4.19-stable review patch. If anyone has any objections, please let me know.
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From: Dave Chinner dchinner@redhat.com
commit a9a238e83fbb0df31c3b9b67003f8f9d1d1b6c96 upstream.
This reverts commit 172b06c32b9497 ("mm: slowly shrink slabs with a relatively small number of objects").
This change changes the agressiveness of shrinker reclaim, causing small cache and low priority reclaim to greatly increase scanning pressure on small caches. As a result, light memory pressure has a disproportionate affect on small caches, and causes large caches to be reclaimed much faster than previously.
As a result, it greatly perturbs the delicate balance of the VFS caches (dentry/inode vs file page cache) such that the inode/dentry caches are reclaimed much, much faster than the page cache and this drives us into several other caching imbalance related problems.
As such, this is a bad change and needs to be reverted.
[ Needs some massaging to retain the later seekless shrinker modifications.]
Link: http://lkml.kernel.org/r/20190130041707.27750-3-david@fromorbit.com Fixes: 172b06c32b9497 ("mm: slowly shrink slabs with a relatively small number of objects") Signed-off-by: Dave Chinner dchinner@redhat.com Cc: Wolfgang Walter linux@stwm.de Cc: Roman Gushchin guro@fb.com Cc: Spock dairinin@gmail.com Cc: Rik van Riel riel@surriel.com Cc: Michal Hocko mhocko@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/vmscan.c | 10 ---------- 1 file changed, 10 deletions(-)
--- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -477,16 +477,6 @@ static unsigned long do_shrink_slab(stru delta *= 4; do_div(delta, shrinker->seeks);
- /* - * Make sure we apply some minimal pressure on default priority - * even on small cgroups. Stale objects are not only consuming memory - * by themselves, but can also hold a reference to a dying cgroup, - * preventing it from being reclaimed. A dying cgroup with all - * corresponding structures like per-cpu stats and kmem caches - * can be really big, so it may lead to a significant waste of memory. - */ - delta = max_t(unsigned long long, delta, min(freeable, batch_size)); - total_scan += delta; if (total_scan < 0) { pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n",