From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753286AbbKZJed (ORCPT ); Thu, 26 Nov 2015 04:34:33 -0500 Received: from mail-wm0-f50.google.com ([74.125.82.50]:37401 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752819AbbKZJea (ORCPT ); Thu, 26 Nov 2015 04:34:30 -0500 Date: Thu, 26 Nov 2015 10:34:27 +0100 From: Michal Hocko To: David Rientjes Cc: Andrew Morton , Mel Gorman , Johannes Weiner , linux-mm@kvack.org, LKML Subject: Re: [PATCH 1/2] mm, oom: Give __GFP_NOFAIL allocations access to memory reserves Message-ID: <20151126093427.GA7953@dhcp22.suse.cz> References: <1448448054-804-1-git-send-email-mhocko@kernel.org> <1448448054-804-2-git-send-email-mhocko@kernel.org> <20151125111801.GD27283@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 25-11-15 12:57:08, David Rientjes wrote: > On Wed, 25 Nov 2015, Michal Hocko wrote: > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 8034909faad2..94b04c1e894a 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, ac); > > + } > > out: > > mutex_unlock(&oom_lock); > > return page; > > Well, sure, that's one way to do it, but for cpuset users, wouldn't this > lead to a depletion of the first system zone since you've dropped > ALLOC_CPUSET and are doing ALLOC_NO_WATERMARKS in the same call? Are you suggesting to do? if (gfp_mask & __GFP_NOFAIL) { page = get_page_from_freelist(gfp_mask, order, ALLOC_NO_WATERMARKS|ALLOC_CPUSET, ac); /* * fallback to ignore cpuset if our nodes are * depleted */ if (!page) get_page_from_freelist(gfp_mask, order, ALLOC_NO_WATERMARKS, ac); } I am not really sure this worth complication. __GFP_NOFAIL should be relatively rare and nodes are rarely depeleted so much that ALLOC_NO_WATERMARKS wouldn't be able to allocate from the first zone in the zone list. I mean I have no problem to do the above it just sounds overcomplicating the situation without making practical difference. If you and others insist I can resping the patch though. -- Michal Hocko SUSE Labs