From: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Subject: mm: vmscan: remove double slab pressure by inc'ing sc->nr_scanned
9092c71bb724 ("mm: use sc->priority for slab shrink targets") has broken
up the relationship between sc->nr_scanned and slab pressure. The
sc->nr_scanned can't double slab pressure anymore. So, it sounds no sense
to still keep sc->nr_scanned inc'ed. Actually, it would prevent from
adding pressure on slab shrink since excessive sc->nr_scanned would
prevent from scan->priority raise.
The bonnie test doesn't show this would change the behavior of slab
shrinkers.
w/ w/o
/sec %CP /sec %CP
Sequential delete: 3960.6 94.6 3997.6 96.2
Random delete: 2518 63.8 2561.6 64.6
The slight increase of "/sec" without the patch would be caused by the
slight increase of CPU usage.
Link: http://lkml.kernel.org/r/1559025859-72759-1-git-send-email-yang.shi@xxxxxxxxxxxxxxxxx
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 5 -----
1 file changed, 5 deletions(-)
--- a/mm/vmscan.c~mm-vmscan-remove-double-slab-pressure-by-incing-sc-nr_scanned
+++ a/mm/vmscan.c
@@ -1137,11 +1137,6 @@ static unsigned long shrink_page_list(st
if (!sc->may_unmap && page_mapped(page))
goto keep_locked;
- /* Double the slab pressure for mapped and swapcache pages */
- if ((page_mapped(page) || PageSwapCache(page)) &&
- !(PageAnon(page) && !PageSwapBacked(page)))
- sc->nr_scanned++;
-
may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
_
