From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 8421C6B002E for ; Tue, 25 Oct 2011 03:40:25 -0400 (EDT) Received: by vws16 with SMTP id 16so218231vws.14 for ; Tue, 25 Oct 2011 00:40:23 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1319524789-22818-1-git-send-email-ccross@android.com> References: <1319524789-22818-1-git-send-email-ccross@android.com> Date: Tue, 25 Oct 2011 10:40:23 +0300 Message-ID: Subject: Re: [PATCH] mm: avoid livelock on !__GFP_FS allocations From: Pekka Enberg Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Colin Cross Cc: linux-kernel@vger.kernel.org, Andrew Morton , Mel Gorman , KAMEZAWA Hiroyuki , Andrea Arcangeli , David Rientjes , linux-mm@kvack.org On Tue, Oct 25, 2011 at 9:39 AM, Colin Cross wrote: > Under the following conditions, __alloc_pages_slowpath can loop > forever: > gfp_mask & __GFP_WAIT is true > gfp_mask & __GFP_FS is false > reclaim and compaction make no progress > order <=3D PAGE_ALLOC_COSTLY_ORDER > > These conditions happen very often during suspend and resume, > when pm_restrict_gfp_mask() effectively converts all GFP_KERNEL > allocations into __GFP_WAIT. Why does it do that? Why don't we fix the gfp mask instead? > The oom killer is not run because gfp_mask & __GFP_FS is false, > but should_alloc_retry will always return true when order is less > than PAGE_ALLOC_COSTLY_ORDER. > > Fix __alloc_pages_slowpath to skip retrying when oom killer is > not allowed by the GFP flags, the same way it would skip if the > oom killer was allowed but disabled. > > Signed-off-by: Colin Cross > --- > > An alternative patch would add a did_some_progress argument to > __alloc_pages_may_oom, and remove the checks in > __alloc_pages_slowpath that require knowledge of when > __alloc_pages_may_oom chooses to run out_of_memory. If > did_some_progress was still zero, it would goto nopage whether > or not __alloc_pages_may_oom was actually called. > > =A0mm/page_alloc.c | =A0 =A04 ++++ > =A01 files changed, 4 insertions(+), 0 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index fef8dc3..dcd99b3 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2193,6 +2193,10 @@ rebalance: > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0} > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0goto restart; > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 } else { > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 /* If we aren't going to tr= y the OOM killer, give up */ > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (!(gfp_mask & __GFP_NOFA= IL)) > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 goto nopage= ; > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0} > =A0 =A0 =A0 =A0} I don't quite understand how __GFP_WAIT is involved here. Which path is causing the infinite loop? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org