Secondary MMUs are currently consulted for access/age information at eviction time, but before then, we don't get accurate age information. That is, pages that are mostly accessed through a secondary MMU (like guest memory, used by KVM) will always just proceed down to the oldest generation, and then at eviction time, if KVM reports the page to be young, the page will be activated/promoted back to the youngest generation.

Do not do look around if there is a secondary MMU we have to interact with.

The added feature bit (0x8), if disabled, will make MGLRU behave as if there are no secondary MMUs subscribed to MMU notifiers except at eviction time.

Suggested-by: Yu Zhao yuzhao@google.com Signed-off-by: James Houghton jthoughton@google.com --- Documentation/admin-guide/mm/multigen_lru.rst | 6 +- include/linux/mmzone.h | 6 +- mm/rmap.c | 9 +- mm/vmscan.c | 144 ++++++++++++++---- 4 files changed, 123 insertions(+), 42 deletions(-)

diff --git a/Documentation/admin-guide/mm/multigen_lru.rst b/Documentation/admin-guide/mm/multigen_lru.rst index 33e068830497..1e578e0c4c0c 100644 --- a/Documentation/admin-guide/mm/multigen_lru.rst +++ b/Documentation/admin-guide/mm/multigen_lru.rst @@ -48,6 +48,10 @@ Values Components verified on x86 varieties other than Intel and AMD. If it is disabled, the multi-gen LRU will suffer a negligible performance degradation. +0x0008 Continuously clear the accessed bit in secondary MMU page + tables instead of waiting until eviction time. This results in + accurate page age information for pages that are mainly used by + a secondary MMU. [yYnN] Apply to all the components above. ====== ===============================================================

@@ -56,7 +60,7 @@ E.g.,

echo y >/sys/kernel/mm/lru_gen/enabled cat /sys/kernel/mm/lru_gen/enabled - 0x0007 + 0x000f echo 5 >/sys/kernel/mm/lru_gen/enabled cat /sys/kernel/mm/lru_gen/enabled 0x0005 diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 8f9c9590a42c..869824ef5f3b 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -400,6 +400,7 @@ enum { LRU_GEN_CORE, LRU_GEN_MM_WALK, LRU_GEN_NONLEAF_YOUNG, + LRU_GEN_SECONDARY_MMU_WALK, NR_LRU_GEN_CAPS };

@@ -557,7 +558,7 @@ 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); @@ -576,8 +577,9 @@ 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 e8fc5ecb59b2..24a3ff639919 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -870,13 +870,10 @@ static bool folio_referenced_one(struct folio *folio, continue; }

- 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 d55e8d07ffc4..0d89f712f45c 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> @@ -2579,6 +2580,12 @@ static bool should_clear_pmd_young(void) return arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG); }

+static bool should_walk_secondary_mmu(void) +{ + return IS_ENABLED(CONFIG_LRU_GEN_WALKS_SECONDARY_MMU) && + get_cap(LRU_GEN_SECONDARY_MMU_WALK); +} + /****************************************************************************** * shorthand helpers ******************************************************************************/ @@ -3276,7 +3283,8 @@ 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);

@@ -3291,10 +3299,15 @@ static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned if (WARN_ON_ONCE(!pfn_valid(pfn))) return -1;

+ /* try to avoid unnecessary memory loads */ + 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);

@@ -3309,6 +3322,10 @@ static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned if (WARN_ON_ONCE(!pfn_valid(pfn))) return -1;

+ /* try to avoid unnecessary memory loads */ + if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + return -1; + return pfn; }

@@ -3317,10 +3334,6 @@ 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; @@ -3343,6 +3356,32 @@ static bool suitable_to_scan(int total, int young) return young * n >= total; }

+static bool lru_gen_notifier_test_young(struct mm_struct *mm, + unsigned long addr) +{ + return should_walk_secondary_mmu() && mmu_notifier_test_young(mm, addr); +} + +static bool lru_gen_notifier_clear_young(struct mm_struct *mm, + unsigned long start, + unsigned long end) +{ + return should_walk_secondary_mmu() && + mmu_notifier_clear_young(mm, start, end); +} + +static bool lru_gen_pmdp_test_and_clear_young(struct vm_area_struct *vma, + unsigned long addr, + pmd_t *pmd) +{ + bool young = pmdp_test_and_clear_young(vma, addr, pmd); + + if (lru_gen_notifier_clear_young(vma->vm_mm, addr, addr + PMD_SIZE)) + young = true; + + return young; +} + static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, struct mm_walk *args) { @@ -3357,8 +3396,9 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); DEFINE_MAX_SEQ(walk->lruvec); int old_gen, new_gen = lru_gen_from_seq(max_seq); + struct mm_struct *mm = args->mm;

- pte = pte_offset_map_nolock(args->mm, pmd, start & PMD_MASK, &ptl); + pte = pte_offset_map_nolock(mm, pmd, start & PMD_MASK, &ptl); if (!pte) return false; if (!spin_trylock(ptl)) { @@ -3376,11 +3416,12 @@ 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)) { + if (!pte_young(ptent) && + !lru_gen_notifier_test_young(mm, addr)) { walk->mm_stats[MM_LEAF_OLD]++; continue; } @@ -3389,8 +3430,9 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, if (!folio) continue;

- if (!ptep_test_and_clear_young(args->vma, addr, pte + i)) - VM_WARN_ON_ONCE(true); + lru_gen_notifier_clear_young(mm, addr, addr + PAGE_SIZE); + if (pte_young(ptent)) + ptep_test_and_clear_young(args->vma, addr, pte + i);

young++; walk->mm_stats[MM_LEAF_YOUNG]++; @@ -3456,22 +3498,25 @@ 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) - goto next; - - if (!pmd_trans_huge(pmd[i])) { - if (should_clear_pmd_young()) + if (pmd_present(pmd[i]) && !pmd_trans_huge(pmd[i])) { + if (should_clear_pmd_young() && + !should_walk_secondary_mmu()) 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 (!lru_gen_pmdp_test_and_clear_young(vma, addr, pmd + i)) { + walk->mm_stats[MM_LEAF_OLD]++; goto next; + }

walk->mm_stats[MM_LEAF_YOUNG]++;

@@ -3528,19 +3573,18 @@ 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)) { - walk->mm_stats[MM_LEAF_OLD]++; + if (pfn == -1) continue; - }

- /* try to avoid unnecessary memory loads */ - if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) + if (!pmd_young(val) && !mm_has_notifiers(args->mm)) { + walk->mm_stats[MM_LEAF_OLD]++; continue; + }

walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); continue; @@ -3548,7 +3592,7 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,

walk->mm_stats[MM_NONLEAF_TOTAL]++;

- if (should_clear_pmd_young()) { + if (should_clear_pmd_young() && !should_walk_secondary_mmu()) { if (!pmd_young(val)) continue;

@@ -3994,6 +4038,26 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) * rmap/PT walk feedback ******************************************************************************/

+static bool should_look_around(struct vm_area_struct *vma, unsigned long addr, + pte_t *pte, int *young) +{ + bool secondary_was_young = + mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE); + + /* + * Look around if (1) the PTE is young and (2) we do not need to + * consult any secondary MMUs. + */ + if (pte_young(ptep_get(pte))) { + ptep_test_and_clear_young(vma, addr, pte); + *young = true; + return !mm_has_notifiers(vma->vm_mm); + } else if (secondary_was_young) + *young = true; + + return false; +} + /* * This function exploits spatial locality when shrink_folio_list() walks the * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. If @@ -4001,7 +4065,7 @@ 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; @@ -4019,16 +4083,20 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) struct lru_gen_mm_state *mm_state = get_mm_state(lruvec); DEFINE_MAX_SEQ(lruvec); int old_gen, new_gen = lru_gen_from_seq(max_seq); + struct mm_struct *mm = pvmw->vma->vm_mm;

lockdep_assert_held(pvmw->ptl); VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio);

+ if (!should_look_around(vma, addr, pte, &young)) + return young; + if (spin_is_contended(pvmw->ptl)) - return; + return young;

/* exclude special VMAs containing anon pages from COW */ if (vma->vm_flags & VM_SPECIAL) - return; + return young;

/* avoid taking the LRU lock under the PTL when possible */ walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL; @@ -4036,6 +4104,9 @@ 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 young; + if (end - start > MIN_LRU_BATCH * PAGE_SIZE) { if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2) end = start + MIN_LRU_BATCH * PAGE_SIZE; @@ -4049,7 +4120,7 @@ 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 young;

arch_enter_lazy_mmu_mode();

@@ -4059,19 +4130,21 @@ 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)) + if (!pte_young(ptent) && + !lru_gen_notifier_test_young(mm, addr)) 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); + lru_gen_notifier_clear_young(mm, addr, addr + PAGE_SIZE); + if (pte_young(ptent)) + ptep_test_and_clear_young(vma, addr, pte + i);

young++;

@@ -4101,6 +4174,8 @@ 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 young; }

/****************************************************************************** @@ -5137,6 +5212,9 @@ static ssize_t enabled_show(struct kobject *kobj, struct kobj_attribute *attr, c if (should_clear_pmd_young()) caps |= BIT(LRU_GEN_NONLEAF_YOUNG);

+ if (should_walk_secondary_mmu()) + caps |= BIT(LRU_GEN_SECONDARY_MMU_WALK); + return sysfs_emit(buf, "0x%04x\n", caps); }

For implementation mmu_notifier_{test,clear}_young, the KVM memslot walker used to take the MMU lock for us. Now make the architectures take it themselves.

Don't relax locking for any architecture except powerpc e500; its implementations of kvm_age_gfn and kvm_test_age_gfn simply return false, so there is no need to grab the KVM MMU lock.

Signed-off-by: James Houghton jthoughton@google.com --- arch/arm64/kvm/mmu.c | 30 ++++++++++++++++++++++-------- arch/loongarch/kvm/mmu.c | 20 +++++++++++++++----- arch/mips/kvm/mmu.c | 21 ++++++++++++++++----- arch/powerpc/kvm/book3s.c | 14 ++++++++++++-- arch/riscv/kvm/mmu.c | 26 ++++++++++++++++++++------ arch/x86/kvm/mmu/mmu.c | 8 ++++++++ virt/kvm/kvm_main.c | 4 ++-- 7 files changed, 95 insertions(+), 28 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 8bcab0cc3fe9..8337009dde77 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1773,25 +1773,39 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range) bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { u64 size = (range->end - range->start) << PAGE_SHIFT; + bool young = false; + + write_lock(&kvm->mmu_lock);

if (!kvm->arch.mmu.pgt) - return false; + goto out;

- return kvm_pgtable_stage2_test_clear_young(kvm->arch.mmu.pgt, - range->start << PAGE_SHIFT, - size, true); + young = kvm_pgtable_stage2_test_clear_young(kvm->arch.mmu.pgt, + range->start << PAGE_SHIFT, + size, true); + +out: + write_unlock(&kvm->mmu_lock); + return young; }

bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { u64 size = (range->end - range->start) << PAGE_SHIFT; + bool young = false; + + write_lock(&kvm->mmu_lock);

if (!kvm->arch.mmu.pgt) - return false; + goto out;

- return kvm_pgtable_stage2_test_clear_young(kvm->arch.mmu.pgt, - range->start << PAGE_SHIFT, - size, false); + young = kvm_pgtable_stage2_test_clear_young(kvm->arch.mmu.pgt, + range->start << PAGE_SHIFT, + size, false); + +out: + write_unlock(&kvm->mmu_lock); + return young; }

phys_addr_t kvm_mmu_get_httbr(void) diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c index 98883aa23ab8..5eb262bcf6b0 100644 --- a/arch/loongarch/kvm/mmu.c +++ b/arch/loongarch/kvm/mmu.c @@ -497,24 +497,34 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range) bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { kvm_ptw_ctx ctx; + bool young; + + spin_lock(&kvm->mmu_lock);

ctx.flag = 0; ctx.ops = kvm_mkold_pte; kvm_ptw_prepare(kvm, &ctx);

- return kvm_ptw_top(kvm->arch.pgd, range->start << PAGE_SHIFT, + young = kvm_ptw_top(kvm->arch.pgd, range->start << PAGE_SHIFT, range->end << PAGE_SHIFT, &ctx); + + spin_unlock(&kvm->mmu_lock); + return young; }

bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { gpa_t gpa = range->start << PAGE_SHIFT; - kvm_pte_t *ptep = kvm_populate_gpa(kvm, NULL, gpa, 0); + kvm_pte_t *ptep; + bool young;

- if (ptep && kvm_pte_present(NULL, ptep) && kvm_pte_young(*ptep)) - return true; + spin_lock(&kvm->mmu_lock); + ptep = kvm_populate_gpa(kvm, NULL, gpa, 0);

- return false; + young = ptep && kvm_pte_present(NULL, ptep) && kvm_pte_young(*ptep); + + spin_unlock(&kvm->mmu_lock); + return young; }

/* diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c index c17157e700c0..db3b7cf22db1 100644 --- a/arch/mips/kvm/mmu.c +++ b/arch/mips/kvm/mmu.c @@ -446,17 +446,28 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)

bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { - return kvm_mips_mkold_gpa_pt(kvm, range->start, range->end); + bool young; + + spin_lock(&kvm->mmu_lock); + young = kvm_mips_mkold_gpa_pt(kvm, range->start, range->end); + spin_unlock(&kvm->mmu_lock); + return young; }

bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { gpa_t gpa = range->start << PAGE_SHIFT; - pte_t *gpa_pte = kvm_mips_pte_for_gpa(kvm, NULL, gpa); + pte_t *gpa_pte; + bool young = false;

- if (!gpa_pte) - return false; - return pte_young(*gpa_pte); + spin_lock(&kvm->mmu_lock); + gpa_pte = kvm_mips_pte_for_gpa(kvm, NULL, gpa); + + if (gpa_pte) + young = pte_young(*gpa_pte); + + spin_unlock(&kvm->mmu_lock); + return young; }

/** diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c index ff6c38373957..f503ab9ac3a5 100644 --- a/arch/powerpc/kvm/book3s.c +++ b/arch/powerpc/kvm/book3s.c @@ -887,12 +887,22 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)

bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { - return kvm->arch.kvm_ops->age_gfn(kvm, range); + bool young; + + spin_lock(&kvm->mmu_lock); + young = kvm->arch.kvm_ops->age_gfn(kvm, range); + spin_unlock(&kvm->mmu_lock); + return young; }

bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { - return kvm->arch.kvm_ops->test_age_gfn(kvm, range); + bool young; + + spin_lock(&kvm->mmu_lock); + young = kvm->arch.kvm_ops->test_age_gfn(kvm, range); + spin_unlock(&kvm->mmu_lock); + return young; }

int kvmppc_core_init_vm(struct kvm *kvm) diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c index b63650f9b966..c78abe8041fb 100644 --- a/arch/riscv/kvm/mmu.c +++ b/arch/riscv/kvm/mmu.c @@ -555,17 +555,24 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) pte_t *ptep; u32 ptep_level = 0; u64 size = (range->end - range->start) << PAGE_SHIFT; + bool young = false; + + spin_lock(&kvm->mmu_lock);

if (!kvm->arch.pgd) - return false; + goto out;

WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);

if (!gstage_get_leaf_entry(kvm, range->start << PAGE_SHIFT, &ptep, &ptep_level)) - return false; + goto out; + + young = ptep_test_and_clear_young(NULL, 0, ptep);

- return ptep_test_and_clear_young(NULL, 0, ptep); +out: + spin_unlock(&kvm->mmu_lock); + return young; }

bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) @@ -573,17 +580,24 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) pte_t *ptep; u32 ptep_level = 0; u64 size = (range->end - range->start) << PAGE_SHIFT; + bool young = false; + + spin_lock(&kvm->mmu_lock);

if (!kvm->arch.pgd) - return false; + goto out;

WARN_ON(size != PAGE_SIZE && size != PMD_SIZE && size != PUD_SIZE);

if (!gstage_get_leaf_entry(kvm, range->start << PAGE_SHIFT, &ptep, &ptep_level)) - return false; + goto out; + + young = pte_young(ptep_get(ptep));

- return pte_young(ptep_get(ptep)); +out: + spin_unlock(&kvm->mmu_lock); + return young; }

int kvm_riscv_gstage_map(struct kvm_vcpu *vcpu, diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 662f62dfb2aa..6a2a557c2c31 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1630,12 +1630,16 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { bool young = false;

+ write_lock(&kvm->mmu_lock); + if (kvm_memslots_have_rmaps(kvm)) young = kvm_handle_gfn_range(kvm, range, kvm_age_rmap);

if (tdp_mmu_enabled) young |= kvm_tdp_mmu_age_gfn_range(kvm, range);

+ write_unlock(&kvm->mmu_lock); + return young; }

@@ -1643,12 +1647,16 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) { bool young = false;

+ write_lock(&kvm->mmu_lock); + if (kvm_memslots_have_rmaps(kvm)) young = kvm_handle_gfn_range(kvm, range, kvm_test_age_rmap);

if (tdp_mmu_enabled) young |= kvm_tdp_mmu_test_age_gfn(kvm, range);

+ write_unlock(&kvm->mmu_lock); + return young; }

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index d197b6725cb3..8d2d3acf18d8 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -901,7 +901,7 @@ static int kvm_mmu_notifier_clear_young(struct mmu_notifier *mn, * more sophisticated heuristic later. */ return kvm_handle_hva_range_no_flush(mn, start, end, - kvm_age_gfn, false); + kvm_age_gfn, true); }

static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn, @@ -911,7 +911,7 @@ static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn, trace_kvm_test_age_hva(address);

return kvm_handle_hva_range_no_flush(mn, address, address + 1, - kvm_test_age_gfn, false); + kvm_test_age_gfn, true); }

static void kvm_mmu_notifier_release(struct mmu_notifier *mn,

Replace the MMU write locks for read locks.

Grabbing the read lock instead of the write lock is safe because the only requirement we have is that the stage-2 page tables do not get deallocated while we are walking them. The stage2_age_walker() callback is safe to race with itself; update the comment to reflect the synchronization change.

Signed-off-by: James Houghton jthoughton@google.com --- arch/arm64/kvm/hyp/pgtable.c | 9 ++++----- arch/arm64/kvm/mmu.c | 8 ++++---- 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index 9e2bbee77491..eabb07c66a07 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -1319,10 +1319,8 @@ static int stage2_age_walker(const struct kvm_pgtable_visit_ctx *ctx, data->young = true;

/* - * stage2_age_walker() is always called while holding the MMU lock for - * write, so this will always succeed. Nonetheless, this deliberately - * follows the race detection pattern of the other stage-2 walkers in - * case the locking mechanics of the MMU notifiers is ever changed. + * This walk may not be exclusive; the PTE is permitted to change + * from under us. */ if (data->mkold && !stage2_try_set_pte(ctx, new)) return -EAGAIN; @@ -1345,7 +1343,8 @@ bool kvm_pgtable_stage2_test_clear_young(struct kvm_pgtable *pgt, u64 addr, struct kvm_pgtable_walker walker = { .cb = stage2_age_walker, .arg = &data, - .flags = KVM_PGTABLE_WALK_LEAF, + .flags = KVM_PGTABLE_WALK_LEAF | + KVM_PGTABLE_WALK_SHARED, };

WARN_ON(kvm_pgtable_walk(pgt, addr, size, &walker)); diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 8337009dde77..40e7427462a7 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1775,7 +1775,7 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) u64 size = (range->end - range->start) << PAGE_SHIFT; bool young = false;

- write_lock(&kvm->mmu_lock); + read_lock(&kvm->mmu_lock);

if (!kvm->arch.mmu.pgt) goto out; @@ -1785,7 +1785,7 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) size, true);

out: - write_unlock(&kvm->mmu_lock); + read_unlock(&kvm->mmu_lock); return young; }

@@ -1794,7 +1794,7 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) u64 size = (range->end - range->start) << PAGE_SHIFT; bool young = false;

- write_lock(&kvm->mmu_lock); + read_lock(&kvm->mmu_lock);

if (!kvm->arch.mmu.pgt) goto out; @@ -1804,7 +1804,7 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) size, false);

out: - write_unlock(&kvm->mmu_lock); + read_unlock(&kvm->mmu_lock); return young; }

This test now has two modes of operation: 1. (default) To check how much vCPU performance was affected by access tracking (previously existed, now supports MGLRU aging). 2. (-p) To also benchmark how fast MGLRU can do aging while vCPUs are faulting in memory.

Mode (1) also serves as a way to verify that aging is working properly for pages only accessed by KVM. It will fail if one does not have the 0x8 lru_gen feature bit.

To support MGLRU, the test creates a memory cgroup, moves itself into it, then uses the lru_gen debugfs output to track memory in that cgroup. The logic to parse the lru_gen debugfs output has been put into selftests/kvm/lib/lru_gen_util.c.

Co-developed-by: Axel Rasmussen axelrasmussen@google.com Signed-off-by: Axel Rasmussen axelrasmussen@google.com Signed-off-by: James Houghton jthoughton@google.com --- tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/access_tracking_perf_test.c | 365 ++++++++++++++-- .../selftests/kvm/include/lru_gen_util.h | 55 +++ .../testing/selftests/kvm/lib/lru_gen_util.c | 391 ++++++++++++++++++ 4 files changed, 782 insertions(+), 30 deletions(-) create mode 100644 tools/testing/selftests/kvm/include/lru_gen_util.h create mode 100644 tools/testing/selftests/kvm/lib/lru_gen_util.c

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index ce8ff8e8ce3a..86415f524c48 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -22,6 +22,7 @@ LIBKVM += lib/elf.c LIBKVM += lib/guest_modes.c LIBKVM += lib/io.c LIBKVM += lib/kvm_util.c +LIBKVM += lib/lru_gen_util.c LIBKVM += lib/memstress.c LIBKVM += lib/guest_sprintf.c LIBKVM += lib/rbtree.c diff --git a/tools/testing/selftests/kvm/access_tracking_perf_test.c b/tools/testing/selftests/kvm/access_tracking_perf_test.c index 3c7defd34f56..15be99ff3bdc 100644 --- a/tools/testing/selftests/kvm/access_tracking_perf_test.c +++ b/tools/testing/selftests/kvm/access_tracking_perf_test.c @@ -38,6 +38,7 @@ #include <inttypes.h> #include <limits.h> #include <pthread.h> +#include <stdio.h> #include <sys/mman.h> #include <sys/types.h> #include <sys/stat.h> @@ -47,6 +48,20 @@ #include "memstress.h" #include "guest_modes.h" #include "processor.h" +#include "lru_gen_util.h" + +static const char *TEST_MEMCG_NAME = "access_tracking_perf_test"; +static const int LRU_GEN_ENABLED = 0x1; +static const int LRU_GEN_MM_WALK = 0x2; +static const int LRU_GEN_SECONDARY_MMU_WALK = 0x8; +static const char *CGROUP_PROCS = "cgroup.procs"; +/* + * If using MGLRU, this test assumes a cgroup v2 or cgroup v1 memory hierarchy + * is mounted at cgroup_root. + * + * Can be changed with -r. + */ +static const char *cgroup_root = "/sys/fs/cgroup";

/* Global variable used to synchronize all of the vCPU threads. */ static int iteration; @@ -62,6 +77,9 @@ static enum { /* The iteration that was last completed by each vCPU. */ static int vcpu_last_completed_iteration[KVM_MAX_VCPUS];

+/* The time at which the last iteration was completed */ +static struct timespec vcpu_last_completed_time[KVM_MAX_VCPUS]; + /* Whether to overlap the regions of memory vCPUs access. */ static bool overlap_memory_access;

@@ -74,6 +92,12 @@ struct test_params {

/* The number of vCPUs to create in the VM. */ int nr_vcpus; + + /* Whether to use lru_gen aging instead of idle page tracking. */ + bool lru_gen; + + /* Whether to test the performance of aging itself. */ + bool benchmark_lru_gen; };

static uint64_t pread_uint64(int fd, const char *filename, uint64_t index) @@ -89,6 +113,50 @@ static uint64_t pread_uint64(int fd, const char *filename, uint64_t index)

}

+static void write_file_long(const char *path, long v) +{ + FILE *f; + + f = fopen(path, "w"); + TEST_ASSERT(f, "fopen(%s) failed", path); + TEST_ASSERT(fprintf(f, "%ld\n", v) > 0, + "fprintf to %s failed", path); + TEST_ASSERT(!fclose(f), "fclose(%s) failed", path); +} + +static char *path_join(const char *parent, const char *child) +{ + char *out = NULL; + + return asprintf(&out, "%s/%s", parent, child) >= 0 ? out : NULL; +} + +static char *memcg_path(const char *memcg) +{ + return path_join(cgroup_root, memcg); +} + +static char *memcg_file_path(const char *memcg, const char *file) +{ + char *mp = memcg_path(memcg); + char *fp; + + if (!mp) + return NULL; + fp = path_join(mp, file); + free(mp); + return fp; +} + +static void move_to_memcg(const char *memcg, pid_t pid) +{ + char *procs = memcg_file_path(memcg, CGROUP_PROCS); + + TEST_ASSERT(procs, "Failed to construct cgroup.procs path"); + write_file_long(procs, pid); + free(procs); +} + #define PAGEMAP_PRESENT (1ULL << 63) #define PAGEMAP_PFN_MASK ((1ULL << 55) - 1)

@@ -242,6 +310,8 @@ static void vcpu_thread_main(struct memstress_vcpu_args *vcpu_args) };

vcpu_last_completed_iteration[vcpu_idx] = current_iteration; + clock_gettime(CLOCK_MONOTONIC, + &vcpu_last_completed_time[vcpu_idx]); } }

@@ -253,38 +323,68 @@ static void spin_wait_for_vcpu(int vcpu_idx, int target_iteration) } }

+static bool all_vcpus_done(int target_iteration, int nr_vcpus) +{ + for (int i = 0; i < nr_vcpus; ++i) + if (READ_ONCE(vcpu_last_completed_iteration[i]) != + target_iteration) + return false; + + return true; +} + /* The type of memory accesses to perform in the VM. */ enum access_type { ACCESS_READ, ACCESS_WRITE, };

-static void run_iteration(struct kvm_vm *vm, int nr_vcpus, const char *description) +static void run_iteration(struct kvm_vm *vm, int nr_vcpus, const char *description, + bool wait) { - struct timespec ts_start; - struct timespec ts_elapsed; int next_iteration, i;

/* Kick off the vCPUs by incrementing iteration. */ next_iteration = ++iteration;

- clock_gettime(CLOCK_MONOTONIC, &ts_start); - /* Wait for all vCPUs to finish the iteration. */ - for (i = 0; i < nr_vcpus; i++) - spin_wait_for_vcpu(i, next_iteration); + if (wait) { + struct timespec ts_start; + struct timespec ts_elapsed; + + clock_gettime(CLOCK_MONOTONIC, &ts_start);

- ts_elapsed = timespec_elapsed(ts_start); - pr_info("%-30s: %ld.%09lds\n", - description, ts_elapsed.tv_sec, ts_elapsed.tv_nsec); + for (i = 0; i < nr_vcpus; i++) + spin_wait_for_vcpu(i, next_iteration); + + ts_elapsed = timespec_elapsed(ts_start); + + pr_info("%-30s: %ld.%09lds\n", + description, ts_elapsed.tv_sec, ts_elapsed.tv_nsec); + } else + pr_info("%-30s\n", description); }

-static void access_memory(struct kvm_vm *vm, int nr_vcpus, - enum access_type access, const char *description) +static void _access_memory(struct kvm_vm *vm, int nr_vcpus, + enum access_type access, const char *description, + bool wait) { memstress_set_write_percent(vm, (access == ACCESS_READ) ? 0 : 100); iteration_work = ITERATION_ACCESS_MEMORY; - run_iteration(vm, nr_vcpus, description); + run_iteration(vm, nr_vcpus, description, wait); +} + +static void access_memory(struct kvm_vm *vm, int nr_vcpus, + enum access_type access, const char *description) +{ + return _access_memory(vm, nr_vcpus, access, description, true); +} + +static void access_memory_async(struct kvm_vm *vm, int nr_vcpus, + enum access_type access, + const char *description) +{ + return _access_memory(vm, nr_vcpus, access, description, false); }

static void mark_memory_idle(struct kvm_vm *vm, int nr_vcpus) @@ -297,19 +397,111 @@ static void mark_memory_idle(struct kvm_vm *vm, int nr_vcpus) */ pr_debug("Marking VM memory idle (slow)...\n"); iteration_work = ITERATION_MARK_IDLE; - run_iteration(vm, nr_vcpus, "Mark memory idle"); + run_iteration(vm, nr_vcpus, "Mark memory idle", true); }

-static void run_test(enum vm_guest_mode mode, void *arg) +static void create_memcg(const char *memcg) +{ + const char *full_memcg_path = memcg_path(memcg); + int ret; + + TEST_ASSERT(full_memcg_path, "Failed to construct full memcg path"); +retry: + ret = mkdir(full_memcg_path, 0755); + if (ret && errno == EEXIST) { + TEST_ASSERT(!rmdir(full_memcg_path), + "Found existing memcg at %s, but rmdir failed", + full_memcg_path); + goto retry; + } + TEST_ASSERT(!ret, "Creating the memcg failed: mkdir(%s) failed", + full_memcg_path); + + pr_info("Created memcg at %s\n", full_memcg_path); +} + +/* + * Test lru_gen aging speed while vCPUs are faulting memory in. + * + * This test will run lru_gen aging until the vCPUs have finished all of + * the faulting work, reporting: + * - vcpu wall time (wall time for slowest vCPU) + * - average aging pass duration + * - total number of aging passes + * - total time spent aging + * + * This test produces the most useful results when the vcpu wall time and the + * total time spent aging are similar (i.e., we want to avoid timing aging + * while the vCPUs aren't doing any work). + */ +static void run_benchmark(enum vm_guest_mode mode, struct kvm_vm *vm, + struct test_params *params) { - struct test_params *params = arg; - struct kvm_vm *vm; int nr_vcpus = params->nr_vcpus; + struct memcg_stats stats; + struct timespec ts_start, ts_max, ts_vcpus_elapsed, + ts_aging_elapsed, ts_aging_elapsed_avg; + int num_passes = 0;

- vm = memstress_create_vm(mode, nr_vcpus, params->vcpu_memory_bytes, 1, - params->backing_src, !overlap_memory_access); + printf("Running lru_gen benchmark...\n");

- memstress_start_vcpu_threads(nr_vcpus, vcpu_thread_main); + clock_gettime(CLOCK_MONOTONIC, &ts_start); + access_memory_async(vm, nr_vcpus, ACCESS_WRITE, + "Populating memory (async)"); + while (!all_vcpus_done(iteration, nr_vcpus)) { + lru_gen_do_aging_quiet(&stats, TEST_MEMCG_NAME); + ++num_passes; + } + + ts_aging_elapsed = timespec_elapsed(ts_start); + ts_aging_elapsed_avg = timespec_div(ts_aging_elapsed, num_passes); + + /* Find out when the slowest vCPU finished. */ + ts_max = ts_start; + for (int i = 0; i < nr_vcpus; ++i) { + struct timespec *vcpu_ts = &vcpu_last_completed_time[i]; + + if (ts_max.tv_sec < vcpu_ts->tv_sec || + (ts_max.tv_sec == vcpu_ts->tv_sec && + ts_max.tv_nsec < vcpu_ts->tv_nsec)) + ts_max = *vcpu_ts; + } + + ts_vcpus_elapsed = timespec_sub(ts_max, ts_start); + + pr_info("%-30s: %ld.%09lds\n", "vcpu wall time", + ts_vcpus_elapsed.tv_sec, ts_vcpus_elapsed.tv_nsec); + + pr_info("%-30s: %ld.%09lds, (passes:%d, total:%ld.%09lds)\n", + "lru_gen avg pass duration", + ts_aging_elapsed_avg.tv_sec, + ts_aging_elapsed_avg.tv_nsec, + num_passes, + ts_aging_elapsed.tv_sec, + ts_aging_elapsed.tv_nsec); +} + +/* + * Test how much access tracking affects vCPU performance. + * + * Supports two modes of access tracking: + * - idle page tracking + * - lru_gen aging + * + * When using lru_gen, this test additionally verifies that the pages are in + * fact getting younger and older, otherwise the performance data would be + * invalid. + * + * The forced lru_gen aging can race with aging that occurs naturally. + */ +static void run_test(enum vm_guest_mode mode, struct kvm_vm *vm, + struct test_params *params) +{ + int nr_vcpus = params->nr_vcpus; + bool lru_gen = params->lru_gen; + struct memcg_stats stats; + long total_pages = nr_vcpus * params->vcpu_memory_bytes / getpagesize(); + int found_gens[5];

pr_info("\n"); access_memory(vm, nr_vcpus, ACCESS_WRITE, "Populating memory"); @@ -319,11 +511,83 @@ static void run_test(enum vm_guest_mode mode, void *arg) access_memory(vm, nr_vcpus, ACCESS_READ, "Reading from populated memory");

/* Repeat on memory that has been marked as idle. */ - mark_memory_idle(vm, nr_vcpus); + if (lru_gen) { + /* Do an initial page table scan */ + lru_gen_do_aging(&stats, TEST_MEMCG_NAME); + TEST_ASSERT(sum_memcg_stats(&stats) >= total_pages, + "Not all pages tracked in lru_gen stats.\n" + "Is lru_gen enabled? Did the memcg get created properly?"); + + /* Find the generation we're currently in (probably youngest) */ + found_gens[0] = lru_gen_find_generation(&stats, total_pages); + + /* Do an aging pass now */ + lru_gen_do_aging(&stats, TEST_MEMCG_NAME); + + /* Same generation, but a newer generation has been made */ + found_gens[1] = lru_gen_find_generation(&stats, total_pages); + TEST_ASSERT(found_gens[1] == found_gens[0], + "unexpected gen change: %d vs. %d", + found_gens[1], found_gens[0]); + } else + mark_memory_idle(vm, nr_vcpus); + access_memory(vm, nr_vcpus, ACCESS_WRITE, "Writing to idle memory"); - mark_memory_idle(vm, nr_vcpus); + + if (lru_gen) { + /* Scan the page tables again */ + lru_gen_do_aging(&stats, TEST_MEMCG_NAME); + + /* The pages should now be young again, so in a newer generation */ + found_gens[2] = lru_gen_find_generation(&stats, total_pages); + TEST_ASSERT(found_gens[2] > found_gens[1], + "pages did not get younger"); + + /* Do another aging pass */ + lru_gen_do_aging(&stats, TEST_MEMCG_NAME); + + /* Same generation; new generation has been made */ + found_gens[3] = lru_gen_find_generation(&stats, total_pages); + TEST_ASSERT(found_gens[3] == found_gens[2], + "unexpected gen change: %d vs. %d", + found_gens[3], found_gens[2]); + } else + mark_memory_idle(vm, nr_vcpus); + access_memory(vm, nr_vcpus, ACCESS_READ, "Reading from idle memory");

+ if (lru_gen) { + /* Scan the pages tables again */ + lru_gen_do_aging(&stats, TEST_MEMCG_NAME); + + /* The pages should now be young again, so in a newer generation */ + found_gens[4] = lru_gen_find_generation(&stats, total_pages); + TEST_ASSERT(found_gens[4] > found_gens[3], + "pages did not get younger"); + } +} + +static void setup_vm_and_run(enum vm_guest_mode mode, void *arg) +{ + struct test_params *params = arg; + int nr_vcpus = params->nr_vcpus; + struct kvm_vm *vm; + + if (params->lru_gen) { + create_memcg(TEST_MEMCG_NAME); + move_to_memcg(TEST_MEMCG_NAME, getpid()); + } + + vm = memstress_create_vm(mode, nr_vcpus, params->vcpu_memory_bytes, 1, + params->backing_src, !overlap_memory_access); + + memstress_start_vcpu_threads(nr_vcpus, vcpu_thread_main); + + if (params->benchmark_lru_gen) + run_benchmark(mode, vm, params); + else + run_test(mode, vm, params); + memstress_join_vcpu_threads(nr_vcpus); memstress_destroy_vm(vm); } @@ -331,8 +595,8 @@ static void run_test(enum vm_guest_mode mode, void *arg) static void help(char *name) { puts(""); - printf("usage: %s [-h] [-m mode] [-b vcpu_bytes] [-v vcpus] [-o] [-s mem_type]\n", - name); + printf("usage: %s [-h] [-m mode] [-b vcpu_bytes] [-v vcpus] [-o]" + " [-s mem_type] [-l] [-r memcg_root]\n", name); puts(""); printf(" -h: Display this help message."); guest_modes_help(); @@ -342,6 +606,9 @@ static void help(char *name) printf(" -v: specify the number of vCPUs to run.\n"); printf(" -o: Overlap guest memory accesses instead of partitioning\n" " them into a separate region of memory for each vCPU.\n"); + printf(" -l: Use MGLRU aging instead of idle page tracking\n"); + printf(" -p: Benchmark MGLRU aging while faulting memory in\n"); + printf(" -r: The memory cgroup hierarchy root to use (when -l is given)\n"); backing_src_help("-s"); puts(""); exit(0); @@ -353,13 +620,15 @@ int main(int argc, char *argv[]) .backing_src = DEFAULT_VM_MEM_SRC, .vcpu_memory_bytes = DEFAULT_PER_VCPU_MEM_SIZE, .nr_vcpus = 1, + .lru_gen = false, + .benchmark_lru_gen = false, }; int page_idle_fd; int opt;

guest_modes_append_default();

- while ((opt = getopt(argc, argv, "hm:b:v:os:")) != -1) { + while ((opt = getopt(argc, argv, "hm:b:v:os:lr:p")) != -1) { switch (opt) { case 'm': guest_modes_cmdline(optarg); @@ -376,6 +645,15 @@ int main(int argc, char *argv[]) case 's': params.backing_src = parse_backing_src_type(optarg); break; + case 'l': + params.lru_gen = true; + break; + case 'p': + params.benchmark_lru_gen = true; + break; + case 'r': + cgroup_root = strdup(optarg); + break; case 'h': default: help(argv[0]); @@ -383,12 +661,39 @@ int main(int argc, char *argv[]) } }

- page_idle_fd = open("/sys/kernel/mm/page_idle/bitmap", O_RDWR); - __TEST_REQUIRE(page_idle_fd >= 0, - "CONFIG_IDLE_PAGE_TRACKING is not enabled"); - close(page_idle_fd); + if (!params.lru_gen) { + page_idle_fd = open("/sys/kernel/mm/page_idle/bitmap", O_RDWR); + __TEST_REQUIRE(page_idle_fd >= 0, + "CONFIG_IDLE_PAGE_TRACKING is not enabled"); + close(page_idle_fd); + } else { + int lru_gen_fd, lru_gen_debug_fd; + long mglru_features; + char mglru_feature_str[8] = {}; + + lru_gen_fd = open("/sys/kernel/mm/lru_gen/enabled", O_RDONLY); + __TEST_REQUIRE(lru_gen_fd >= 0, + "CONFIG_LRU_GEN is not enabled"); + TEST_ASSERT(read(lru_gen_fd, &mglru_feature_str, 7) > 0, + "couldn't read lru_gen features"); + mglru_features = strtol(mglru_feature_str, NULL, 16); + __TEST_REQUIRE(mglru_features & LRU_GEN_ENABLED, + "lru_gen is not enabled"); + __TEST_REQUIRE(mglru_features & LRU_GEN_MM_WALK, + "lru_gen does not support MM_WALK"); + __TEST_REQUIRE(mglru_features & LRU_GEN_SECONDARY_MMU_WALK, + "lru_gen does not support SECONDARY_MMU_WALK"); + + lru_gen_debug_fd = open(DEBUGFS_LRU_GEN, O_RDWR); + __TEST_REQUIRE(lru_gen_debug_fd >= 0, + "Cannot access %s", DEBUGFS_LRU_GEN); + close(lru_gen_debug_fd); + } + + TEST_ASSERT(!params.benchmark_lru_gen || params.lru_gen, + "-p specified without -l");

- for_each_guest_mode(run_test, &params); + for_each_guest_mode(setup_vm_and_run, &params);

return 0; } diff --git a/tools/testing/selftests/kvm/include/lru_gen_util.h b/tools/testing/selftests/kvm/include/lru_gen_util.h new file mode 100644 index 000000000000..4eef8085a3cb --- /dev/null +++ b/tools/testing/selftests/kvm/include/lru_gen_util.h @@ -0,0 +1,55 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Tools for integrating with lru_gen, like parsing the lru_gen debugfs output. + * + * Copyright (C) 2024, Google LLC. + */ +#ifndef SELFTEST_KVM_LRU_GEN_UTIL_H +#define SELFTEST_KVM_LRU_GEN_UTIL_H + +#include <inttypes.h> +#include <limits.h> +#include <stdlib.h> + +#include "test_util.h" + +#define MAX_NR_GENS 16 /* MAX_NR_GENS in include/linux/mmzone.h */ +#define MAX_NR_NODES 4 /* Maximum number of nodes we support */ + +static const char *DEBUGFS_LRU_GEN = "/sys/kernel/debug/lru_gen"; + +struct generation_stats { + int gen; + long age_ms; + long nr_anon; + long nr_file; +}; + +struct node_stats { + int node; + int nr_gens; /* Number of populated gens entries. */ + struct generation_stats gens[MAX_NR_GENS]; +}; + +struct memcg_stats { + unsigned long memcg_id; + int nr_nodes; /* Number of populated nodes entries. */ + struct node_stats nodes[MAX_NR_NODES]; +}; + +void print_memcg_stats(const struct memcg_stats *stats, const char *name); + +void read_memcg_stats(struct memcg_stats *stats, const char *memcg); + +void read_print_memcg_stats(struct memcg_stats *stats, const char *memcg); + +long sum_memcg_stats(const struct memcg_stats *stats); + +void lru_gen_do_aging(struct memcg_stats *stats, const char *memcg); + +void lru_gen_do_aging_quiet(struct memcg_stats *stats, const char *memcg); + +int lru_gen_find_generation(const struct memcg_stats *stats, + unsigned long total_pages); + +#endif /* SELFTEST_KVM_LRU_GEN_UTIL_H */ diff --git a/tools/testing/selftests/kvm/lib/lru_gen_util.c b/tools/testing/selftests/kvm/lib/lru_gen_util.c new file mode 100644 index 000000000000..3c02a635a9f7 --- /dev/null +++ b/tools/testing/selftests/kvm/lib/lru_gen_util.c @@ -0,0 +1,391 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2024, Google LLC. + */ + +#include <time.h> + +#include "lru_gen_util.h" + +/* + * Tracks state while we parse memcg lru_gen stats. The file we're parsing is + * structured like this (some extra whitespace elided): + * + * memcg (id) (path) + * node (id) + * (gen_nr) (age_in_ms) (nr_anon_pages) (nr_file_pages) + */ +struct memcg_stats_parse_context { + bool consumed; /* Whether or not this line was consumed */ + /* Next parse handler to invoke */ + void (*next_handler)(struct memcg_stats *, + struct memcg_stats_parse_context *, char *); + int current_node_idx; /* Current index in nodes array */ + const char *name; /* The name of the memcg we're looking for */ +}; + +static void memcg_stats_handle_searching(struct memcg_stats *stats, + struct memcg_stats_parse_context *ctx, + char *line); +static void memcg_stats_handle_in_memcg(struct memcg_stats *stats, + struct memcg_stats_parse_context *ctx, + char *line); +static void memcg_stats_handle_in_node(struct memcg_stats *stats, + struct memcg_stats_parse_context *ctx, + char *line); + +struct split_iterator { + char *str; + char *save; +}; + +static char *split_next(struct split_iterator *it) +{ + char *ret = strtok_r(it->str, " \t\n\r", &it->save); + + it->str = NULL; + return ret; +} + +static void memcg_stats_handle_searching(struct memcg_stats *stats, + struct memcg_stats_parse_context *ctx, + char *line) +{ + struct split_iterator it = { .str = line }; + char *prefix = split_next(&it); + char *memcg_id = split_next(&it); + char *memcg_name = split_next(&it); + char *end; + + ctx->consumed = true; + + if (!prefix || strcmp("memcg", prefix)) + return; /* Not a memcg line (maybe empty), skip */ + + TEST_ASSERT(memcg_id && memcg_name, + "malformed memcg line; no memcg id or memcg_name"); + + if (strcmp(memcg_name + 1, ctx->name)) + return; /* Wrong memcg, skip */ + + /* Found it! */ + + stats->memcg_id = strtoul(memcg_id, &end, 10); + TEST_ASSERT(*end == '\0', "malformed memcg id '%s'", memcg_id); + if (!stats->memcg_id) + return; /* Removed memcg? */ + + ctx->next_handler = memcg_stats_handle_in_memcg; +} + +static void memcg_stats_handle_in_memcg(struct memcg_stats *stats, + struct memcg_stats_parse_context *ctx, + char *line) +{ + struct split_iterator it = { .str = line }; + char *prefix = split_next(&it); + char *id = split_next(&it); + long found_node_id; + char *end; + + ctx->consumed = true; + ctx->current_node_idx = -1; + + if (!prefix) + return; /* Skip empty lines */ + + if (!strcmp("memcg", prefix)) { + /* Memcg done, found next one; stop. */ + ctx->next_handler = NULL; + return; + } else if (strcmp("node", prefix)) + TEST_ASSERT(false, "found malformed line after 'memcg ...'," + "token: '%s'", prefix); + + /* At this point we know we have a node line. Parse the ID. */ + + TEST_ASSERT(id, "malformed node line; no node id"); + + found_node_id = strtol(id, &end, 10); + TEST_ASSERT(*end == '\0', "malformed node id '%s'", id); + + ctx->current_node_idx = stats->nr_nodes++; + TEST_ASSERT(ctx->current_node_idx < MAX_NR_NODES, + "memcg has stats for too many nodes, max is %d", + MAX_NR_NODES); + stats->nodes[ctx->current_node_idx].node = found_node_id; + + ctx->next_handler = memcg_stats_handle_in_node; +} + +static void memcg_stats_handle_in_node(struct memcg_stats *stats, + struct memcg_stats_parse_context *ctx, + char *line) +{ + /* Have to copy since we might not consume */ + char *my_line = strdup(line); + struct split_iterator it = { .str = my_line }; + char *gen, *age, *nr_anon, *nr_file; + struct node_stats *node_stats; + struct generation_stats *gen_stats; + char *end; + + TEST_ASSERT(it.str, "failed to copy input line"); + + gen = split_next(&it); + + /* Skip empty lines */ + if (!gen) + goto out_consume; /* Skip empty lines */ + + if (!strcmp("memcg", gen) || !strcmp("node", gen)) { + /* + * Reached next memcg or node section. Don't consume, let the + * other handler deal with this. + */ + ctx->next_handler = memcg_stats_handle_in_memcg; + goto out; + } + + node_stats = &stats->nodes[ctx->current_node_idx]; + TEST_ASSERT(node_stats->nr_gens < MAX_NR_GENS, + "found too many generation lines; max is %d", + MAX_NR_GENS); + gen_stats = &node_stats->gens[node_stats->nr_gens++]; + + age = split_next(&it); + nr_anon = split_next(&it); + nr_file = split_next(&it); + + TEST_ASSERT(age && nr_anon && nr_file, + "malformed generation line; not enough tokens"); + + gen_stats->gen = (int)strtol(gen, &end, 10); + TEST_ASSERT(*end == '\0', "malformed generation number '%s'", gen); + + gen_stats->age_ms = strtol(age, &end, 10); + TEST_ASSERT(*end == '\0', "malformed generation age '%s'", age); + + gen_stats->nr_anon = strtol(nr_anon, &end, 10); + TEST_ASSERT(*end == '\0', "malformed anonymous page count '%s'", + nr_anon); + + gen_stats->nr_file = strtol(nr_file, &end, 10); + TEST_ASSERT(*end == '\0', "malformed file page count '%s'", nr_file); + +out_consume: + ctx->consumed = true; +out: + free(my_line); +} + +/* Pretty-print lru_gen @stats. */ +void print_memcg_stats(const struct memcg_stats *stats, const char *name) +{ + int node, gen; + + fprintf(stderr, "stats for memcg %s (id %lu):\n", + name, stats->memcg_id); + for (node = 0; node < stats->nr_nodes; ++node) { + fprintf(stderr, "\tnode %d\n", stats->nodes[node].node); + for (gen = 0; gen < stats->nodes[node].nr_gens; ++gen) { + const struct generation_stats *gstats = + &stats->nodes[node].gens[gen]; + + fprintf(stderr, + "\t\tgen %d\tage_ms %ld" + "\tnr_anon %ld\tnr_file %ld\n", + gstats->gen, gstats->age_ms, gstats->nr_anon, + gstats->nr_file); + } + } +} + +/* Re-read lru_gen debugfs information for @memcg into @stats. */ +void read_memcg_stats(struct memcg_stats *stats, const char *memcg) +{ + FILE *f; + ssize_t read = 0; + char *line = NULL; + size_t bufsz; + struct memcg_stats_parse_context ctx = { + .next_handler = memcg_stats_handle_searching, + .name = memcg, + }; + + memset(stats, 0, sizeof(struct memcg_stats)); + + f = fopen(DEBUGFS_LRU_GEN, "r"); + TEST_ASSERT(f, "fopen(%s) failed", DEBUGFS_LRU_GEN); + + while (ctx.next_handler && (read = getline(&line, &bufsz, f)) > 0) { + ctx.consumed = false; + + do { + ctx.next_handler(stats, &ctx, line); + if (!ctx.next_handler) + break; + } while (!ctx.consumed); + } + + if (read < 0 && !feof(f)) + TEST_ASSERT(false, "getline(%s) failed", DEBUGFS_LRU_GEN); + + TEST_ASSERT(stats->memcg_id > 0, "Couldn't find memcg: %s\n" + "Did the memcg get created in the proper mount?", + memcg); + if (line) + free(line); + TEST_ASSERT(!fclose(f), "fclose(%s) failed", DEBUGFS_LRU_GEN); +} + +/* + * Find all pages tracked by lru_gen for this memcg in generation @target_gen. + * + * If @target_gen is negative, look for all generations. + */ +static long sum_memcg_stats_for_gen(int target_gen, + const struct memcg_stats *stats) +{ + int node, gen; + long total_nr = 0; + + for (node = 0; node < stats->nr_nodes; ++node) { + const struct node_stats *node_stats = &stats->nodes[node]; + + for (gen = 0; gen < node_stats->nr_gens; ++gen) { + const struct generation_stats *gen_stats = + &node_stats->gens[gen]; + + if (target_gen >= 0 && gen_stats->gen != target_gen) + continue; + + total_nr += gen_stats->nr_anon + gen_stats->nr_file; + } + } + + return total_nr; +} + +/* Find all pages tracked by lru_gen for this memcg. */ +long sum_memcg_stats(const struct memcg_stats *stats) +{ + return sum_memcg_stats_for_gen(-1, stats); +} + +/* Read the memcg stats and optionally print if this is a debug build. */ +void read_print_memcg_stats(struct memcg_stats *stats, const char *memcg) +{ + read_memcg_stats(stats, memcg); +#ifdef DEBUG + print_memcg_stats(stats, memcg); +#endif +} + +/* + * If lru_gen aging should force page table scanning. + * + * If you want to set this to false, you will need to do eviction + * before doing extra aging passes. + */ +static const bool force_scan = true; + +static void run_aging_impl(unsigned long memcg_id, int node_id, int max_gen) +{ + FILE *f = fopen(DEBUGFS_LRU_GEN, "w"); + char *command; + size_t sz; + + TEST_ASSERT(f, "fopen(%s) failed", DEBUGFS_LRU_GEN); + sz = asprintf(&command, "+ %lu %d %d 1 %d\n", + memcg_id, node_id, max_gen, force_scan); + TEST_ASSERT(sz > 0, "creating aging command failed"); + + pr_debug("Running aging command: %s", command); + if (fwrite(command, sizeof(char), sz, f) < sz) { + TEST_ASSERT(false, "writing aging command %s to %s failed", + command, DEBUGFS_LRU_GEN); + } + + TEST_ASSERT(!fclose(f), "fclose(%s) failed", DEBUGFS_LRU_GEN); +} + +static void _lru_gen_do_aging(struct memcg_stats *stats, const char *memcg, + bool verbose) +{ + int node, gen; + struct timespec ts_start; + struct timespec ts_elapsed; + + pr_debug("lru_gen: invoking aging...\n"); + + /* Must read memcg stats to construct the proper aging command. */ + read_print_memcg_stats(stats, memcg); + + if (verbose) + clock_gettime(CLOCK_MONOTONIC, &ts_start); + + for (node = 0; node < stats->nr_nodes; ++node) { + int max_gen = 0; + + for (gen = 0; gen < stats->nodes[node].nr_gens; ++gen) { + int this_gen = stats->nodes[node].gens[gen].gen; + + max_gen = max_gen > this_gen ? max_gen : this_gen; + } + + run_aging_impl(stats->memcg_id, stats->nodes[node].node, + max_gen); + } + + if (verbose) { + ts_elapsed = timespec_elapsed(ts_start); + pr_info("%-30s: %ld.%09lds\n", "lru_gen: Aging", + ts_elapsed.tv_sec, ts_elapsed.tv_nsec); + } + + /* Re-read so callers get updated information */ + read_print_memcg_stats(stats, memcg); +} + +/* Do aging, and print how long it took. */ +void lru_gen_do_aging(struct memcg_stats *stats, const char *memcg) +{ + return _lru_gen_do_aging(stats, memcg, true); +} + +/* Do aging, don't print anything. */ +void lru_gen_do_aging_quiet(struct memcg_stats *stats, const char *memcg) +{ + return _lru_gen_do_aging(stats, memcg, false); +} + +/* + * Find which generation contains more than half of @total_pages, assuming that + * such a generation exists. + */ +int lru_gen_find_generation(const struct memcg_stats *stats, + unsigned long total_pages) +{ + int node, gen, gen_idx, min_gen = INT_MAX, max_gen = -1; + + for (node = 0; node < stats->nr_nodes; ++node) + for (gen_idx = 0; gen_idx < stats->nodes[node].nr_gens; + ++gen_idx) { + gen = stats->nodes[node].gens[gen_idx].gen; + max_gen = gen > max_gen ? gen : max_gen; + min_gen = gen < min_gen ? gen : min_gen; + } + + for (gen = min_gen; gen < max_gen; ++gen) + /* See if the most pages are in this generation. */ + if (sum_memcg_stats_for_gen(gen, stats) > + total_pages / 2) + return gen; + + TEST_ASSERT(false, "No generation includes majority of %lu pages.", + total_pages); + + /* unreachable, but make the compiler happy */ + return -1; +}