4.20-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dave Chinner <dchinner@xxxxxxxxxx>
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@xxxxxxxxxxxxx
Fixes: 172b06c32b9497 ("mm: slowly shrink slabs with a relatively small number of objects")
Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Cc: Wolfgang Walter <linux@xxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Spock <dairinin@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 10 ----------
1 file changed, 10 deletions(-)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -487,16 +487,6 @@ static unsigned long do_shrink_slab(stru
delta = freeable / 2;
}
- /*
- * 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",
