (!swappiness) + type = LRU_GEN_FILE; + else if (min_seq[LRU_GEN_ANON] < min_seq[LRU_GEN_FILE]) + type = LRU_GEN_ANON; + else if (swappiness == 1) + type = LRU_GEN_FILE; + else if (swappiness == 200) + type = LRU_GEN_ANON; + else + type = get_type_to_scan(lruvec, swappiness, &tier); + + for (i = !swappiness; i < ANON_AND_FILE; i++) { + if (tier < 0) + tier = get_tier_idx(lruvec, type); + + scanned = scan_pages(lruvec, sc, type, tier, list); + if (scanned) + break; + + type = !type; + tier = -1; + } + + *type_scanned = type; + + return scanned; +} + +static int evict_pages(struct lruvec *lruvec, struct scan_control *sc, int swappiness) +{ + int type; + int scanned; + int reclaimed; + LIST_HEAD(list); + struct page *page; + enum vm_event_item item; + struct reclaim_stat stat; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + struct pglist_data *pgdat = lruvec_pgdat(lruvec); + + spin_lock_irq(&lruvec->lru_lock); + + scanned = isolate_pages(lruvec, sc, swappiness, &type, &list); + + if (try_to_inc_min_seq(lruvec, swappiness)) + scanned++; + + if (get_nr_gens(lruvec, LRU_GEN_FILE) == MIN_NR_GENS) + scanned = 0; + + spin_unlock_irq(&lruvec->lru_lock); + + if (list_empty(&list)) + return scanned; + + reclaimed = shrink_page_list(&list, pgdat, sc, &stat, false); + + /* + * To avoid livelock, don't add rejected pages back to the same lists + * they were isolated from. See lru_gen_add_page(). + */ + list_for_each_entry(page, &list, lru) { + ClearPageReferenced(page); + ClearPageWorkingset(page); + + if (PageReclaim(page) && (PageDirty(page) || PageWriteback(page))) + ClearPageActive(page); + else + SetPageActive(page); + } + + spin_lock_irq(&lruvec->lru_lock); + + move_pages_to_lru(lruvec, &list); + + item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT; + if (!cgroup_reclaim(sc)) + __count_vm_events(item, reclaimed); + __count_memcg_events(memcg, item, reclaimed); + __count_vm_events(PGSTEAL_ANON + type, reclaimed); + + spin_unlock_irq(&lruvec->lru_lock); + + mem_cgroup_uncharge_list(&list); + free_unref_page_list(&list); + + sc->nr_reclaimed += reclaimed; + + return scanned; +} + +static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool can_swap) +{ + bool need_aging; + long nr_to_scan; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + DEFINE_MAX_SEQ(lruvec); + DEFINE_MIN_SEQ(lruvec); + + if (mem_cgroup_below_min(memcg) || + (mem_cgroup_below_low(memcg) && !sc->memcg_low_reclaim)) + return 0; + + nr_to_scan = get_nr_evictable(lruvec, max_seq, min_seq, can_swap, &need_aging); + if (!nr_to_scan) + return 0; + + /* reset the priority if the target has been met */ + nr_to_scan >>= sc->nr_reclaimed < sc->nr_to_reclaim ? sc->priority : DEF_PRIORITY; + + if (!mem_cgroup_online(memcg)) + nr_to_scan++; + + if (!nr_to_scan) + return 0; + + if (!need_aging) + return nr_to_scan; + + /* leave the work to lru_gen_age_node() */ + if (current_is_kswapd()) + return 0; + + /* try other memcgs before going to the aging path */ + if (!cgroup_reclaim(sc) && !sc->force_deactivate) { + sc->skipped_deactivate = true; + return 0; + } + + inc_max_seq(lruvec, max_seq); + + return nr_to_scan; +} + +static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) +{ + struct blk_plug plug; + long scanned = 0; + + lru_add_drain(); + + blk_start_plug(&plug); + + while (true) { + int delta; + int swappiness; + long nr_to_scan; + + if (sc->may_swap) + swappiness = get_swappiness(lruvec, sc); + else if (!cgroup_reclaim(sc) && get_swappiness(lruvec, sc)) + swappiness = 1; + else + swappiness = 0; + + nr_to_scan = get_nr_to_scan(lruvec, sc, swappiness); + if (!nr_to_scan) + break; + + delta = evict_pages(lruvec, sc, swappiness); + if (!delta) + break; + + scanned += delta; + if (scanned >= nr_to_scan) + break; + + cond_resched(); + } + + blk_finish_plug(&plug); +} + /****************************************************************************** * initialization ******************************************************************************/ @@ -2819,6 +3598,16 @@ static int __init init_lru_gen(void) }; late_initcall(init_lru_gen); +#else + +static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) +{ +} + +static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) +{ +} + #endif /* CONFIG_LRU_GEN */ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) @@ -2832,6 +3621,11 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) struct blk_plug plug; bool scan_adjusted; + if (lru_gen_enabled()) { + lru_gen_shrink_lruvec(lruvec, sc); + return; + } + get_scan_count(lruvec, sc, nr); /* Record the original scan target for proportional adjustments later */ @@ -3305,6 +4099,9 @@ static void snapshot_refaults(struct mem_cgroup *target_memcg, pg_data_t *pgdat) struct lruvec *target_lruvec; unsigned long refaults; + if (lru_gen_enabled()) + return; + target_lruvec = mem_cgroup_lruvec(target_memcg, pgdat); refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_ANON); target_lruvec->refaults[0] = refaults; @@ -3679,6 +4476,11 @@ static void age_active_anon(struct pglist_data *pgdat, struct mem_cgroup *memcg; struct lruvec *lruvec; + if (lru_gen_enabled()) { + lru_gen_age_node(pgdat, sc); + return; + } + if (!total_swap_pages) return; diff --git a/mm/workingset.c b/mm/workingset.c index 4a30e4a813a5..18b242e36494 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -185,7 +185,6 @@ static unsigned int bucket_order __read_mostly; static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction, bool workingset) { - eviction >>= bucket_order; eviction &= EVICTION_MASK; eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid; eviction = (eviction << NODES_SHIFT) | pgdat->node_id; @@ -210,10 +209,116 @@ static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat, *memcgidp = memcgid; *pgdat = NODE_DATA(nid); - *evictionp = entry << bucket_order; + *evictionp = entry; *workingsetp = workingset; } +#ifdef CONFIG_LRU_GEN + +static int page_lru_refs(struct page *page) +{ + unsigned long flags = READ_ONCE(page->flags); + + BUILD_BUG_ON(LRU_GEN_WIDTH + LRU_REFS_WIDTH > BITS_PER_LONG - EVICTION_SHIFT); + + /* see the comment on MAX_NR_TIERS */ + return flags & BIT(PG_workingset) ? (flags & LRU_REFS_MASK) >> LRU_REFS_PGOFF : 0; +} + +static void *lru_gen_eviction(struct page *page) +{ + int hist, tier; + unsigned long token; + unsigned long min_seq; + struct lruvec *lruvec; + struct lru_gen_struct *lrugen; + int type = page_is_file_lru(page); + int refs = page_lru_refs(page); + int delta = thp_nr_pages(page); + bool workingset = PageWorkingset(page); + struct mem_cgroup *memcg = page_memcg(page); + struct pglist_data *pgdat = page_pgdat(page); + + lruvec = mem_cgroup_lruvec(memcg, pgdat); + lrugen = &lruvec->lrugen; + min_seq = READ_ONCE(lrugen->min_seq[type]); + token = (min_seq << LRU_REFS_WIDTH) | refs; + + hist = lru_hist_from_seq(min_seq); + tier = lru_tier_from_refs(refs + workingset); + atomic_long_add(delta, &lrugen->evicted[hist][type][tier]); + + return pack_shadow(mem_cgroup_id(memcg), pgdat, token, workingset); +} + +static void lru_gen_refault(struct page *page, void *shadow) +{ + int hist, tier, refs; + int memcg_id; + bool workingset; + unsigned long token; + unsigned long min_seq; + struct lruvec *lruvec; + struct lru_gen_struct *lrugen; + struct mem_cgroup *memcg; + struct pglist_data *pgdat; + int type = page_is_file_lru(page); + int delta = thp_nr_pages(page); + + unpack_shadow(shadow, &memcg_id, &pgdat, &token, &workingset); + + refs = token & (BIT(LRU_REFS_WIDTH) - 1); + if (refs && !workingset) + return; + + if (page_pgdat(page) != pgdat) + return; + + rcu_read_lock(); + memcg = page_memcg_rcu(page); + if (mem_cgroup_id(memcg) != memcg_id) + goto unlock; + + token >>= LRU_REFS_WIDTH; + lruvec = mem_cgroup_lruvec(memcg, pgdat); + lrugen = &lruvec->lrugen; + min_seq = READ_ONCE(lrugen->min_seq[type]); + if (token != (min_seq & (EVICTION_MASK >> LRU_REFS_WIDTH))) + goto unlock; + + hist = lru_hist_from_seq(min_seq); + tier = lru_tier_from_refs(refs + workingset); + atomic_long_add(delta, &lrugen->refaulted[hist][type][tier]); + mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + type, delta); + + /* + * Count the following two cases as stalls: + * 1. For pages accessed through page tables, hotter pages pushed out + * hot pages which refaulted immediately. + * 2. For pages accessed through file descriptors, numbers of accesses + * might have been beyond the limit. + */ + if (lru_gen_in_fault() || refs + workingset == BIT(LRU_REFS_WIDTH)) { + SetPageWorkingset(page); + mod_lruvec_state(lruvec, WORKINGSET_RESTORE_BASE + type, delta); + } +unlock: + rcu_read_unlock(); +} + +#else + +static void *lru_gen_eviction(struct page *page) +{ + return NULL; +} + +static void lru_gen_refault(struct page *page, void *shadow) +{ +} + +#endif /* CONFIG_LRU_GEN */ + /** * workingset_age_nonresident - age non-resident entries as LRU ages * @lruvec: the lruvec that was aged @@ -262,11 +367,15 @@ void *workingset_eviction(struct page *page, struct mem_cgroup *target_memcg) VM_BUG_ON_PAGE(page_count(page), page); VM_BUG_ON_PAGE(!PageLocked(page), page); + if (lru_gen_enabled()) + return lru_gen_eviction(page); + lruvec = mem_cgroup_lruvec(target_memcg, pgdat); workingset_age_nonresident(lruvec, thp_nr_pages(page)); /* XXX: target_memcg can be NULL, go through lruvec */ memcgid = mem_cgroup_id(lruvec_memcg(lruvec)); eviction = atomic_long_read(&lruvec->nonresident_age); + eviction >>= bucket_order; return pack_shadow(memcgid, pgdat, eviction, PageWorkingset(page)); } @@ -294,7 +403,13 @@ void workingset_refault(struct page *page, void *shadow) bool workingset; int memcgid; + if (lru_gen_enabled()) { + lru_gen_refault(page, shadow); + return; + } + unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset); + eviction <<= bucket_order; rcu_read_lock(); /* -- Gitee From cb402c9e1a0b0972d089521ca4f085a5890605cd Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Thu, 27 Jan 2022 20:43:22 -0700 Subject: [PATCH 06/13] FROMLIST: mm: multi-gen LRU: exploit locality in rmap MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Searching the rmap for PTEs mapping each page on an LRU list (to test and clear the accessed bit) can be expensive because pages from different VMAs (PA space) are not cache friendly to the rmap (VA space). For workloads mostly using mapped pages, the rmap has a high CPU cost in the reclaim path. This patch exploits spatial locality to reduce the trips into the rmap. When shrink_page_list() walks the rmap and finds a young PTE, a new function lru_gen_look_around() scans at most BITS_PER_LONG-1 adjacent PTEs. On finding another young PTE, it clears the accessed bit and updates the gen counter of the page mapped by this PTE to (max_seq%MAX_NR_GENS)+1. Server benchmark results: Single workload: fio (buffered I/O): no change Single workload: memcached (anon): +[4, 6]% Ops/sec KB/sec patch1-6: 964656.80 37520.88 patch1-7: 1014393.57 39455.42 Configurations: no change Client benchmark results: kswapd profiles: patch1-6 36.13% lzo1x_1_do_compress (real work) 19.16% page_vma_mapped_walk 6.55% _raw_spin_unlock_irq 4.02% do_raw_spin_lock 2.32% anon_vma_interval_tree_iter_first 2.11% ptep_clear_flush 1.76% __zram_bvec_write 1.64% folio_referenced_one 1.40% memmove 1.35% obj_malloc patch1-7 45.54% lzo1x_1_do_compress (real work) 9.56% page_vma_mapped_walk 6.70% _raw_spin_unlock_irq 2.78% ptep_clear_flush 2.47% do_raw_spin_lock 2.22% __zram_bvec_write 1.87% lru_gen_look_around 1.78% memmove 1.77% obj_malloc 1.44% free_unref_page_list Configurations: no change Link: https://lore.kernel.org/r/20220309021230.721028-8-yuzhao@google.com/ Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I9a290343840f3cf925c891c8e360c7cdc24ffb9c --- include/linux/memcontrol.h | 29 +++++++ include/linux/mmzone.h | 6 ++ include/linux/swap.h | 1 + mm/memcontrol.c | 1 + mm/rmap.c | 7 ++ mm/swap.c | 4 +- mm/vmscan.c | 156 +++++++++++++++++++++++++++++++++++++ 7 files changed, 202 insertions(+), 2 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 631a3bfeb066..8792bdbd9006 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1009,6 +1009,23 @@ void unlock_page_memcg(struct page *page); void __mod_memcg_state(struct mem_cgroup *memcg, int idx, int val); +/* try to stablize page_memcg() for all the pages in a memcg */ +static inline bool mem_cgroup_trylock_pages(struct mem_cgroup *memcg) +{ + rcu_read_lock(); + + if (mem_cgroup_disabled() || !atomic_read(&memcg->moving_account)) + return true; + + rcu_read_unlock(); + return false; +} + +static inline void mem_cgroup_unlock_pages(void) +{ + rcu_read_unlock(); +} + /* idx can be of type enum memcg_stat_item or node_stat_item */ static inline void mod_memcg_state(struct mem_cgroup *memcg, int idx, int val) @@ -1525,6 +1542,18 @@ static inline void unlock_page_memcg(struct page *page) { } +static inline bool mem_cgroup_trylock_pages(struct mem_cgroup *memcg) +{ + /* to match page_memcg_rcu() */ + rcu_read_lock(); + return true; +} + +static inline void mem_cgroup_unlock_pages(void) +{ + rcu_read_unlock(); +} + static inline void mem_cgroup_handle_over_high(void) { } diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 45cfbdcd80ee..8796f71badaa 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -328,6 +328,7 @@ enum lruvec_flags { #ifndef __GENERATING_BOUNDS_H struct lruvec; +struct page_vma_mapped_walk; #define LRU_GEN_MASK ((BIT(LRU_GEN_WIDTH) - 1) << LRU_GEN_PGOFF) #define LRU_REFS_MASK ((BIT(LRU_REFS_WIDTH) - 1) << LRU_REFS_PGOFF) @@ -381,6 +382,7 @@ struct lru_gen_struct { }; void lru_gen_init_lruvec(struct lruvec *lruvec); +void lru_gen_look_around(struct page_vma_mapped_walk *pvmw); #ifdef CONFIG_MEMCG void lru_gen_init_memcg(struct mem_cgroup *memcg); @@ -393,6 +395,10 @@ static inline void lru_gen_init_lruvec(struct lruvec *lruvec) { } +static inline void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) +{ +} + #ifdef CONFIG_MEMCG static inline void lru_gen_init_memcg(struct mem_cgroup *memcg) { diff --git a/include/linux/swap.h b/include/linux/swap.h index 2b68047db2d9..b2c0fce206d9 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -358,6 +358,7 @@ extern void lru_add_drain_cpu(int cpu); extern void lru_add_drain_cpu_zone(struct zone *zone); extern void lru_add_drain_all(void); extern void rotate_reclaimable_page(struct page *page); +extern void activate_page(struct page *page); extern void deactivate_file_page(struct page *page); extern void deactivate_page(struct page *page); extern void mark_page_lazyfree(struct page *page); diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 37dc3ef8f328..55edd97821e0 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2854,6 +2854,7 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg) * - LRU isolation * - lock_page_memcg() * - exclusive reference + * - mem_cgroup_trylock_pages() */ page->memcg_data = (unsigned long)memcg; } diff --git a/mm/rmap.c b/mm/rmap.c index 0dc39cf94345..2a6556f278bb 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -72,6 +72,7 @@ #include #include #include +#include #include @@ -789,6 +790,12 @@ static bool page_referenced_one(struct page *page, struct vm_area_struct *vma, } if (pvmw.pte) { + if (lru_gen_enabled() && pte_young(*pvmw.pte) && + !(vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ))) { + lru_gen_look_around(&pvmw); + referenced++; + } + if (ptep_clear_flush_young_notify(vma, address, pvmw.pte)) { /* diff --git a/mm/swap.c b/mm/swap.c index acc56d3658b2..f69113bcb06d 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -337,7 +337,7 @@ static bool need_activate_page_drain(int cpu) return pagevec_count(&per_cpu(lru_pvecs.activate_page, cpu)) != 0; } -static void activate_page(struct page *page) +void activate_page(struct page *page) { page = compound_head(page); if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { @@ -357,7 +357,7 @@ static inline void activate_page_drain(int cpu) { } -static void activate_page(struct page *page) +void activate_page(struct page *page) { struct lruvec *lruvec; diff --git a/mm/vmscan.c b/mm/vmscan.c index ef0aeae80dd7..4602848a62cb 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1321,6 +1321,11 @@ static unsigned int shrink_page_list(struct list_head *page_list, if (!sc->may_unmap && page_mapped(page)) goto keep_locked; + /* page_update_gen() tried to promote this page? */ + if (lru_gen_enabled() && !ignore_references && + page_mapped(page) && PageReferenced(page)) + goto keep_locked; + may_enter_fs = (sc->gfp_mask & __GFP_FS) || (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); @@ -2929,6 +2934,31 @@ static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv) * the aging ******************************************************************************/ +static int page_update_gen(struct page *page, int gen) +{ + unsigned long old_flags, new_flags; + + VM_BUG_ON(gen >= MAX_NR_GENS); + VM_BUG_ON(!rcu_read_lock_held()); + + do { + new_flags = old_flags = READ_ONCE(page->flags); + + /* for shrink_page_list() */ + if (!(new_flags & LRU_GEN_MASK)) { + new_flags |= BIT(PG_referenced); + continue; + } + + new_flags &= ~LRU_GEN_MASK; + new_flags |= (gen + 1UL) << LRU_GEN_PGOFF; + new_flags &= ~(LRU_REFS_MASK | LRU_REFS_FLAGS); + } while (new_flags != old_flags && + cmpxchg(&page->flags, old_flags, new_flags) != old_flags); + + return ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; +} + static int page_inc_gen(struct lruvec *lruvec, struct page *page, bool reclaiming) { unsigned long old_flags, new_flags; @@ -2940,6 +2970,11 @@ static int page_inc_gen(struct lruvec *lruvec, struct page *page, bool reclaimin new_flags = old_flags = READ_ONCE(page->flags); VM_BUG_ON_PAGE(!(new_flags & LRU_GEN_MASK), page); + new_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; + /* page_update_gen() has promoted this page? */ + if (new_gen >= 0 && new_gen != old_gen) + return new_gen; + new_gen = (old_gen + 1) % MAX_NR_GENS; new_flags &= ~LRU_GEN_MASK; @@ -3164,6 +3199,122 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); } +/* + * This function exploits spatial locality when shrink_page_list() walks the + * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. + */ +void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) +{ + int i; + pte_t *pte; + unsigned long start; + unsigned long end; + unsigned long addr; + struct page *page; + unsigned long bitmap[BITS_TO_LONGS(MIN_LRU_BATCH)] = {}; + struct mem_cgroup *memcg = page_memcg(pvmw->page); + struct pglist_data *pgdat = page_pgdat(pvmw->page); + struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); + DEFINE_MAX_SEQ(lruvec); + int old_gen, new_gen = lru_gen_from_seq(max_seq); + + lockdep_assert_held(pvmw->ptl); + VM_BUG_ON_PAGE(PageLRU(pvmw->page), pvmw->page); + + if (spin_is_contended(pvmw->ptl)) + return; + + start = max(pvmw->address & PMD_MASK, pvmw->vma->vm_start); + end = pmd_addr_end(pvmw->address, pvmw->vma->vm_end); + + if (end - start > MIN_LRU_BATCH * PAGE_SIZE) { + if (pvmw->address - start < MIN_LRU_BATCH * PAGE_SIZE / 2) + end = start + MIN_LRU_BATCH * PAGE_SIZE; + else if (end - pvmw->address < MIN_LRU_BATCH * PAGE_SIZE / 2) + start = end - MIN_LRU_BATCH * PAGE_SIZE; + else { + start = pvmw->address - MIN_LRU_BATCH * PAGE_SIZE / 2; + end = pvmw->address + MIN_LRU_BATCH * PAGE_SIZE / 2; + } + } + + pte = pvmw->pte - (pvmw->address - start) / PAGE_SIZE; + + rcu_read_lock(); + arch_enter_lazy_mmu_mode(); + + for (i = 0, addr = start; addr != end; i++, addr += PAGE_SIZE) { + unsigned long pfn = pte_pfn(pte[i]); + + VM_BUG_ON(addr < pvmw->vma->vm_start || addr >= pvmw->vma->vm_end); + + if (!pte_present(pte[i]) || is_zero_pfn(pfn)) + continue; + + if (WARN_ON_ONCE(pte_devmap(pte[i]) || pte_special(pte[i]))) + continue; + + if (!pte_young(pte[i])) + continue; + + VM_BUG_ON(!pfn_valid(pfn)); + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + continue; + + page = compound_head(pfn_to_page(pfn)); + if (page_to_nid(page) != pgdat->node_id) + continue; + + if (page_memcg_rcu(page) != memcg) + continue; + + if (!ptep_test_and_clear_young(pvmw->vma, addr, pte + i)) + continue; + + if (pte_dirty(pte[i]) && !PageDirty(page) && + !(PageAnon(page) && PageSwapBacked(page) && !PageSwapCache(page))) + set_page_dirty(page); + + old_gen = page_lru_gen(page); + if (old_gen < 0) + SetPageReferenced(page); + else if (old_gen != new_gen) + __set_bit(i, bitmap); + } + + arch_leave_lazy_mmu_mode(); + rcu_read_unlock(); + + if (bitmap_weight(bitmap, MIN_LRU_BATCH) < PAGEVEC_SIZE) { + for_each_set_bit(i, bitmap, MIN_LRU_BATCH) + activate_page(pte_page(pte[i])); + return; + } + + /* page_update_gen() requires stable page_memcg() */ + if (!mem_cgroup_trylock_pages(memcg)) + return; + + spin_lock_irq(&lruvec->lru_lock); + new_gen = lru_gen_from_seq(lruvec->lrugen.max_seq); + + for_each_set_bit(i, bitmap, MIN_LRU_BATCH) { + page = compound_head(pte_page(pte[i])); + if (page_memcg_rcu(page) != memcg) + continue; + + old_gen = page_update_gen(page, new_gen); + if (old_gen < 0 || old_gen == new_gen) + continue; + + lru_gen_update_size(lruvec, page, old_gen, new_gen); + } + + spin_unlock_irq(&lruvec->lru_lock); + + mem_cgroup_unlock_pages(); +} + /****************************************************************************** * the eviction ******************************************************************************/ @@ -3197,6 +3348,11 @@ static bool sort_page(struct lruvec *lruvec, struct page *page, int tier_idx) return true; } + if (gen != lru_gen_from_seq(lrugen->min_seq[type])) { + list_move(&page->lru, &lrugen->lists[gen][type][zone]); + return true; + } + if (tier > tier_idx) { int hist = lru_hist_from_seq(lrugen->min_seq[type]); -- Gitee From 7790ba9b63aa7234c4e9564b7f40b7862d4db548 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Thu, 27 Jan 2022 19:23:01 -0700 Subject: [PATCH 07/13] FROMLIST: mm: multi-gen LRU: support page table walks MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit To further exploit spatial locality, the aging prefers to walk page tables to search for young PTEs and promote hot pages. A kill switch will be added in the next patch to disable this behavior. When disabled, the aging relies on the rmap only. NB: this behavior has nothing similar with the page table scanning in the 2.4 kernel [1], which searches page tables for old PTEs, adds cold pages to swapcache and unmaps them. To avoid confusion, the term "iteration" specifically means the traversal of an entire mm_struct list; the term "walk" will be applied to page tables and the rmap, as usual. An mm_struct list is maintained for each memcg, and an mm_struct follows its owner task to the new memcg when this task is migrated. Given an lruvec, the aging iterates lruvec_memcg()->mm_list and calls walk_page_range() with each mm_struct on this list to promote hot pages before it increments max_seq. When multiple page table walkers iterate the same list, each of them gets a unique mm_struct; therefore they can run concurrently. Page table walkers ignore any misplaced pages, e.g., if an mm_struct was migrated, pages it left in the previous memcg will not be promoted when its current memcg is under reclaim. Similarly, page table walkers will not promote pages from nodes other than the one under reclaim. This patch uses the following optimizations when walking page tables: 1. It tracks the usage of mm_struct's between context switches so that page table walkers can skip processes that have been sleeping since the last iteration. 2. It uses generational Bloom filters to record populated branches so that page table walkers can reduce their search space based on the query results, e.g., to skip page tables containing mostly holes or misplaced pages. 3. It takes advantage of the accessed bit in non-leaf PMD entries when CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG=y. 4. It does not zigzag between a PGD table and the same PMD table spanning multiple VMAs. IOW, it finishes all the VMAs within the range of the same PMD table before it returns to a PGD table. This improves the cache performance for workloads that have large numbers of tiny VMAs [2], especially when CONFIG_PGTABLE_LEVELS=5. Server benchmark results: Single workload: fio (buffered I/O): no change Single workload: memcached (anon): +[5.5, 7.5]% Ops/sec KB/sec patch1-7: 1014393.57 39455.42 patch1-8: 1078507.59 41949.15 Configurations: no change Client benchmark results: kswapd profiles: patch1-7 45.54% lzo1x_1_do_compress (real work) 9.56% page_vma_mapped_walk 6.70% _raw_spin_unlock_irq 2.78% ptep_clear_flush 2.47% do_raw_spin_lock 2.22% __zram_bvec_write 1.87% lru_gen_look_around 1.78% memmove 1.77% obj_malloc 1.44% free_unref_page_list patch1-8 47.02% lzo1x_1_do_compress (real work) 6.73% page_vma_mapped_walk 6.14% _raw_spin_unlock_irq 3.39% walk_pte_range 2.63% ptep_clear_flush 2.29% __zram_bvec_write 2.10% do_raw_spin_lock 1.81% memmove 1.73% obj_malloc 1.53% free_unref_page_list Configurations: no change [1] https://lwn.net/Articles/23732/ [2] https://source.android.com/devices/tech/debug/scudo Link: https://lore.kernel.org/r/20220309021230.721028-9-yuzhao@google.com/ Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I5a3c97cf8ebf8d65d5f9528cd979a637c190053e --- fs/exec.c | 2 + include/linux/memcontrol.h | 5 + include/linux/mm_types.h | 79 +++ include/linux/mmzone.h | 59 +++ include/linux/swap.h | 4 + kernel/exit.c | 1 + kernel/fork.c | 10 +- kernel/sched/core.c | 1 + mm/memcontrol.c | 24 + mm/vmscan.c | 974 ++++++++++++++++++++++++++++++++++++- 10 files changed, 1144 insertions(+), 15 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index cf2077bffc0a..2d1e0f594c47 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -997,6 +997,7 @@ static int exec_mmap(struct mm_struct *mm) active_mm = tsk->active_mm; tsk->active_mm = mm; tsk->mm = mm; + lru_gen_add_mm(mm); /* * This prevents preemption while active_mm is being loaded and * it and mm are being updated, which could cause problems for @@ -1009,6 +1010,7 @@ static int exec_mmap(struct mm_struct *mm) activate_mm(active_mm, mm); if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM)) local_irq_enable(); + lru_gen_use_mm(mm); tsk->mm->vmacache_seqnum = 0; vmacache_flush(tsk); task_unlock(tsk); diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 8792bdbd9006..0256319e1a4d 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -372,6 +372,11 @@ struct mem_cgroup { struct deferred_split deferred_split_queue; #endif +#ifdef CONFIG_LRU_GEN + /* per-memcg mm_struct list */ + struct lru_gen_mm_list mm_list; +#endif + #ifdef CONFIG_DYNAMIC_HUGETLB struct dhugetlb_pool *hpool; #endif diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 9de02b116185..0cf0305f885c 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -3,6 +3,7 @@ #define _LINUX_MM_TYPES_H #include +#include #include #include @@ -16,6 +17,8 @@ #include #include #include +#include +#include #include @@ -590,6 +593,23 @@ struct mm_struct { u32 pasid; #endif +#ifdef CONFIG_LRU_GEN + struct { + /* this mm_struct is on lru_gen_mm_list */ + struct list_head list; +#ifdef CONFIG_MEMCG + /* points to the memcg of "owner" above */ + struct mem_cgroup *memcg; +#endif + /* + * Set when switching to this mm_struct, as a hint of + * whether it has been used since the last time per-node + * page table walkers cleared the corresponding bits. + */ + nodemask_t nodes; + } lru_gen; +#endif /* CONFIG_LRU_GEN */ + #ifdef CONFIG_MEMORY_RELIABLE atomic_long_t reserve_0; #endif @@ -648,6 +668,65 @@ static inline cpumask_t *mm_cpumask(struct mm_struct *mm) return (struct cpumask *)&mm->cpu_bitmap; } +#ifdef CONFIG_LRU_GEN + +struct lru_gen_mm_list { + /* mm_struct list for page table walkers */ + struct list_head fifo; + /* protects the list above */ + spinlock_t lock; +}; + +void lru_gen_add_mm(struct mm_struct *mm); +void lru_gen_del_mm(struct mm_struct *mm); +#ifdef CONFIG_MEMCG +void lru_gen_migrate_mm(struct mm_struct *mm); +#endif + +static inline void lru_gen_init_mm(struct mm_struct *mm) +{ + INIT_LIST_HEAD(&mm->lru_gen.list); +#ifdef CONFIG_MEMCG + mm->lru_gen.memcg = NULL; +#endif + nodes_clear(mm->lru_gen.nodes); +} + +static inline void lru_gen_use_mm(struct mm_struct *mm) +{ + /* unlikely but not a bug when racing with lru_gen_migrate_mm() */ + VM_WARN_ON(list_empty(&mm->lru_gen.list)); + + if (!(current->flags & PF_KTHREAD) && !nodes_full(mm->lru_gen.nodes)) + nodes_setall(mm->lru_gen.nodes); +} + +#else /* !CONFIG_LRU_GEN */ + +static inline void lru_gen_add_mm(struct mm_struct *mm) +{ +} + +static inline void lru_gen_del_mm(struct mm_struct *mm) +{ +} + +#ifdef CONFIG_MEMCG +static inline void lru_gen_migrate_mm(struct mm_struct *mm) +{ +} +#endif + +static inline void lru_gen_init_mm(struct mm_struct *mm) +{ +} + +static inline void lru_gen_use_mm(struct mm_struct *mm) +{ +} + +#endif /* CONFIG_LRU_GEN */ + struct mmu_gather; extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end); diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 8796f71badaa..d4f8a08d3358 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -381,6 +381,58 @@ struct lru_gen_struct { atomic_long_t refaulted[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS]; }; +enum { + MM_PTE_TOTAL, /* total leaf entries */ + MM_PTE_OLD, /* old leaf entries */ + MM_PTE_YOUNG, /* young leaf entries */ + MM_PMD_TOTAL, /* total non-leaf entries */ + MM_PMD_FOUND, /* non-leaf entries found in Bloom filters */ + MM_PMD_ADDED, /* non-leaf entries added to Bloom filters */ + NR_MM_STATS +}; + +/* mnemonic codes for the mm stats above */ +#define MM_STAT_CODES "toydfa" + +/* double-buffering Bloom filters */ +#define NR_BLOOM_FILTERS 2 + +struct lru_gen_mm_state { + /* set to max_seq after each iteration */ + unsigned long seq; + /* where the current iteration starts (inclusive) */ + struct list_head *head; + /* where the last iteration ends (exclusive) */ + struct list_head *tail; + /* to wait for the last page table walker to finish */ + struct wait_queue_head wait; + /* Bloom filters flip after each iteration */ + unsigned long *filters[NR_BLOOM_FILTERS]; + /* the mm stats for debugging */ + unsigned long stats[NR_HIST_GENS][NR_MM_STATS]; + /* the number of concurrent page table walkers */ + int nr_walkers; +}; + +struct lru_gen_mm_walk { + /* the lruvec under reclaim */ + struct lruvec *lruvec; + /* unstable max_seq from lru_gen_struct */ + unsigned long max_seq; + /* the next address within an mm to scan */ + unsigned long next_addr; + /* to batch page table entries */ + unsigned long bitmap[BITS_TO_LONGS(MIN_LRU_BATCH)]; + /* to batch promoted pages */ + int nr_pages[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES]; + /* to batch the mm stats */ + int mm_stats[NR_MM_STATS]; + /* total batched items */ + int batched; + bool can_swap; + bool full_scan; +}; + void lru_gen_init_lruvec(struct lruvec *lruvec); void lru_gen_look_around(struct page_vma_mapped_walk *pvmw); @@ -431,6 +483,8 @@ struct lruvec { #ifdef CONFIG_LRU_GEN /* evictable pages divided into generations */ struct lru_gen_struct lrugen; + /* to concurrently iterate lru_gen_mm_list */ + struct lru_gen_mm_state mm_state; #endif #ifdef CONFIG_MEMCG struct pglist_data *pgdat; @@ -969,6 +1023,11 @@ typedef struct pglist_data { unsigned long flags; +#ifdef CONFIG_LRU_GEN + /* kswap mm walk data */ + struct lru_gen_mm_walk mm_walk; +#endif + ZONE_PADDING(_pad2_) KABI_RESERVE(1) diff --git a/include/linux/swap.h b/include/linux/swap.h index b2c0fce206d9..03b161cca81a 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -142,6 +142,10 @@ union swap_header { */ struct reclaim_state { unsigned long reclaimed_slab; +#ifdef CONFIG_LRU_GEN + /* per-thread mm walk data */ + struct lru_gen_mm_walk *mm_walk; +#endif }; #ifdef __KERNEL__ diff --git a/kernel/exit.c b/kernel/exit.c index d13d67fc5f4e..b7dd10a362f7 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -422,6 +422,7 @@ void mm_update_next_owner(struct mm_struct *mm) goto retry; } WRITE_ONCE(mm->owner, c); + lru_gen_migrate_mm(mm); task_unlock(c); put_task_struct(c); } diff --git a/kernel/fork.c b/kernel/fork.c index c8ec029e158a..124ed3c9ceb5 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1062,7 +1062,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, goto fail_nocontext; mm->user_ns = get_user_ns(user_ns); - + lru_gen_init_mm(mm); sp_init_mm(mm); return mm; @@ -1110,6 +1110,7 @@ static inline void __mmput(struct mm_struct *mm) } if (mm->binfmt) module_put(mm->binfmt->module); + lru_gen_del_mm(mm); mmdrop(mm); } @@ -2533,6 +2534,13 @@ pid_t kernel_clone(struct kernel_clone_args *args) get_task_struct(p); } + if (IS_ENABLED(CONFIG_LRU_GEN) && !(clone_flags & CLONE_VM)) { + /* lock the task to synchronize with memcg migration */ + task_lock(p); + lru_gen_add_mm(p->mm); + task_unlock(p); + } + wake_up_new_task(p); /* forking complete and child started to run, tell ptracer */ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 51c707897c8d..d331afe48215 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3813,6 +3813,7 @@ context_switch(struct rq *rq, struct task_struct *prev, * finish_task_switch()'s mmdrop(). */ switch_mm_irqs_off(prev->active_mm, next->mm, next); + lru_gen_use_mm(next->mm); if (!prev->mm) { // from kernel /* will mmdrop() in finish_task_switch(). */ diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 55edd97821e0..9127a4b7f9d4 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6712,6 +6712,29 @@ static void mem_cgroup_move_task(void) } #endif +#ifdef CONFIG_LRU_GEN +static void mem_cgroup_attach(struct cgroup_taskset *tset) +{ + struct cgroup_subsys_state *css; + struct task_struct *task = NULL; + + cgroup_taskset_for_each_leader(task, css, tset) + break; + + if (!task) + return; + + task_lock(task); + if (task->mm && task->mm->owner == task) + lru_gen_migrate_mm(task->mm); + task_unlock(task); +} +#else +static void mem_cgroup_attach(struct cgroup_taskset *tset) +{ +} +#endif /* CONFIG_LRU_GEN */ + /* * Cgroup retains root cgroups across [un]mount cycles making it necessary * to verify whether we're attached to the default hierarchy on each mount @@ -6967,6 +6990,7 @@ struct cgroup_subsys memory_cgrp_subsys = { .css_reset = mem_cgroup_css_reset, .css_rstat_flush = mem_cgroup_css_rstat_flush, .can_attach = mem_cgroup_can_attach, + .attach = mem_cgroup_attach, .cancel_attach = mem_cgroup_cancel_attach, .post_attach = mem_cgroup_move_task, .bind = mem_cgroup_bind, diff --git a/mm/vmscan.c b/mm/vmscan.c index 4602848a62cb..06338527a807 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -52,6 +52,8 @@ #include #include #include +#include +#include #include #include @@ -2837,6 +2839,374 @@ static bool __maybe_unused seq_is_valid(struct lruvec *lruvec) get_nr_gens(lruvec, LRU_GEN_ANON) <= MAX_NR_GENS; } +/****************************************************************************** + * mm_struct list + ******************************************************************************/ + +static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg) +{ + static struct lru_gen_mm_list mm_list = { + .fifo = LIST_HEAD_INIT(mm_list.fifo), + .lock = __SPIN_LOCK_UNLOCKED(mm_list.lock), + }; + +#ifdef CONFIG_MEMCG + if (memcg) + return &memcg->mm_list; +#endif + VM_BUG_ON(!mem_cgroup_disabled()); + + return &mm_list; +} + +void lru_gen_add_mm(struct mm_struct *mm) +{ + int nid; + struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm); + struct lru_gen_mm_list *mm_list = get_mm_list(memcg); + + VM_BUG_ON_MM(!list_empty(&mm->lru_gen.list), mm); +#ifdef CONFIG_MEMCG + VM_BUG_ON_MM(mm->lru_gen.memcg, mm); + mm->lru_gen.memcg = memcg; +#endif + spin_lock(&mm_list->lock); + + for_each_node_state(nid, N_MEMORY) { + struct lruvec *lruvec = get_lruvec(memcg, nid); + + if (!lruvec) + continue; + + if (lruvec->mm_state.tail == &mm_list->fifo) + lruvec->mm_state.tail = &mm->lru_gen.list; + } + + list_add_tail(&mm->lru_gen.list, &mm_list->fifo); + + spin_unlock(&mm_list->lock); +} + +void lru_gen_del_mm(struct mm_struct *mm) +{ + int nid; + struct lru_gen_mm_list *mm_list; + struct mem_cgroup *memcg = NULL; + + if (list_empty(&mm->lru_gen.list)) + return; + +#ifdef CONFIG_MEMCG + memcg = mm->lru_gen.memcg; +#endif + mm_list = get_mm_list(memcg); + + spin_lock(&mm_list->lock); + + for_each_node(nid) { + struct lruvec *lruvec = get_lruvec(memcg, nid); + + if (!lruvec) + continue; + + if (lruvec->mm_state.tail == &mm->lru_gen.list) + lruvec->mm_state.tail = lruvec->mm_state.tail->next; + + if (lruvec->mm_state.head != &mm->lru_gen.list) + continue; + + lruvec->mm_state.head = lruvec->mm_state.head->next; + if (lruvec->mm_state.head == &mm_list->fifo) + WRITE_ONCE(lruvec->mm_state.seq, lruvec->mm_state.seq + 1); + } + + list_del_init(&mm->lru_gen.list); + + spin_unlock(&mm_list->lock); + +#ifdef CONFIG_MEMCG + mem_cgroup_put(mm->lru_gen.memcg); + mm->lru_gen.memcg = NULL; +#endif +} + +#ifdef CONFIG_MEMCG +void lru_gen_migrate_mm(struct mm_struct *mm) +{ + struct mem_cgroup *memcg; + + lockdep_assert_held(&mm->owner->alloc_lock); + + /* for mm_update_next_owner() */ + if (mem_cgroup_disabled()) + return; + + rcu_read_lock(); + memcg = mem_cgroup_from_task(mm->owner); + rcu_read_unlock(); + if (memcg == mm->lru_gen.memcg) + return; + + VM_BUG_ON_MM(!mm->lru_gen.memcg, mm); + VM_BUG_ON_MM(list_empty(&mm->lru_gen.list), mm); + + lru_gen_del_mm(mm); + lru_gen_add_mm(mm); +} +#endif + +/* + * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when + * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of + * bits in a bitmap, k is the number of hash functions and n is the number of + * inserted items. + * + * Page table walkers use one of the two filters to reduce their search space. + * To get rid of non-leaf entries that no longer have enough leaf entries, the + * aging uses the double-buffering technique to flip to the other filter each + * time it produces a new generation. For non-leaf entries that have enough + * leaf entries, the aging carries them over to the next generation in + * walk_pmd_range(); the eviction also report them when walking the rmap + * in lru_gen_look_around(). + * + * For future optimizations: + * 1. It's not necessary to keep both filters all the time. The spare one can be + * freed after the RCU grace period and reallocated if needed again. + * 2. And when reallocating, it's worth scaling its size according to the number + * of inserted entries in the other filter, to reduce the memory overhead on + * small systems and false positives on large systems. + * 3. Jenkins' hash function is an alternative to Knuth's. + */ +#define BLOOM_FILTER_SHIFT 15 + +static inline int filter_gen_from_seq(unsigned long seq) +{ + return seq % NR_BLOOM_FILTERS; +} + +static void get_item_key(void *item, int *key) +{ + u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2); + + BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32)); + + key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1); + key[1] = hash >> BLOOM_FILTER_SHIFT; +} + +static void reset_bloom_filter(struct lruvec *lruvec, unsigned long seq) +{ + unsigned long *filter; + int gen = filter_gen_from_seq(seq); + + lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock); + + filter = lruvec->mm_state.filters[gen]; + if (filter) { + bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT)); + return; + } + + filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT), GFP_ATOMIC); + WRITE_ONCE(lruvec->mm_state.filters[gen], filter); +} + +static void update_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item) +{ + int key[2]; + unsigned long *filter; + int gen = filter_gen_from_seq(seq); + + filter = READ_ONCE(lruvec->mm_state.filters[gen]); + if (!filter) + return; + + get_item_key(item, key); + + if (!test_bit(key[0], filter)) + set_bit(key[0], filter); + if (!test_bit(key[1], filter)) + set_bit(key[1], filter); +} + +static bool test_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item) +{ + int key[2]; + unsigned long *filter; + int gen = filter_gen_from_seq(seq); + + filter = READ_ONCE(lruvec->mm_state.filters[gen]); + if (!filter) + return true; + + get_item_key(item, key); + + return test_bit(key[0], filter) && test_bit(key[1], filter); +} + +static void reset_mm_stats(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, bool last) +{ + int i; + int hist; + + lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock); + + if (walk) { + hist = lru_hist_from_seq(walk->max_seq); + + for (i = 0; i < NR_MM_STATS; i++) { + WRITE_ONCE(lruvec->mm_state.stats[hist][i], + lruvec->mm_state.stats[hist][i] + walk->mm_stats[i]); + walk->mm_stats[i] = 0; + } + } + + if (NR_HIST_GENS > 1 && last) { + hist = lru_hist_from_seq(lruvec->mm_state.seq + 1); + + for (i = 0; i < NR_MM_STATS; i++) + WRITE_ONCE(lruvec->mm_state.stats[hist][i], 0); + } +} + +static bool should_skip_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk) +{ + int type; + unsigned long size = 0; + struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); + + if (!walk->full_scan && cpumask_empty(mm_cpumask(mm)) && + !node_isset(pgdat->node_id, mm->lru_gen.nodes)) + return true; + + node_clear(pgdat->node_id, mm->lru_gen.nodes); + + for (type = !walk->can_swap; type < ANON_AND_FILE; type++) { + size += type ? get_mm_counter(mm, MM_FILEPAGES) : + get_mm_counter(mm, MM_ANONPAGES) + + get_mm_counter(mm, MM_SHMEMPAGES); + } + + if (size < MIN_LRU_BATCH) + return true; + + if (mm_is_oom_victim(mm)) + return true; + + return !mmget_not_zero(mm); +} + +static bool iterate_mm_list(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, + struct mm_struct **iter) +{ + bool first = false; + bool last = true; + struct mm_struct *mm = NULL; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + struct lru_gen_mm_list *mm_list = get_mm_list(memcg); + struct lru_gen_mm_state *mm_state = &lruvec->mm_state; + + /* + * There are four interesting cases for this page table walker: + * 1. It tries to start a new iteration of mm_list with a stale max_seq; + * there is nothing to be done. + * 2. It's the first of the current generation, and it needs to reset + * the Bloom filter for the next generation. + * 3. It reaches the end of mm_list, and it needs to increment + * mm_state->seq; the iteration is done. + * 4. It's the last of the current generation, and it needs to reset the + * mm stats counters for the next generation. + */ + if (*iter) + mmput_async(*iter); + else if (walk->max_seq <= READ_ONCE(mm_state->seq)) + return false; + + spin_lock(&mm_list->lock); + + VM_BUG_ON(mm_state->seq + 1 < walk->max_seq); + VM_BUG_ON(*iter && mm_state->seq > walk->max_seq); + VM_BUG_ON(*iter && !mm_state->nr_walkers); + + if (walk->max_seq <= mm_state->seq) { + if (!*iter) + last = false; + goto done; + } + + if (!mm_state->nr_walkers) { + VM_BUG_ON(mm_state->head && mm_state->head != &mm_list->fifo); + + mm_state->head = mm_list->fifo.next; + first = true; + } + + while (!mm && mm_state->head != &mm_list->fifo) { + mm = list_entry(mm_state->head, struct mm_struct, lru_gen.list); + + mm_state->head = mm_state->head->next; + + /* full scan for those added after the last iteration */ + if (!mm_state->tail || mm_state->tail == &mm->lru_gen.list) { + mm_state->tail = mm_state->head; + walk->full_scan = true; + } + + if (should_skip_mm(mm, walk)) + mm = NULL; + } + + if (mm_state->head == &mm_list->fifo) + WRITE_ONCE(mm_state->seq, mm_state->seq + 1); +done: + if (*iter && !mm) + mm_state->nr_walkers--; + if (!*iter && mm) + mm_state->nr_walkers++; + + if (mm_state->nr_walkers) + last = false; + + if (mm && first) + reset_bloom_filter(lruvec, walk->max_seq + 1); + + if (*iter || last) + reset_mm_stats(lruvec, walk, last); + + spin_unlock(&mm_list->lock); + + *iter = mm; + + return last; +} + +static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long max_seq) +{ + bool success = false; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + struct lru_gen_mm_list *mm_list = get_mm_list(memcg); + struct lru_gen_mm_state *mm_state = &lruvec->mm_state; + + if (max_seq <= READ_ONCE(mm_state->seq)) + return false; + + spin_lock(&mm_list->lock); + + VM_BUG_ON(mm_state->seq + 1 < max_seq); + + if (max_seq > mm_state->seq && !mm_state->nr_walkers) { + VM_BUG_ON(mm_state->head && mm_state->head != &mm_list->fifo); + + WRITE_ONCE(mm_state->seq, mm_state->seq + 1); + reset_mm_stats(lruvec, NULL, true); + success = true; + } + + spin_unlock(&mm_list->lock); + + return success; +} + /****************************************************************************** * refault feedback loop ******************************************************************************/ @@ -2990,6 +3360,476 @@ static int page_inc_gen(struct lruvec *lruvec, struct page *page, bool reclaimin return new_gen; } +static void update_batch_size(struct lru_gen_mm_walk *walk, struct page *page, + int old_gen, int new_gen) +{ + int type = page_is_file_lru(page); + int zone = page_zonenum(page); + int delta = thp_nr_pages(page); + + VM_BUG_ON(old_gen >= MAX_NR_GENS); + VM_BUG_ON(new_gen >= MAX_NR_GENS); + + walk->batched++; + + walk->nr_pages[old_gen][type][zone] -= delta; + walk->nr_pages[new_gen][type][zone] += delta; +} + +static void reset_batch_size(struct lruvec *lruvec, struct lru_gen_mm_walk *walk) +{ + int gen, type, zone; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + walk->batched = 0; + + for_each_gen_type_zone(gen, type, zone) { + enum lru_list lru = type * LRU_INACTIVE_FILE; + int delta = walk->nr_pages[gen][type][zone]; + + if (!delta) + continue; + + walk->nr_pages[gen][type][zone] = 0; + WRITE_ONCE(lrugen->nr_pages[gen][type][zone], + lrugen->nr_pages[gen][type][zone] + delta); + + if (lru_gen_is_active(lruvec, gen)) + lru += LRU_ACTIVE; + __update_lru_size(lruvec, lru, zone, delta); + } +} + +static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk *walk) +{ + struct address_space *mapping; + struct vm_area_struct *vma = walk->vma; + struct lru_gen_mm_walk *priv = walk->private; + + if (!vma_is_accessible(vma) || is_vm_hugetlb_page(vma) || + (vma->vm_flags & (VM_LOCKED | VM_SPECIAL | VM_SEQ_READ | VM_RAND_READ)) || + vma == get_gate_vma(vma->vm_mm)) + return true; + + if (vma_is_anonymous(vma)) + return !priv->can_swap; + + if (WARN_ON_ONCE(!vma->vm_file || !vma->vm_file->f_mapping)) + return true; + + mapping = vma->vm_file->f_mapping; + if (mapping_unevictable(mapping)) + return true; + + /* check readpage to exclude special mappings like dax, etc. */ + return shmem_mapping(mapping) ? !priv->can_swap : !mapping->a_ops->readpage; +} + +/* + * Some userspace memory allocators map many single-page VMAs. Instead of + * returning back to the PGD table for each of such VMAs, finish an entire PMD + * table to reduce zigzags and improve cache performance. + */ +static bool get_next_vma(struct mm_walk *walk, unsigned long mask, unsigned long size, + unsigned long *start, unsigned long *end) +{ + unsigned long next = round_up(*end, size); + + VM_BUG_ON(mask & size); + VM_BUG_ON(*start >= *end); + VM_BUG_ON((next & mask) != (*start & mask)); + + while (walk->vma) { + if (next >= walk->vma->vm_end) { + walk->vma = walk->vma->vm_next; + continue; + } + + if ((next & mask) != (walk->vma->vm_start & mask)) + return false; + + if (should_skip_vma(walk->vma->vm_start, walk->vma->vm_end, walk)) { + walk->vma = walk->vma->vm_next; + continue; + } + + *start = max(next, walk->vma->vm_start); + next = (next | ~mask) + 1; + /* rounded-up boundaries can wrap to 0 */ + *end = next && next < walk->vma->vm_end ? next : walk->vma->vm_end; + + return true; + } + + return false; +} + +static bool suitable_to_scan(int total, int young) +{ + int n = clamp_t(int, cache_line_size() / sizeof(pte_t), 2, 8); + + /* suitable if the average number of young PTEs per cacheline is >=1 */ + return young * n >= total; +} + +static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, + struct mm_walk *walk) +{ + int i; + pte_t *pte; + spinlock_t *ptl; + unsigned long addr; + int total = 0; + int young = 0; + struct lru_gen_mm_walk *priv = walk->private; + struct mem_cgroup *memcg = lruvec_memcg(priv->lruvec); + struct pglist_data *pgdat = lruvec_pgdat(priv->lruvec); + int old_gen, new_gen = lru_gen_from_seq(priv->max_seq); + + VM_BUG_ON(pmd_leaf(*pmd)); + + ptl = pte_lockptr(walk->mm, pmd); + if (!spin_trylock(ptl)) + return false; + + arch_enter_lazy_mmu_mode(); + + pte = pte_offset_map(pmd, start & PMD_MASK); +restart: + for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) { + struct page *page; + unsigned long pfn = pte_pfn(pte[i]); + + VM_BUG_ON(addr < walk->vma->vm_start || addr >= walk->vma->vm_end); + + total++; + priv->mm_stats[MM_PTE_TOTAL]++; + + if (!pte_present(pte[i]) || is_zero_pfn(pfn)) + continue; + + if (WARN_ON_ONCE(pte_devmap(pte[i]) || pte_special(pte[i]))) + continue; + + if (!pte_young(pte[i])) { + priv->mm_stats[MM_PTE_OLD]++; + continue; + } + + VM_BUG_ON(!pfn_valid(pfn)); + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + continue; + + page = compound_head(pfn_to_page(pfn)); + if (page_to_nid(page) != pgdat->node_id) + continue; + + if (page_memcg_rcu(page) != memcg) + continue; + + if (!ptep_test_and_clear_young(walk->vma, addr, pte + i)) + continue; + + young++; + priv->mm_stats[MM_PTE_YOUNG]++; + + if (pte_dirty(pte[i]) && !PageDirty(page) && + !(PageAnon(page) && PageSwapBacked(page) && !PageSwapCache(page))) + set_page_dirty(page); + + old_gen = page_update_gen(page, new_gen); + if (old_gen >= 0 && old_gen != new_gen) + update_batch_size(priv, page, old_gen, new_gen); + } + + if (i < PTRS_PER_PTE && get_next_vma(walk, PMD_MASK, PAGE_SIZE, &start, &end)) + goto restart; + + pte_unmap(pte); + + arch_leave_lazy_mmu_mode(); + spin_unlock(ptl); + + return suitable_to_scan(total, young); +} + +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) +static void walk_pmd_range_locked(pud_t *pud, unsigned long next, struct vm_area_struct *vma, + struct mm_walk *walk, unsigned long *start) +{ + int i; + pmd_t *pmd; + spinlock_t *ptl; + struct lru_gen_mm_walk *priv = walk->private; + struct mem_cgroup *memcg = lruvec_memcg(priv->lruvec); + struct pglist_data *pgdat = lruvec_pgdat(priv->lruvec); + int old_gen, new_gen = lru_gen_from_seq(priv->max_seq); + + VM_BUG_ON(pud_leaf(*pud)); + + /* try to batch at most 1+MIN_LRU_BATCH+1 entries */ + if (*start == -1) { + *start = next; + return; + } + + i = next == -1 ? 0 : pmd_index(next) - pmd_index(*start); + if (i && i <= MIN_LRU_BATCH) { + __set_bit(i - 1, priv->bitmap); + return; + } + + pmd = pmd_offset(pud, *start); + + ptl = pmd_lockptr(walk->mm, pmd); + if (!spin_trylock(ptl)) + goto done; + + arch_enter_lazy_mmu_mode(); + + do { + struct page *page; + unsigned long pfn = pmd_pfn(pmd[i]); + unsigned long addr = i ? (*start & PMD_MASK) + i * PMD_SIZE : *start; + + VM_BUG_ON(addr < vma->vm_start || addr >= vma->vm_end); + + if (!pmd_present(pmd[i]) || is_huge_zero_pmd(pmd[i])) + goto next; + + if (WARN_ON_ONCE(pmd_devmap(pmd[i]))) + goto next; + + if (!pmd_trans_huge(pmd[i])) { + if (IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)) + pmdp_test_and_clear_young(vma, addr, pmd + i); + goto next; + } + + VM_BUG_ON(!pfn_valid(pfn)); + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + goto next; + + page = pfn_to_page(pfn); + VM_BUG_ON_PAGE(PageTail(page), page); + if (page_to_nid(page) != pgdat->node_id) + goto next; + + if (page_memcg_rcu(page) != memcg) + goto next; + + if (!pmdp_test_and_clear_young(vma, addr, pmd + i)) + goto next; + + priv->mm_stats[MM_PTE_YOUNG]++; + + if (pmd_dirty(pmd[i]) && !PageDirty(page) && + !(PageAnon(page) && PageSwapBacked(page) && !PageSwapCache(page))) + set_page_dirty(page); + + old_gen = page_update_gen(page, new_gen); + if (old_gen >= 0 && old_gen != new_gen) + update_batch_size(priv, page, old_gen, new_gen); +next: + i = i > MIN_LRU_BATCH ? 0 : + find_next_bit(priv->bitmap, MIN_LRU_BATCH, i) + 1; + } while (i <= MIN_LRU_BATCH); + + arch_leave_lazy_mmu_mode(); + spin_unlock(ptl); +done: + *start = -1; + bitmap_zero(priv->bitmap, MIN_LRU_BATCH); +} +#else +static void walk_pmd_range_locked(pud_t *pud, unsigned long next, struct vm_area_struct *vma, + struct mm_walk *walk, unsigned long *start) +{ +} +#endif + +static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, + struct mm_walk *walk) +{ + int i; + pmd_t *pmd; + unsigned long next; + unsigned long addr; + struct vm_area_struct *vma; + unsigned long pos = -1; + struct lru_gen_mm_walk *priv = walk->private; + + VM_BUG_ON(pud_leaf(*pud)); + + /* + * Finish an entire PMD in two passes: the first only reaches to PTE + * tables to avoid taking the PMD lock; the second, if necessary, takes + * the PMD lock to clear the accessed bit in PMD entries. + */ + pmd = pmd_offset(pud, start & PUD_MASK); +restart: + /* walk_pte_range() may call get_next_vma() */ + vma = walk->vma; + for (i = pmd_index(start), addr = start; addr != end; i++, addr = next) { + pmd_t val = pmd_read_atomic(pmd + i); + + /* for pmd_read_atomic() */ + barrier(); + + next = pmd_addr_end(addr, end); + + if (!pmd_present(val)) { + priv->mm_stats[MM_PTE_TOTAL]++; + continue; + } + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + if (pmd_trans_huge(val)) { + unsigned long pfn = pmd_pfn(val); + struct pglist_data *pgdat = lruvec_pgdat(priv->lruvec); + + priv->mm_stats[MM_PTE_TOTAL]++; + + if (is_huge_zero_pmd(val)) + continue; + + if (!pmd_young(val)) { + priv->mm_stats[MM_PTE_OLD]++; + continue; + } + + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + continue; + + walk_pmd_range_locked(pud, addr, vma, walk, &pos); + continue; + } +#endif + priv->mm_stats[MM_PMD_TOTAL]++; + +#ifdef CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG + if (!pmd_young(val)) + continue; + + walk_pmd_range_locked(pud, addr, vma, walk, &pos); +#endif + if (!priv->full_scan && !test_bloom_filter(priv->lruvec, priv->max_seq, pmd + i)) + continue; + + priv->mm_stats[MM_PMD_FOUND]++; + + if (!walk_pte_range(&val, addr, next, walk)) + continue; + + priv->mm_stats[MM_PMD_ADDED]++; + + /* carry over to the next generation */ + update_bloom_filter(priv->lruvec, priv->max_seq + 1, pmd + i); + } + + walk_pmd_range_locked(pud, -1, vma, walk, &pos); + + if (i < PTRS_PER_PMD && get_next_vma(walk, PUD_MASK, PMD_SIZE, &start, &end)) + goto restart; +} + +static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end, + struct mm_walk *walk) +{ + int i; + pud_t *pud; + unsigned long addr; + unsigned long next; + struct lru_gen_mm_walk *priv = walk->private; + + VM_BUG_ON(p4d_leaf(*p4d)); + + pud = pud_offset(p4d, start & P4D_MASK); +restart: + for (i = pud_index(start), addr = start; addr != end; i++, addr = next) { + pud_t val = READ_ONCE(pud[i]); + + next = pud_addr_end(addr, end); + + if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val))) + continue; + + walk_pmd_range(&val, addr, next, walk); + + if (priv->batched >= MAX_LRU_BATCH) { + end = (addr | ~PUD_MASK) + 1; + goto done; + } + } + + if (i < PTRS_PER_PUD && get_next_vma(walk, P4D_MASK, PUD_SIZE, &start, &end)) + goto restart; + + end = round_up(end, P4D_SIZE); +done: + /* rounded-up boundaries can wrap to 0 */ + priv->next_addr = end && walk->vma ? max(end, walk->vma->vm_start) : 0; + + return -EAGAIN; +} + +static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_mm_walk *walk) +{ + static const struct mm_walk_ops mm_walk_ops = { + .test_walk = should_skip_vma, + .p4d_entry = walk_pud_range, + }; + + int err; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + struct pglist_data *pgdat = lruvec_pgdat(lruvec); + + walk->next_addr = FIRST_USER_ADDRESS; + + do { + err = -EBUSY; + + /* page_update_gen() requires stable page_memcg() */ + if (!mem_cgroup_trylock_pages(memcg)) + break; + + /* the caller might be holding the lock for write */ + if (mmap_read_trylock(mm)) { + unsigned long start = walk->next_addr; + unsigned long end = mm->highest_vm_end; + + err = walk_page_range(mm, start, end, &mm_walk_ops, walk); + + mmap_read_unlock(mm); + + if (walk->batched) { + spin_lock_irq(&lruvec->lru_lock); + reset_batch_size(lruvec, walk); + spin_unlock_irq(&lruvec->lru_lock); + } + } + + mem_cgroup_unlock_pages(); + + cond_resched(); + } while (err == -EAGAIN && walk->next_addr && !mm_is_oom_victim(mm)); +} + +static struct lru_gen_mm_walk *alloc_mm_walk(void) +{ + if (current->reclaim_state && current->reclaim_state->mm_walk) + return current->reclaim_state->mm_walk; + + return kzalloc(sizeof(struct lru_gen_mm_walk), + __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN); +} + +static void free_mm_walk(struct lru_gen_mm_walk *walk) +{ + if (!current->reclaim_state || !current->reclaim_state->mm_walk) + kfree(walk); +} + static void inc_min_seq(struct lruvec *lruvec) { int type; @@ -3048,20 +3888,16 @@ static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap) return success; } -static void inc_max_seq(struct lruvec *lruvec, unsigned long max_seq) +static void inc_max_seq(struct lruvec *lruvec) { int prev, next; int type, zone; struct lru_gen_struct *lrugen = &lruvec->lrugen; - struct pglist_data *pgdat = lruvec_pgdat(lruvec); spin_lock_irq(&lruvec->lru_lock); VM_BUG_ON(!seq_is_valid(lruvec)); - if (max_seq != lrugen->max_seq) - goto unlock; - inc_min_seq(lruvec); /* @@ -3095,10 +3931,72 @@ static void inc_max_seq(struct lruvec *lruvec, unsigned long max_seq) /* make sure preceding modifications appear */ smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1); -unlock: + spin_unlock_irq(&lruvec->lru_lock); } +static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq, + struct scan_control *sc, bool can_swap, bool full_scan) +{ + bool success; + struct lru_gen_mm_walk *walk; + struct mm_struct *mm = NULL; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + VM_BUG_ON(max_seq > READ_ONCE(lrugen->max_seq)); + + /* + * If the hardware doesn't automatically set the accessed bit, fallback + * to lru_gen_look_around(), which only clears the accessed bit in a + * handful of PTEs. Spreading the work out over a period of time usually + * is less efficient, but it avoids bursty page faults. + */ + if (!full_scan && !arch_has_hw_pte_young()) { + success = iterate_mm_list_nowalk(lruvec, max_seq); + goto done; + } + + walk = alloc_mm_walk(); + if (!walk) { + success = iterate_mm_list_nowalk(lruvec, max_seq); + goto done; + } + + walk->lruvec = lruvec; + walk->max_seq = max_seq; + walk->can_swap = can_swap; + walk->full_scan = full_scan; + + do { + success = iterate_mm_list(lruvec, walk, &mm); + if (mm) + walk_mm(lruvec, mm, walk); + + cond_resched(); + } while (mm); + + free_mm_walk(walk); +done: + if (!success) { + if (!current_is_kswapd() && !sc->priority) + wait_event_killable(lruvec->mm_state.wait, + max_seq < READ_ONCE(lrugen->max_seq)); + + return max_seq < READ_ONCE(lrugen->max_seq); + } + + VM_BUG_ON(max_seq != READ_ONCE(lrugen->max_seq)); + + inc_max_seq(lruvec); + /* either this sees any waiters or they will see updated max_seq */ + if (wq_has_sleeper(&lruvec->mm_state.wait)) + wake_up_all(&lruvec->mm_state.wait); + + wakeup_flusher_threads(WB_REASON_VMSCAN); + + return true; +} + static long get_nr_evictable(struct lruvec *lruvec, unsigned long max_seq, unsigned long *min_seq, bool can_swap, bool *need_aging) { @@ -3180,7 +4078,7 @@ static void age_lruvec(struct lruvec *lruvec, struct scan_control *sc) nr_to_scan++; if (nr_to_scan && need_aging && (!mem_cgroup_below_low(memcg) || sc->memcg_low_reclaim)) - inc_max_seq(lruvec, max_seq); + try_to_inc_max_seq(lruvec, max_seq, sc, swappiness, false); } static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) @@ -3189,6 +4087,8 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) VM_BUG_ON(!current_is_kswapd()); + current->reclaim_state->mm_walk = &pgdat->mm_walk; + memcg = mem_cgroup_iter(NULL, NULL, NULL); do { struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); @@ -3197,11 +4097,16 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) cond_resched(); } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); + + current->reclaim_state->mm_walk = NULL; } /* * This function exploits spatial locality when shrink_page_list() walks the * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. + * If the scan was done cacheline efficiently, it adds the PMD entry pointing + * to the PTE table to the Bloom filter. This process is a feedback loop from + * the eviction to the aging. */ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) { @@ -3211,6 +4116,8 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) unsigned long end; unsigned long addr; struct page *page; + struct lru_gen_mm_walk *walk; + int young = 0; unsigned long bitmap[BITS_TO_LONGS(MIN_LRU_BATCH)] = {}; struct mem_cgroup *memcg = page_memcg(pvmw->page); struct pglist_data *pgdat = page_pgdat(pvmw->page); @@ -3271,6 +4178,8 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) if (!ptep_test_and_clear_young(pvmw->vma, addr, pte + i)) continue; + young++; + if (pte_dirty(pte[i]) && !PageDirty(page) && !(PageAnon(page) && PageSwapBacked(page) && !PageSwapCache(page))) set_page_dirty(page); @@ -3285,7 +4194,13 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) arch_leave_lazy_mmu_mode(); rcu_read_unlock(); - if (bitmap_weight(bitmap, MIN_LRU_BATCH) < PAGEVEC_SIZE) { + /* feedback from rmap walkers to page table walkers */ + if (suitable_to_scan(i, young)) + update_bloom_filter(lruvec, max_seq, pvmw->pmd); + + walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL; + + if (!walk && bitmap_weight(bitmap, MIN_LRU_BATCH) < PAGEVEC_SIZE) { for_each_set_bit(i, bitmap, MIN_LRU_BATCH) activate_page(pte_page(pte[i])); return; @@ -3295,8 +4210,10 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) if (!mem_cgroup_trylock_pages(memcg)) return; - spin_lock_irq(&lruvec->lru_lock); - new_gen = lru_gen_from_seq(lruvec->lrugen.max_seq); + if (!walk) { + spin_lock_irq(&lruvec->lru_lock); + new_gen = lru_gen_from_seq(lruvec->lrugen.max_seq); + } for_each_set_bit(i, bitmap, MIN_LRU_BATCH) { page = compound_head(pte_page(pte[i])); @@ -3307,10 +4224,14 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) if (old_gen < 0 || old_gen == new_gen) continue; - lru_gen_update_size(lruvec, page, old_gen, new_gen); + if (walk) + update_batch_size(walk, page, old_gen, new_gen); + else + lru_gen_update_size(lruvec, page, old_gen, new_gen); } - spin_unlock_irq(&lruvec->lru_lock); + if (!walk) + spin_unlock_irq(&lruvec->lru_lock); mem_cgroup_unlock_pages(); } @@ -3576,6 +4497,7 @@ static int evict_pages(struct lruvec *lruvec, struct scan_control *sc, int swapp struct page *page; enum vm_event_item item; struct reclaim_stat stat; + struct lru_gen_mm_walk *walk; struct mem_cgroup *memcg = lruvec_memcg(lruvec); struct pglist_data *pgdat = lruvec_pgdat(lruvec); @@ -3614,6 +4536,10 @@ static int evict_pages(struct lruvec *lruvec, struct scan_control *sc, int swapp move_pages_to_lru(lruvec, &list); + walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL; + if (walk && walk->batched) + reset_batch_size(lruvec, walk); + item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT; if (!cgroup_reclaim(sc)) __count_vm_events(item, reclaimed); @@ -3668,20 +4594,25 @@ static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool return 0; } - inc_max_seq(lruvec, max_seq); + if (try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false)) + return nr_to_scan; - return nr_to_scan; + return min_seq[LRU_GEN_FILE] + MIN_NR_GENS <= max_seq ? nr_to_scan : 0; } static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) { struct blk_plug plug; long scanned = 0; + struct pglist_data *pgdat = lruvec_pgdat(lruvec); lru_add_drain(); blk_start_plug(&plug); + if (current_is_kswapd()) + current->reclaim_state->mm_walk = &pgdat->mm_walk; + while (true) { int delta; int swappiness; @@ -3709,6 +4640,9 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc cond_resched(); } + if (current_is_kswapd()) + current->reclaim_state->mm_walk = NULL; + blk_finish_plug(&plug); } @@ -3725,15 +4659,21 @@ void lru_gen_init_lruvec(struct lruvec *lruvec) for_each_gen_type_zone(gen, type, zone) INIT_LIST_HEAD(&lrugen->lists[gen][type][zone]); + + lruvec->mm_state.seq = MIN_NR_GENS; + init_waitqueue_head(&lruvec->mm_state.wait); } #ifdef CONFIG_MEMCG void lru_gen_init_memcg(struct mem_cgroup *memcg) { + INIT_LIST_HEAD(&memcg->mm_list.fifo); + spin_lock_init(&memcg->mm_list.lock); } void lru_gen_exit_memcg(struct mem_cgroup *memcg) { + int i; int nid; for_each_node(nid) { @@ -3741,6 +4681,11 @@ void lru_gen_exit_memcg(struct mem_cgroup *memcg) VM_BUG_ON(memchr_inv(lruvec->lrugen.nr_pages, 0, sizeof(lruvec->lrugen.nr_pages))); + + for (i = 0; i < NR_BLOOM_FILTERS; i++) { + bitmap_free(lruvec->mm_state.filters[i]); + lruvec->mm_state.filters[i] = NULL; + } } } #endif @@ -3749,6 +4694,7 @@ static int __init init_lru_gen(void) { BUILD_BUG_ON(MIN_NR_GENS + 1 >= MAX_NR_GENS); BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS); + BUILD_BUG_ON(sizeof(MM_STAT_CODES) != NR_MM_STATS + 1); return 0; }; -- Gitee From 097e7c1567dcd307c52607ebf7b968abfb5a8614 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Thu, 27 Jan 2022 19:59:54 -0700 Subject: [PATCH 08/13] FROMLIST: mm: multi-gen LRU: optimize multiple memcgs MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When multiple memcgs are available, it is possible to make better choices based on generations and tiers and therefore improve the overall performance under global memory pressure. This patch adds a rudimentary optimization to select memcgs that can drop single-use unmapped clean pages first. Doing so reduces the chance of going into the aging path or swapping. These two operations can be costly. A typical example that benefits from this optimization is a server running mixed types of workloads, e.g., heavy anon workload in one memcg and heavy buffered I/O workload in the other. Though this optimization can be applied to both kswapd and direct reclaim, it is only added to kswapd to keep the patchset manageable. Later improvements will cover the direct reclaim path. Server benchmark results: Mixed workloads: fio (buffered I/O): -[23, 25]% IOPS BW patch1-8: 2960k 11.3GiB/s patch1-9: 2248k 8783MiB/s memcached (anon): +[210, 214]% Ops/sec KB/sec patch1-8: 606940.09 23576.89 patch1-9: 1895197.49 73619.93 Mixed workloads: fio (buffered I/O): -[4, 6]% IOPS BW 5.18-ed4643521e6a: 2369k 9255MiB/s patch1-9: 2248k 8783MiB/s memcached (anon): +[510, 516]% Ops/sec KB/sec 5.18-ed4643521e6a: 309189.58 12010.61 patch1-9: 1895197.49 73619.93 Configurations: (changes since patch 6) cat mixed.sh modprobe brd rd_nr=2 rd_size=56623104 swapoff -a mkswap /dev/ram0 swapon /dev/ram0 mkfs.ext4 /dev/ram1 mount -t ext4 /dev/ram1 /mnt memtier_benchmark -S /var/run/memcached/memcached.sock \ -P memcache_binary -n allkeys --key-minimum=1 \ --key-maximum=50000000 --key-pattern=P:P -c 1 -t 36 \ --ratio 1:0 --pipeline 8 -d 2000 fio -name=mglru --numjobs=36 --directory=/mnt --size=1408m \ --buffered=1 --ioengine=io_uring --iodepth=128 \ --iodepth_batch_submit=32 --iodepth_batch_complete=32 \ --rw=randread --random_distribution=random --norandommap \ --time_based --ramp_time=10m --runtime=90m --group_reporting & pid=$! sleep 200 memtier_benchmark -S /var/run/memcached/memcached.sock \ -P memcache_binary -n allkeys --key-minimum=1 \ --key-maximum=50000000 --key-pattern=R:R -c 1 -t 36 \ --ratio 0:1 --pipeline 8 --randomize --distinct-client-seed kill -INT $pid wait Client benchmark results: no change (CONFIG_MEMCG=n) Link: https://lore.kernel.org/r/20220309021230.721028-10-yuzhao@google.com/ Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I0641467dbd7c5ba0645602cec7fe8d6fdb750edb --- mm/vmscan.c | 46 +++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 41 insertions(+), 5 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 06338527a807..25fc34537c38 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -130,6 +130,13 @@ struct scan_control { /* The file pages on the current node are dangerously low */ unsigned int file_is_tiny:1; +#ifdef CONFIG_LRU_GEN + /* help make better choices when multiple memcgs are available */ + unsigned int memcgs_need_aging:1; + unsigned int memcgs_need_swapping:1; + unsigned int memcgs_avoid_swapping:1; +#endif + /* can't shrink slab pages */ unsigned int no_shrink_slab:1; @@ -3782,7 +3789,6 @@ static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_ int err; struct mem_cgroup *memcg = lruvec_memcg(lruvec); - struct pglist_data *pgdat = lruvec_pgdat(lruvec); walk->next_addr = FIRST_USER_ADDRESS; @@ -4087,6 +4093,22 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) VM_BUG_ON(!current_is_kswapd()); + /* + * To reduce the chance of going into the aging path or swapping, which + * can be costly, optimistically skip them unless their corresponding + * flags were cleared in the eviction path. This improves the overall + * performance when multiple memcgs are available. + */ + if (!sc->memcgs_need_aging) { + sc->memcgs_need_aging = true; + sc->memcgs_avoid_swapping = !sc->memcgs_need_swapping; + sc->memcgs_need_swapping = true; + return; + } + + sc->memcgs_need_swapping = true; + sc->memcgs_avoid_swapping = true; + current->reclaim_state->mm_walk = &pgdat->mm_walk; memcg = mem_cgroup_iter(NULL, NULL, NULL); @@ -4488,7 +4510,8 @@ static int isolate_pages(struct lruvec *lruvec, struct scan_control *sc, int swa return scanned; } -static int evict_pages(struct lruvec *lruvec, struct scan_control *sc, int swappiness) +static int evict_pages(struct lruvec *lruvec, struct scan_control *sc, int swappiness, + bool *swapped) { int type; int scanned; @@ -4553,6 +4576,9 @@ static int evict_pages(struct lruvec *lruvec, struct scan_control *sc, int swapp sc->nr_reclaimed += reclaimed; + if (type == LRU_GEN_ANON && swapped) + *swapped = true; + return scanned; } @@ -4581,8 +4607,10 @@ static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool if (!nr_to_scan) return 0; - if (!need_aging) + if (!need_aging) { + sc->memcgs_need_aging = false; return nr_to_scan; + } /* leave the work to lru_gen_age_node() */ if (current_is_kswapd()) @@ -4604,6 +4632,8 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc { struct blk_plug plug; long scanned = 0; + bool swapped = false; + unsigned long reclaimed = sc->nr_reclaimed; struct pglist_data *pgdat = lruvec_pgdat(lruvec); lru_add_drain(); @@ -4629,13 +4659,19 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc if (!nr_to_scan) break; - delta = evict_pages(lruvec, sc, swappiness); + delta = evict_pages(lruvec, sc, swappiness, &swapped); if (!delta) break; + if (sc->memcgs_avoid_swapping && swappiness < 200 && swapped) + break; + scanned += delta; - if (scanned >= nr_to_scan) + if (scanned >= nr_to_scan) { + if (!swapped && sc->nr_reclaimed - reclaimed >= MIN_LRU_BATCH) + sc->memcgs_need_swapping = false; break; + } cond_resched(); } -- Gitee From b51e6879d5bfd5094b651349df6ce572ef3c7325 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Thu, 27 Jan 2022 19:52:09 -0700 Subject: [PATCH 09/13] FROMLIST: mm: multi-gen LRU: kill switch MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add /sys/kernel/mm/lru_gen/enabled as a kill switch. Components that can be disabled include: 0x0001: the multi-gen LRU core 0x0002: walking page table, when arch_has_hw_pte_young() returns true 0x0004: clearing the accessed bit in non-leaf PMD entries, when CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG=y [yYnN]: apply to all the components above E.g., echo y >/sys/kernel/mm/lru_gen/enabled cat /sys/kernel/mm/lru_gen/enabled 0x0007 echo 5 >/sys/kernel/mm/lru_gen/enabled cat /sys/kernel/mm/lru_gen/enabled 0x0005 NB: the page table walks happen on the scale of seconds under heavy memory pressure, in which case the mmap_lock contention is a lesser concern, compared with the LRU lock contention and the I/O congestion. So far the only well-known case of the mmap_lock contention happens on Android, due to Scudo [1] which allocates several thousand VMAs for merely a few hundred MBs. The SPF and the Maple Tree also have provided their own assessments [2][3]. However, if walking page tables does worsen the mmap_lock contention, the kill switch can be used to disable it. In this case the multi-gen LRU will suffer a minor performance degradation, as shown previously. Clearing the accessed bit in non-leaf PMD entries can also be disabled, since this behavior was not tested on x86 varieties other than Intel and AMD. [1] https://source.android.com/devices/tech/debug/scudo [2] https://lore.kernel.org/lkml/20220128131006.67712-1-michel@lespinasse.org/ [3] https://lore.kernel.org/lkml/20220202024137.2516438-1-Liam.Howlett@oracle.com/ Link: https://lore.kernel.org/r/20220309021230.721028-11-yuzhao@google.com/ Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I71801d9470a2588cad8bfd14fbcfafc7b010aa03 --- include/linux/cgroup.h | 15 +- include/linux/mm_inline.h | 12 +- include/linux/mmzone.h | 9 ++ kernel/cgroup/cgroup-internal.h | 1 - mm/Kconfig | 6 + mm/vmscan.c | 250 +++++++++++++++++++++++++++++++- 6 files changed, 284 insertions(+), 9 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 9226ec130ba3..4bbffe6c4621 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -432,6 +432,18 @@ static inline void cgroup_put(struct cgroup *cgrp) css_put(&cgrp->self); } +extern struct mutex cgroup_mutex; + +static inline void cgroup_lock(void) +{ + mutex_lock(&cgroup_mutex); +} + +static inline void cgroup_unlock(void) +{ + mutex_unlock(&cgroup_mutex); +} + /** * task_css_set_check - obtain a task's css_set with extra access conditions * @task: the task to obtain css_set for @@ -446,7 +458,6 @@ static inline void cgroup_put(struct cgroup *cgrp) * as locks used during the cgroup_subsys::attach() methods. */ #ifdef CONFIG_PROVE_RCU -extern struct mutex cgroup_mutex; extern spinlock_t css_set_lock; #define task_css_set_check(task, __c) \ rcu_dereference_check((task)->cgroups, \ @@ -704,6 +715,8 @@ struct cgroup; static inline u64 cgroup_id(struct cgroup *cgrp) { return 1; } static inline void css_get(struct cgroup_subsys_state *css) {} static inline void css_put(struct cgroup_subsys_state *css) {} +static inline void cgroup_lock(void) {} +static inline void cgroup_unlock(void) {} static inline int cgroup_attach_task_all(struct task_struct *from, struct task_struct *t) { return 0; } static inline int cgroupstats_build(struct cgroupstats *stats, diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index 9a357cf0726c..e1abaa5a9d63 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -111,7 +111,15 @@ static __always_inline enum lru_list page_lru(struct page *page) static inline bool lru_gen_enabled(void) { - return true; +#ifdef CONFIG_LRU_GEN_ENABLED + DECLARE_STATIC_KEY_TRUE(lru_gen_caps[NR_LRU_GEN_CAPS]); + + return static_branch_likely(&lru_gen_caps[LRU_GEN_CORE]); +#else + DECLARE_STATIC_KEY_FALSE(lru_gen_caps[NR_LRU_GEN_CAPS]); + + return static_branch_unlikely(&lru_gen_caps[LRU_GEN_CORE]); +#endif } static inline bool lru_gen_in_fault(void) @@ -201,7 +209,7 @@ static inline bool lru_gen_add_page(struct lruvec *lruvec, struct page *page, bo int zone = page_zonenum(page); struct lru_gen_struct *lrugen = &lruvec->lrugen; - if (PageUnevictable(page)) + if (PageUnevictable(page) || !lrugen->enabled) return false; /* * There are three common cases for this page: diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index d4f8a08d3358..a74e18411676 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -341,6 +341,13 @@ enum { LRU_GEN_FILE, }; +enum { + LRU_GEN_CORE, + LRU_GEN_MM_WALK, + LRU_GEN_NONLEAF_YOUNG, + NR_LRU_GEN_CAPS +}; + #define MIN_LRU_BATCH BITS_PER_LONG #define MAX_LRU_BATCH (MIN_LRU_BATCH * 128) @@ -379,6 +386,8 @@ struct lru_gen_struct { /* can be modified without holding the LRU lock */ atomic_long_t evicted[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS]; atomic_long_t refaulted[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS]; + /* whether the multi-gen LRU is enabled */ + bool enabled; }; enum { diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h index 3f116765bb00..7b0842630257 100644 --- a/kernel/cgroup/cgroup-internal.h +++ b/kernel/cgroup/cgroup-internal.h @@ -165,7 +165,6 @@ struct cgroup_mgctx { #define DEFINE_CGROUP_MGCTX(name) \ struct cgroup_mgctx name = CGROUP_MGCTX_INIT(name) -extern struct mutex cgroup_mutex; extern spinlock_t css_set_lock; extern struct cgroup_subsys *cgroup_subsys[]; extern struct list_head cgroup_roots; diff --git a/mm/Kconfig b/mm/Kconfig index 77befc7051d1..967145c9594f 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -980,6 +980,12 @@ config LRU_GEN help A high performance LRU implementation to overcommit memory. +config LRU_GEN_ENABLED + bool "Enable by default" + depends on LRU_GEN + help + This option enables the multi-gen LRU by default. + config LRU_GEN_STATS bool "Full stats for debugging" depends on LRU_GEN diff --git a/mm/vmscan.c b/mm/vmscan.c index 25fc34537c38..adff118105a1 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -54,6 +54,7 @@ #include #include #include +#include #include #include @@ -2767,6 +2768,12 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, #ifdef CONFIG_LRU_GEN +#ifdef CONFIG_LRU_GEN_ENABLED +DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS); +#else +DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS); +#endif + /****************************************************************************** * shorthand helpers ******************************************************************************/ @@ -2803,6 +2810,15 @@ static int page_lru_tier(struct page *page) return lru_tier_from_refs(refs); } +static bool get_cap(int cap) +{ +#ifdef CONFIG_LRU_GEN_ENABLED + return static_branch_likely(&lru_gen_caps[cap]); +#else + return static_branch_unlikely(&lru_gen_caps[cap]); +#endif +} + static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid) { struct pglist_data *pgdat = NODE_DATA(nid); @@ -3608,7 +3624,8 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long next, struct vm_area goto next; if (!pmd_trans_huge(pmd[i])) { - if (IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)) + if (IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) && + get_cap(LRU_GEN_NONLEAF_YOUNG)) pmdp_test_and_clear_young(vma, addr, pmd + i); goto next; } @@ -3715,10 +3732,12 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, priv->mm_stats[MM_PMD_TOTAL]++; #ifdef CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG - if (!pmd_young(val)) - continue; + if (get_cap(LRU_GEN_NONLEAF_YOUNG)) { + if (!pmd_young(val)) + continue; - walk_pmd_range_locked(pud, addr, vma, walk, &pos); + walk_pmd_range_locked(pud, addr, vma, walk, &pos); + } #endif if (!priv->full_scan && !test_bloom_filter(priv->lruvec, priv->max_seq, pmd + i)) continue; @@ -3957,7 +3976,7 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq, * handful of PTEs. Spreading the work out over a period of time usually * is less efficient, but it avoids bursty page faults. */ - if (!full_scan && !arch_has_hw_pte_young()) { + if (!full_scan && (!arch_has_hw_pte_young() || !get_cap(LRU_GEN_MM_WALK))) { success = iterate_mm_list_nowalk(lruvec, max_seq); goto done; } @@ -4682,6 +4701,223 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc blk_finish_plug(&plug); } +/****************************************************************************** + * state change + ******************************************************************************/ + +static bool __maybe_unused state_is_valid(struct lruvec *lruvec) +{ + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + if (lrugen->enabled) { + enum lru_list lru; + + for_each_evictable_lru(lru) { + if (!list_empty(&lruvec->lists[lru])) + return false; + } + } else { + int gen, type, zone; + + for_each_gen_type_zone(gen, type, zone) { + if (!list_empty(&lrugen->lists[gen][type][zone])) + return false; + + /* unlikely but not a bug when reset_batch_size() is pending */ + VM_WARN_ON(lrugen->nr_pages[gen][type][zone]); + } + } + + return true; +} + +static bool fill_evictable(struct lruvec *lruvec) +{ + enum lru_list lru; + int remaining = MAX_LRU_BATCH; + + for_each_evictable_lru(lru) { + int type = is_file_lru(lru); + bool active = is_active_lru(lru); + struct list_head *head = &lruvec->lists[lru]; + + while (!list_empty(head)) { + bool success; + struct page *page = lru_to_page(head); + + VM_BUG_ON_PAGE(PageTail(page), page); + VM_BUG_ON_PAGE(PageUnevictable(page), page); + VM_BUG_ON_PAGE(PageActive(page) != active, page); + VM_BUG_ON_PAGE(page_is_file_lru(page) != type, page); + VM_BUG_ON_PAGE(page_lru_gen(page) < MAX_NR_GENS, page); + + prefetchw_prev_lru_page(page, head, flags); + + del_page_from_lru_list(page, lruvec, page_lru(page)); + success = lru_gen_add_page(lruvec, page, false); + VM_BUG_ON(!success); + + if (!--remaining) + return false; + } + } + + return true; +} + +static bool drain_evictable(struct lruvec *lruvec) +{ + int gen, type, zone; + int remaining = MAX_LRU_BATCH; + + for_each_gen_type_zone(gen, type, zone) { + struct list_head *head = &lruvec->lrugen.lists[gen][type][zone]; + + while (!list_empty(head)) { + bool success; + struct page *page = lru_to_page(head); + + VM_BUG_ON_PAGE(PageTail(page), page); + VM_BUG_ON_PAGE(PageUnevictable(page), page); + VM_BUG_ON_PAGE(PageActive(page), page); + VM_BUG_ON_PAGE(page_is_file_lru(page) != type, page); + VM_BUG_ON_PAGE(page_zonenum(page) != zone, page); + + prefetchw_prev_lru_page(page, head, flags); + + success = lru_gen_del_page(lruvec, page, false); + VM_BUG_ON(!success); + add_page_to_lru_list(page, lruvec, page_lru(page)); + + if (!--remaining) + return false; + } + } + + return true; +} + +static void lru_gen_change_state(bool enable) +{ + static DEFINE_MUTEX(state_mutex); + + struct mem_cgroup *memcg; + + cgroup_lock(); + cpus_read_lock(); + get_online_mems(); + mutex_lock(&state_mutex); + + if (enable == lru_gen_enabled()) + goto unlock; + + if (enable) + static_branch_enable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]); + else + static_branch_disable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]); + + memcg = mem_cgroup_iter(NULL, NULL, NULL); + do { + int nid; + + for_each_node(nid) { + struct pglist_data *pgdat = NODE_DATA(nid); + struct lruvec *lruvec = get_lruvec(memcg, nid); + + if (!lruvec) + continue; + + if (!pgdat) { + lruvec->lrugen.enabled = enable; + continue; + } + + spin_lock_irq(&lruvec->lru_lock); + + VM_BUG_ON(!seq_is_valid(lruvec)); + VM_BUG_ON(!state_is_valid(lruvec)); + + lruvec->lrugen.enabled = enable; + + while (!(enable ? fill_evictable(lruvec) : drain_evictable(lruvec))) { + spin_unlock_irq(&lruvec->lru_lock); + cond_resched(); + spin_lock_irq(&lruvec->lru_lock); + } + + spin_unlock_irq(&lruvec->lru_lock); + } + + cond_resched(); + } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); +unlock: + mutex_unlock(&state_mutex); + put_online_mems(); + cpus_read_unlock(); + cgroup_unlock(); +} + +/****************************************************************************** + * sysfs interface + ******************************************************************************/ + +static ssize_t show_enable(struct kobject *kobj, struct kobj_attribute *attr, char *buf) +{ + unsigned int caps = 0; + + if (get_cap(LRU_GEN_CORE)) + caps |= BIT(LRU_GEN_CORE); + + if (arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK)) + caps |= BIT(LRU_GEN_MM_WALK); + + if (IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) && get_cap(LRU_GEN_NONLEAF_YOUNG)) + caps |= BIT(LRU_GEN_NONLEAF_YOUNG); + + return snprintf(buf, PAGE_SIZE, "0x%04x\n", caps); +} + +static ssize_t store_enable(struct kobject *kobj, struct kobj_attribute *attr, + const char *buf, size_t len) +{ + int i; + unsigned int caps; + + if (tolower(*buf) == 'n') + caps = 0; + else if (tolower(*buf) == 'y') + caps = -1; + else if (kstrtouint(buf, 0, &caps)) + return -EINVAL; + + for (i = 0; i < NR_LRU_GEN_CAPS; i++) { + bool enable = caps & BIT(i); + + if (i == LRU_GEN_CORE) + lru_gen_change_state(enable); + else if (enable) + static_branch_enable(&lru_gen_caps[i]); + else + static_branch_disable(&lru_gen_caps[i]); + } + + return len; +} + +static struct kobj_attribute lru_gen_enabled_attr = __ATTR( + enabled, 0644, show_enable, store_enable +); + +static struct attribute *lru_gen_attrs[] = { + &lru_gen_enabled_attr.attr, + NULL +}; + +static struct attribute_group lru_gen_attr_group = { + .name = "lru_gen", + .attrs = lru_gen_attrs, +}; + /****************************************************************************** * initialization ******************************************************************************/ @@ -4692,6 +4928,7 @@ void lru_gen_init_lruvec(struct lruvec *lruvec) struct lru_gen_struct *lrugen = &lruvec->lrugen; lrugen->max_seq = MIN_NR_GENS + 1; + lrugen->enabled = lru_gen_enabled(); for_each_gen_type_zone(gen, type, zone) INIT_LIST_HEAD(&lrugen->lists[gen][type][zone]); @@ -4732,6 +4969,9 @@ static int __init init_lru_gen(void) BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS); BUILD_BUG_ON(sizeof(MM_STAT_CODES) != NR_MM_STATS + 1); + if (sysfs_create_group(mm_kobj, &lru_gen_attr_group)) + pr_err("lru_gen: failed to create sysfs group\n"); + return 0; }; late_initcall(init_lru_gen); -- Gitee From 8a2e2026425c2cddcc48214d89be908e4673e954 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Thu, 27 Jan 2022 20:08:50 -0700 Subject: [PATCH 10/13] FROMLIST: mm: multi-gen LRU: thrashing prevention MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add /sys/kernel/mm/lru_gen/min_ttl_ms for thrashing prevention, as requested by many desktop users [1]. When set to value N, it prevents the working set of N milliseconds from getting evicted. The OOM killer is triggered if this working set cannot be kept in memory. Based on the average human detectable lag (~100ms), N=1000 usually eliminates intolerable lags due to thrashing. Larger values like N=3000 make lags less noticeable at the risk of premature OOM kills. Compared with the size-based approach, e.g., [2], this time-based approach has the following advantages: 1. It is easier to configure because it is agnostic to applications and memory sizes. 2. It is more reliable because it is directly wired to the OOM killer. [1] https://lore.kernel.org/lkml/Ydza%2FzXKY9ATRoh6@google.com/ [2] https://lore.kernel.org/lkml/20211130201652.2218636d@mail.inbox.lv/ Link: https://lore.kernel.org/r/20220309021230.721028-12-yuzhao@google.com/ Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I482d33f3beaf7723d2f3eeaaa5b4f12bcb9b48a1 --- include/linux/mmzone.h | 2 ++ mm/vmscan.c | 69 +++++++++++++++++++++++++++++++++++++++--- 2 files changed, 67 insertions(+), 4 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index a74e18411676..f0259c610d6d 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -373,6 +373,8 @@ struct lru_gen_struct { unsigned long max_seq; /* the eviction increments the oldest generation numbers */ unsigned long min_seq[ANON_AND_FILE]; + /* the birth time of each generation in jiffies */ + unsigned long timestamps[MAX_NR_GENS]; /* the multi-gen LRU lists */ struct list_head lists[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES]; /* the sizes of the above lists */ diff --git a/mm/vmscan.c b/mm/vmscan.c index adff118105a1..91b4b59aa932 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3954,6 +3954,7 @@ static void inc_max_seq(struct lruvec *lruvec) for (type = 0; type < ANON_AND_FILE; type++) reset_ctrl_pos(lruvec, type, false); + WRITE_ONCE(lrugen->timestamps[next], jiffies); /* make sure preceding modifications appear */ smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1); @@ -4079,7 +4080,8 @@ static long get_nr_evictable(struct lruvec *lruvec, unsigned long max_seq, return total > 0 ? total : 0; } -static void age_lruvec(struct lruvec *lruvec, struct scan_control *sc) +static bool age_lruvec(struct lruvec *lruvec, struct scan_control *sc, + unsigned long min_ttl) { bool need_aging; long nr_to_scan; @@ -4088,14 +4090,22 @@ static void age_lruvec(struct lruvec *lruvec, struct scan_control *sc) DEFINE_MAX_SEQ(lruvec); DEFINE_MIN_SEQ(lruvec); + if (min_ttl) { + int gen = lru_gen_from_seq(min_seq[LRU_GEN_FILE]); + unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]); + + if (time_is_after_jiffies(birth + min_ttl)) + return false; + } + mem_cgroup_calculate_protection(NULL, memcg); if (mem_cgroup_below_min(memcg)) - return; + return false; nr_to_scan = get_nr_evictable(lruvec, max_seq, min_seq, swappiness, &need_aging); if (!nr_to_scan) - return; + return false; nr_to_scan >>= sc->priority; @@ -4104,11 +4114,18 @@ static void age_lruvec(struct lruvec *lruvec, struct scan_control *sc) if (nr_to_scan && need_aging && (!mem_cgroup_below_low(memcg) || sc->memcg_low_reclaim)) try_to_inc_max_seq(lruvec, max_seq, sc, swappiness, false); + + return true; } +/* to protect the working set of the last N jiffies */ +static unsigned long lru_gen_min_ttl __read_mostly; + static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) { struct mem_cgroup *memcg; + bool success = false; + unsigned long min_ttl = READ_ONCE(lru_gen_min_ttl); VM_BUG_ON(!current_is_kswapd()); @@ -4134,12 +4151,29 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) do { struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); - age_lruvec(lruvec, sc); + if (age_lruvec(lruvec, sc, min_ttl)) + success = true; cond_resched(); } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); current->reclaim_state->mm_walk = NULL; + + /* + * The main goal is to OOM kill if every generation from all memcgs is + * younger than min_ttl. However, another theoretical possibility is all + * memcgs are either below min or empty. + */ + if (!success && mutex_trylock(&oom_lock)) { + struct oom_control oc = { + .gfp_mask = sc->gfp_mask, + .order = sc->order, + }; + + out_of_memory(&oc); + + mutex_unlock(&oom_lock); + } } /* @@ -4861,6 +4895,28 @@ static void lru_gen_change_state(bool enable) * sysfs interface ******************************************************************************/ +static ssize_t show_min_ttl(struct kobject *kobj, struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%u\n", jiffies_to_msecs(READ_ONCE(lru_gen_min_ttl))); +} + +static ssize_t store_min_ttl(struct kobject *kobj, struct kobj_attribute *attr, + const char *buf, size_t len) +{ + unsigned int msecs; + + if (kstrtouint(buf, 0, &msecs)) + return -EINVAL; + + WRITE_ONCE(lru_gen_min_ttl, msecs_to_jiffies(msecs)); + + return len; +} + +static struct kobj_attribute lru_gen_min_ttl_attr = __ATTR( + min_ttl_ms, 0644, show_min_ttl, store_min_ttl +); + static ssize_t show_enable(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { unsigned int caps = 0; @@ -4909,6 +4965,7 @@ static struct kobj_attribute lru_gen_enabled_attr = __ATTR( ); static struct attribute *lru_gen_attrs[] = { + &lru_gen_min_ttl_attr.attr, &lru_gen_enabled_attr.attr, NULL }; @@ -4924,12 +4981,16 @@ static struct attribute_group lru_gen_attr_group = { void lru_gen_init_lruvec(struct lruvec *lruvec) { + int i; int gen, type, zone; struct lru_gen_struct *lrugen = &lruvec->lrugen; lrugen->max_seq = MIN_NR_GENS + 1; lrugen->enabled = lru_gen_enabled(); + for (i = 0; i <= MIN_NR_GENS + 1; i++) + lrugen->timestamps[i] = jiffies; + for_each_gen_type_zone(gen, type, zone) INIT_LIST_HEAD(&lrugen->lists[gen][type][zone]); -- Gitee From 433011f9fe612c9ccdf71a502f03ad088ad2fe33 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Thu, 27 Jan 2022 20:12:41 -0700 Subject: [PATCH 11/13] FROMLIST: mm: multi-gen LRU: debugfs interface MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add /sys/kernel/debug/lru_gen for working set estimation and proactive reclaim. These features are required to optimize job scheduling (bin packing) in data centers [1][2]. Compared with the page table-based approach and the PFN-based approach, e.g., mm/damon/[vp]addr.c, this lruvec-based approach has the following advantages: 1. It offers better choices because it is aware of memcgs, NUMA nodes, shared mappings and unmapped page cache. 2. It is more scalable because it is O(nr_hot_pages), whereas the PFN-based approach is O(nr_total_pages). Add /sys/kernel/debug/lru_gen_full for debugging. [1] https://dl.acm.org/doi/10.1145/3297858.3304053 [2] https://dl.acm.org/doi/10.1145/3503222.3507731 Link: https://lore.kernel.org/r/20220309021230.721028-13-yuzhao@google.com/ Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: Ie558098e0a24a647f77f4eacc4d72576173fc0b8 --- include/linux/nodemask.h | 1 + mm/vmscan.c | 346 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 347 insertions(+) diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h index 2636f08d685c..e3f685755ade 100644 --- a/include/linux/nodemask.h +++ b/include/linux/nodemask.h @@ -489,6 +489,7 @@ static inline int num_node_state(enum node_states state) #define first_online_node 0 #define first_memory_node 0 #define next_online_node(nid) (MAX_NUMNODES) +#define next_memory_node(nid) (MAX_NUMNODES) #define nr_node_ids 1U #define nr_online_nodes 1U diff --git a/mm/vmscan.c b/mm/vmscan.c index 91b4b59aa932..ee94108d87be 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -55,6 +55,7 @@ #include #include #include +#include #include #include @@ -4975,6 +4976,348 @@ static struct attribute_group lru_gen_attr_group = { .attrs = lru_gen_attrs, }; +/****************************************************************************** + * debugfs interface + ******************************************************************************/ + +static void *lru_gen_seq_start(struct seq_file *m, loff_t *pos) +{ + struct mem_cgroup *memcg; + loff_t nr_to_skip = *pos; + + m->private = kvmalloc(PATH_MAX, GFP_KERNEL); + if (!m->private) + return ERR_PTR(-ENOMEM); + + memcg = mem_cgroup_iter(NULL, NULL, NULL); + do { + int nid; + + for_each_node_state(nid, N_MEMORY) { + if (!nr_to_skip--) + return get_lruvec(memcg, nid); + } + } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); + + return NULL; +} + +static void lru_gen_seq_stop(struct seq_file *m, void *v) +{ + if (!IS_ERR_OR_NULL(v)) + mem_cgroup_iter_break(NULL, lruvec_memcg(v)); + + kvfree(m->private); + m->private = NULL; +} + +static void *lru_gen_seq_next(struct seq_file *m, void *v, loff_t *pos) +{ + int nid = lruvec_pgdat(v)->node_id; + struct mem_cgroup *memcg = lruvec_memcg(v); + + ++*pos; + + nid = next_memory_node(nid); + if (nid == MAX_NUMNODES) { + memcg = mem_cgroup_iter(NULL, memcg, NULL); + if (!memcg) + return NULL; + + nid = first_memory_node; + } + + return get_lruvec(memcg, nid); +} + +static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, + unsigned long max_seq, unsigned long *min_seq, + unsigned long seq) +{ + int i; + int type, tier; + int hist = lru_hist_from_seq(seq); + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + for (tier = 0; tier < MAX_NR_TIERS; tier++) { + seq_printf(m, " %10d", tier); + for (type = 0; type < ANON_AND_FILE; type++) { + unsigned long n[3] = {}; + + if (seq == max_seq) { + n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]); + n[1] = READ_ONCE(lrugen->avg_total[type][tier]); + + seq_printf(m, " %10luR %10luT %10lu ", n[0], n[1], n[2]); + } else if (seq == min_seq[type] || NR_HIST_GENS > 1) { + n[0] = atomic_long_read(&lrugen->refaulted[hist][type][tier]); + n[1] = atomic_long_read(&lrugen->evicted[hist][type][tier]); + if (tier) + n[2] = READ_ONCE(lrugen->protected[hist][type][tier - 1]); + + seq_printf(m, " %10lur %10lue %10lup", n[0], n[1], n[2]); + } else + seq_puts(m, " 0 0 0 "); + } + seq_putc(m, '\n'); + } + + seq_puts(m, " "); + for (i = 0; i < NR_MM_STATS; i++) { + if (seq == max_seq && NR_HIST_GENS == 1) + seq_printf(m, " %10lu%c", READ_ONCE(lruvec->mm_state.stats[hist][i]), + toupper(MM_STAT_CODES[i])); + else if (seq != max_seq && NR_HIST_GENS > 1) + seq_printf(m, " %10lu%c", READ_ONCE(lruvec->mm_state.stats[hist][i]), + MM_STAT_CODES[i]); + else + seq_puts(m, " 0 "); + } + seq_putc(m, '\n'); +} + +static int lru_gen_seq_show(struct seq_file *m, void *v) +{ + unsigned long seq; + bool full = !debugfs_real_fops(m->file)->write; + struct lruvec *lruvec = v; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + int nid = lruvec_pgdat(lruvec)->node_id; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + DEFINE_MAX_SEQ(lruvec); + DEFINE_MIN_SEQ(lruvec); + + if (nid == first_memory_node) { + const char *path = memcg ? m->private : ""; + +#ifdef CONFIG_MEMCG + if (memcg) + cgroup_path(memcg->css.cgroup, m->private, PATH_MAX); +#endif + seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path); + } + + seq_printf(m, " node %5d\n", nid); + + if (!full) + seq = min_seq[LRU_GEN_ANON]; + else if (max_seq >= MAX_NR_GENS) + seq = max_seq - MAX_NR_GENS + 1; + else + seq = 0; + + for (; seq <= max_seq; seq++) { + int type, zone; + int gen = lru_gen_from_seq(seq); + unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]); + + seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth)); + + for (type = 0; type < ANON_AND_FILE; type++) { + long size = 0; + char mark = full && seq < min_seq[type] ? 'x' : ' '; + + for (zone = 0; zone < MAX_NR_ZONES; zone++) + size += READ_ONCE(lrugen->nr_pages[gen][type][zone]); + + seq_printf(m, " %10lu%c", max(size, 0L), mark); + } + + seq_putc(m, '\n'); + + if (full) + lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq); + } + + return 0; +} + +static const struct seq_operations lru_gen_seq_ops = { + .start = lru_gen_seq_start, + .stop = lru_gen_seq_stop, + .next = lru_gen_seq_next, + .show = lru_gen_seq_show, +}; + +static int run_aging(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc, + bool can_swap, bool full_scan) +{ + DEFINE_MAX_SEQ(lruvec); + + if (seq == max_seq) + try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, full_scan); + + return seq > max_seq ? -EINVAL : 0; +} + +static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc, + int swappiness, unsigned long nr_to_reclaim) +{ + struct blk_plug plug; + int err = -EINTR; + DEFINE_MAX_SEQ(lruvec); + + if (seq + MIN_NR_GENS > max_seq) + return -EINVAL; + + sc->nr_reclaimed = 0; + + blk_start_plug(&plug); + + while (!signal_pending(current)) { + DEFINE_MIN_SEQ(lruvec); + + if (seq < min_seq[!swappiness] || sc->nr_reclaimed >= nr_to_reclaim || + !evict_pages(lruvec, sc, swappiness, NULL)) { + err = 0; + break; + } + + cond_resched(); + } + + blk_finish_plug(&plug); + + return err; +} + +static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq, + struct scan_control *sc, int swappiness, unsigned long opt) +{ + struct lruvec *lruvec; + int err = -EINVAL; + struct mem_cgroup *memcg = NULL; + + if (!mem_cgroup_disabled()) { + rcu_read_lock(); + memcg = mem_cgroup_from_id(memcg_id); +#ifdef CONFIG_MEMCG + if (memcg && !css_tryget(&memcg->css)) + memcg = NULL; +#endif + rcu_read_unlock(); + + if (!memcg) + goto done; + } + if (memcg_id != mem_cgroup_id(memcg)) + goto done; + + if (nid < 0 || nid >= MAX_NUMNODES || !node_state(nid, N_MEMORY)) + goto done; + + lruvec = get_lruvec(memcg, nid); + + if (swappiness < 0) + swappiness = get_swappiness(lruvec, sc); + else if (swappiness > 200) + goto done; + + switch (cmd) { + case '+': + err = run_aging(lruvec, seq, sc, swappiness, opt); + break; + case '-': + err = run_eviction(lruvec, seq, sc, swappiness, opt); + break; + } +done: + mem_cgroup_put(memcg); + + return err; +} + +static ssize_t lru_gen_seq_write(struct file *file, const char __user *src, + size_t len, loff_t *pos) +{ + void *buf; + char *cur, *next; + unsigned int flags; + int err = 0; + struct scan_control sc = { + .may_writepage = true, + .may_unmap = true, + .may_swap = true, + .reclaim_idx = MAX_NR_ZONES - 1, + .gfp_mask = GFP_KERNEL, + }; + + buf = kvmalloc(len + 1, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + if (copy_from_user(buf, src, len)) { + kvfree(buf); + return -EFAULT; + } + + next = buf; + next[len] = '\0'; + + sc.reclaim_state.mm_walk = alloc_mm_walk(); + if (!sc.reclaim_state.mm_walk) { + kvfree(buf); + return -ENOMEM; + } + + set_task_reclaim_state(current, &sc.reclaim_state); + flags = memalloc_noreclaim_save(); + + while ((cur = strsep(&next, ",;\n"))) { + int n; + int end; + char cmd; + unsigned int memcg_id; + unsigned int nid; + unsigned long seq; + unsigned int swappiness = -1; + unsigned long opt = -1; + + cur = skip_spaces(cur); + if (!*cur) + continue; + + n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid, + &seq, &end, &swappiness, &end, &opt, &end); + if (n < 4 || cur[end]) { + err = -EINVAL; + break; + } + + err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt); + if (err) + break; + } + + memalloc_noreclaim_restore(flags); + set_task_reclaim_state(current, NULL); + + free_mm_walk(sc.reclaim_state.mm_walk); + kvfree(buf); + + return err ? : len; +} + +static int lru_gen_seq_open(struct inode *inode, struct file *file) +{ + return seq_open(file, &lru_gen_seq_ops); +} + +static const struct file_operations lru_gen_rw_fops = { + .open = lru_gen_seq_open, + .read = seq_read, + .write = lru_gen_seq_write, + .llseek = seq_lseek, + .release = seq_release, +}; + +static const struct file_operations lru_gen_ro_fops = { + .open = lru_gen_seq_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, +}; + /****************************************************************************** * initialization ******************************************************************************/ @@ -5033,6 +5376,9 @@ static int __init init_lru_gen(void) if (sysfs_create_group(mm_kobj, &lru_gen_attr_group)) pr_err("lru_gen: failed to create sysfs group\n"); + debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops); + debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops); + return 0; }; late_initcall(init_lru_gen); -- Gitee From 00600a172fb3bc9da65a1974131944be518ae0b0 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Sun, 23 Jan 2022 16:44:43 -0700 Subject: [PATCH 12/13] FROMLIST: mm: multi-gen LRU: admin guide MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add an admin guide. Link: https://lore.kernel.org/r/20220309021230.721028-14-yuzhao@google.com/ Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I6fafbd7eb3ef6819cfcd30376459f14893f17c63 --- Documentation/admin-guide/mm/index.rst | 1 + Documentation/admin-guide/mm/multigen_lru.rst | 152 ++++++++++++++++++ mm/Kconfig | 3 +- 3 files changed, 155 insertions(+), 1 deletion(-) create mode 100644 Documentation/admin-guide/mm/multigen_lru.rst diff --git a/Documentation/admin-guide/mm/index.rst b/Documentation/admin-guide/mm/index.rst index db38553224c8..d188181b93b7 100644 --- a/Documentation/admin-guide/mm/index.rst +++ b/Documentation/admin-guide/mm/index.rst @@ -32,6 +32,7 @@ the Linux memory management. idle_page_tracking ksm memory-hotplug + multigen_lru nommu-mmap numa_memory_policy numaperf diff --git a/Documentation/admin-guide/mm/multigen_lru.rst b/Documentation/admin-guide/mm/multigen_lru.rst new file mode 100644 index 000000000000..3d9a6ef84229 --- /dev/null +++ b/Documentation/admin-guide/mm/multigen_lru.rst @@ -0,0 +1,152 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +Multi-Gen LRU +============= +The multi-gen LRU is an alternative LRU implementation that optimizes +page reclaim and improves performance under memory pressure. Page +reclaim decides the kernel's caching policy and ability to overcommit +memory. It directly impacts the kswapd CPU usage and RAM efficiency. + +Quick start +=========== +Build the kernel with the following configurations. + +* ``CONFIG_LRU_GEN=y`` +* ``CONFIG_LRU_GEN_ENABLED=y`` + +All set! + +Runtime options +=============== +``/sys/kernel/mm/lru_gen/`` contains stable ABIs described in the +following subsections. + +Kill switch +----------- +``enable`` accepts different values to enable or disable the following +components. Its default value depends on ``CONFIG_LRU_GEN_ENABLED``. +All the components should be enabled unless some of them have +unforeseen side effects. Writing to ``enable`` has no effect when a +component is not supported by the hardware, and valid values will be +accepted even when the main switch is off. + +====== =============================================================== +Values Components +====== =============================================================== +0x0001 The main switch for the multi-gen LRU. +0x0002 Clearing the accessed bit in leaf page table entries in large + batches, when MMU sets it (e.g., on x86). This behavior can + theoretically worsen lock contention (mmap_lock). If it is + disabled, the multi-gen LRU will suffer a minor performance + degradation. +0x0004 Clearing the accessed bit in non-leaf page table entries as + well, when MMU sets it (e.g., on x86). This behavior was not + verified on x86 varieties other than Intel and AMD. If it is + disabled, the multi-gen LRU will suffer a negligible + performance degradation. +[yYnN] Apply to all the components above. +====== =============================================================== + +E.g., +:: + + echo y >/sys/kernel/mm/lru_gen/enabled + cat /sys/kernel/mm/lru_gen/enabled + 0x0007 + echo 5 >/sys/kernel/mm/lru_gen/enabled + cat /sys/kernel/mm/lru_gen/enabled + 0x0005 + +Thrashing prevention +-------------------- +Personal computers are more sensitive to thrashing because it can +cause janks (lags when rendering UI) and negatively impact user +experience. The multi-gen LRU offers thrashing prevention to the +majority of laptop and desktop users who do not have ``oomd``. + +Users can write ``N`` to ``min_ttl_ms`` to prevent the working set of +``N`` milliseconds from getting evicted. The OOM killer is triggered +if this working set cannot be kept in memory. In other words, this +option works as an adjustable pressure relief valve, and when open, it +terminates applications that are hopefully not being used. + +Based on the average human detectable lag (~100ms), ``N=1000`` usually +eliminates intolerable janks due to thrashing. Larger values like +``N=3000`` make janks less noticeable at the risk of premature OOM +kills. + +The default value ``0`` means disabled. + +Experimental features +===================== +``/sys/kernel/debug/lru_gen`` accepts commands described in the +following subsections. Multiple command lines are supported, so does +concatenation with delimiters ``,`` and ``;``. + +``/sys/kernel/debug/lru_gen_full`` provides additional stats for +debugging. ``CONFIG_LRU_GEN_STATS=y`` keeps historical stats from +evicted generations in this file. + +Working set estimation +---------------------- +Working set estimation measures how much memory an application +requires in a given time interval, and it is usually done with little +impact on the performance of the application. E.g., data centers want +to optimize job scheduling (bin packing) to improve memory +utilizations. When a new job comes in, the job scheduler needs to find +out whether each server it manages can allocate a certain amount of +memory for this new job before it can pick a candidate. To do so, this +job scheduler needs to estimate the working sets of the existing jobs. + +When it is read, ``lru_gen`` returns a histogram of numbers of pages +accessed over different time intervals for each memcg and node. +``MAX_NR_GENS`` decides the number of bins for each histogram. +:: + + memcg memcg_id memcg_path + node node_id + min_gen_nr age_in_ms nr_anon_pages nr_file_pages + ... + max_gen_nr age_in_ms nr_anon_pages nr_file_pages + +Each generation contains an estimated number of pages that have been +accessed within ``age_in_ms`` non-cumulatively. E.g., ``min_gen_nr`` +contains the coldest pages and ``max_gen_nr`` contains the hottest +pages, since ``age_in_ms`` of the former is the largest and that of +the latter is the smallest. + +Users can write ``+ memcg_id node_id max_gen_nr +[can_swap[full_scan]]`` to ``lru_gen`` to create a new generation +``max_gen_nr+1``. ``can_swap`` defaults to the swap setting and, if it +is set to ``1``, it forces the scan of anon pages when swap is off. +``full_scan`` defaults to ``1`` and, if it is set to ``0``, it reduces +the overhead as well as the coverage when scanning page tables. + +A typical use case is that a job scheduler writes to ``lru_gen`` at a +certain time interval to create new generations, and it ranks the +servers it manages based on the sizes of their cold memory defined by +this time interval. + +Proactive reclaim +----------------- +Proactive reclaim induces memory reclaim when there is no memory +pressure and usually targets cold memory only. E.g., when a new job +comes in, the job scheduler wants to proactively reclaim memory on the +server it has selected to improve the chance of successfully landing +this new job. + +Users can write ``- memcg_id node_id min_gen_nr [swappiness +[nr_to_reclaim]]`` to ``lru_gen`` to evict generations less than or +equal to ``min_gen_nr``. Note that ``min_gen_nr`` should be less than +``max_gen_nr-1`` as ``max_gen_nr`` and ``max_gen_nr-1`` are not fully +aged and therefore cannot be evicted. ``swappiness`` overrides the +default value in ``/proc/sys/vm/swappiness``. ``nr_to_reclaim`` limits +the number of pages to evict. + +A typical use case is that a job scheduler writes to ``lru_gen`` +before it tries to land a new job on a server, and if it fails to +materialize the cold memory without impacting the existing jobs on +this server, it retries on the next server according to the ranking +result obtained from the working set estimation step described +earlier. diff --git a/mm/Kconfig b/mm/Kconfig index 967145c9594f..547c2df26dae 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -978,7 +978,8 @@ config LRU_GEN # the following options can use up the spare bits in page flags depends on !MAXSMP && (64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP) help - A high performance LRU implementation to overcommit memory. + A high performance LRU implementation to overcommit memory. See + Documentation/admin-guide/mm/multigen_lru.rst for details. config LRU_GEN_ENABLED bool "Enable by default" -- Gitee From c729aab63a39248b2e3e48a302fe401dae56f0ce Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Sun, 6 Mar 2022 20:35:00 -0700 Subject: [PATCH 13/13] FROMLIST: mm: multi-gen LRU: design doc MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add a design doc. Link: https://lore.kernel.org/r/20220309021230.721028-15-yuzhao@google.com/ Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Bug: 227651406 Signed-off-by: Kalesh Singh Change-Id: I1d66302e618416291ebf9647e20625fb76613c89 --- Documentation/vm/index.rst | 1 + Documentation/vm/multigen_lru.rst | 160 ++++++++++++++++++++++++++++++ 2 files changed, 161 insertions(+) create mode 100644 Documentation/vm/multigen_lru.rst diff --git a/Documentation/vm/index.rst b/Documentation/vm/index.rst index 6f5ffef4b716..313fbe2778d8 100644 --- a/Documentation/vm/index.rst +++ b/Documentation/vm/index.rst @@ -26,6 +26,7 @@ algorithms. If you are looking for advice on simply allocating memory, see the ksm memory-model mmu_notifier + multigen_lru numa overcommit-accounting page_migration diff --git a/Documentation/vm/multigen_lru.rst b/Documentation/vm/multigen_lru.rst new file mode 100644 index 000000000000..8f6498002576 --- /dev/null +++ b/Documentation/vm/multigen_lru.rst @@ -0,0 +1,160 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +Multi-Gen LRU +============= +The multi-gen LRU is an alternative LRU implementation that optimizes +page reclaim and improves performance under memory pressure. Page +reclaim decides the kernel's caching policy and ability to overcommit +memory. It directly impacts the kswapd CPU usage and RAM efficiency. + +Design overview +=============== +Objectives +---------- +The design objectives are: + +* Good representation of access recency +* Try to profit from spatial locality +* Fast paths to make obvious choices +* Simple self-correcting heuristics + +The representation of access recency is at the core of all LRU +implementations. In the multi-gen LRU, each generation represents a +group of pages with similar access recency. Generations establish a +common frame of reference and therefore help make better choices, +e.g., between different memcgs on a computer or different computers in +a data center (for job scheduling). + +Exploiting spatial locality improves efficiency when gathering the +accessed bit. A rmap walk targets a single page and does not try to +profit from discovering a young PTE. A page table walk can sweep all +the young PTEs in an address space, but the address space can be too +large to make a profit. The key is to optimize both methods and use +them in combination. + +Fast paths reduce code complexity and runtime overhead. Unmapped pages +do not require TLB flushes; clean pages do not require writeback. +These facts are only helpful when other conditions, e.g., access +recency, are similar. With generations as a common frame of reference, +additional factors stand out. But obvious choices might not be good +choices; thus self-correction is required. + +The benefits of simple self-correcting heuristics are self-evident. +Again, with generations as a common frame of reference, this becomes +attainable. Specifically, pages in the same generation can be +categorized based on additional factors, and a feedback loop can +statistically compare the refault percentages across those categories +and infer which of them are better choices. + +Assumptions +----------- +The protection of hot pages and the selection of cold pages are based +on page access channels and patterns. There are two access channels: + +* Accesses through page tables +* Accesses through file descriptors + +The protection of the former channel is by design stronger because: + +1. The uncertainty in determining the access patterns of the former + channel is higher due to the approximation of the accessed bit. +2. The cost of evicting the former channel is higher due to the TLB + flushes required and the likelihood of encountering the dirty bit. +3. The penalty of underprotecting the former channel is higher because + applications usually do not prepare themselves for major page + faults like they do for blocked I/O. E.g., GUI applications + commonly use dedicated I/O threads to avoid blocking the rendering + threads. + +There are also two access patterns: + +* Accesses exhibiting temporal locality +* Accesses not exhibiting temporal locality + +For the reasons listed above, the former channel is assumed to follow +the former pattern unless ``VM_SEQ_READ`` or ``VM_RAND_READ`` is +present, and the latter channel is assumed to follow the latter +pattern unless outlying refaults have been observed. + +Workflow overview +================= +Evictable pages are divided into multiple generations for each +``lruvec``. The youngest generation number is stored in +``lrugen->max_seq`` for both anon and file types as they are aged on +an equal footing. The oldest generation numbers are stored in +``lrugen->min_seq[]`` separately for anon and file types as clean file +pages can be evicted regardless of swap constraints. These three +variables are monotonically increasing. + +Generation numbers are truncated into ``order_base_2(MAX_NR_GENS+1)`` +bits in order to fit into the gen counter in ``page->flags``. Each +truncated generation number is an index to ``lrugen->lists[]``. The +sliding window technique is used to track at least ``MIN_NR_GENS`` and +at most ``MAX_NR_GENS`` generations. The gen counter stores a value +within ``[1, MAX_NR_GENS]`` while a page is on one of +``lrugen->lists[]``; otherwise it stores zero. + +Each generation is divided into multiple tiers. Tiers represent +different ranges of numbers of accesses through file descriptors. A +page accessed ``N`` times through file descriptors is in tier +``order_base_2(N)``. In contrast to moving across generations, which +requires the LRU lock, moving across tiers only requires operations on +``page->flags`` and therefore has a negligible cost. A feedback loop +modeled after the PID controller monitors refaults over all the tiers +from anon and file types and decides which tiers from which types to +evict or protect. + +There are two conceptually independent procedures: the aging and the +eviction. They form a closed-loop system, i.e., the page reclaim. + +Aging +----- +The aging produces young generations. Given an ``lruvec``, it +increments ``max_seq`` when ``max_seq-min_seq+1`` approaches +``MIN_NR_GENS``. The aging promotes hot pages to the youngest +generation when it finds them accessed through page tables; the +demotion of cold pages happens consequently when it increments +``max_seq``. The aging uses page table walks and rmap walks to find +young PTEs. For the former, it iterates ``lruvec_memcg()->mm_list`` +and calls ``walk_page_range()`` with each ``mm_struct`` on this list +to scan PTEs. On finding a young PTE, it clears the accessed bit and +updates the gen counter of the page mapped by this PTE to +``(max_seq%MAX_NR_GENS)+1``. After each iteration of this list, it +increments ``max_seq``. For the latter, when the eviction walks the +rmap and finds a young PTE, the aging scans the adjacent PTEs and +follows the same steps just described. + +Eviction +-------- +The eviction consumes old generations. Given an ``lruvec``, it +increments ``min_seq`` when ``lrugen->lists[]`` indexed by +``min_seq%MAX_NR_GENS`` becomes empty. To select a type and a tier to +evict from, it first compares ``min_seq[]`` to select the older type. +If both types are equally old, it selects the one whose first tier has +a lower refault percentage. The first tier contains single-use +unmapped clean pages, which are the best bet. The eviction sorts a +page according to the gen counter if the aging has found this page +accessed through page tables and updated the gen counter. It also +moves a page to the next generation, i.e., ``min_seq+1``, if this page +was accessed multiple times through file descriptors and the feedback +loop has detected outlying refaults from the tier this page is in. To +do this, the feedback loop uses the first tier as the baseline, for +the reason stated earlier. + +Summary +------- +The multi-gen LRU can be disassembled into the following parts: + +* Generations +* Page table walks +* Rmap walks +* Bloom filters +* The PID controller + +The aging and the eviction is a producer-consumer model; specifically, +the latter drives the former by the sliding window over generations. +Within the aging, rmap walks drive page table walks by inserting hot +densely populated page tables to the Bloom filters. Within the +eviction, the PID controller uses refaults as the feedback to select +types to evict and tiers to protect. -- Gitee