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mm: vmstat: use a single setter function and callback for adjusting percpu thresholds

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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>
This commit is contained in:
Mel Gorman
2011-01-13 15:45:43 -08:00
committed by Linus Torvalds
parent 88f5acf88a
commit b44129b306
3 changed files with 30 additions and 35 deletions
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19
mm/vmscan.c
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@@ -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);