From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DF65C282C0 for ; Sun, 27 Jan 2019 10:56:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CBF8C214C6 for ; Sun, 27 Jan 2019 10:56:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726671AbfA0K4S (ORCPT ); Sun, 27 Jan 2019 05:56:18 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:21595 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726453AbfA0K4S (ORCPT ); Sun, 27 Jan 2019 05:56:18 -0500 Received: from fsav106.sakura.ne.jp (fsav106.sakura.ne.jp [27.133.134.233]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id x0RAuF88050388; Sun, 27 Jan 2019 19:56:15 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav106.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav106.sakura.ne.jp); Sun, 27 Jan 2019 19:56:15 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav106.sakura.ne.jp) Received: from [192.168.1.8] (softbank126126163036.bbtec.net [126.126.163.36]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id x0RAuAXl050345 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Sun, 27 Jan 2019 19:56:15 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH v2] oom, oom_reaper: do not enqueue same task twice To: Michal Hocko Cc: =?UTF-8?Q?Arkadiusz_Mi=c5=9bkiewicz?= , Andrew Morton , Tejun Heo , cgroups@vger.kernel.org, Aleksa Sarai , Jay Kamat , Roman Gushchin , Johannes Weiner , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm References: <1cdbef13-564d-61a6-95f4-579d2cad243d@gmail.com> <20190125163731.GJ50184@devbig004.ftw2.facebook.com> <480296c4-ed7a-3265-e84a-298e42a0f1d5@I-love.SAKURA.ne.jp> <6da6ca69-5a6e-a9f6-d091-f89a8488982a@gmail.com> <72aa8863-a534-b8df-6b9e-f69cf4dd5c4d@i-love.sakura.ne.jp> <33a07810-6dbc-36be-5bb6-a279773ccf69@i-love.sakura.ne.jp> <34e97b46-0792-cc66-e0f2-d72576cdec59@i-love.sakura.ne.jp> <2b0c7d6c-c58a-da7d-6f0a-4900694ec2d3@gmail.com> <1d161137-55a5-126f-b47e-b2625bd798ca@i-love.sakura.ne.jp> <20190127083724.GA18811@dhcp22.suse.cz> From: Tetsuo Handa Message-ID: Date: Sun, 27 Jan 2019 19:56:06 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190127083724.GA18811@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Archived-At: List-Archive: List-Post: On 2019/01/27 17:37, Michal Hocko wrote: > Thanks for the analysis and the patch. This should work, I believe but > I am not really thrilled to overload the meaning of the MMF_UNSTABLE. > The flag is meant to signal accessing address space is not stable and it > is not aimed to synchronize oom reaper with the oom path. > > Can we make use mark_oom_victim directly? I didn't get to think that > through right now so I might be missing something but this should > prevent repeating queueing as well. Yes, TIF_MEMDIE would work. But you are planning to remove TIF_MEMDIE. Also, TIF_MEMDIE can't avoid enqueuing many threads sharing mm_struct to the OOM reaper. There is no need to enqueue many threads sharing mm_struct because the OOM reaper acts on mm_struct rather than task_struct. Thus, enqueuing based on per mm_struct flag sounds better, but MMF_OOM_VICTIM cannot be set from wake_oom_reaper(victim) because victim's mm might be already inside exit_mmap() when wake_oom_reaper(victim) is called after task_unlock(victim). We could reintroduce MMF_OOM_KILLED in commit 855b018325737f76 ("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task") if you don't like overloading the meaning of the MMF_UNSTABLE. But since MMF_UNSTABLE is available in Linux 4.9+ kernels (which covers all LTS stable versions with the OOM reaper support), we can temporarily use MMF_UNSTABLE for ease of backporting.