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 274F7C433EF for ; Tue, 19 Oct 2021 11:54:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C5B4060FF2 for ; Tue, 19 Oct 2021 11:54:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org C5B4060FF2 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 32D766B006C; Tue, 19 Oct 2021 07:54:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2DD29900002; Tue, 19 Oct 2021 07:54:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1CD4D6B0072; Tue, 19 Oct 2021 07:54:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0007.hostedemail.com [216.40.44.7]) by kanga.kvack.org (Postfix) with ESMTP id 0DF5A6B006C for ; Tue, 19 Oct 2021 07:54:44 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id BBF4C2930A for ; Tue, 19 Oct 2021 11:54:43 +0000 (UTC) X-FDA: 78713030046.24.4EE5E71 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by imf24.hostedemail.com (Postfix) with ESMTP id F381CB00009F for ; Tue, 19 Oct 2021 11:54:40 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 5A89821960; Tue, 19 Oct 2021 11:54:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1634644482; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=kjUTORhMXSDVDvRms+kcqq6S1tclrHNa5RDL4eI+HuY=; b=ZmH1pqyD7BkKSJl7yYLpQEnGlTjj70gOVzsOJHYIdgNSd2zzONjFac9hDbtdtUw389EkQc jeUbkHgPM5fwPIJBNvug1/6S07uPjuxtovZ0Rij5pUXDx1fijf2SNc3pN86ca6utdTFaSe Rv/kFcZoGCSZaHr78PXkwDnoIj+W8Ec= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 07825A3B84; Tue, 19 Oct 2021 11:54:41 +0000 (UTC) Date: Tue, 19 Oct 2021 13:54:41 +0200 From: Michal Hocko To: Vasily Averin 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 Subject: Re: [PATCH memcg 0/1] false global OOM triggered by memcg-limited task Message-ID: References: <9d10df01-0127-fb40-81c3-cc53c9733c3e@virtuozzo.com> <6b751abe-aa52-d1d8-2631-ec471975cc3a@virtuozzo.com> <339ae4b5-6efd-8fc2-33f1-2eb3aee71cb2@virtuozzo.com> <687bf489-f7a7-5604-25c5-0c1a09e0905b@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <687bf489-f7a7-5604-25c5-0c1a09e0905b@virtuozzo.com> X-Rspamd-Queue-Id: F381CB00009F Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=ZmH1pqyD; spf=pass (imf24.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-Stat-Signature: 5m9w4b8bmhs9watzy7qq3idmd5rs53jb X-Rspamd-Server: rspam05 X-HE-Tag: 1634644480-406548 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue 19-10-21 13:30:06, Vasily Averin wrote: > 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 You are right. I am not sure there is a way out of this though. The task can only retry for ever in this case. There is nothing actionable here. We cannot kill the task and there is no other way to release the memory. -- Michal Hocko SUSE Labs