The patch titled
mm-page-allocator-adjust-the-per-cpu-counter-threshold-when-memory-is-low-update
has been added to the -mm tree. Its filename is
mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-update.patch
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------------------------------------------------------
Subject: mm-page-allocator-adjust-the-per-cpu-counter-threshold-when-memory-is-low-update
From: Mel Gorman <mel@xxxxxxxxx>
mm: vmscan: Comment on why kswapd reduces the per-cpu vmstat threshold
While kswapd is awake, the per-cpu vmstat threshold is reduced to
reduce per-cpu drift to acceptable levels. Add a comment explaining
why.
Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff -puN mm/vmscan.c~mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-update mm/vmscan.c
--- a/mm/vmscan.c~mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-update
+++ a/mm/vmscan.c
@@ -2441,6 +2441,19 @@ static int kswapd(void *p)
*/
if (!sleeping_prematurely(pgdat, order, remaining)) {
trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
+
+ /*
+ * 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();
_
Patches currently in -mm which might be from mel@xxxxxxxxx are
linux-next.patch
mm-page-allocator-adjust-the-per-cpu-counter-threshold-when-memory-is-low.patch
mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds.patch
mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-fix.patch
mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-update.patch
factor-out-kswapd-sleeping-logic-from-kswapd.patch
add-debugging-aid-for-memory-initialisation-problems.patch
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