memcg: avoid percpu cached charge draining at softlimit

Based on Michal Hocko's comment. We are not draining per cpu cached charges during soft limit reclaim because background reclaim doesn't care about charges. It tries to free some memory and charges will not give any. Cached charges might influence only selection of the biggest soft limit offender but as the call is done only after the selection has been already done it makes no change. Signed-off-by: KAMEZAWA Hiroyuki <[email protected]> Cc: Daisuke Nishimura <[email protected]> Reviewed-by: Michal Hocko <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
diverger · Jun 16, 2011 · fbc29a2 · fbc29a2
1 parent 26fe616
commit fbc29a2
Showing 1 changed file with 7 additions and 1 deletion.
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
@@ -1670,7 +1670,13 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
 		victim = mem_cgroup_select_victim(root_mem);
 		if (victim == root_mem) {
 			loop++;
-			if (loop >= 1)
+			/*
+			 * We are not draining per cpu cached charges during
+			 * soft limit reclaim  because global reclaim doesn't
+			 * care about charges. It tries to free some memory and
+			 * charges will not give any.
+			 */
+			if (!check_soft && loop >= 1)
 				drain_all_stock_async(root_mem);
 			if (loop >= 2) {
 				/*