From 8788f6781486769d9598dcaedc3fe0eb12fc3e59 Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Fri, 30 Dec 2022 14:52:51 -0700 Subject: 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 Cc: Alexander Viro Cc: Andrea Righi Cc: Johannes Weiner Cc: Michael Larabel Signed-off-by: Andrew Morton --- mm/memory.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'mm/memory.c') 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) -- cgit v1.2.3-70-g09d2