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| author | Mel Gorman <mel@csn.ul.ie> | 2009-06-16 15:33:23 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2009-07-02 16:50:57 -0700 |
| commit | cc2b6aacfc0e7a9288ed7ea518ff122454ccf7fb (patch) | |
| tree | 5e3cabc3fe3fcbf52ff7cedd3177032b8f32dabf /mm | |
| parent | bf7d6057f101bd046f35bd865a7640eac727f7f3 (diff) | |
| download | lwn-cc2b6aacfc0e7a9288ed7ea518ff122454ccf7fb.tar.gz lwn-cc2b6aacfc0e7a9288ed7ea518ff122454ccf7fb.zip | |
vmscan: count the number of times zone_reclaim() scans and fails
commit 24cf72518c79cdcda486ed26074ff8151291cf65 upstream.
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/vmscan.c | 3 | ||||
| -rw-r--r-- | mm/vmstat.c | 3 |
2 files changed, 6 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index d51e9937ff20..2500b01e7a78 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2452,6 +2452,9 @@ 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) + count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); + return ret; } #endif diff --git a/mm/vmstat.c b/mm/vmstat.c index 74d66dba0cbe..ddb360a09efd 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -675,6 +675,9 @@ static const char * const vmstat_text[] = { TEXTS_FOR_ZONES("pgscan_kswapd") TEXTS_FOR_ZONES("pgscan_direct") +#ifdef CONFIG_NUMA + "zone_reclaim_failed", +#endif "pginodesteal", "slabs_scanned", "kswapd_steal", |