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authorKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>2010-08-10 00:19:54 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2010-08-10 03:45:03 (GMT)
commit4dc4b3d971b23e12d483ba9f3b93b648c54b298a (patch)
tree845cc8debe146f683510841982323c338eb10000 /mm/vmscan.c
parent57250a5bf0f6ff68dc339572adbd881a11f366fa (diff)
vmscan: shrink_slab() requires the number of lru_pages, not the page order
Presently shrink_slab() has the following scanning equation. lru_scanned max_pass basic_scan_objects = 4 x ------------- x ----------------------------- lru_pages shrinker->seeks (default:2) scan_objects = min(basic_scan_objects, max_pass * 2) If we pass very small value as lru_pages instead real number of lru pages, shrink_slab() drop much objects rather than necessary. And now, __zone_reclaim() pass 'order' as lru_pages by mistake. That produces a bad result. For example, if we receive very low memory pressure (scan = 32, order = 0), shrink_slab() via zone_reclaim() always drop _all_ icache/dcache objects. (see above equation, very small lru_pages make very big scan_objects result). This patch fixes it. [akpm@linux-foundation.org: fix layout, typos] Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Acked-by: Christoph Lameter <cl@linux-foundation.org> Acked-by: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
-rw-r--r--mm/vmscan.c17
1 files changed, 13 insertions, 4 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index a3d669f..9789a2c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2635,10 +2635,19 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
* Note that shrink_slab will free memory on all zones and may
* take a long time.
*/
- while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
- (zone_page_state(zone, NR_SLAB_RECLAIMABLE) + nr_pages >
- nr_slab_pages0))
- ;
+ for (;;) {
+ unsigned long lru_pages = zone_reclaimable_pages(zone);
+
+ /* No reclaimable slab or very low memory pressure */
+ if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages))
+ break;
+
+ /* Freed enough memory */
+ nr_slab_pages1 = zone_page_state(zone,
+ NR_SLAB_RECLAIMABLE);
+ if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
+ break;
+ }
/*
* Update nr_reclaimed by the number of slab pages we

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