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authorJohannes Weiner <hannes@cmpxchg.org>2011-05-24 20:11:09 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2011-05-25 11:39:01 -0400
commitafc7e326a3f5bafc41324d7926c324414e343ee5 (patch)
treec7b06a424b7a35840a41dca008291ca5dcad9b42
parenta71ae47a2cbfa542c69f695809124da4e4dd9e8f (diff)
mm: vmscan: correct use of pgdat_balanced in sleeping_prematurely
There are a few reports of people experiencing hangs when copying large amounts of data with kswapd using a large amount of CPU which appear to be due to recent reclaim changes. SLUB using high orders is the trigger but not the root cause as SLUB has been using high orders for a while. The root cause was bugs introduced into reclaim which are addressed by the following two patches. Patch 1 corrects logic introduced by commit 1741c877 ("mm: kswapd: keep kswapd awake for high-order allocations until a percentage of the node is balanced") to allow kswapd to go to sleep when balanced for high orders. Patch 2 notes that it is possible for kswapd to miss every cond_resched() and updates shrink_slab() so it'll at least reach that scheduling point. Chris Wood reports that these two patches in isolation are sufficient to prevent the system hanging. AFAIK, they should also resolve similar hangs experienced by James Bottomley. This patch: Johannes Weiner poined out that the logic in commit 1741c877 ("mm: kswapd: keep kswapd awake for high-order allocations until a percentage of the node is balanced") is backwards. Instead of allowing kswapd to go to sleep when balancing for high order allocations, it keeps it kswapd running uselessly. Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Wu Fengguang <fengguang.wu@intel.com> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Tested-by: Colin King <colin.king@canonical.com> Cc: Raghavendra D Prabhu <raghu.prabhu13@gmail.com> Cc: Jan Kara <jack@suse.cz> Cc: Chris Mason <chris.mason@oracle.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Rik van Riel <riel@redhat.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: Wu Fengguang <fengguang.wu@intel.com> Cc: <stable@kernel.org> [2.6.38+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/vmscan.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c9177202c8ce..66698f603aa4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2287,7 +2287,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2287 * must be balanced 2287 * must be balanced
2288 */ 2288 */
2289 if (order) 2289 if (order)
2290 return pgdat_balanced(pgdat, balanced, classzone_idx); 2290 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2291 else 2291 else
2292 return !all_zones_ok; 2292 return !all_zones_ok;
2293} 2293}