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authorMel Gorman <mgorman@suse.de>2011-07-08 18:39:38 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2011-07-09 00:14:43 -0400
commitd7868dae893c83c50c7824bc2bc75f93d114669f (patch)
tree7c9e56513ecbbf086c81ebff77310f80e0232ecc
parent08951e545918c1594434d000d88a7793e2452a9b (diff)
mm: vmscan: do not apply pressure to slab if we are not applying pressure to zone
During allocator-intensive workloads, kswapd will be woken frequently causing free memory to oscillate between the high and min watermark. This is expected behaviour. When kswapd applies pressure to zones during node balancing, it checks if the zone is above a high+balance_gap threshold. If it is, it does not apply pressure but it unconditionally shrinks slab on a global basis which is excessive. In the event kswapd is being kept awake due to a high small unreclaimable zone, it skips zone shrinking but still calls shrink_slab(). Once pressure has been applied, the check for zone being unreclaimable is being made before the check is made if all_unreclaimable should be set. This miss of unreclaimable can cause has_under_min_watermark_zone to be set due to an unreclaimable zone preventing kswapd backing off on congestion_wait(). Signed-off-by: Mel Gorman <mgorman@suse.de> Reported-by: Pádraig Brady <P@draigBrady.com> Tested-by: Pádraig Brady <P@draigBrady.com> Tested-by: Andrew Lutomirski <luto@mit.edu> Acked-by: Rik van Riel <riel@redhat.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/vmscan.c23
1 files changed, 13 insertions, 10 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 04c49fe781fe..a0245861934a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2510,18 +2510,18 @@ loop_again:
2510 KSWAPD_ZONE_BALANCE_GAP_RATIO); 2510 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2511 if (!zone_watermark_ok_safe(zone, order, 2511 if (!zone_watermark_ok_safe(zone, order,
2512 high_wmark_pages(zone) + balance_gap, 2512 high_wmark_pages(zone) + balance_gap,
2513 end_zone, 0)) 2513 end_zone, 0)) {
2514 shrink_zone(priority, zone, &sc); 2514 shrink_zone(priority, zone, &sc);
2515 reclaim_state->reclaimed_slab = 0;
2516 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2517 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2518 total_scanned += sc.nr_scanned;
2519 2515
2520 if (zone->all_unreclaimable) 2516 reclaim_state->reclaimed_slab = 0;
2521 continue; 2517 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2522 if (nr_slab == 0 && 2518 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2523 !zone_reclaimable(zone)) 2519 total_scanned += sc.nr_scanned;
2524 zone->all_unreclaimable = 1; 2520
2521 if (nr_slab == 0 && !zone_reclaimable(zone))
2522 zone->all_unreclaimable = 1;
2523 }
2524
2525 /* 2525 /*
2526 * If we've done a decent amount of scanning and 2526 * If we've done a decent amount of scanning and
2527 * the reclaim ratio is low, start doing writepage 2527 * the reclaim ratio is low, start doing writepage
@@ -2531,6 +2531,9 @@ loop_again:
2531 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 2531 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2532 sc.may_writepage = 1; 2532 sc.may_writepage = 1;
2533 2533
2534 if (zone->all_unreclaimable)
2535 continue;
2536
2534 if (!zone_watermark_ok_safe(zone, order, 2537 if (!zone_watermark_ok_safe(zone, order,
2535 high_wmark_pages(zone), end_zone, 0)) { 2538 high_wmark_pages(zone), end_zone, 0)) {
2536 all_zones_ok = 0; 2539 all_zones_ok = 0;