From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752283AbbKYKvm (ORCPT ); Wed, 25 Nov 2015 05:51:42 -0500 Received: from mail-pa0-f48.google.com ([209.85.220.48]:34536 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751174AbbKYKvk (ORCPT ); Wed, 25 Nov 2015 05:51:40 -0500 Date: Wed, 25 Nov 2015 02:51:38 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Michal Hocko cc: Andrew Morton , Mel Gorman , Johannes Weiner , linux-mm@kvack.org, LKML , Michal Hocko Subject: Re: [PATCH 1/2] mm, oom: Give __GFP_NOFAIL allocations access to memory reserves In-Reply-To: <1448448054-804-2-git-send-email-mhocko@kernel.org> Message-ID: References: <1448448054-804-1-git-send-email-mhocko@kernel.org> <1448448054-804-2-git-send-email-mhocko@kernel.org> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 25 Nov 2015, Michal Hocko wrote: > From: Michal Hocko > > __GFP_NOFAIL is a big hammer used to ensure that the allocation > request can never fail. This is a strong requirement and as such > it also deserves a special treatment when the system is OOM. The > primary problem here is that the allocation request might have > come with some locks held and the oom victim might be blocked > on the same locks. This is basically an OOM deadlock situation. > > This patch tries to reduce the risk of such a deadlocks by giving > __GFP_NOFAIL allocations a special treatment and let them dive into > memory reserves after oom killer invocation. This should help them > to make a progress and release resources they are holding. The OOM > victim should compensate for the reserves consumption. > > Suggested-by: Andrea Arcangeli > Signed-off-by: Michal Hocko > --- > mm/page_alloc.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 8034909faad2..70db11c27046 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2766,8 +2766,13 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order, > goto out; > } > /* Exhausted what can be done so it's blamo time */ > - if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) > + if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) { > *did_some_progress = 1; > + > + if (gfp_mask & __GFP_NOFAIL) > + page = get_page_from_freelist(gfp_mask, order, > + ALLOC_NO_WATERMARKS|ALLOC_CPUSET, ac); > + } > out: > mutex_unlock(&oom_lock); > return page; I don't understand why you're setting ALLOC_CPUSET if you're giving them "special treatment". If you want to allow access to memory reserves to prevent an oom livelock, then why not also allow it access to allocate outside its cpuset?