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FAILED: patch "[PATCH] mm: allow set/clear page_type again" failed to apply to 6.11-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.11-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.11.y git checkout FETCH_HEAD git cherry-pick -x 9d08ec41a0645283d79a2e642205d488feaceacf # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110524-runner-gravity-4288@gregkh' --subject-prefix 'PATCH 6.11.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 9d08ec41a0645283d79a2e642205d488feaceacf Mon Sep 17 00:00:00 2001 From: Yu Zhao <yuzhao(a)google.com> Date: Sat, 19 Oct 2024 22:22:12 -0600 Subject: [PATCH] mm: allow set/clear page_type again Some page flags (page->flags) were converted to page types (page->page_types). A recent example is PG_hugetlb. From the exclusive writer's perspective, e.g., a thread doing __folio_set_hugetlb(), there is a difference between the page flag and type APIs: the former allows the same non-atomic operation to be repeated whereas the latter does not. For example, calling __folio_set_hugetlb() twice triggers VM_BUG_ON_FOLIO(), since the second call expects the type (PG_hugetlb) not to be set previously. Using add_hugetlb_folio() as an example, it calls __folio_set_hugetlb() in the following error-handling path. And when that happens, it triggers the aforementioned VM_BUG_ON_FOLIO(). if (folio_test_hugetlb(folio)) { rc = hugetlb_vmemmap_restore_folio(h, folio); if (rc) { spin_lock_irq(&hugetlb_lock); add_hugetlb_folio(h, folio, false); ... It is possible to make hugeTLB comply with the new requirements from the page type API. However, a straightforward fix would be to just allow the same page type to be set or cleared again inside the API, to avoid any changes to its callers. Link: https://lkml.kernel.org/r/20241020042212.296781-1-yuzhao@google.com Fixes: d99e3140a4d3 ("mm: turn folio_test_hugetlb into a PageType") Signed-off-by: Yu Zhao <yuzhao(a)google.com> Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org> Cc: Muchun Song <muchun.song(a)linux.dev> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 1b3a76710487..cc839e4365c1 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -975,12 +975,16 @@ static __always_inline bool folio_test_##fname(const struct folio *folio) \ } \ static __always_inline void __folio_set_##fname(struct folio *folio) \ { \ + if (folio_test_##fname(folio)) \ + return; \ VM_BUG_ON_FOLIO(data_race(folio->page.page_type) != UINT_MAX, \ folio); \ folio->page.page_type = (unsigned int)PGTY_##lname << 24; \ } \ static __always_inline void __folio_clear_##fname(struct folio *folio) \ { \ + if (folio->page.page_type == UINT_MAX) \ + return; \ VM_BUG_ON_FOLIO(!folio_test_##fname(folio), folio); \ folio->page.page_type = UINT_MAX; \ } @@ -993,11 +997,15 @@ static __always_inline int Page##uname(const struct page *page) \ } \ static __always_inline void __SetPage##uname(struct page *page) \ { \ + if (Page##uname(page)) \ + return; \ VM_BUG_ON_PAGE(data_race(page->page_type) != UINT_MAX, page); \ page->page_type = (unsigned int)PGTY_##lname << 24; \ } \ static __always_inline void __ClearPage##uname(struct page *page) \ { \ + if (page->page_type == UINT_MAX) \ + return; \ VM_BUG_ON_PAGE(!Page##uname(page), page); \ page->page_type = UINT_MAX; \ }

3 months, 3 weeks

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FAILED: patch "[PATCH] mm: multi-gen LRU: use {ptep,pmdp}_clear_young_notify()" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 1d4832becdc2cdb2cffe2a6050c9d9fd8ff1c58c # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110510-props-clutter-f4ae@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 1d4832becdc2cdb2cffe2a6050c9d9fd8ff1c58c Mon Sep 17 00:00:00 2001 From: Yu Zhao <yuzhao(a)google.com> Date: Sat, 19 Oct 2024 01:29:39 +0000 Subject: [PATCH] mm: multi-gen LRU: use {ptep,pmdp}_clear_young_notify() When the MM_WALK capability is enabled, memory that is mostly accessed by a VM appears younger than it really is, therefore this memory will be less likely to be evicted. Therefore, the presence of a running VM can significantly increase swap-outs for non-VM memory, regressing the performance for the rest of the system. Fix this regression by always calling {ptep,pmdp}_clear_young_notify() whenever we clear the young bits on PMDs/PTEs. [jthoughton(a)google.com: fix link-time error] Link: https://lkml.kernel.org/r/20241019012940.3656292-3-jthoughton@google.com Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") Signed-off-by: Yu Zhao <yuzhao(a)google.com> Signed-off-by: James Houghton <jthoughton(a)google.com> Reported-by: David Stevens <stevensd(a)google.com> Cc: Axel Rasmussen <axelrasmussen(a)google.com> Cc: David Matlack <dmatlack(a)google.com> Cc: David Rientjes <rientjes(a)google.com> Cc: Oliver Upton <oliver.upton(a)linux.dev> Cc: Paolo Bonzini <pbonzini(a)redhat.com> Cc: Sean Christopherson <seanjc(a)google.com> Cc: Wei Xu <weixugc(a)google.com> Cc: <stable(a)vger.kernel.org> Cc: kernel test robot <lkp(a)intel.com> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 9342e5692dab..5b1c984daf45 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -555,7 +555,7 @@ struct lru_gen_memcg { void lru_gen_init_pgdat(struct pglist_data *pgdat); void lru_gen_init_lruvec(struct lruvec *lruvec); -void lru_gen_look_around(struct page_vma_mapped_walk *pvmw); +bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw); void lru_gen_init_memcg(struct mem_cgroup *memcg); void lru_gen_exit_memcg(struct mem_cgroup *memcg); @@ -574,8 +574,9 @@ static inline void lru_gen_init_lruvec(struct lruvec *lruvec) { } -static inline void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) +static inline bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) { + return false; } static inline void lru_gen_init_memcg(struct mem_cgroup *memcg) diff --git a/mm/rmap.c b/mm/rmap.c index a8797d1b3d49..73d5998677d4 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -885,13 +885,10 @@ static bool folio_referenced_one(struct folio *folio, return false; } - if (pvmw.pte) { - if (lru_gen_enabled() && - pte_young(ptep_get(pvmw.pte))) { - lru_gen_look_around(&pvmw); + if (lru_gen_enabled() && pvmw.pte) { + if (lru_gen_look_around(&pvmw)) referenced++; - } - + } else if (pvmw.pte) { if (ptep_clear_flush_young_notify(vma, address, pvmw.pte)) referenced++; diff --git a/mm/vmscan.c b/mm/vmscan.c index 4f1d33e4b360..ddaaff67642e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -56,6 +56,7 @@ #include <linux/khugepaged.h> #include <linux/rculist_nulls.h> #include <linux/random.h> +#include <linux/mmu_notifier.h> #include <asm/tlbflush.h> #include <asm/div64.h> @@ -3294,7 +3295,8 @@ static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk return false; } -static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr) +static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr, + struct pglist_data *pgdat) { unsigned long pfn = pte_pfn(pte); @@ -3306,13 +3308,20 @@ static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte))) return -1; + if (!pte_young(pte) && !mm_has_notifiers(vma->vm_mm)) + return -1; + if (WARN_ON_ONCE(!pfn_valid(pfn))) return -1; + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + return -1; + return pfn; } -static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr) +static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr, + struct pglist_data *pgdat) { unsigned long pfn = pmd_pfn(pmd); @@ -3324,9 +3333,15 @@ static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned if (WARN_ON_ONCE(pmd_devmap(pmd))) return -1; + if (!pmd_young(pmd) && !mm_has_notifiers(vma->vm_mm)) + return -1; + if (WARN_ON_ONCE(!pfn_valid(pfn))) return -1; + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + return -1; + return pfn; } @@ -3335,10 +3350,6 @@ static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg, { struct folio *folio; - /* try to avoid unnecessary memory loads */ - if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) - return NULL; - folio = pfn_folio(pfn); if (folio_nid(folio) != pgdat->node_id) return NULL; @@ -3394,20 +3405,16 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, total++; walk->mm_stats[MM_LEAF_TOTAL]++; - pfn = get_pte_pfn(ptent, args->vma, addr); + pfn = get_pte_pfn(ptent, args->vma, addr, pgdat); if (pfn == -1) continue; - if (!pte_young(ptent)) { - continue; - } - folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap); if (!folio) continue; - if (!ptep_test_and_clear_young(args->vma, addr, pte + i)) - VM_WARN_ON_ONCE(true); + if (!ptep_clear_young_notify(args->vma, addr, pte + i)) + continue; young++; walk->mm_stats[MM_LEAF_YOUNG]++; @@ -3473,21 +3480,25 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area /* don't round down the first address */ addr = i ? (*first & PMD_MASK) + i * PMD_SIZE : *first; - pfn = get_pmd_pfn(pmd[i], vma, addr); - if (pfn == -1) + if (!pmd_present(pmd[i])) goto next; if (!pmd_trans_huge(pmd[i])) { - if (!walk->force_scan && should_clear_pmd_young()) + if (!walk->force_scan && should_clear_pmd_young() && + !mm_has_notifiers(args->mm)) pmdp_test_and_clear_young(vma, addr, pmd + i); goto next; } + pfn = get_pmd_pfn(pmd[i], vma, addr, pgdat); + if (pfn == -1) + goto next; + folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap); if (!folio) goto next; - if (!pmdp_test_and_clear_young(vma, addr, pmd + i)) + if (!pmdp_clear_young_notify(vma, addr, pmd + i)) goto next; walk->mm_stats[MM_LEAF_YOUNG]++; @@ -3545,24 +3556,18 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, } if (pmd_trans_huge(val)) { - unsigned long pfn = pmd_pfn(val); struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); + unsigned long pfn = get_pmd_pfn(val, vma, addr, pgdat); walk->mm_stats[MM_LEAF_TOTAL]++; - if (!pmd_young(val)) { - continue; - } - - /* try to avoid unnecessary memory loads */ - if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) - continue; - - walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); + if (pfn != -1) + walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); continue; } - if (!walk->force_scan && should_clear_pmd_young()) { + if (!walk->force_scan && should_clear_pmd_young() && + !mm_has_notifiers(args->mm)) { if (!pmd_young(val)) continue; @@ -4036,13 +4041,13 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) * the PTE table to the Bloom filter. This forms a feedback loop between the * eviction and the aging. */ -void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) +bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) { int i; unsigned long start; unsigned long end; struct lru_gen_mm_walk *walk; - int young = 0; + int young = 1; pte_t *pte = pvmw->pte; unsigned long addr = pvmw->address; struct vm_area_struct *vma = pvmw->vma; @@ -4058,12 +4063,15 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) lockdep_assert_held(pvmw->ptl); VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio); + if (!ptep_clear_young_notify(vma, addr, pte)) + return false; + if (spin_is_contended(pvmw->ptl)) - return; + return true; /* exclude special VMAs containing anon pages from COW */ if (vma->vm_flags & VM_SPECIAL) - return; + return true; /* avoid taking the LRU lock under the PTL when possible */ walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL; @@ -4071,6 +4079,9 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) start = max(addr & PMD_MASK, vma->vm_start); end = min(addr | ~PMD_MASK, vma->vm_end - 1) + 1; + if (end - start == PAGE_SIZE) + return true; + if (end - start > MIN_LRU_BATCH * PAGE_SIZE) { if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2) end = start + MIN_LRU_BATCH * PAGE_SIZE; @@ -4084,7 +4095,7 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) /* folio_update_gen() requires stable folio_memcg() */ if (!mem_cgroup_trylock_pages(memcg)) - return; + return true; arch_enter_lazy_mmu_mode(); @@ -4094,19 +4105,16 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) unsigned long pfn; pte_t ptent = ptep_get(pte + i); - pfn = get_pte_pfn(ptent, vma, addr); + pfn = get_pte_pfn(ptent, vma, addr, pgdat); if (pfn == -1) continue; - if (!pte_young(ptent)) - continue; - folio = get_pfn_folio(pfn, memcg, pgdat, can_swap); if (!folio) continue; - if (!ptep_test_and_clear_young(vma, addr, pte + i)) - VM_WARN_ON_ONCE(true); + if (!ptep_clear_young_notify(vma, addr, pte + i)) + continue; young++; @@ -4136,6 +4144,8 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) /* feedback from rmap walkers to page table walkers */ if (mm_state && suitable_to_scan(i, young)) update_bloom_filter(mm_state, max_seq, pvmw->pmd); + + return true; } /******************************************************************************

3 months, 3 weeks

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FAILED: patch "[PATCH] mm: multi-gen LRU: use {ptep,pmdp}_clear_young_notify()" failed to apply to 6.6-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 1d4832becdc2cdb2cffe2a6050c9d9fd8ff1c58c # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110509-doable-blemish-19d2@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 1d4832becdc2cdb2cffe2a6050c9d9fd8ff1c58c Mon Sep 17 00:00:00 2001 From: Yu Zhao <yuzhao(a)google.com> Date: Sat, 19 Oct 2024 01:29:39 +0000 Subject: [PATCH] mm: multi-gen LRU: use {ptep,pmdp}_clear_young_notify() When the MM_WALK capability is enabled, memory that is mostly accessed by a VM appears younger than it really is, therefore this memory will be less likely to be evicted. Therefore, the presence of a running VM can significantly increase swap-outs for non-VM memory, regressing the performance for the rest of the system. Fix this regression by always calling {ptep,pmdp}_clear_young_notify() whenever we clear the young bits on PMDs/PTEs. [jthoughton(a)google.com: fix link-time error] Link: https://lkml.kernel.org/r/20241019012940.3656292-3-jthoughton@google.com Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") Signed-off-by: Yu Zhao <yuzhao(a)google.com> Signed-off-by: James Houghton <jthoughton(a)google.com> Reported-by: David Stevens <stevensd(a)google.com> Cc: Axel Rasmussen <axelrasmussen(a)google.com> Cc: David Matlack <dmatlack(a)google.com> Cc: David Rientjes <rientjes(a)google.com> Cc: Oliver Upton <oliver.upton(a)linux.dev> Cc: Paolo Bonzini <pbonzini(a)redhat.com> Cc: Sean Christopherson <seanjc(a)google.com> Cc: Wei Xu <weixugc(a)google.com> Cc: <stable(a)vger.kernel.org> Cc: kernel test robot <lkp(a)intel.com> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 9342e5692dab..5b1c984daf45 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -555,7 +555,7 @@ struct lru_gen_memcg { void lru_gen_init_pgdat(struct pglist_data *pgdat); void lru_gen_init_lruvec(struct lruvec *lruvec); -void lru_gen_look_around(struct page_vma_mapped_walk *pvmw); +bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw); void lru_gen_init_memcg(struct mem_cgroup *memcg); void lru_gen_exit_memcg(struct mem_cgroup *memcg); @@ -574,8 +574,9 @@ static inline void lru_gen_init_lruvec(struct lruvec *lruvec) { } -static inline void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) +static inline bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) { + return false; } static inline void lru_gen_init_memcg(struct mem_cgroup *memcg) diff --git a/mm/rmap.c b/mm/rmap.c index a8797d1b3d49..73d5998677d4 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -885,13 +885,10 @@ static bool folio_referenced_one(struct folio *folio, return false; } - if (pvmw.pte) { - if (lru_gen_enabled() && - pte_young(ptep_get(pvmw.pte))) { - lru_gen_look_around(&pvmw); + if (lru_gen_enabled() && pvmw.pte) { + if (lru_gen_look_around(&pvmw)) referenced++; - } - + } else if (pvmw.pte) { if (ptep_clear_flush_young_notify(vma, address, pvmw.pte)) referenced++; diff --git a/mm/vmscan.c b/mm/vmscan.c index 4f1d33e4b360..ddaaff67642e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -56,6 +56,7 @@ #include <linux/khugepaged.h> #include <linux/rculist_nulls.h> #include <linux/random.h> +#include <linux/mmu_notifier.h> #include <asm/tlbflush.h> #include <asm/div64.h> @@ -3294,7 +3295,8 @@ static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk return false; } -static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr) +static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr, + struct pglist_data *pgdat) { unsigned long pfn = pte_pfn(pte); @@ -3306,13 +3308,20 @@ static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte))) return -1; + if (!pte_young(pte) && !mm_has_notifiers(vma->vm_mm)) + return -1; + if (WARN_ON_ONCE(!pfn_valid(pfn))) return -1; + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + return -1; + return pfn; } -static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr) +static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr, + struct pglist_data *pgdat) { unsigned long pfn = pmd_pfn(pmd); @@ -3324,9 +3333,15 @@ static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned if (WARN_ON_ONCE(pmd_devmap(pmd))) return -1; + if (!pmd_young(pmd) && !mm_has_notifiers(vma->vm_mm)) + return -1; + if (WARN_ON_ONCE(!pfn_valid(pfn))) return -1; + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + return -1; + return pfn; } @@ -3335,10 +3350,6 @@ static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg, { struct folio *folio; - /* try to avoid unnecessary memory loads */ - if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) - return NULL; - folio = pfn_folio(pfn); if (folio_nid(folio) != pgdat->node_id) return NULL; @@ -3394,20 +3405,16 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, total++; walk->mm_stats[MM_LEAF_TOTAL]++; - pfn = get_pte_pfn(ptent, args->vma, addr); + pfn = get_pte_pfn(ptent, args->vma, addr, pgdat); if (pfn == -1) continue; - if (!pte_young(ptent)) { - continue; - } - folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap); if (!folio) continue; - if (!ptep_test_and_clear_young(args->vma, addr, pte + i)) - VM_WARN_ON_ONCE(true); + if (!ptep_clear_young_notify(args->vma, addr, pte + i)) + continue; young++; walk->mm_stats[MM_LEAF_YOUNG]++; @@ -3473,21 +3480,25 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area /* don't round down the first address */ addr = i ? (*first & PMD_MASK) + i * PMD_SIZE : *first; - pfn = get_pmd_pfn(pmd[i], vma, addr); - if (pfn == -1) + if (!pmd_present(pmd[i])) goto next; if (!pmd_trans_huge(pmd[i])) { - if (!walk->force_scan && should_clear_pmd_young()) + if (!walk->force_scan && should_clear_pmd_young() && + !mm_has_notifiers(args->mm)) pmdp_test_and_clear_young(vma, addr, pmd + i); goto next; } + pfn = get_pmd_pfn(pmd[i], vma, addr, pgdat); + if (pfn == -1) + goto next; + folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap); if (!folio) goto next; - if (!pmdp_test_and_clear_young(vma, addr, pmd + i)) + if (!pmdp_clear_young_notify(vma, addr, pmd + i)) goto next; walk->mm_stats[MM_LEAF_YOUNG]++; @@ -3545,24 +3556,18 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, } if (pmd_trans_huge(val)) { - unsigned long pfn = pmd_pfn(val); struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); + unsigned long pfn = get_pmd_pfn(val, vma, addr, pgdat); walk->mm_stats[MM_LEAF_TOTAL]++; - if (!pmd_young(val)) { - continue; - } - - /* try to avoid unnecessary memory loads */ - if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) - continue; - - walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); + if (pfn != -1) + walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); continue; } - if (!walk->force_scan && should_clear_pmd_young()) { + if (!walk->force_scan && should_clear_pmd_young() && + !mm_has_notifiers(args->mm)) { if (!pmd_young(val)) continue; @@ -4036,13 +4041,13 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) * the PTE table to the Bloom filter. This forms a feedback loop between the * eviction and the aging. */ -void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) +bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) { int i; unsigned long start; unsigned long end; struct lru_gen_mm_walk *walk; - int young = 0; + int young = 1; pte_t *pte = pvmw->pte; unsigned long addr = pvmw->address; struct vm_area_struct *vma = pvmw->vma; @@ -4058,12 +4063,15 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) lockdep_assert_held(pvmw->ptl); VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio); + if (!ptep_clear_young_notify(vma, addr, pte)) + return false; + if (spin_is_contended(pvmw->ptl)) - return; + return true; /* exclude special VMAs containing anon pages from COW */ if (vma->vm_flags & VM_SPECIAL) - return; + return true; /* avoid taking the LRU lock under the PTL when possible */ walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL; @@ -4071,6 +4079,9 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) start = max(addr & PMD_MASK, vma->vm_start); end = min(addr | ~PMD_MASK, vma->vm_end - 1) + 1; + if (end - start == PAGE_SIZE) + return true; + if (end - start > MIN_LRU_BATCH * PAGE_SIZE) { if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2) end = start + MIN_LRU_BATCH * PAGE_SIZE; @@ -4084,7 +4095,7 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) /* folio_update_gen() requires stable folio_memcg() */ if (!mem_cgroup_trylock_pages(memcg)) - return; + return true; arch_enter_lazy_mmu_mode(); @@ -4094,19 +4105,16 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) unsigned long pfn; pte_t ptent = ptep_get(pte + i); - pfn = get_pte_pfn(ptent, vma, addr); + pfn = get_pte_pfn(ptent, vma, addr, pgdat); if (pfn == -1) continue; - if (!pte_young(ptent)) - continue; - folio = get_pfn_folio(pfn, memcg, pgdat, can_swap); if (!folio) continue; - if (!ptep_test_and_clear_young(vma, addr, pte + i)) - VM_WARN_ON_ONCE(true); + if (!ptep_clear_young_notify(vma, addr, pte + i)) + continue; young++; @@ -4136,6 +4144,8 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) /* feedback from rmap walkers to page table walkers */ if (mm_state && suitable_to_scan(i, young)) update_bloom_filter(mm_state, max_seq, pvmw->pmd); + + return true; } /******************************************************************************

3 months, 3 weeks

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FAILED: patch "[PATCH] mm: multi-gen LRU: use {ptep,pmdp}_clear_young_notify()" failed to apply to 6.11-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.11-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.11.y git checkout FETCH_HEAD git cherry-pick -x 1d4832becdc2cdb2cffe2a6050c9d9fd8ff1c58c # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110508-poppy-cameo-fa1b@gregkh' --subject-prefix 'PATCH 6.11.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 1d4832becdc2cdb2cffe2a6050c9d9fd8ff1c58c Mon Sep 17 00:00:00 2001 From: Yu Zhao <yuzhao(a)google.com> Date: Sat, 19 Oct 2024 01:29:39 +0000 Subject: [PATCH] mm: multi-gen LRU: use {ptep,pmdp}_clear_young_notify() When the MM_WALK capability is enabled, memory that is mostly accessed by a VM appears younger than it really is, therefore this memory will be less likely to be evicted. Therefore, the presence of a running VM can significantly increase swap-outs for non-VM memory, regressing the performance for the rest of the system. Fix this regression by always calling {ptep,pmdp}_clear_young_notify() whenever we clear the young bits on PMDs/PTEs. [jthoughton(a)google.com: fix link-time error] Link: https://lkml.kernel.org/r/20241019012940.3656292-3-jthoughton@google.com Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") Signed-off-by: Yu Zhao <yuzhao(a)google.com> Signed-off-by: James Houghton <jthoughton(a)google.com> Reported-by: David Stevens <stevensd(a)google.com> Cc: Axel Rasmussen <axelrasmussen(a)google.com> Cc: David Matlack <dmatlack(a)google.com> Cc: David Rientjes <rientjes(a)google.com> Cc: Oliver Upton <oliver.upton(a)linux.dev> Cc: Paolo Bonzini <pbonzini(a)redhat.com> Cc: Sean Christopherson <seanjc(a)google.com> Cc: Wei Xu <weixugc(a)google.com> Cc: <stable(a)vger.kernel.org> Cc: kernel test robot <lkp(a)intel.com> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 9342e5692dab..5b1c984daf45 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -555,7 +555,7 @@ struct lru_gen_memcg { void lru_gen_init_pgdat(struct pglist_data *pgdat); void lru_gen_init_lruvec(struct lruvec *lruvec); -void lru_gen_look_around(struct page_vma_mapped_walk *pvmw); +bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw); void lru_gen_init_memcg(struct mem_cgroup *memcg); void lru_gen_exit_memcg(struct mem_cgroup *memcg); @@ -574,8 +574,9 @@ static inline void lru_gen_init_lruvec(struct lruvec *lruvec) { } -static inline void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) +static inline bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) { + return false; } static inline void lru_gen_init_memcg(struct mem_cgroup *memcg) diff --git a/mm/rmap.c b/mm/rmap.c index a8797d1b3d49..73d5998677d4 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -885,13 +885,10 @@ static bool folio_referenced_one(struct folio *folio, return false; } - if (pvmw.pte) { - if (lru_gen_enabled() && - pte_young(ptep_get(pvmw.pte))) { - lru_gen_look_around(&pvmw); + if (lru_gen_enabled() && pvmw.pte) { + if (lru_gen_look_around(&pvmw)) referenced++; - } - + } else if (pvmw.pte) { if (ptep_clear_flush_young_notify(vma, address, pvmw.pte)) referenced++; diff --git a/mm/vmscan.c b/mm/vmscan.c index 4f1d33e4b360..ddaaff67642e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -56,6 +56,7 @@ #include <linux/khugepaged.h> #include <linux/rculist_nulls.h> #include <linux/random.h> +#include <linux/mmu_notifier.h> #include <asm/tlbflush.h> #include <asm/div64.h> @@ -3294,7 +3295,8 @@ static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk return false; } -static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr) +static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr, + struct pglist_data *pgdat) { unsigned long pfn = pte_pfn(pte); @@ -3306,13 +3308,20 @@ static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte))) return -1; + if (!pte_young(pte) && !mm_has_notifiers(vma->vm_mm)) + return -1; + if (WARN_ON_ONCE(!pfn_valid(pfn))) return -1; + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + return -1; + return pfn; } -static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr) +static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr, + struct pglist_data *pgdat) { unsigned long pfn = pmd_pfn(pmd); @@ -3324,9 +3333,15 @@ static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned if (WARN_ON_ONCE(pmd_devmap(pmd))) return -1; + if (!pmd_young(pmd) && !mm_has_notifiers(vma->vm_mm)) + return -1; + if (WARN_ON_ONCE(!pfn_valid(pfn))) return -1; + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + return -1; + return pfn; } @@ -3335,10 +3350,6 @@ static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg, { struct folio *folio; - /* try to avoid unnecessary memory loads */ - if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) - return NULL; - folio = pfn_folio(pfn); if (folio_nid(folio) != pgdat->node_id) return NULL; @@ -3394,20 +3405,16 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, total++; walk->mm_stats[MM_LEAF_TOTAL]++; - pfn = get_pte_pfn(ptent, args->vma, addr); + pfn = get_pte_pfn(ptent, args->vma, addr, pgdat); if (pfn == -1) continue; - if (!pte_young(ptent)) { - continue; - } - folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap); if (!folio) continue; - if (!ptep_test_and_clear_young(args->vma, addr, pte + i)) - VM_WARN_ON_ONCE(true); + if (!ptep_clear_young_notify(args->vma, addr, pte + i)) + continue; young++; walk->mm_stats[MM_LEAF_YOUNG]++; @@ -3473,21 +3480,25 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area /* don't round down the first address */ addr = i ? (*first & PMD_MASK) + i * PMD_SIZE : *first; - pfn = get_pmd_pfn(pmd[i], vma, addr); - if (pfn == -1) + if (!pmd_present(pmd[i])) goto next; if (!pmd_trans_huge(pmd[i])) { - if (!walk->force_scan && should_clear_pmd_young()) + if (!walk->force_scan && should_clear_pmd_young() && + !mm_has_notifiers(args->mm)) pmdp_test_and_clear_young(vma, addr, pmd + i); goto next; } + pfn = get_pmd_pfn(pmd[i], vma, addr, pgdat); + if (pfn == -1) + goto next; + folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap); if (!folio) goto next; - if (!pmdp_test_and_clear_young(vma, addr, pmd + i)) + if (!pmdp_clear_young_notify(vma, addr, pmd + i)) goto next; walk->mm_stats[MM_LEAF_YOUNG]++; @@ -3545,24 +3556,18 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, } if (pmd_trans_huge(val)) { - unsigned long pfn = pmd_pfn(val); struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); + unsigned long pfn = get_pmd_pfn(val, vma, addr, pgdat); walk->mm_stats[MM_LEAF_TOTAL]++; - if (!pmd_young(val)) { - continue; - } - - /* try to avoid unnecessary memory loads */ - if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) - continue; - - walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); + if (pfn != -1) + walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); continue; } - if (!walk->force_scan && should_clear_pmd_young()) { + if (!walk->force_scan && should_clear_pmd_young() && + !mm_has_notifiers(args->mm)) { if (!pmd_young(val)) continue; @@ -4036,13 +4041,13 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) * the PTE table to the Bloom filter. This forms a feedback loop between the * eviction and the aging. */ -void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) +bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw) { int i; unsigned long start; unsigned long end; struct lru_gen_mm_walk *walk; - int young = 0; + int young = 1; pte_t *pte = pvmw->pte; unsigned long addr = pvmw->address; struct vm_area_struct *vma = pvmw->vma; @@ -4058,12 +4063,15 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) lockdep_assert_held(pvmw->ptl); VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio); + if (!ptep_clear_young_notify(vma, addr, pte)) + return false; + if (spin_is_contended(pvmw->ptl)) - return; + return true; /* exclude special VMAs containing anon pages from COW */ if (vma->vm_flags & VM_SPECIAL) - return; + return true; /* avoid taking the LRU lock under the PTL when possible */ walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL; @@ -4071,6 +4079,9 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) start = max(addr & PMD_MASK, vma->vm_start); end = min(addr | ~PMD_MASK, vma->vm_end - 1) + 1; + if (end - start == PAGE_SIZE) + return true; + if (end - start > MIN_LRU_BATCH * PAGE_SIZE) { if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2) end = start + MIN_LRU_BATCH * PAGE_SIZE; @@ -4084,7 +4095,7 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) /* folio_update_gen() requires stable folio_memcg() */ if (!mem_cgroup_trylock_pages(memcg)) - return; + return true; arch_enter_lazy_mmu_mode(); @@ -4094,19 +4105,16 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) unsigned long pfn; pte_t ptent = ptep_get(pte + i); - pfn = get_pte_pfn(ptent, vma, addr); + pfn = get_pte_pfn(ptent, vma, addr, pgdat); if (pfn == -1) continue; - if (!pte_young(ptent)) - continue; - folio = get_pfn_folio(pfn, memcg, pgdat, can_swap); if (!folio) continue; - if (!ptep_test_and_clear_young(vma, addr, pte + i)) - VM_WARN_ON_ONCE(true); + if (!ptep_clear_young_notify(vma, addr, pte + i)) + continue; young++; @@ -4136,6 +4144,8 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) /* feedback from rmap walkers to page table walkers */ if (mm_state && suitable_to_scan(i, young)) update_bloom_filter(mm_state, max_seq, pvmw->pmd); + + return true; } /******************************************************************************

3 months, 3 weeks

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FAILED: patch "[PATCH] mm: multi-gen LRU: remove MM_LEAF_OLD and MM_NONLEAF_TOTAL" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x ddd6d8e975b171ea3f63a011a75820883ff0d479 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110504-flagship-precook-4a47@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From ddd6d8e975b171ea3f63a011a75820883ff0d479 Mon Sep 17 00:00:00 2001 From: Yu Zhao <yuzhao(a)google.com> Date: Sat, 19 Oct 2024 01:29:38 +0000 Subject: [PATCH] mm: multi-gen LRU: remove MM_LEAF_OLD and MM_NONLEAF_TOTAL stats Patch series "mm: multi-gen LRU: Have secondary MMUs participate in MM_WALK". Today, the MM_WALK capability causes MGLRU to clear the young bit from PMDs and PTEs during the page table walk before eviction, but MGLRU does not call the clear_young() MMU notifier in this case. By not calling this notifier, the MM walk takes less time/CPU, but it causes pages that are accessed mostly through KVM / secondary MMUs to appear younger than they should be. We do call the clear_young() notifier today, but only when attempting to evict the page, so we end up clearing young/accessed information less frequently for secondary MMUs than for mm PTEs, and therefore they appear younger and are less likely to be evicted. Therefore, memory that is *not* being accessed mostly by KVM will be evicted *more* frequently, worsening performance. ChromeOS observed a tab-open latency regression when enabling MGLRU with a setup that involved running a VM: Tab-open latency histogram (ms) Version p50 mean p95 p99 max base 1315 1198 2347 3454 10319 mglru 2559 1311 7399 12060 43758 fix 1119 926 2470 4211 6947 This series replaces the final non-selftest patchs from this series[1], which introduced a similar change (and a new MMU notifier) with KVM optimizations. I'll send a separate series (to Sean and Paolo) for the KVM optimizations. This series also makes proactive reclaim with MGLRU possible for KVM memory. I have verified that this functions correctly with the selftest from [1], but given that that test is a KVM selftest, I'll send it with the rest of the KVM optimizations later. Andrew, let me know if you'd like to take the test now anyway. [1]: https://lore.kernel.org/linux-mm/20240926013506.860253-18-jthoughton@google… This patch (of 2): The removed stats, MM_LEAF_OLD and MM_NONLEAF_TOTAL, are not very helpful and become more complicated to properly compute when adding test/clear_young() notifiers in MGLRU's mm walk. Link: https://lkml.kernel.org/r/20241019012940.3656292-1-jthoughton@google.com Link: https://lkml.kernel.org/r/20241019012940.3656292-2-jthoughton@google.com Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") Signed-off-by: Yu Zhao <yuzhao(a)google.com> Signed-off-by: James Houghton <jthoughton(a)google.com> Cc: Axel Rasmussen <axelrasmussen(a)google.com> Cc: David Matlack <dmatlack(a)google.com> Cc: David Rientjes <rientjes(a)google.com> Cc: David Stevens <stevensd(a)google.com> Cc: Oliver Upton <oliver.upton(a)linux.dev> Cc: Paolo Bonzini <pbonzini(a)redhat.com> Cc: Sean Christopherson <seanjc(a)google.com> Cc: Wei Xu <weixugc(a)google.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 17506e4a2835..9342e5692dab 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -458,9 +458,7 @@ struct lru_gen_folio { enum { MM_LEAF_TOTAL, /* total leaf entries */ - MM_LEAF_OLD, /* old leaf entries */ MM_LEAF_YOUNG, /* young leaf entries */ - MM_NONLEAF_TOTAL, /* total non-leaf entries */ MM_NONLEAF_FOUND, /* non-leaf entries found in Bloom filters */ MM_NONLEAF_ADDED, /* non-leaf entries added to Bloom filters */ NR_MM_STATS diff --git a/mm/vmscan.c b/mm/vmscan.c index eb4e8440c507..4f1d33e4b360 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3399,7 +3399,6 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, continue; if (!pte_young(ptent)) { - walk->mm_stats[MM_LEAF_OLD]++; continue; } @@ -3552,7 +3551,6 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, walk->mm_stats[MM_LEAF_TOTAL]++; if (!pmd_young(val)) { - walk->mm_stats[MM_LEAF_OLD]++; continue; } @@ -3564,8 +3562,6 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, continue; } - walk->mm_stats[MM_NONLEAF_TOTAL]++; - if (!walk->force_scan && should_clear_pmd_young()) { if (!pmd_young(val)) continue; @@ -5254,11 +5250,11 @@ static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, for (tier = 0; tier < MAX_NR_TIERS; tier++) { seq_printf(m, " %10d", tier); for (type = 0; type < ANON_AND_FILE; type++) { - const char *s = " "; + const char *s = "xxx"; unsigned long n[3] = {}; if (seq == max_seq) { - s = "RT "; + s = "RTx"; n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]); n[1] = READ_ONCE(lrugen->avg_total[type][tier]); } else if (seq == min_seq[type] || NR_HIST_GENS > 1) { @@ -5280,14 +5276,14 @@ static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, seq_puts(m, " "); for (i = 0; i < NR_MM_STATS; i++) { - const char *s = " "; + const char *s = "xxxx"; unsigned long n = 0; if (seq == max_seq && NR_HIST_GENS == 1) { - s = "LOYNFA"; + s = "TYFA"; n = READ_ONCE(mm_state->stats[hist][i]); } else if (seq != max_seq && NR_HIST_GENS > 1) { - s = "loynfa"; + s = "tyfa"; n = READ_ONCE(mm_state->stats[hist][i]); }

3 months, 3 weeks

1
0
0 0

FAILED: patch "[PATCH] mm: multi-gen LRU: remove MM_LEAF_OLD and MM_NONLEAF_TOTAL" failed to apply to 6.6-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x ddd6d8e975b171ea3f63a011a75820883ff0d479 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110502-removal-babied-f697@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From ddd6d8e975b171ea3f63a011a75820883ff0d479 Mon Sep 17 00:00:00 2001 From: Yu Zhao <yuzhao(a)google.com> Date: Sat, 19 Oct 2024 01:29:38 +0000 Subject: [PATCH] mm: multi-gen LRU: remove MM_LEAF_OLD and MM_NONLEAF_TOTAL stats Patch series "mm: multi-gen LRU: Have secondary MMUs participate in MM_WALK". Today, the MM_WALK capability causes MGLRU to clear the young bit from PMDs and PTEs during the page table walk before eviction, but MGLRU does not call the clear_young() MMU notifier in this case. By not calling this notifier, the MM walk takes less time/CPU, but it causes pages that are accessed mostly through KVM / secondary MMUs to appear younger than they should be. We do call the clear_young() notifier today, but only when attempting to evict the page, so we end up clearing young/accessed information less frequently for secondary MMUs than for mm PTEs, and therefore they appear younger and are less likely to be evicted. Therefore, memory that is *not* being accessed mostly by KVM will be evicted *more* frequently, worsening performance. ChromeOS observed a tab-open latency regression when enabling MGLRU with a setup that involved running a VM: Tab-open latency histogram (ms) Version p50 mean p95 p99 max base 1315 1198 2347 3454 10319 mglru 2559 1311 7399 12060 43758 fix 1119 926 2470 4211 6947 This series replaces the final non-selftest patchs from this series[1], which introduced a similar change (and a new MMU notifier) with KVM optimizations. I'll send a separate series (to Sean and Paolo) for the KVM optimizations. This series also makes proactive reclaim with MGLRU possible for KVM memory. I have verified that this functions correctly with the selftest from [1], but given that that test is a KVM selftest, I'll send it with the rest of the KVM optimizations later. Andrew, let me know if you'd like to take the test now anyway. [1]: https://lore.kernel.org/linux-mm/20240926013506.860253-18-jthoughton@google… This patch (of 2): The removed stats, MM_LEAF_OLD and MM_NONLEAF_TOTAL, are not very helpful and become more complicated to properly compute when adding test/clear_young() notifiers in MGLRU's mm walk. Link: https://lkml.kernel.org/r/20241019012940.3656292-1-jthoughton@google.com Link: https://lkml.kernel.org/r/20241019012940.3656292-2-jthoughton@google.com Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") Signed-off-by: Yu Zhao <yuzhao(a)google.com> Signed-off-by: James Houghton <jthoughton(a)google.com> Cc: Axel Rasmussen <axelrasmussen(a)google.com> Cc: David Matlack <dmatlack(a)google.com> Cc: David Rientjes <rientjes(a)google.com> Cc: David Stevens <stevensd(a)google.com> Cc: Oliver Upton <oliver.upton(a)linux.dev> Cc: Paolo Bonzini <pbonzini(a)redhat.com> Cc: Sean Christopherson <seanjc(a)google.com> Cc: Wei Xu <weixugc(a)google.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 17506e4a2835..9342e5692dab 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -458,9 +458,7 @@ struct lru_gen_folio { enum { MM_LEAF_TOTAL, /* total leaf entries */ - MM_LEAF_OLD, /* old leaf entries */ MM_LEAF_YOUNG, /* young leaf entries */ - MM_NONLEAF_TOTAL, /* total non-leaf entries */ MM_NONLEAF_FOUND, /* non-leaf entries found in Bloom filters */ MM_NONLEAF_ADDED, /* non-leaf entries added to Bloom filters */ NR_MM_STATS diff --git a/mm/vmscan.c b/mm/vmscan.c index eb4e8440c507..4f1d33e4b360 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3399,7 +3399,6 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, continue; if (!pte_young(ptent)) { - walk->mm_stats[MM_LEAF_OLD]++; continue; } @@ -3552,7 +3551,6 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, walk->mm_stats[MM_LEAF_TOTAL]++; if (!pmd_young(val)) { - walk->mm_stats[MM_LEAF_OLD]++; continue; } @@ -3564,8 +3562,6 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, continue; } - walk->mm_stats[MM_NONLEAF_TOTAL]++; - if (!walk->force_scan && should_clear_pmd_young()) { if (!pmd_young(val)) continue; @@ -5254,11 +5250,11 @@ static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, for (tier = 0; tier < MAX_NR_TIERS; tier++) { seq_printf(m, " %10d", tier); for (type = 0; type < ANON_AND_FILE; type++) { - const char *s = " "; + const char *s = "xxx"; unsigned long n[3] = {}; if (seq == max_seq) { - s = "RT "; + s = "RTx"; n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]); n[1] = READ_ONCE(lrugen->avg_total[type][tier]); } else if (seq == min_seq[type] || NR_HIST_GENS > 1) { @@ -5280,14 +5276,14 @@ static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, seq_puts(m, " "); for (i = 0; i < NR_MM_STATS; i++) { - const char *s = " "; + const char *s = "xxxx"; unsigned long n = 0; if (seq == max_seq && NR_HIST_GENS == 1) { - s = "LOYNFA"; + s = "TYFA"; n = READ_ONCE(mm_state->stats[hist][i]); } else if (seq != max_seq && NR_HIST_GENS > 1) { - s = "loynfa"; + s = "tyfa"; n = READ_ONCE(mm_state->stats[hist][i]); }

3 months, 3 weeks

1
0
0 0

FAILED: patch "[PATCH] mm: multi-gen LRU: remove MM_LEAF_OLD and MM_NONLEAF_TOTAL" failed to apply to 6.11-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.11-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.11.y git checkout FETCH_HEAD git cherry-pick -x ddd6d8e975b171ea3f63a011a75820883ff0d479 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110501-scrubber-eating-d64d@gregkh' --subject-prefix 'PATCH 6.11.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From ddd6d8e975b171ea3f63a011a75820883ff0d479 Mon Sep 17 00:00:00 2001 From: Yu Zhao <yuzhao(a)google.com> Date: Sat, 19 Oct 2024 01:29:38 +0000 Subject: [PATCH] mm: multi-gen LRU: remove MM_LEAF_OLD and MM_NONLEAF_TOTAL stats Patch series "mm: multi-gen LRU: Have secondary MMUs participate in MM_WALK". Today, the MM_WALK capability causes MGLRU to clear the young bit from PMDs and PTEs during the page table walk before eviction, but MGLRU does not call the clear_young() MMU notifier in this case. By not calling this notifier, the MM walk takes less time/CPU, but it causes pages that are accessed mostly through KVM / secondary MMUs to appear younger than they should be. We do call the clear_young() notifier today, but only when attempting to evict the page, so we end up clearing young/accessed information less frequently for secondary MMUs than for mm PTEs, and therefore they appear younger and are less likely to be evicted. Therefore, memory that is *not* being accessed mostly by KVM will be evicted *more* frequently, worsening performance. ChromeOS observed a tab-open latency regression when enabling MGLRU with a setup that involved running a VM: Tab-open latency histogram (ms) Version p50 mean p95 p99 max base 1315 1198 2347 3454 10319 mglru 2559 1311 7399 12060 43758 fix 1119 926 2470 4211 6947 This series replaces the final non-selftest patchs from this series[1], which introduced a similar change (and a new MMU notifier) with KVM optimizations. I'll send a separate series (to Sean and Paolo) for the KVM optimizations. This series also makes proactive reclaim with MGLRU possible for KVM memory. I have verified that this functions correctly with the selftest from [1], but given that that test is a KVM selftest, I'll send it with the rest of the KVM optimizations later. Andrew, let me know if you'd like to take the test now anyway. [1]: https://lore.kernel.org/linux-mm/20240926013506.860253-18-jthoughton@google… This patch (of 2): The removed stats, MM_LEAF_OLD and MM_NONLEAF_TOTAL, are not very helpful and become more complicated to properly compute when adding test/clear_young() notifiers in MGLRU's mm walk. Link: https://lkml.kernel.org/r/20241019012940.3656292-1-jthoughton@google.com Link: https://lkml.kernel.org/r/20241019012940.3656292-2-jthoughton@google.com Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") Signed-off-by: Yu Zhao <yuzhao(a)google.com> Signed-off-by: James Houghton <jthoughton(a)google.com> Cc: Axel Rasmussen <axelrasmussen(a)google.com> Cc: David Matlack <dmatlack(a)google.com> Cc: David Rientjes <rientjes(a)google.com> Cc: David Stevens <stevensd(a)google.com> Cc: Oliver Upton <oliver.upton(a)linux.dev> Cc: Paolo Bonzini <pbonzini(a)redhat.com> Cc: Sean Christopherson <seanjc(a)google.com> Cc: Wei Xu <weixugc(a)google.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 17506e4a2835..9342e5692dab 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -458,9 +458,7 @@ struct lru_gen_folio { enum { MM_LEAF_TOTAL, /* total leaf entries */ - MM_LEAF_OLD, /* old leaf entries */ MM_LEAF_YOUNG, /* young leaf entries */ - MM_NONLEAF_TOTAL, /* total non-leaf entries */ MM_NONLEAF_FOUND, /* non-leaf entries found in Bloom filters */ MM_NONLEAF_ADDED, /* non-leaf entries added to Bloom filters */ NR_MM_STATS diff --git a/mm/vmscan.c b/mm/vmscan.c index eb4e8440c507..4f1d33e4b360 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3399,7 +3399,6 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, continue; if (!pte_young(ptent)) { - walk->mm_stats[MM_LEAF_OLD]++; continue; } @@ -3552,7 +3551,6 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, walk->mm_stats[MM_LEAF_TOTAL]++; if (!pmd_young(val)) { - walk->mm_stats[MM_LEAF_OLD]++; continue; } @@ -3564,8 +3562,6 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, continue; } - walk->mm_stats[MM_NONLEAF_TOTAL]++; - if (!walk->force_scan && should_clear_pmd_young()) { if (!pmd_young(val)) continue; @@ -5254,11 +5250,11 @@ static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, for (tier = 0; tier < MAX_NR_TIERS; tier++) { seq_printf(m, " %10d", tier); for (type = 0; type < ANON_AND_FILE; type++) { - const char *s = " "; + const char *s = "xxx"; unsigned long n[3] = {}; if (seq == max_seq) { - s = "RT "; + s = "RTx"; n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]); n[1] = READ_ONCE(lrugen->avg_total[type][tier]); } else if (seq == min_seq[type] || NR_HIST_GENS > 1) { @@ -5280,14 +5276,14 @@ static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, seq_puts(m, " "); for (i = 0; i < NR_MM_STATS; i++) { - const char *s = " "; + const char *s = "xxxx"; unsigned long n = 0; if (seq == max_seq && NR_HIST_GENS == 1) { - s = "LOYNFA"; + s = "TYFA"; n = READ_ONCE(mm_state->stats[hist][i]); } else if (seq != max_seq && NR_HIST_GENS > 1) { - s = "loynfa"; + s = "tyfa"; n = READ_ONCE(mm_state->stats[hist][i]); }

3 months, 3 weeks

1
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FAILED: patch "[PATCH] mm: avoid unconditional one-tick sleep when swapcache_prepare" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 01626a18230246efdcea322aa8f067e60ffe5ccd # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110506-octane-phosphate-f084@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 01626a18230246efdcea322aa8f067e60ffe5ccd Mon Sep 17 00:00:00 2001 From: Barry Song <baohua(a)kernel.org> Date: Fri, 27 Sep 2024 09:19:36 +1200 Subject: [PATCH] mm: avoid unconditional one-tick sleep when swapcache_prepare fails Commit 13ddaf26be32 ("mm/swap: fix race when skipping swapcache") introduced an unconditional one-tick sleep when `swapcache_prepare()` fails, which has led to reports of UI stuttering on latency-sensitive Android devices. To address this, we can use a waitqueue to wake up tasks that fail `swapcache_prepare()` sooner, instead of always sleeping for a full tick. While tasks may occasionally be woken by an unrelated `do_swap_page()`, this method is preferable to two scenarios: rapid re-entry into page faults, which can cause livelocks, and multiple millisecond sleeps, which visibly degrade user experience. Oven's testing shows that a single waitqueue resolves the UI stuttering issue. If a 'thundering herd' problem becomes apparent later, a waitqueue hash similar to `folio_wait_table[PAGE_WAIT_TABLE_SIZE]` for page bit locks can be introduced. [v-songbaohua(a)oppo.com: wake_up only when swapcache_wq waitqueue is active] Link: https://lkml.kernel.org/r/20241008130807.40833-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240926211936.75373-1-21cnbao@gmail.com Fixes: 13ddaf26be32 ("mm/swap: fix race when skipping swapcache") Signed-off-by: Barry Song <v-songbaohua(a)oppo.com> Reported-by: Oven Liyang <liyangouwen1(a)oppo.com> Tested-by: Oven Liyang <liyangouwen1(a)oppo.com> Cc: Kairui Song <kasong(a)tencent.com> Cc: "Huang, Ying" <ying.huang(a)intel.com> Cc: Yu Zhao <yuzhao(a)google.com> Cc: David Hildenbrand <david(a)redhat.com> Cc: Chris Li <chrisl(a)kernel.org> Cc: Hugh Dickins <hughd(a)google.com> Cc: Johannes Weiner <hannes(a)cmpxchg.org> Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org> Cc: Michal Hocko <mhocko(a)suse.com> Cc: Minchan Kim <minchan(a)kernel.org> Cc: Yosry Ahmed <yosryahmed(a)google.com> Cc: SeongJae Park <sj(a)kernel.org> Cc: Kalesh Singh <kaleshsingh(a)google.com> Cc: Suren Baghdasaryan <surenb(a)google.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/memory.c b/mm/memory.c index 3ccee51adfbb..bdf77a3ec47b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4187,6 +4187,8 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf) } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ +static DECLARE_WAIT_QUEUE_HEAD(swapcache_wq); + /* * We enter with non-exclusive mmap_lock (to exclude vma changes, * but allow concurrent faults), and pte mapped but not yet locked. @@ -4199,6 +4201,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; struct folio *swapcache, *folio = NULL; + DECLARE_WAITQUEUE(wait, current); struct page *page; struct swap_info_struct *si = NULL; rmap_t rmap_flags = RMAP_NONE; @@ -4297,7 +4300,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) * Relax a bit to prevent rapid * repeated page faults. */ + add_wait_queue(&swapcache_wq, &wait); schedule_timeout_uninterruptible(1); + remove_wait_queue(&swapcache_wq, &wait); goto out_page; } need_clear_cache = true; @@ -4604,8 +4609,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) pte_unmap_unlock(vmf->pte, vmf->ptl); out: /* Clear the swap cache pin for direct swapin after PTL unlock */ - if (need_clear_cache) + if (need_clear_cache) { swapcache_clear(si, entry, nr_pages); + if (waitqueue_active(&swapcache_wq)) + wake_up(&swapcache_wq); + } if (si) put_swap_device(si); return ret; @@ -4620,8 +4628,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) folio_unlock(swapcache); folio_put(swapcache); } - if (need_clear_cache) + if (need_clear_cache) { swapcache_clear(si, entry, nr_pages); + if (waitqueue_active(&swapcache_wq)) + wake_up(&swapcache_wq); + } if (si) put_swap_device(si); return ret;

3 months, 3 weeks

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FAILED: patch "[PATCH] mm: avoid unconditional one-tick sleep when swapcache_prepare" failed to apply to 6.6-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 01626a18230246efdcea322aa8f067e60ffe5ccd # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110505-january-napped-4f1b@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 01626a18230246efdcea322aa8f067e60ffe5ccd Mon Sep 17 00:00:00 2001 From: Barry Song <baohua(a)kernel.org> Date: Fri, 27 Sep 2024 09:19:36 +1200 Subject: [PATCH] mm: avoid unconditional one-tick sleep when swapcache_prepare fails Commit 13ddaf26be32 ("mm/swap: fix race when skipping swapcache") introduced an unconditional one-tick sleep when `swapcache_prepare()` fails, which has led to reports of UI stuttering on latency-sensitive Android devices. To address this, we can use a waitqueue to wake up tasks that fail `swapcache_prepare()` sooner, instead of always sleeping for a full tick. While tasks may occasionally be woken by an unrelated `do_swap_page()`, this method is preferable to two scenarios: rapid re-entry into page faults, which can cause livelocks, and multiple millisecond sleeps, which visibly degrade user experience. Oven's testing shows that a single waitqueue resolves the UI stuttering issue. If a 'thundering herd' problem becomes apparent later, a waitqueue hash similar to `folio_wait_table[PAGE_WAIT_TABLE_SIZE]` for page bit locks can be introduced. [v-songbaohua(a)oppo.com: wake_up only when swapcache_wq waitqueue is active] Link: https://lkml.kernel.org/r/20241008130807.40833-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240926211936.75373-1-21cnbao@gmail.com Fixes: 13ddaf26be32 ("mm/swap: fix race when skipping swapcache") Signed-off-by: Barry Song <v-songbaohua(a)oppo.com> Reported-by: Oven Liyang <liyangouwen1(a)oppo.com> Tested-by: Oven Liyang <liyangouwen1(a)oppo.com> Cc: Kairui Song <kasong(a)tencent.com> Cc: "Huang, Ying" <ying.huang(a)intel.com> Cc: Yu Zhao <yuzhao(a)google.com> Cc: David Hildenbrand <david(a)redhat.com> Cc: Chris Li <chrisl(a)kernel.org> Cc: Hugh Dickins <hughd(a)google.com> Cc: Johannes Weiner <hannes(a)cmpxchg.org> Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org> Cc: Michal Hocko <mhocko(a)suse.com> Cc: Minchan Kim <minchan(a)kernel.org> Cc: Yosry Ahmed <yosryahmed(a)google.com> Cc: SeongJae Park <sj(a)kernel.org> Cc: Kalesh Singh <kaleshsingh(a)google.com> Cc: Suren Baghdasaryan <surenb(a)google.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/memory.c b/mm/memory.c index 3ccee51adfbb..bdf77a3ec47b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4187,6 +4187,8 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf) } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ +static DECLARE_WAIT_QUEUE_HEAD(swapcache_wq); + /* * We enter with non-exclusive mmap_lock (to exclude vma changes, * but allow concurrent faults), and pte mapped but not yet locked. @@ -4199,6 +4201,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; struct folio *swapcache, *folio = NULL; + DECLARE_WAITQUEUE(wait, current); struct page *page; struct swap_info_struct *si = NULL; rmap_t rmap_flags = RMAP_NONE; @@ -4297,7 +4300,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) * Relax a bit to prevent rapid * repeated page faults. */ + add_wait_queue(&swapcache_wq, &wait); schedule_timeout_uninterruptible(1); + remove_wait_queue(&swapcache_wq, &wait); goto out_page; } need_clear_cache = true; @@ -4604,8 +4609,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) pte_unmap_unlock(vmf->pte, vmf->ptl); out: /* Clear the swap cache pin for direct swapin after PTL unlock */ - if (need_clear_cache) + if (need_clear_cache) { swapcache_clear(si, entry, nr_pages); + if (waitqueue_active(&swapcache_wq)) + wake_up(&swapcache_wq); + } if (si) put_swap_device(si); return ret; @@ -4620,8 +4628,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) folio_unlock(swapcache); folio_put(swapcache); } - if (need_clear_cache) + if (need_clear_cache) { swapcache_clear(si, entry, nr_pages); + if (waitqueue_active(&swapcache_wq)) + wake_up(&swapcache_wq); + } if (si) put_swap_device(si); return ret;

3 months, 3 weeks

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FAILED: patch "[PATCH] mm: avoid unconditional one-tick sleep when swapcache_prepare" failed to apply to 6.11-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.11-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.11.y git checkout FETCH_HEAD git cherry-pick -x 01626a18230246efdcea322aa8f067e60ffe5ccd # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2024110504-water-overarch-bbef@gregkh' --subject-prefix 'PATCH 6.11.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 01626a18230246efdcea322aa8f067e60ffe5ccd Mon Sep 17 00:00:00 2001 From: Barry Song <baohua(a)kernel.org> Date: Fri, 27 Sep 2024 09:19:36 +1200 Subject: [PATCH] mm: avoid unconditional one-tick sleep when swapcache_prepare fails Commit 13ddaf26be32 ("mm/swap: fix race when skipping swapcache") introduced an unconditional one-tick sleep when `swapcache_prepare()` fails, which has led to reports of UI stuttering on latency-sensitive Android devices. To address this, we can use a waitqueue to wake up tasks that fail `swapcache_prepare()` sooner, instead of always sleeping for a full tick. While tasks may occasionally be woken by an unrelated `do_swap_page()`, this method is preferable to two scenarios: rapid re-entry into page faults, which can cause livelocks, and multiple millisecond sleeps, which visibly degrade user experience. Oven's testing shows that a single waitqueue resolves the UI stuttering issue. If a 'thundering herd' problem becomes apparent later, a waitqueue hash similar to `folio_wait_table[PAGE_WAIT_TABLE_SIZE]` for page bit locks can be introduced. [v-songbaohua(a)oppo.com: wake_up only when swapcache_wq waitqueue is active] Link: https://lkml.kernel.org/r/20241008130807.40833-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240926211936.75373-1-21cnbao@gmail.com Fixes: 13ddaf26be32 ("mm/swap: fix race when skipping swapcache") Signed-off-by: Barry Song <v-songbaohua(a)oppo.com> Reported-by: Oven Liyang <liyangouwen1(a)oppo.com> Tested-by: Oven Liyang <liyangouwen1(a)oppo.com> Cc: Kairui Song <kasong(a)tencent.com> Cc: "Huang, Ying" <ying.huang(a)intel.com> Cc: Yu Zhao <yuzhao(a)google.com> Cc: David Hildenbrand <david(a)redhat.com> Cc: Chris Li <chrisl(a)kernel.org> Cc: Hugh Dickins <hughd(a)google.com> Cc: Johannes Weiner <hannes(a)cmpxchg.org> Cc: Matthew Wilcox (Oracle) <willy(a)infradead.org> Cc: Michal Hocko <mhocko(a)suse.com> Cc: Minchan Kim <minchan(a)kernel.org> Cc: Yosry Ahmed <yosryahmed(a)google.com> Cc: SeongJae Park <sj(a)kernel.org> Cc: Kalesh Singh <kaleshsingh(a)google.com> Cc: Suren Baghdasaryan <surenb(a)google.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> diff --git a/mm/memory.c b/mm/memory.c index 3ccee51adfbb..bdf77a3ec47b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4187,6 +4187,8 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf) } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ +static DECLARE_WAIT_QUEUE_HEAD(swapcache_wq); + /* * We enter with non-exclusive mmap_lock (to exclude vma changes, * but allow concurrent faults), and pte mapped but not yet locked. @@ -4199,6 +4201,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; struct folio *swapcache, *folio = NULL; + DECLARE_WAITQUEUE(wait, current); struct page *page; struct swap_info_struct *si = NULL; rmap_t rmap_flags = RMAP_NONE; @@ -4297,7 +4300,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) * Relax a bit to prevent rapid * repeated page faults. */ + add_wait_queue(&swapcache_wq, &wait); schedule_timeout_uninterruptible(1); + remove_wait_queue(&swapcache_wq, &wait); goto out_page; } need_clear_cache = true; @@ -4604,8 +4609,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) pte_unmap_unlock(vmf->pte, vmf->ptl); out: /* Clear the swap cache pin for direct swapin after PTL unlock */ - if (need_clear_cache) + if (need_clear_cache) { swapcache_clear(si, entry, nr_pages); + if (waitqueue_active(&swapcache_wq)) + wake_up(&swapcache_wq); + } if (si) put_swap_device(si); return ret; @@ -4620,8 +4628,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) folio_unlock(swapcache); folio_put(swapcache); } - if (need_clear_cache) + if (need_clear_cache) { swapcache_clear(si, entry, nr_pages); + if (waitqueue_active(&swapcache_wq)) + wake_up(&swapcache_wq); + } if (si) put_swap_device(si); return ret;

3 months, 3 weeks

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