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Subject[PATCH 4.19 69/85] Revert "mm: slowly shrink slabs with a relatively small number of objects"
Date
4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

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",

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