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authorJohannes Weiner <jweiner@redhat.com>2012-01-12 17:18:06 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-08-01 12:27:19 -0700
commit4d01a2e38a9c27d3de083ecc561b32b6a55fc7eb (patch)
tree99676c408822e631b1576e04241bd12d7d9cf875
parentd2b02236b85226c9f2cd28e32a9fdf197584e448 (diff)
mm: vmscan: convert global reclaim to per-memcg LRU lists
commit b95a2f2d486d0d768a92879c023a03757b9c7e58 upstream - WARNING: this is a substitute patch. Stable note: Not tracked in Bugzilla. This is a partial backport of an upstream commit addressing a completely different issue that accidentally contained an important fix. The workload this patch helps was memcached when IO is started in the background. memcached should stay resident but without this patch it gets swapped. Sometimes this manifests as a drop in throughput but mostly it was observed through /proc/vmstat. Commit [246e87a9: memcg: fix get_scan_count() for small targets] was meant to fix a problem whereby small scan targets on memcg were ignored causing priority to raise too sharply. It forced scanning to take place if the target was small, memcg or kswapd. From the time it was introduced it caused excessive reclaim by kswapd with workloads being pushed to swap that previously would have stayed resident. This was accidentally fixed in commit [b95a2f2d: mm: vmscan: convert global reclaim to per-memcg LRU lists] by making it harder for kswapd to force scan small targets but that patchset is not suitable for backporting. This was later changed again by commit [90126375: mm/vmscan: push lruvec pointer into get_scan_count()] into a format that looks like it would be a straight-forward backport but there is a subtle difference due to the use of lruvecs. The impact of the accidental fix is to make it harder for kswapd to force scan small targets by taking zone->all_unreclaimable into account. This patch is the closest equivalent available based on what is backported. Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--mm/vmscan.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 39bb4161bb06..6697b7ab99c2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1850,7 +1850,8 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
unsigned long nr_force_scan[2];
/* kswapd does zone balancing and needs to scan this zone */
- if (scanning_global_lru(sc) && current_is_kswapd())
+ if (scanning_global_lru(sc) && current_is_kswapd() &&
+ zone->all_unreclaimable)
force_scan = true;
/* memcg may have small limit and need to avoid priority drop */
if (!scanning_global_lru(sc))