From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f173.google.com (mail-io0-f173.google.com [209.85.223.173]) by kanga.kvack.org (Postfix) with ESMTP id AE6E06B0253 for ; Wed, 17 Feb 2016 08:37:02 -0500 (EST) Received: by mail-io0-f173.google.com with SMTP id z135so37013781iof.0 for ; Wed, 17 Feb 2016 05:37:02 -0800 (PST) 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 s9si5080792igg.47.2016.02.17.05.37.01 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 17 Feb 2016 05:37:02 -0800 (PST) Subject: Re: [PATCH 4/6] mm,oom: exclude oom_task_origin processes if they are OOM-unkillable. From: Tetsuo Handa References: <201602171928.GDE00540.SLJMOFFQOHtFVO@I-love.SAKURA.ne.jp> <201602171933.HFD51078.LOSFVMFQFOJHOt@I-love.SAKURA.ne.jp> <20160217131034.GH29196@dhcp22.suse.cz> In-Reply-To: <20160217131034.GH29196@dhcp22.suse.cz> Message-Id: <201602172236.FHF87070.LOVFtJSOFFMHQO@I-love.SAKURA.ne.jp> Date: Wed, 17 Feb 2016 22:36:47 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@kernel.org Cc: akpm@linux-foundation.org, rientjes@google.com, mgorman@suse.de, oleg@redhat.com, torvalds@linux-foundation.org, hughd@google.com, andrea@kernel.org, riel@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Michal Hocko wrote: > On Wed 17-02-16 19:33:07, Tetsuo Handa wrote: > > >From 4924ca3031444bfb831b2d4f004e5a613ad48d68 Mon Sep 17 00:00:00 2001 > > From: Tetsuo Handa > > Date: Wed, 17 Feb 2016 16:35:12 +0900 > > Subject: [PATCH 4/6] mm,oom: exclude oom_task_origin processes if they are OOM-unkillable. > > > > oom_scan_process_thread() returns OOM_SCAN_SELECT when there is a > > thread which returns oom_task_origin() == true. But it is possible > > that that thread is marked as OOM-unkillable. > > > > This patch changes oom_scan_process_thread() not to select it > > if it is marked as OOM-unkillable. > > oom_task_origin is only swapoff and ksm_store right now. I seriously > doubt anybody sane will run them as OOM disabled (directly or > indirectly). I think that the OOM reaper will update such task as OOM-unkillable after reaping that task's memory. This patch is intended for not to fall into infinite loop after the OOM reaper updated it. > > But you have a point that returing anything but OOM_SCAN_CONTINUE for > OOM_SCORE_ADJ_MIN from oom_scan_process_thread sounds suboptimal. > Sure such a check would be racy but do we actually care about a OOM vs. > oom_score_adj_write. I am dubious to say the least. > > So wouldn't it make more sense to check for OOM_SCORE_ADJ_MIN at the > very top of oom_scan_process_thread instead? Are you suggesting something like below? (OOM_SCORE_ADJ_MIN check needs to be done after TIF_MEMDIE check) enum oom_scan_t oom_scan_process_thread(struct oom_control *oc, struct task_struct *task, unsigned long totalpages) { if (oom_unkillable_task(task, NULL, oc->nodemask)) return OOM_SCAN_CONTINUE; /* * This task already has access to memory reserves and is being killed. * Don't allow any other task to have access to the reserves. */ if (test_tsk_thread_flag(task, TIF_MEMDIE)) { if (!is_sysrq_oom(oc)) return OOM_SCAN_ABORT; } if (!task->mm || task->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) return OOM_SCAN_CONTINUE; (...snipped...) } -- 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