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vmscan: protect reading of reclaim_stat with lru_lock 

Rik van Riel pointed out reading reclaim_stat should be protected
lru_lock, otherwise vmscan might sweep 2x much pages.

This fault was introduced by

  commit 4f98a2fee8
  Author: Rik van Riel <riel@redhat.com>
  Date:   Sat Oct 18 20:26:32 2008 -0700

    vmscan: split LRU lists into anon & file sets

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KOSAKI Motohiro 2010-08-09 17:19:51 -07:00 committed by Linus Torvalds
parent 1574804899
commit 58c37f6e0d
1 changed files with 9 additions and 11 deletions
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20
mm/vmscan.c
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@ -1627,6 +1627,13 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
}
}
/*
* With swappiness at 100, anonymous and file have the same priority.
* This scanning priority is essentially the inverse of IO cost.
*/
anon_prio = sc->swappiness;
file_prio = 200 - sc->swappiness;
/*
* OK, so we have swap space and a fair amount of page cache
* pages. We use the recently rotated / recently scanned
@ -1638,27 +1645,17 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
*
* anon in [0], file in [1]
*/
spin_lock_irq(&zone->lru_lock);
if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
spin_lock_irq(&zone->lru_lock);
reclaim_stat->recent_scanned[0] /= 2;
reclaim_stat->recent_rotated[0] /= 2;
spin_unlock_irq(&zone->lru_lock);
}
if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
spin_lock_irq(&zone->lru_lock);
reclaim_stat->recent_scanned[1] /= 2;
reclaim_stat->recent_rotated[1] /= 2;
spin_unlock_irq(&zone->lru_lock);
}
/*
* With swappiness at 100, anonymous and file have the same priority.
* This scanning priority is essentially the inverse of IO cost.
*/
anon_prio = sc->swappiness;
file_prio = 200 - sc->swappiness;
/*
* The amount of pressure on anon vs file pages is inversely
* proportional to the fraction of recently scanned pages on
@ -1669,6 +1666,7 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
fp /= reclaim_stat->recent_rotated[1] + 1;
spin_unlock_irq(&zone->lru_lock);
fraction[0] = ap;
fraction[1] = fp;