diff options
author | Yu Zhao <yuzhao@google.com> | 2022-12-30 14:52:51 -0700 |
---|---|---|
committer | Andrew Morton <akpm@linux-foundation.org> | 2023-01-18 17:12:57 -0800 |
commit | 8788f6781486769d9598dcaedc3fe0eb12fc3e59 (patch) | |
tree | 6016e5f416dff55046e98aab401486edef2bf045 | |
parent | 997931ce02b72f15c40e742ee035ce5643ba574f (diff) | |
download | lwn-8788f6781486769d9598dcaedc3fe0eb12fc3e59.tar.gz lwn-8788f6781486769d9598dcaedc3fe0eb12fc3e59.zip |
mm: add vma_has_recency()
Add vma_has_recency() to indicate whether a VMA may exhibit temporal
locality that the LRU algorithm relies on.
This function returns false for VMAs marked by VM_SEQ_READ or
VM_RAND_READ. While the former flag indicates linear access, i.e., a
special case of spatial locality, both flags indicate a lack of temporal
locality, i.e., the reuse of an area within a relatively small duration.
"Recency" is chosen over "locality" to avoid confusion between temporal
and spatial localities.
Before this patch, the active/inactive LRU only ignored the accessed bit
from VMAs marked by VM_SEQ_READ. After this patch, the active/inactive
LRU and MGLRU share the same logic: they both ignore the accessed bit if
vma_has_recency() returns false.
For the active/inactive LRU, the following fio test showed a [6, 8]%
increase in IOPS when randomly accessing mapped files under memory
pressure.
kb=$(awk '/MemTotal/ { print $2 }' /proc/meminfo)
kb=$((kb - 8*1024*1024))
modprobe brd rd_nr=1 rd_size=$kb
dd if=/dev/zero of=/dev/ram0 bs=1M
mkfs.ext4 /dev/ram0
mount /dev/ram0 /mnt/
swapoff -a
fio --name=test --directory=/mnt/ --ioengine=mmap --numjobs=8 \
--size=8G --rw=randrw --time_based --runtime=10m \
--group_reporting
The discussion that led to this patch is here [1]. Additional test
results are available in that thread.
[1] https://lore.kernel.org/r/Y31s%2FK8T85jh05wH@google.com/
Link: https://lkml.kernel.org/r/20221230215252.2628425-1-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Righi <andrea.righi@canonical.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michael Larabel <Michael@MichaelLarabel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r-- | include/linux/mm_inline.h | 8 | ||||
-rw-r--r-- | mm/memory.c | 7 | ||||
-rw-r--r-- | mm/rmap.c | 42 | ||||
-rw-r--r-- | mm/vmscan.c | 5 |
4 files changed, 33 insertions, 29 deletions
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index acf03147fff8..4abebf2615a3 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -594,4 +594,12 @@ pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr, #endif } +static inline bool vma_has_recency(struct vm_area_struct *vma) +{ + if (vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ)) + return false; + + return true; +} + #endif diff --git a/mm/memory.c b/mm/memory.c index b0dda866ffe6..90f8f72777c7 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1402,8 +1402,7 @@ again: force_flush = 1; } } - if (pte_young(ptent) && - likely(!(vma->vm_flags & VM_SEQ_READ))) + if (pte_young(ptent) && likely(vma_has_recency(vma))) mark_page_accessed(page); } rss[mm_counter(page)]--; @@ -5115,8 +5114,8 @@ static inline void mm_account_fault(struct pt_regs *regs, #ifdef CONFIG_LRU_GEN static void lru_gen_enter_fault(struct vm_area_struct *vma) { - /* the LRU algorithm doesn't apply to sequential or random reads */ - current->in_lru_fault = !(vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ)); + /* the LRU algorithm only applies to accesses with recency */ + current->in_lru_fault = vma_has_recency(vma); } static void lru_gen_exit_fault(void) diff --git a/mm/rmap.c b/mm/rmap.c index 32e48b1c5847..ab74e0547a52 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -823,25 +823,14 @@ static bool folio_referenced_one(struct folio *folio, } if (pvmw.pte) { - if (lru_gen_enabled() && pte_young(*pvmw.pte) && - !(vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ))) { + if (lru_gen_enabled() && pte_young(*pvmw.pte)) { lru_gen_look_around(&pvmw); referenced++; } if (ptep_clear_flush_young_notify(vma, address, - pvmw.pte)) { - /* - * Don't treat a reference through - * a sequentially read mapping as such. - * If the folio has been used in another mapping, - * we will catch it; if this other mapping is - * already gone, the unmap path will have set - * the referenced flag or activated the folio. - */ - if (likely(!(vma->vm_flags & VM_SEQ_READ))) - referenced++; - } + pvmw.pte)) + referenced++; } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { if (pmdp_clear_flush_young_notify(vma, address, pvmw.pmd)) @@ -875,7 +864,20 @@ static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg) struct folio_referenced_arg *pra = arg; struct mem_cgroup *memcg = pra->memcg; - if (!mm_match_cgroup(vma->vm_mm, memcg)) + /* + * Ignore references from this mapping if it has no recency. If the + * folio has been used in another mapping, we will catch it; if this + * other mapping is already gone, the unmap path will have set the + * referenced flag or activated the folio in zap_pte_range(). + */ + if (!vma_has_recency(vma)) + return true; + + /* + * If we are reclaiming on behalf of a cgroup, skip counting on behalf + * of references from different cgroups. + */ + if (memcg && !mm_match_cgroup(vma->vm_mm, memcg)) return true; return false; @@ -906,6 +908,7 @@ int folio_referenced(struct folio *folio, int is_locked, .arg = (void *)&pra, .anon_lock = folio_lock_anon_vma_read, .try_lock = true, + .invalid_vma = invalid_folio_referenced_vma, }; *vm_flags = 0; @@ -921,15 +924,6 @@ int folio_referenced(struct folio *folio, int is_locked, return 1; } - /* - * If we are reclaiming on behalf of a cgroup, skip - * counting on behalf of references from different - * cgroups - */ - if (memcg) { - rwc.invalid_vma = invalid_folio_referenced_vma; - } - rmap_walk(folio, &rwc); *vm_flags = pra.vm_flags; diff --git a/mm/vmscan.c b/mm/vmscan.c index 7c3fd900a89d..fe30b8c43f92 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3794,7 +3794,10 @@ static int should_skip_vma(unsigned long start, unsigned long end, struct mm_wal if (is_vm_hugetlb_page(vma)) return true; - if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL | VM_SEQ_READ | VM_RAND_READ)) + if (!vma_has_recency(vma)) + return true; + + if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) return true; if (vma == get_gate_vma(vma->vm_mm)) |