From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f198.google.com (mail-io0-f198.google.com [209.85.223.198]) by kanga.kvack.org (Postfix) with ESMTP id A60886B0005 for ; Tue, 19 Jul 2016 06:52:48 -0400 (EDT) Received: by mail-io0-f198.google.com with SMTP id r71so33063877ioi.3 for ; Tue, 19 Jul 2016 03:52:48 -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 f27si6743764ioi.41.2016.07.19.03.52.47 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 19 Jul 2016 03:52:47 -0700 (PDT) Subject: Re: oom-reaper choosing wrong processes. References: <20160718231850.GA23178@codemonkey.org.uk> <20160719090857.GB9490@dhcp22.suse.cz> From: Tetsuo Handa Message-ID: Date: Tue, 19 Jul 2016 19:52:28 +0900 MIME-Version: 1.0 In-Reply-To: <20160719090857.GB9490@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , Dave Jones Cc: linux-mm@kvack.org On 2016/07/19 8:18, Dave Jones wrote: > Whoa. Why did it pick systemd-journal ? I guess that it is because all trinity processes' mm already had MMF_OOM_REAPED set. The OOM reaper sets MMF_OOM_REAPED when OOM reap operation succeeded. But "[ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name" listing includes processes whose mm already has MMF_OOM_REAPED set. As a result, trinity-c15 and trinity-c4 are shown again in the listing. While I can't confirm that trinity-c10, trinity-c2, trinity-c0 and trinity-c11 are already OOM killed, I guess they are already OOM killed and their mm already had MMF_OOM_REAPED set. > My 'skip over !trinity processes' code kicks in, and it then kills the right processes, and the box lives on, > but if I hadn't have had that diff, the wrong process would have been killed. As of Linux 4.7, processes whose mm already has MMF_OOM_REAPED can be selected for many times due to not checking MMF_OOM_REAPED when using task_will_free_mem() shortcut in out_of_memory(). (It will be fixed in Linux 4.8.) That is, I guess that your system had already hit panic("Out of memory and no killable processes...\n") if trinity processes with MMF_OOM_REAPED mm were not selected again and again. -- 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