From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753219AbdF0NcU (ORCPT ); Tue, 27 Jun 2017 09:32:20 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:52029 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752413AbdF0NcN (ORCPT ); Tue, 27 Jun 2017 09:32:13 -0400 To: mhocko@kernel.org Cc: linux-mm@kvack.org, rientjes@google.com, oleg@redhat.com, andrea@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] mm, oom: allow oom reaper to race with exit_mmap From: Tetsuo Handa References: <20170626130346.26314-1-mhocko@kernel.org> <201706271952.FEB21375.SFJFHOQLOtVOMF@I-love.SAKURA.ne.jp> <20170627112650.GK28072@dhcp22.suse.cz> <201706272039.HGG51520.QOMHFVOFtOSJFL@I-love.SAKURA.ne.jp> <20170627120317.GL28072@dhcp22.suse.cz> In-Reply-To: <20170627120317.GL28072@dhcp22.suse.cz> Message-Id: <201706272231.ABH00025.FMOFOJSVLOQHFt@I-love.SAKURA.ne.jp> X-Mailer: Winbiff [Version 2.51 PL2] X-Accept-Language: ja,en,zh Date: Tue, 27 Jun 2017 22:31:58 +0900 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 Michal Hocko wrote: > On Tue 27-06-17 20:39:28, Tetsuo Handa wrote: > > Michal Hocko wrote: > > > > I wonder why you prefer timeout based approach. Your patch will after all > > > > set MMF_OOM_SKIP if operations between down_write() and up_write() took > > > > more than one second. > > > > > > if we reach down_write then we have unmapped the address space in > > > exit_mmap and oom reaper cannot do much more. > > > > So, by the time down_write() is called, majority of memory is already released, isn't it? > > In most cases yes. To be put it in other words. By the time exit_mmap > takes down_write there is nothing more oom reaper could reclaim. > Then, aren't there two exceptions which your patch cannot guarantee; down_write(&mm->mmap_sem) in __ksm_exit() and __khugepaged_exit() ? Since for some reason exit_mmap() cannot be brought to before ksm_exit(mm)/khugepaged_exit(mm) calls, ksm_exit(mm); khugepaged_exit(mm); /* must run before exit_mmap */ exit_mmap(mm); shouldn't we try __oom_reap_task_mm() before calling these down_write() if mm is OOM victim's? From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 86DC96B0279 for ; Tue, 27 Jun 2017 09:32:02 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id e3so26205528pfc.4 for ; Tue, 27 Jun 2017 06:32:02 -0700 (PDT) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [2001:e42:101:1:202:181:97:72]) by mx.google.com with ESMTPS id k85si1912048pfb.470.2017.06.27.06.32.01 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 27 Jun 2017 06:32:01 -0700 (PDT) Subject: Re: [RFC PATCH] mm, oom: allow oom reaper to race with exit_mmap From: Tetsuo Handa References: <20170626130346.26314-1-mhocko@kernel.org> <201706271952.FEB21375.SFJFHOQLOtVOMF@I-love.SAKURA.ne.jp> <20170627112650.GK28072@dhcp22.suse.cz> <201706272039.HGG51520.QOMHFVOFtOSJFL@I-love.SAKURA.ne.jp> <20170627120317.GL28072@dhcp22.suse.cz> In-Reply-To: <20170627120317.GL28072@dhcp22.suse.cz> Message-Id: <201706272231.ABH00025.FMOFOJSVLOQHFt@I-love.SAKURA.ne.jp> Date: Tue, 27 Jun 2017 22:31:58 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@kernel.org Cc: linux-mm@kvack.org, rientjes@google.com, oleg@redhat.com, andrea@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Michal Hocko wrote: > On Tue 27-06-17 20:39:28, Tetsuo Handa wrote: > > Michal Hocko wrote: > > > > I wonder why you prefer timeout based approach. Your patch will after all > > > > set MMF_OOM_SKIP if operations between down_write() and up_write() took > > > > more than one second. > > > > > > if we reach down_write then we have unmapped the address space in > > > exit_mmap and oom reaper cannot do much more. > > > > So, by the time down_write() is called, majority of memory is already released, isn't it? > > In most cases yes. To be put it in other words. By the time exit_mmap > takes down_write there is nothing more oom reaper could reclaim. > Then, aren't there two exceptions which your patch cannot guarantee; down_write(&mm->mmap_sem) in __ksm_exit() and __khugepaged_exit() ? Since for some reason exit_mmap() cannot be brought to before ksm_exit(mm)/khugepaged_exit(mm) calls, ksm_exit(mm); khugepaged_exit(mm); /* must run before exit_mmap */ exit_mmap(mm); shouldn't we try __oom_reap_task_mm() before calling these down_write() if mm is OOM victim's? -- 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/ . Don't email: email@kvack.org