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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 99767C433F5 for ; Tue, 19 Oct 2021 10:30:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7893A61381 for ; Tue, 19 Oct 2021 10:30:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235197AbhJSKcs (ORCPT ); Tue, 19 Oct 2021 06:32:48 -0400 Received: from relay.sw.ru ([185.231.240.75]:41566 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230117AbhJSKcq (ORCPT ); Tue, 19 Oct 2021 06:32:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Content-Type:MIME-Version:Date:Message-ID:From: Subject; bh=foWliLIfpQWzapm4jJyfpBLdUGM8c6MljuN+v8bBOMc=; b=HdOLW0+VUbhUAxYyo xFMPtfsWVBp7UcoRg/Zyv+rg7ln267R85lA7sDQe4R3blKbiQDbiviad9ir7keWF83BPjZ9eXkR5a bfXlJDPi5jOXZ9Kh+XwmYPvarrYj3wU4HWh9bCk1K/JcHXJQiSdnyiJkUl6iPplUlxMovK5UQCd24 =; Received: from [172.29.1.17] by relay.sw.ru with esmtp (Exim 4.94.2) (envelope-from ) id 1mcmO3-006Sfx-3x; Tue, 19 Oct 2021 13:30:27 +0300 Subject: Re: [PATCH memcg 0/1] false global OOM triggered by memcg-limited task To: Michal Hocko Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Roman Gushchin , Uladzislau Rezki , Vlastimil Babka , Shakeel Butt , Mel Gorman , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel@openvz.org References: <9d10df01-0127-fb40-81c3-cc53c9733c3e@virtuozzo.com> <6b751abe-aa52-d1d8-2631-ec471975cc3a@virtuozzo.com> <339ae4b5-6efd-8fc2-33f1-2eb3aee71cb2@virtuozzo.com> From: Vasily Averin Message-ID: <687bf489-f7a7-5604-25c5-0c1a09e0905b@virtuozzo.com> Date: Tue, 19 Oct 2021 13:30:06 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19.10.2021 11:49, Michal Hocko wrote: > On Tue 19-10-21 09:30:18, Vasily Averin wrote: > [...] >> With my patch ("memcg: prohibit unconditional exceeding the limit of dying tasks") try_charge_memcg() can fail: >> a) due to fatal signal >> b) when mem_cgroup_oom -> mem_cgroup_out_of_memory -> out_of_memory() returns false (when select_bad_process() found nothing) >> >> To handle a) we can follow to your suggestion and skip excution of out_of_memory() in pagefault_out_of memory() >> To handle b) we can go to retry: if mem_cgroup_oom() return OOM_FAILED. > How is b) possible without current being killed? Do we allow remote > charging? out_of_memory for memcg_oom select_bad_process mem_cgroup_scan_tasks oom_evaluate_task oom_badness /* * Do not even consider tasks which are explicitly marked oom * unkillable or have been already oom reaped or the are in * the middle of vfork */ adj = (long)p->signal->oom_score_adj; if (adj == OOM_SCORE_ADJ_MIN || test_bit(MMF_OOM_SKIP, &p->mm->flags) || in_vfork(p)) { task_unlock(p); return LONG_MIN; } This time we handle userspace page fault, so we cannot be kenrel thread, and cannot be in_vfork(). However task can be marked as oom unkillable, i.e. have p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN It can be set via oom_score_adj_write(). Thank you, Vasily Averin