[PATCH] mm: vmscan: check mem cgroup over reclaimed

[Hillf Danton]

To avoid reduction in performance of reclaimee, checking overreclaim is added
after shrinking lru list, when pages are reclaimed from mem cgroup.

If over reclaim occurs, shrinking remaining lru lists is skipped, and no more
reclaim for reclaim/compaction.

Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx>
---

--- a/mm/vmscan.c	Mon Jan 23 00:23:10 2012
+++ b/mm/vmscan.c	Mon Jan 23 09:57:20 2012
@@ -2086,6 +2086,7 @@ static void shrink_mem_cgroup_zone(int p
 	unsigned long nr_reclaimed, nr_scanned;
 	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
 	struct blk_plug plug;
+	bool memcg_over_reclaimed = false;

 restart:
 	nr_reclaimed = 0;
@@ -2103,6 +2104,11 @@ restart:

 				nr_reclaimed += shrink_list(lru, nr_to_scan,
 							    mz, sc, priority);
+
+				memcg_over_reclaimed = !scanning_global_lru(mz)
+					&& (nr_reclaimed >= nr_to_reclaim);
+				if (memcg_over_reclaimed)
+					goto out;
 			}
 		}
 		/*
@@ -2116,6 +2122,7 @@ restart:
 		if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
 			break;
 	}
+out:
 	blk_finish_plug(&plug);
 	sc->nr_reclaimed += nr_reclaimed;

@@ -2127,7 +2134,8 @@ restart:
 		shrink_active_list(SWAP_CLUSTER_MAX, mz, sc, priority, 0);

 	/* reclaim/compaction might need reclaim to continue */
-	if (should_continue_reclaim(mz, nr_reclaimed,
+	if (!memcg_over_reclaimed &&
+	    should_continue_reclaim(mz, nr_reclaimed,
 					sc->nr_scanned - nr_scanned, sc))
 		goto restart;
--
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