mm: vmscan: only update per-cpu thresholds for online CPU

When kswapd is awake reclaiming, the per-cpu stat thresholds are lowered
to get more accurate counts to avoid breaching watermarks.  This
threshold update iterates over all possible CPUs which is unnecessary.
Only online CPUs need to be updated.  If a new CPU is onlined,
refresh_zone_stat_thresholds() will set the thresholds correctly.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/vmstat.c b/mm/vmstat.c
index e574e883fa709faefad9b65545284203d79ed114..e9ab104b956f127f79598231863bd62b7f559147 100644 (file)
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -200,7 +200,7 @@ void set_pgdat_percpu_threshold(pg_data_t *pgdat,
                        continue;
 
                threshold = (*calculate_pressure)(zone);
-               for_each_possible_cpu(cpu)
+               for_each_online_cpu(cpu)
                        per_cpu_ptr(zone->pageset, cpu)->stat_threshold
                                                        = threshold;
        }