From: Andrew Barry Date: Wed, 25 May 2011 00:12:52 +0000 (-0700) Subject: mm/page_alloc.c: prevent unending loop in __alloc_pages_slowpath() X-Git-Tag: v2.6.39.1~64 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=bc50c5751c34128e0cbc30e7f5ea990bd1199429;p=karo-tx-linux.git mm/page_alloc.c: prevent unending loop in __alloc_pages_slowpath() commit cfa54a0fcfc1017c6f122b6f21aaba36daa07f71 upstream. I believe I found a problem in __alloc_pages_slowpath, which allows a process to get stuck endlessly looping, even when lots of memory is available. Running an I/O and memory intensive stress-test I see a 0-order page allocation with __GFP_IO and __GFP_WAIT, running on a system with very little free memory. Right about the same time that the stress-test gets killed by the OOM-killer, the utility trying to allocate memory gets stuck in __alloc_pages_slowpath even though most of the systems memory was freed by the oom-kill of the stress-test. The utility ends up looping from the rebalance label down through the wait_iff_congested continiously. Because order=0, __alloc_pages_direct_compact skips the call to get_page_from_freelist. Because all of the reclaimable memory on the system has already been reclaimed, __alloc_pages_direct_reclaim skips the call to get_page_from_freelist. Since there is no __GFP_FS flag, the block with __alloc_pages_may_oom is skipped. The loop hits the wait_iff_congested, then jumps back to rebalance without ever trying to get_page_from_freelist. This loop repeats infinitely. The test case is pretty pathological. Running a mix of I/O stress-tests that do a lot of fork() and consume all of the system memory, I can pretty reliably hit this on 600 nodes, in about 12 hours. 32GB/node. Signed-off-by: Andrew Barry Signed-off-by: Minchan Kim Reviewed-by: Rik van Riel Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3f8bce264df6..e78b324d4064 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2064,6 +2064,7 @@ restart: first_zones_zonelist(zonelist, high_zoneidx, NULL, &preferred_zone); +rebalance: /* This is the last chance, in general, before the goto nopage. */ page = get_page_from_freelist(gfp_mask, nodemask, order, zonelist, high_zoneidx, alloc_flags & ~ALLOC_NO_WATERMARKS, @@ -2071,7 +2072,6 @@ restart: if (page) goto got_pg; -rebalance: /* Allocate without watermarks if the context allows */ if (alloc_flags & ALLOC_NO_WATERMARKS) { page = __alloc_pages_high_priority(gfp_mask, order,