Commit 9786bf84 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
Browse files

vmscan: clip swap_cluster_max in shrink_all_memory()



shrink_inactive_list() scans in sc->swap_cluster_max chunks until it hits
the scan limit it was passed.

shrink_inactive_list()
{
	do {
		isolate_pages(swap_cluster_max)
		shrink_page_list()
	} while (nr_scanned < max_scan);
}

This assumes that swap_cluster_max is not bigger than the scan limit
because the latter is checked only after at least one iteration.

In shrink_all_memory() sc->swap_cluster_max is initialized to the overall
reclaim goal in the beginning but not decreased while reclaim is making
progress which leads to subsequent calls to shrink_inactive_list()
reclaiming way too much in the one iteration that is done unconditionally.

Set sc->swap_cluster_max always to the proper goal before doing
  shrink_all_zones()
    shrink_list()
      shrink_inactive_list().

While the current shrink_all_memory() happily reclaims more than actually
requested, this patch fixes it to never exceed the goal:

unpatched
   wanted=10000 reclaimed=13356
   wanted=10000 reclaimed=19711
   wanted=10000 reclaimed=10289
   wanted=10000 reclaimed=17306
   wanted=10000 reclaimed=10700
   wanted=10000 reclaimed=10004
   wanted=10000 reclaimed=13301
   wanted=10000 reclaimed=10976
   wanted=10000 reclaimed=10605
   wanted=10000 reclaimed=10088
   wanted=10000 reclaimed=15000

patched
   wanted=10000 reclaimed=10000
   wanted=10000 reclaimed=9599
   wanted=10000 reclaimed=8476
   wanted=10000 reclaimed=8326
   wanted=10000 reclaimed=10000
   wanted=10000 reclaimed=10000
   wanted=10000 reclaimed=9919
   wanted=10000 reclaimed=10000
   wanted=10000 reclaimed=10000
   wanted=10000 reclaimed=10000
   wanted=10000 reclaimed=10000
   wanted=10000 reclaimed=9624
   wanted=10000 reclaimed=10000
   wanted=10000 reclaimed=10000
   wanted=8500 reclaimed=8092
   wanted=316 reclaimed=316
Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarMinChan Kim <minchan.kim@gmail.com>
Acked-by: default avatarNigel Cunningham <ncunningham@crca.org.au>
Acked-by: default avatar"Rafael J. Wysocki" <rjw@sisk.pl>
Reviewed-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d979677c
......@@ -2109,7 +2109,6 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.may_unmap = 0,
.swap_cluster_max = nr_pages,
.may_writepage = 1,
.isolate_pages = isolate_pages_global,
};
......@@ -2151,6 +2150,7 @@ unsigned long shrink_all_memory(unsigned long nr_pages)
unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
sc.nr_scanned = 0;
sc.swap_cluster_max = nr_to_scan;
shrink_all_zones(nr_to_scan, prio, pass, &sc);
if (sc.nr_reclaimed >= nr_pages)
goto out;
......
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