4.20-stable review patch. If anyone has any objections, please let me know.
------------------ From: Dave Chinner <[email protected]> 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/[email protected] Fixes: 172b06c32b9497 ("mm: slowly shrink slabs with a relatively small number of objects") Signed-off-by: Dave Chinner <[email protected]> Cc: Wolfgang Walter <[email protected]> Cc: Roman Gushchin <[email protected]> Cc: Spock <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Michal Hocko <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- 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",
