Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754770Ab1EXIen (ORCPT ); Tue, 24 May 2011 04:34:43 -0400 Received: from mail-qw0-f46.google.com ([209.85.216.46]:56021 "EHLO mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754697Ab1EXIel convert rfc822-to-8bit (ORCPT ); Tue, 24 May 2011 04:34:41 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=b4DSc6+b82aHfCuDwN/Jq/Z9KZHJfaCzmtDzwTgIkKIkWp5devAwuWvIhYSqi9/oax iEBwEQ/HwM9kzf9IePWtMfb87LrVW2SIHXmDBiVRF1nenFz8lVyYR8pIm7JY8GJLu+oF 36iYf9TT1Wfm8uoaFLlv2J6wDfvV2gjWTIJ9Q= MIME-Version: 1.0 In-Reply-To: <4DDB3A1E.6090206@jp.fujitsu.com> References: <4DCDA347.9080207@cray.com> <4DD2991B.5040707@cray.com> <20110520164924.GB2386@barrios-desktop> <4DDB3A1E.6090206@jp.fujitsu.com> Date: Tue, 24 May 2011 17:34:40 +0900 Message-ID: Subject: Re: Unending loop in __alloc_pages_slowpath following OOM-kill; rfc: patch. From: Minchan Kim To: KOSAKI Motohiro Cc: abarry@cray.com, akpm@linux-foundation.org, linux-mm@kvack.org, mgorman@suse.de, riel@redhat.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, Wu Fengguang Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4628 Lines: 110 On Tue, May 24, 2011 at 1:54 PM, KOSAKI Motohiro wrote: >>>From 8bd3f16736548375238161d1bd85f7d7c381031f Mon Sep 17 00:00:00 2001 >> From: Minchan Kim >> Date: Sat, 21 May 2011 01:37:41 +0900 >> Subject: [PATCH] Prevent unending loop in __alloc_pages_slowpath >> >> From: Andrew Barry >> >> 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 >> Reviewed-by: Minchan Kim >> Cc: Mel Gorman >> --- >>  mm/page_alloc.c |    2 +- >>  1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 3f8bce2..e78b324 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, > > I'm sorry I missed this thread long time. No problem. It would be better than not review. > > In this case, I think we should call drain_all_pages(). then following > patch is better. Strictly speaking, this problem isn't related to drain_all_pages. This problem caused by lru empty but I admit it could work well if your patch applied. So yours could help, too. > However I also think your patch is valuable. because while the task is > sleeping in wait_iff_congested(), an another task may free some pages. > thus, rebalance path should try to get free pages. iow, you makes sense. Yes. Off-topic. I would like to move cond_resched below get_page_from_freelist in __alloc_pages_direct_reclaim. Otherwise, it is likely we can be stolen pages to other processes. One more benefit is that if it's apparently OOM path(ie, did_some_progress = 0), we can reduce OOM kill latency due to remove unnecessary cond_resched. > > So, I'd like to propose to merge both your and my patch. Recently, there was discussion on drain_all_pages with Wu. He saw much overhead in 8-core system, AFAIR. I Cced Wu. How about checking per-cpu before calling drain_all_pages() than unconditional calling? if (per_cpu_ptr(zone->pageset, smp_processor_id()) drain_all_pages(); Of course, It can miss other CPU free pages. But above routine assume local cpu direct reclaim is successful but it failed by per-cpu. So I think it works. Thanks for good suggestion and Reviewed-by, KOSAKI. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/