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authorMel Gorman <mel@csn.ul.ie>2011-01-13 15:45:43 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 17:32:31 -0800
commitb44129b30652c8771db2265939bb8b463724043d (patch)
treed5b669ff4faea020b03e894706f49d5d1ae56907 /mm/vmscan.c
parent88f5acf88ae6a9778f6d25d0d5d7ec2d57764a97 (diff)
downloadop-kernel-dev-b44129b30652c8771db2265939bb8b463724043d.zip
op-kernel-dev-b44129b30652c8771db2265939bb8b463724043d.tar.gz
mm: vmstat: use a single setter function and callback for adjusting percpu thresholds
reduce_pgdat_percpu_threshold() and restore_pgdat_percpu_threshold() exist to adjust the per-cpu vmstat thresholds while kswapd is awake to avoid errors due to counter drift. The functions duplicate some code so this patch replaces them with a single set_pgdat_percpu_threshold() that takes a callback function to calculate the desired threshold as a parameter. [akpm@linux-foundation.org: readability tweak] [kosaki.motohiro@jp.fujitsu.com: set_pgdat_percpu_threshold(): don't use for_each_online_cpu] Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Christoph Lameter <cl@linux.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
-rw-r--r--mm/vmscan.c19
1 files changed, 17 insertions, 2 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5da4295e..86f8c34 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2448,9 +2448,24 @@ static int kswapd(void *p)
*/
if (!sleeping_prematurely(pgdat, order, remaining)) {
trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
- restore_pgdat_percpu_threshold(pgdat);
+
+ /*
+ * vmstat counters are not perfectly
+ * accurate and the estimated value
+ * for counters such as NR_FREE_PAGES
+ * can deviate from the true value by
+ * nr_online_cpus * threshold. To
+ * avoid the zone watermarks being
+ * breached while under pressure, we
+ * reduce the per-cpu vmstat threshold
+ * while kswapd is awake and restore
+ * them before going back to sleep.
+ */
+ set_pgdat_percpu_threshold(pgdat,
+ calculate_normal_threshold);
schedule();
- reduce_pgdat_percpu_threshold(pgdat);
+ set_pgdat_percpu_threshold(pgdat,
+ calculate_pressure_threshold);
} else {
if (remaining)
count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
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