vmscan: do not evict inactive pages when skipping an active list scan

In AIM7 runs, recent kernels start swapping out anonymous pages well
before they should.  This is due to shrink_list falling through to
shrink_inactive_list if !inactive_anon_is_low(zone, sc), when all we
really wanted to do is pre-age some anonymous pages to give them extra
time to be referenced while on the inactive list.

The obvious fix is to make sure that shrink_list does not fall through to
scanning/reclaiming inactive pages when we called it to scan one of the
active lists.

This change should be safe because the loop in shrink_zone ensures that we
will still shrink the anon and file inactive lists whenever we should.

[kosaki.motohiro@jp.fujitsu.com: inactive_file_is_low() should be inactive_anon_is_low()]
Reported-by: Larry Woodman <lwoodman@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tomasz Chmielewski <mangoo@wpkg.org>
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>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2ef59d5..0465818 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1463,20 +1463,26 @@ static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
        return low;
 }
 
+static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
+                               int file)
+{
+       if (file)
+               return inactive_file_is_low(zone, sc);
+       else
+               return inactive_anon_is_low(zone, sc);
+}
+
 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
        struct zone *zone, struct scan_control *sc, int priority)
 {
        int file = is_file_lru(lru);
 
-       if (lru == LRU_ACTIVE_FILE && inactive_file_is_low(zone, sc)) {
-               shrink_active_list(nr_to_scan, zone, sc, priority, file);
+       if (is_active_lru(lru)) {
+               if (inactive_list_is_low(zone, sc, file))
+                   shrink_active_list(nr_to_scan, zone, sc, priority, file);
                return 0;
        }
 
-       if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
-               shrink_active_list(nr_to_scan, zone, sc, priority, file);
-               return 0;
-       }
        return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
 }