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[202.181.97.72]) by mx.google.com with ESMTPS id d24si10142577pgg.147.2019.07.01.06.39.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 01 Jul 2019 06:39:10 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) client-ip=202.181.97.72; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) smtp.mailfrom=penguin-kernel@i-love.sakura.ne.jp Received: from fsav305.sakura.ne.jp (fsav305.sakura.ne.jp [153.120.85.136]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id x61Dd3Bh068986; Mon, 1 Jul 2019 22:39:03 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav305.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav305.sakura.ne.jp); Mon, 01 Jul 2019 22:39:03 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav305.sakura.ne.jp) Received: from [192.168.1.8] (softbank126012062002.bbtec.net [126.12.62.2]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id x61Dd1Bx068912 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Mon, 1 Jul 2019 22:39:03 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH] mm: mempolicy: don't select exited threads as OOM victims To: Michal Hocko Cc: Shakeel Butt , linux-mm@kvack.org References: <1561807474-10317-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20190701111708.GP6376@dhcp22.suse.cz> <15099126-5d0f-51eb-7134-46c5c2db3bf0@i-love.sakura.ne.jp> <20190701131736.GX6376@dhcp22.suse.cz> From: Tetsuo Handa Message-ID: Date: Mon, 1 Jul 2019 22:38:58 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190701131736.GX6376@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 2019/07/01 22:17, Michal Hocko wrote: > On Mon 01-07-19 22:04:22, Tetsuo Handa wrote: >> But I realized that this patch was too optimistic. We need to wait for mm-less >> threads until MMF_OOM_SKIP is set if the process was already an OOM victim. > > If the process is an oom victim then _all_ threads are so as well > because that is the address space property. And we already do check that > before reaching oom_badness IIRC. So what is the actual problem you are > trying to solve here? I'm talking about behavioral change after tsk became an OOM victim. If tsk->signal->oom_mm != NULL, we have to wait for MMF_OOM_SKIP even if tsk->mm == NULL. Otherwise, the OOM killer selects next OOM victim as soon as oom_unkillable_task() returned true because has_intersects_mems_allowed() returned false because mempolicy_nodemask_intersects() returned false because all thread's mm became NULL (despite tsk->signal->oom_mm != NULL). static int oom_evaluate_task(struct task_struct *task, void *arg) { if (oom_unkillable_task(task, NULL, oc->nodemask)) goto next; if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) { if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags)) goto next; goto abort; } }