From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751372AbdAYHBR (ORCPT ); Wed, 25 Jan 2017 02:01:17 -0500 Received: from out0-146.mail.aliyun.com ([140.205.0.146]:60718 "EHLO out0-146.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751286AbdAYHBQ (ORCPT ); Wed, 25 Jan 2017 02:01:16 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R201e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03278;MF=hillf.zj@alibaba-inc.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---.7W1HKdI_1485327651; Reply-To: "Hillf Danton" From: "Hillf Danton" To: "'Michal Hocko'" Cc: "'Andrew Morton'" , "'Johannes Weiner'" , "'Tetsuo Handa'" , "'David Rientjes'" , "'Mel Gorman'" , , "'LKML'" References: <20161220134904.21023-1-mhocko@kernel.org> <20161220134904.21023-3-mhocko@kernel.org> <001f01d272f7$e53acbd0$afb06370$@alibaba-inc.com> <20170124124048.GE6867@dhcp22.suse.cz> In-Reply-To: <20170124124048.GE6867@dhcp22.suse.cz> Subject: Re: [PATCH 2/3] mm, oom: do not enfore OOM killer for __GFP_NOFAIL automatically Date: Wed, 25 Jan 2017 15:00:51 +0800 Message-ID: <003a01d276d8$c41e0180$4c5a0480$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQI5GhCbBXj+0AWvuNrZg+/tQ4jXjAKoT3afAkvunb0BwIhoHKBFzqtw Content-Language: zh-cn Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, January 24, 2017 8:41 PM Michal Hocko wrote: > On Fri 20-01-17 16:33:36, Hillf Danton wrote: > > > > On Tuesday, December 20, 2016 9:49 PM Michal Hocko wrote: > > > > > > @@ -1013,7 +1013,7 @@ bool out_of_memory(struct oom_control *oc) > > > * make sure exclude 0 mask - all other users should have at least > > > * ___GFP_DIRECT_RECLAIM to get here. > > > */ > > > - if (oc->gfp_mask && !(oc->gfp_mask & (__GFP_FS|__GFP_NOFAIL))) > > > + if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS)) > > > return true; > > > > > As to GFP_NOFS|__GFP_NOFAIL request, can we check gfp mask > > one bit after another? > > > > if (oc->gfp_mask) { > > if (!(oc->gfp_mask & __GFP_FS)) > > return false; > > > > /* No service for request that can handle fail result itself */ > > if (!(oc->gfp_mask & __GFP_NOFAIL)) > > return false; > > } > > I really do not understand this request. It's a request of both NOFS and NOFAIL, and I think we can keep it from hitting oom killer by shuffling the current gfp checks. I hope it can make nit sense to your work. > This patch is removing the __GFP_NOFAIL part... Yes, and I don't stick to handling NOFAIL requests inside oom. > Besides that why should they return false? It's feedback to page allocator that no kill is issued, and extra attention is needed. thanks Hillf