From 75cd1e8f7b2737a8bb2f1817f23e83135579569f Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Tue, 24 May 2011 17:11:09 -0700 Subject: [PATCH] mm: vmscan: correct use of pgdat_balanced in sleeping_prematurely commit afc7e326a3f5bafc41324d7926c324414e343ee5 upstream. 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 Reviewed-by: Rik van Riel Signed-off-by: Johannes Weiner Reviewed-by: Wu Fengguang Cc: James Bottomley Tested-by: Colin King Cc: Raghavendra D Prabhu Cc: Jan Kara Cc: Chris Mason Cc: Christoph Lameter Cc: Pekka Enberg Cc: Rik van Riel Reviewed-by: Minchan Kim Reviewed-by: Wu Fengguang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 8bfd45050a61..1aa262b1d5e2 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2286,7 +2286,7 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, * must be balanced */ if (order) - return pgdat_balanced(pgdat, balanced, classzone_idx); + return !pgdat_balanced(pgdat, balanced, classzone_idx); else return !all_zones_ok; } -- 2.39.5