2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Andrew Barry <aba...@cray.com> 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 <aba...@cray.com> Signed-off-by: Minchan Kim <minchan....@gmail.com> Reviewed-by: Rik van Riel<r...@redhat.com> Acked-by: Mel Gorman <mgor...@suse.de> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gre...@suse.de> Signed-off-by: Andi Kleen <a...@linux.intel.com> --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-2.6.35.y/mm/page_alloc.c =================================================================== --- linux-2.6.35.y.orig/mm/page_alloc.c +++ linux-2.6.35.y/mm/page_alloc.c @@ -2027,6 +2027,7 @@ restart: */ alloc_flags = gfp_to_alloc_flags(gfp_mask); +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, @@ -2034,7 +2035,6 @@ 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, _______________________________________________ stable mailing list stable@linux.kernel.org http://linux.kernel.org/mailman/listinfo/stable