From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753508AbdF2UNa (ORCPT ); Thu, 29 Jun 2017 16:13:30 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:30993 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751615AbdF2UN3 (ORCPT ); Thu, 29 Jun 2017 16:13:29 -0400 To: guro@fb.com Cc: linux-mm@kvack.org, mhocko@kernel.org, vdavydov.dev@gmail.com, hannes@cmpxchg.org, tj@kernel.org, kernel-team@fb.com, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [v3 1/6] mm, oom: use oom_victims counter to synchronize oom victim selection From: Tetsuo Handa References: <201706220040.v5M0eSnK074332@www262.sakura.ne.jp> <20170622165858.GA30035@castle> <201706230537.IDB21366.SQHJVFOOFOMFLt@I-love.SAKURA.ne.jp> <201706230652.FDH69263.OtOLFSFMHFOQJV@I-love.SAKURA.ne.jp> <20170629184748.GB27714@castle> In-Reply-To: <20170629184748.GB27714@castle> Message-Id: <201706300513.BGC60962.LQFJOOtMOFVFSH@I-love.SAKURA.ne.jp> X-Mailer: Winbiff [Version 2.51 PL2] X-Accept-Language: ja,en,zh Date: Fri, 30 Jun 2017 05:13:13 +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 Roman Gushchin wrote: > On Fri, Jun 23, 2017 at 06:52:20AM +0900, Tetsuo Handa wrote: > > Tetsuo Handa wrote: > > Oops, I misinterpreted. This is where a multithreaded OOM victim with or without > > the OOM reaper can get stuck forever. Think about a process with two threads is > > selected by the OOM killer and only one of these two threads can get TIF_MEMDIE. > > > > Thread-1 Thread-2 The OOM killer The OOM reaper > > > > Calls down_write(¤t->mm->mmap_sem). > > Enters __alloc_pages_slowpath(). > > Enters __alloc_pages_slowpath(). > > Takes oom_lock. > > Calls out_of_memory(). > > Selects Thread-1 as an OOM victim. > > Gets SIGKILL. Gets SIGKILL. > > Gets TIF_MEMDIE. > > Releases oom_lock. > > Leaves __alloc_pages_slowpath() because Thread-1 has TIF_MEMDIE. > > Takes oom_lock. > > Will do nothing because down_read_trylock() fails. > > Releases oom_lock. > > Gives up and sets MMF_OOM_SKIP after one second. > > Takes oom_lock. > > Calls out_of_memory(). > > Will not check MMF_OOM_SKIP because Thread-1 still has TIF_MEMDIE. // <= get stuck waiting for Thread-1. > > Releases oom_lock. > > Will not leave __alloc_pages_slowpath() because Thread-2 does not have TIF_MEMDIE. > > Will not call up_write(¤t->mm->mmap_sem). > > Reaches do_exit(). > > Calls down_read(¤t->mm->mmap_sem) in exit_mm() in do_exit(). // <= get stuck waiting for Thread-2. > > Will not call up_read(¤t->mm->mmap_sem) in exit_mm() in do_exit(). > > Will not clear TIF_MEMDIE in exit_oom_victim() in exit_mm() in do_exit(). > > That's interesting... Does it mean, that we have to give an access to the reserves > to all threads to guarantee the forward progress? Yes, for we don't have __GFP_KILLABLE flag. > > What do you think about Michal's approach? He posted a link in the thread. Please read that thread. 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 1991C6B0292 for ; Thu, 29 Jun 2017 16:13:39 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id y62so96373823pfa.3 for ; Thu, 29 Jun 2017 13:13:39 -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 q2si4666210plh.464.2017.06.29.13.13.37 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 29 Jun 2017 13:13:38 -0700 (PDT) Subject: Re: [v3 1/6] mm, oom: use oom_victims counter to synchronize oom victim selection From: Tetsuo Handa References: <201706220040.v5M0eSnK074332@www262.sakura.ne.jp> <20170622165858.GA30035@castle> <201706230537.IDB21366.SQHJVFOOFOMFLt@I-love.SAKURA.ne.jp> <201706230652.FDH69263.OtOLFSFMHFOQJV@I-love.SAKURA.ne.jp> <20170629184748.GB27714@castle> In-Reply-To: <20170629184748.GB27714@castle> Message-Id: <201706300513.BGC60962.LQFJOOtMOFVFSH@I-love.SAKURA.ne.jp> Date: Fri, 30 Jun 2017 05:13:13 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: guro@fb.com Cc: linux-mm@kvack.org, mhocko@kernel.org, vdavydov.dev@gmail.com, hannes@cmpxchg.org, tj@kernel.org, kernel-team@fb.com, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Roman Gushchin wrote: > On Fri, Jun 23, 2017 at 06:52:20AM +0900, Tetsuo Handa wrote: > > Tetsuo Handa wrote: > > Oops, I misinterpreted. This is where a multithreaded OOM victim with or without > > the OOM reaper can get stuck forever. Think about a process with two threads is > > selected by the OOM killer and only one of these two threads can get TIF_MEMDIE. > > > > Thread-1 Thread-2 The OOM killer The OOM reaper > > > > Calls down_write(¤t->mm->mmap_sem). > > Enters __alloc_pages_slowpath(). > > Enters __alloc_pages_slowpath(). > > Takes oom_lock. > > Calls out_of_memory(). > > Selects Thread-1 as an OOM victim. > > Gets SIGKILL. Gets SIGKILL. > > Gets TIF_MEMDIE. > > Releases oom_lock. > > Leaves __alloc_pages_slowpath() because Thread-1 has TIF_MEMDIE. > > Takes oom_lock. > > Will do nothing because down_read_trylock() fails. > > Releases oom_lock. > > Gives up and sets MMF_OOM_SKIP after one second. > > Takes oom_lock. > > Calls out_of_memory(). > > Will not check MMF_OOM_SKIP because Thread-1 still has TIF_MEMDIE. // <= get stuck waiting for Thread-1. > > Releases oom_lock. > > Will not leave __alloc_pages_slowpath() because Thread-2 does not have TIF_MEMDIE. > > Will not call up_write(¤t->mm->mmap_sem). > > Reaches do_exit(). > > Calls down_read(¤t->mm->mmap_sem) in exit_mm() in do_exit(). // <= get stuck waiting for Thread-2. > > Will not call up_read(¤t->mm->mmap_sem) in exit_mm() in do_exit(). > > Will not clear TIF_MEMDIE in exit_oom_victim() in exit_mm() in do_exit(). > > That's interesting... Does it mean, that we have to give an access to the reserves > to all threads to guarantee the forward progress? Yes, for we don't have __GFP_KILLABLE flag. > > What do you think about Michal's approach? He posted a link in the thread. Please read that thread. -- 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