From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 53E433D3314 for ; Mon, 27 Apr 2026 18:23:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777314220; cv=none; b=tkqVGj0/J/JatgBTepMLvgAB+bxwMf9nCNlM7XF9YmL8XqsAB+26TE5V5LL7JnUWLnHcTAXCbEnNg5gFJXkQf6DKnTjPJlkxKGwqVmOczQEc696XcIItblE8i9zwUbD5vadEXuHcorgq2PScHYh7ehoi5fBiAkPs433CZhBJEpE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777314220; c=relaxed/simple; bh=XXMsBYlMiM+S+N/Ux7Ga++SKLqet5Wu9wVLg0w6J27E=; h=Date:To:From:Subject:Message-Id; b=CGdhVYXifv/R2SNm+EEsfD3dQD3RlC7D2mgDSK+Osq4c8l7YBmBanOtuFY4YjFg141M0NwRMH5S6cTt6UyetpzTyLOA6jQFI2fdk+rjvqZpMJWVqTdE1EkrqWn1K+/D3jy4ob+eJ/67+WPeYE4tQBd5RBBviV+4c7sW/HHJwEBs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=SPi/hwge; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="SPi/hwge" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2BE0DC2BCB5; Mon, 27 Apr 2026 18:23:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1777314220; bh=XXMsBYlMiM+S+N/Ux7Ga++SKLqet5Wu9wVLg0w6J27E=; h=Date:To:From:Subject:From; b=SPi/hwge1Gz19dsSfeVJvRGu4onrzywPHkA47ncBJZ3wwsHxQ4F9MprzNJpQOaBK9 ASVNG55a9wi9+lIjtZFsLKpBt0f26rY7JrK2cljlBIiK1SQVVmYdy1t7nMcE2yGCUl yAUoAbRAfJeanF8r0t21XSHfcu5hTy4Z3NInAfzw= Date: Mon, 27 Apr 2026 11:23:39 -0700 To: mm-commits@vger.kernel.org,kasong@tencent.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-vmscan-unify-writeback-reclaim-statistic-and-throttling.patch added to mm-new branch Message-Id: <20260427182340.2BE0DC2BCB5@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/vmscan: unify writeback reclaim statistic and throttling has been added to the -mm mm-new branch. Its filename is mm-vmscan-unify-writeback-reclaim-statistic-and-throttling.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmscan-unify-writeback-reclaim-statistic-and-throttling.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Kairui Song Subject: mm/vmscan: unify writeback reclaim statistic and throttling Date: Tue, 28 Apr 2026 02:07:06 +0800 Currently MGLRU and non-MGLRU handle the reclaim statistic and writeback handling very differently, especially throttling. Basically MGLRU just ignored the throttling part. Let's just unify this part, use a helper to deduplicate the code so both setups will share the same behavior. Test using following reproducer using bash: echo "Setup a slow device using dm delay" dd if=/dev/zero of=/var/tmp/backing bs=1M count=2048 LOOP=$(losetup --show -f /var/tmp/backing) mkfs.ext4 -q $LOOP echo "0 $(blockdev --getsz $LOOP) delay $LOOP 0 0 $LOOP 0 1000" | \ dmsetup create slow_dev mkdir -p /mnt/slow && mount /dev/mapper/slow_dev /mnt/slow echo "Start writeback pressure" sync && echo 3 > /proc/sys/vm/drop_caches mkdir /sys/fs/cgroup/test_wb echo 128M > /sys/fs/cgroup/test_wb/memory.max (echo $BASHPID > /sys/fs/cgroup/test_wb/cgroup.procs && \ dd if=/dev/zero of=/mnt/slow/testfile bs=1M count=192) echo "Clean up" echo "0 $(blockdev --getsz $LOOP) error" | dmsetup load slow_dev dmsetup resume slow_dev umount -l /mnt/slow && sync dmsetup remove slow_dev Before this commit, `dd` will get OOM killed immediately if MGLRU is enabled. Classic LRU is fine. After this commit, throttling is now effective and no more spin on LRU or premature OOM. Stress test on other workloads also looks good. Global throttling is not here yet, we will fix that separately later. Link: https://lore.kernel.org/20260428-mglru-reclaim-v7-15-02fabb92dc43@tencent.com Signed-off-by: Kairui Song Suggested-by: Chen Ridong Tested-by: Leno Hou Reviewed-by: Axel Rasmussen Reviewed-by: Baolin Wang Cc: Barry Song Cc: Chris Li Cc: David Hildenbrand Cc: David Stevens Cc: Johannes Weiner Cc: Kalesh Singh Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Vernon Yang Cc: Wei Xu Cc: Yafang Cc: Yuanchu Xie Cc: Yu Zhao Signed-off-by: Andrew Morton --- mm/vmscan.c | 92 +++++++++++++++++++++++--------------------------- 1 file changed, 43 insertions(+), 49 deletions(-) --- a/mm/vmscan.c~mm-vmscan-unify-writeback-reclaim-statistic-and-throttling +++ a/mm/vmscan.c @@ -1942,6 +1942,44 @@ static int current_may_throttle(void) return !(current->flags & PF_LOCAL_THROTTLE); } +static void handle_reclaim_writeback(unsigned long nr_taken, + struct pglist_data *pgdat, + struct scan_control *sc, + struct reclaim_stat *stat) +{ + /* + * If dirty folios are scanned that are not queued for IO, it + * implies that flushers are not doing their job. This can + * happen when memory pressure pushes dirty folios to the end of + * the LRU before the dirty limits are breached and the dirty + * data has expired. It can also happen when the proportion of + * dirty folios grows not through writes but through memory + * pressure reclaiming all the clean cache. And in some cases, + * the flushers simply cannot keep up with the allocation + * rate. Nudge the flusher threads in case they are asleep. + */ + if (stat->nr_unqueued_dirty == nr_taken) { + wakeup_flusher_threads(WB_REASON_VMSCAN); + /* + * For cgroupv1 dirty throttling is achieved by waking up + * the kernel flusher here and later waiting on folios + * which are in writeback to finish (see shrink_folio_list()). + * + * Flusher may not be able to issue writeback quickly + * enough for cgroupv1 writeback throttling to work + * on a large system. + */ + if (!writeback_throttling_sane(sc)) + reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK); + } + + sc->nr.dirty += stat->nr_dirty; + sc->nr.congested += stat->nr_congested; + sc->nr.writeback += stat->nr_writeback; + sc->nr.immediate += stat->nr_immediate; + sc->nr.taken += nr_taken; +} + /* * shrink_inactive_list() is a helper for shrink_node(). It returns the number * of reclaimed pages @@ -2005,39 +2043,7 @@ static unsigned long shrink_inactive_lis lruvec_lock_irq(lruvec); lru_note_cost_unlock_irq(lruvec, file, stat.nr_pageout, nr_scanned - nr_reclaimed); - - /* - * If dirty folios are scanned that are not queued for IO, it - * implies that flushers are not doing their job. This can - * happen when memory pressure pushes dirty folios to the end of - * the LRU before the dirty limits are breached and the dirty - * data has expired. It can also happen when the proportion of - * dirty folios grows not through writes but through memory - * pressure reclaiming all the clean cache. And in some cases, - * the flushers simply cannot keep up with the allocation - * rate. Nudge the flusher threads in case they are asleep. - */ - if (stat.nr_unqueued_dirty == nr_taken) { - wakeup_flusher_threads(WB_REASON_VMSCAN); - /* - * For cgroupv1 dirty throttling is achieved by waking up - * the kernel flusher here and later waiting on folios - * which are in writeback to finish (see shrink_folio_list()). - * - * Flusher may not be able to issue writeback quickly - * enough for cgroupv1 writeback throttling to work - * on a large system. - */ - if (!writeback_throttling_sane(sc)) - reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK); - } - - sc->nr.dirty += stat.nr_dirty; - sc->nr.congested += stat.nr_congested; - sc->nr.writeback += stat.nr_writeback; - sc->nr.immediate += stat.nr_immediate; - sc->nr.taken += nr_taken; - + handle_reclaim_writeback(nr_taken, pgdat, sc, &stat); trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id, nr_scanned, nr_reclaimed, &stat, sc->priority, file); return nr_reclaimed; @@ -4829,26 +4835,13 @@ static int evict_folios(unsigned long nr retry: reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false, memcg); sc->nr_reclaimed += reclaimed; + /* Retry pass is only meant for clean folios without new isolation */ + if (isolated) + handle_reclaim_writeback(isolated, pgdat, sc, &stat); trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id, type_scanned, reclaimed, &stat, sc->priority, type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON); - /* - * If too many file cache in the coldest generation can't be evicted - * due to being dirty, wake up the flusher. - */ - if (stat.nr_unqueued_dirty == isolated) { - wakeup_flusher_threads(WB_REASON_VMSCAN); - - /* - * For cgroupv1 dirty throttling is achieved by waking up - * the kernel flusher here and later waiting on folios - * which are in writeback to finish (see shrink_folio_list()). - */ - if (!writeback_throttling_sane(sc)) - reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK); - } - list_for_each_entry_safe_reverse(folio, next, &list, lru) { DEFINE_MIN_SEQ(lruvec); @@ -4891,6 +4884,7 @@ retry: if (!list_empty(&list)) { skip_retry = true; + isolated = 0; goto retry; } _ Patches currently in -mm which might be from kasong@tencent.com are mm-mglru-consolidate-common-code-for-retrieving-evictable-size.patch mm-mglru-rename-variables-related-to-aging-and-rotation.patch mm-mglru-relocate-the-lru-scan-batch-limit-to-callers.patch mm-mglru-restructure-the-reclaim-loop.patch mm-mglru-scan-and-count-the-exact-number-of-folios.patch mm-mglru-use-a-smaller-batch-for-reclaim.patch mm-mglru-dont-abort-scan-immediately-right-after-aging.patch mm-mglru-remove-redundant-swap-constrained-check-upon-isolation.patch mm-mglru-use-the-common-routine-for-dirty-writeback-reactivation.patch mm-mglru-simplify-and-improve-dirty-writeback-handling.patch mm-mglru-remove-no-longer-used-reclaim-argument-for-folio-protection.patch mm-vmscan-remove-sc-file_taken.patch mm-vmscan-remove-sc-unqueued_dirty.patch mm-vmscan-unify-writeback-reclaim-statistic-and-throttling.patch