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Commit 9198e96c authored by Daisuke Nishimura's avatar Daisuke Nishimura Committed by Linus Torvalds
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vmscan: handle may_swap more strictly 



Commit 2e2e4259 ("vmscan,memcg:
reintroduce sc->may_swap) add may_swap flag and handle it at
get_scan_ratio().

But the result of get_scan_ratio() is ignored when priority == 0, so anon
lru is scanned even if may_swap == 0 or nr_swap_pages == 0.  IMHO, this is
not an expected behavior.

As for memcg especially, because of this behavior many and many pages are
swapped-out just in vain when oom is invoked by mem+swap limit.

This patch is for handling may_swap flag more strictly.

Signed-off-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewed-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3eb4140f

mm/vmscan.c

+9 −9
Original line number Diff line number Diff line
@@ -1430,13 +1430,6 @@ static void get_scan_ratio(struct zone *zone, struct scan_control *sc, 
	unsigned long ap, fp;

	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);



	/* If we have no swap space, do not bother scanning anon pages. */

	if (!sc->may_swap || (nr_swap_pages <= 0)) {

		percent[0] = 0;

		percent[1] = 100;

		return;

	}



	anon  = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) +

		zone_nr_pages(zone, sc, LRU_INACTIVE_ANON);

	file  = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) +
@@ -1534,7 +1527,14 @@ static void shrink_zone(int priority, struct zone *zone, 
	enum lru_list l;

	unsigned long nr_reclaimed = sc->nr_reclaimed;

	unsigned long swap_cluster_max = sc->swap_cluster_max;

	int noswap = 0;



	/* If we have no swap space, do not bother scanning anon pages. */

	if (!sc->may_swap || (nr_swap_pages <= 0)) {

		noswap = 1;

		percent[0] = 0;

		percent[1] = 100;

	} else

		get_scan_ratio(zone, sc, percent);



	for_each_evictable_lru(l) {
@@ -1542,7 +1542,7 @@ static void shrink_zone(int priority, struct zone *zone, 
		unsigned long scan;



		scan = zone_nr_pages(zone, sc, l);

		if (priority) {

		if (priority || noswap) {

			scan >>= priority;

			scan = (scan * percent[file]) / 100;

		}