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Fri, 30 Dec 2022 13:52:59 -0800 (PST) Date: Fri, 30 Dec 2022 14:52:51 -0700 Message-Id: <20221230215252.2628425-1-yuzhao@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.39.0.314.g84b9a713c41-goog Subject: [PATCH mm-unstable v2 1/2] mm: add vma_has_recency() From: Yu Zhao To: Andrew Morton Cc: Alexander Viro , Andrea Righi , Johannes Weiner , Michael Larabel , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@google.com, Yu Zhao Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: F08411C0005 X-Stat-Signature: qc3x6isgqn5ko4goco8jg94ddsf6d18i X-Rspam-User: X-HE-Tag: 1672437179-453417 X-HE-Meta: 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 FU1r7FKH ExE4FVW4xWIYC0Z9qvravtFyIp8crwj0hRkD7xxvqAfsnFdBeEK/MaVGnj37nuqlEWZQfuILKIZt0/4cHtGQJOD6b0OZ2GPA8l9q6vI44zl+9OcPfHHTqr9BjAiI4Hcfz5MutwdBj6/5QQMbBhQQHFyeYId38dsMwqYG0xHtepwd9erGau7R2XhbA6OF5ZUHZ2AruHxVAyiKfFEhnV5ywT4SoRGM8ZwxTzU301s6Eyz1/48rPHBRgXfDv84km9M+h7LetJ8QpU+fTXg1wE0EAVUtI6GP0FN8dyRRWEUG7UXhsfy9d9779NhyrdL7sUkAo6adVOMdGDUD9+YzpqsFld0hjJfTCxplsvw0/NKsj0+EL6tVpI4JGKaW2l0z8OzLDmci4HtOp1Pi/dK/HMyjuf/TxUynB2iQKvjsM X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: This patch adds 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/ Signed-off-by: Yu Zhao --- include/linux/mm_inline.h | 8 ++++++++ mm/memory.c | 7 +++---- mm/rmap.c | 42 +++++++++++++++++---------------------- 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 d1c1f211a86f..fe5b8449e14a 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -595,4 +595,12 @@ 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 4000e9f017e0..ee72badad847 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1402,8 +1402,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, 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)]--; @@ -5148,8 +5147,8 @@ 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 8a24b90d9531..9abffdd63a6a 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 6929402db149..cdf96aec39dc 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)) -- 2.39.0.314.g84b9a713c41-goog