path: root/mm
diff options
authorMel Gorman <mel@csn.ul.ie>2009-06-16 15:33:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:46 -0700
commit24cf72518c79cdcda486ed26074ff8151291cf65 (patch)
tree0db04965fb57135e68edf62c332c3a3825c1e3b5 /mm
parentfa5e084e43eb14c14942027e1e2e894aeed96097 (diff)
vmscan: count the number of times zone_reclaim() scans and fails
On NUMA machines, the administrator can configure zone_reclaim_mode that is a more targetted form of direct reclaim. On machines with large NUMA distances for example, a zone_reclaim_mode defaults to 1 meaning that clean unmapped pages will be reclaimed if the zone watermarks are not being met. There is a heuristic that determines if the scan is worthwhile but it is possible that the heuristic will fail and the CPU gets tied up scanning uselessly. Detecting the situation requires some guesswork and experimentation so this patch adds a counter "zreclaim_failed" to /proc/vmstat. If during high CPU utilisation this counter is increasing rapidly, then the resolution to the problem may be to set /proc/sys/vm/zone_reclaim_mode to 0. [akpm@linux-foundation.org: name things consistently] Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: Christoph Lameter <cl@linux-foundation.org> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
2 files changed, 6 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 16c82a868e2..3018ad75613 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2519,6 +2519,9 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
ret = __zone_reclaim(zone, gfp_mask, order);
zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
+ if (!ret)
return ret;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 1e3aa8139f2..138bed53706 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -673,6 +673,9 @@ static const char * const vmstat_text[] = {
+ "zone_reclaim_failed",