197 lines
6.1 KiB
Diff
197 lines
6.1 KiB
Diff
From 6c7f552a48b49a8612786a28a2239fbc24fac289 Mon Sep 17 00:00:00 2001
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From: Yu Zhao <yuzhao@google.com>
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Date: Fri, 30 Dec 2022 14:52:51 -0700
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Subject: [PATCH 19/29] mm: add vma_has_recency()
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Add vma_has_recency() to indicate whether a VMA may exhibit temporal
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locality that the LRU algorithm relies on.
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This function returns false for VMAs marked by VM_SEQ_READ or
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VM_RAND_READ. While the former flag indicates linear access, i.e., a
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special case of spatial locality, both flags indicate a lack of temporal
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locality, i.e., the reuse of an area within a relatively small duration.
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"Recency" is chosen over "locality" to avoid confusion between temporal
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and spatial localities.
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Before this patch, the active/inactive LRU only ignored the accessed bit
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from VMAs marked by VM_SEQ_READ. After this patch, the active/inactive
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LRU and MGLRU share the same logic: they both ignore the accessed bit if
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vma_has_recency() returns false.
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For the active/inactive LRU, the following fio test showed a [6, 8]%
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increase in IOPS when randomly accessing mapped files under memory
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pressure.
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kb=$(awk '/MemTotal/ { print $2 }' /proc/meminfo)
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kb=$((kb - 8*1024*1024))
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modprobe brd rd_nr=1 rd_size=$kb
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dd if=/dev/zero of=/dev/ram0 bs=1M
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mkfs.ext4 /dev/ram0
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mount /dev/ram0 /mnt/
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swapoff -a
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fio --name=test --directory=/mnt/ --ioengine=mmap --numjobs=8 \
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--size=8G --rw=randrw --time_based --runtime=10m \
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--group_reporting
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The discussion that led to this patch is here [1]. Additional test
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results are available in that thread.
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[1] https://lore.kernel.org/r/Y31s%2FK8T85jh05wH@google.com/
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Link: https://lkml.kernel.org/r/20221230215252.2628425-1-yuzhao@google.com
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Signed-off-by: Yu Zhao <yuzhao@google.com>
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Cc: Alexander Viro <viro@zeniv.linux.org.uk>
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Cc: Andrea Righi <andrea.righi@canonical.com>
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Cc: Johannes Weiner <hannes@cmpxchg.org>
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Cc: Michael Larabel <Michael@MichaelLarabel.com>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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---
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include/linux/mm_inline.h | 9 +++++++++
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mm/memory.c | 8 ++++----
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mm/rmap.c | 42 +++++++++++++++++----------------------
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mm/vmscan.c | 5 ++++-
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4 files changed, 35 insertions(+), 29 deletions(-)
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--- a/include/linux/mm_inline.h
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+++ b/include/linux/mm_inline.h
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@@ -333,4 +333,13 @@ static __always_inline void del_page_fro
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update_lru_size(lruvec, page_lru(page), page_zonenum(page),
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-thp_nr_pages(page));
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}
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+
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+static inline bool vma_has_recency(struct vm_area_struct *vma)
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+{
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+ if (vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ))
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+ return false;
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+
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+ return true;
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+}
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+
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#endif
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--- a/mm/memory.c
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+++ b/mm/memory.c
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@@ -41,6 +41,7 @@
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#include <linux/kernel_stat.h>
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#include <linux/mm.h>
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+#include <linux/mm_inline.h>
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#include <linux/sched/mm.h>
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#include <linux/sched/coredump.h>
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#include <linux/sched/numa_balancing.h>
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@@ -1353,8 +1354,7 @@ again:
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force_flush = 1;
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set_page_dirty(page);
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}
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- if (pte_young(ptent) &&
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- likely(!(vma->vm_flags & VM_SEQ_READ)))
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+ if (pte_young(ptent) && likely(vma_has_recency(vma)))
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mark_page_accessed(page);
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}
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rss[mm_counter(page)]--;
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@@ -4808,8 +4808,8 @@ static inline void mm_account_fault(stru
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#ifdef CONFIG_LRU_GEN
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static void lru_gen_enter_fault(struct vm_area_struct *vma)
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{
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- /* the LRU algorithm doesn't apply to sequential or random reads */
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- current->in_lru_fault = !(vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ));
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+ /* the LRU algorithm only applies to accesses with recency */
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+ current->in_lru_fault = vma_has_recency(vma);
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}
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static void lru_gen_exit_fault(void)
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--- a/mm/rmap.c
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+++ b/mm/rmap.c
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@@ -794,25 +794,14 @@ static bool page_referenced_one(struct p
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}
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if (pvmw.pte) {
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- if (lru_gen_enabled() && pte_young(*pvmw.pte) &&
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- !(vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ))) {
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+ if (lru_gen_enabled() && pte_young(*pvmw.pte)) {
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lru_gen_look_around(&pvmw);
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referenced++;
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}
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if (ptep_clear_flush_young_notify(vma, address,
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- pvmw.pte)) {
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- /*
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- * Don't treat a reference through
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- * a sequentially read mapping as such.
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- * If the page has been used in another mapping,
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- * we will catch it; if this other mapping is
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- * already gone, the unmap path will have set
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- * PG_referenced or activated the page.
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- */
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- if (likely(!(vma->vm_flags & VM_SEQ_READ)))
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- referenced++;
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- }
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+ pvmw.pte))
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+ referenced++;
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} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
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if (pmdp_clear_flush_young_notify(vma, address,
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pvmw.pmd))
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@@ -846,7 +835,20 @@ static bool invalid_page_referenced_vma(
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struct page_referenced_arg *pra = arg;
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struct mem_cgroup *memcg = pra->memcg;
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- if (!mm_match_cgroup(vma->vm_mm, memcg))
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+ /*
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+ * Ignore references from this mapping if it has no recency. If the
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+ * page has been used in another mapping, we will catch it; if this
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+ * other mapping is already gone, the unmap path will have set the
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+ * referenced flag or activated the page in zap_pte_range().
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+ */
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+ if (!vma_has_recency(vma))
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+ return true;
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+
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+ /*
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+ * If we are reclaiming on behalf of a cgroup, skip counting on behalf
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+ * of references from different cgroups.
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+ */
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+ if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
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return true;
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return false;
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@@ -876,6 +878,7 @@ int page_referenced(struct page *page,
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.rmap_one = page_referenced_one,
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.arg = (void *)&pra,
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.anon_lock = page_lock_anon_vma_read,
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+ .invalid_vma = invalid_page_referenced_vma,
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};
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*vm_flags = 0;
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@@ -891,15 +894,6 @@ int page_referenced(struct page *page,
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return 1;
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}
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- /*
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- * If we are reclaiming on behalf of a cgroup, skip
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- * counting on behalf of references from different
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- * cgroups
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- */
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- if (memcg) {
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- rwc.invalid_vma = invalid_page_referenced_vma;
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- }
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-
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rmap_walk(page, &rwc);
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*vm_flags = pra.vm_flags;
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--- a/mm/vmscan.c
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+++ b/mm/vmscan.c
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@@ -3486,7 +3486,10 @@ static int should_skip_vma(unsigned long
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if (is_vm_hugetlb_page(vma))
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return true;
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- if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL | VM_SEQ_READ | VM_RAND_READ))
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+ if (!vma_has_recency(vma))
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+ return true;
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+
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+ if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL))
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return true;
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if (vma == get_gate_vma(vma->vm_mm))
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