From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f44.google.com (mail-wm0-f44.google.com [74.125.82.44]) by kanga.kvack.org (Postfix) with ESMTP id A205F828DF for ; Tue, 12 Jan 2016 14:52:03 -0500 (EST) Received: by mail-wm0-f44.google.com with SMTP id f206so266975857wmf.0 for ; Tue, 12 Jan 2016 11:52:03 -0800 (PST) Received: from mail-wm0-f68.google.com (mail-wm0-f68.google.com. [74.125.82.68]) by mx.google.com with ESMTPS id b73si33454591wmi.91.2016.01.12.11.52.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Jan 2016 11:52:02 -0800 (PST) Received: by mail-wm0-f68.google.com with SMTP id l65so33078162wmf.3 for ; Tue, 12 Jan 2016 11:52:02 -0800 (PST) Date: Tue, 12 Jan 2016 20:52:00 +0100 From: Michal Hocko Subject: Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Message-ID: <20160112195200.GB4515@dhcp22.suse.cz> References: <20160107091512.GB27868@dhcp22.suse.cz> <201601072231.DGG78695.OOFVLHJFFQOStM@I-love.SAKURA.ne.jp> <20160107145841.GN27868@dhcp22.suse.cz> <201601080038.CIF04698.VFJHSOQLOFFMOt@I-love.SAKURA.ne.jp> <20160111151835.GH27317@dhcp22.suse.cz> <201601122032.FHH13586.MOQVFFOJStFHOL@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201601122032.FHH13586.MOQVFFOJStFHOL@I-love.SAKURA.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: rientjes@google.com, akpm@linux-foundation.org, mgorman@suse.de, torvalds@linux-foundation.org, oleg@redhat.com, hughd@google.com, andrea@kernel.org, riel@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Tue 12-01-16 20:32:18, Tetsuo Handa wrote: > Michal Hocko wrote: > > On Fri 08-01-16 00:38:43, Tetsuo Handa wrote: > > > Michal Hocko wrote: > > > > @@ -333,6 +333,14 @@ static struct task_struct *select_bad_process(struct oom_control *oc, > > > > if (points == chosen_points && thread_group_leader(chosen)) > > > > continue; > > > > > > > > + /* > > > > + * If the current major task is already ooom killed and this > > > > + * is sysrq+f request then we rather choose somebody else > > > > + * because the current oom victim might be stuck. > > > > + */ > > > > + if (is_sysrq_oom(sc) && test_tsk_thread_flag(p, TIF_MEMDIE)) > > > > + continue; > > > > + > > > > chosen = p; > > > > chosen_points = points; > > > > } > > > > > > Do we want to require SysRq-f for each thread in a process? > > > If g has 1024 p, dump_tasks() will do > > > > > > pr_info("[%5d] %5d %5d %8lu %8lu %7ld %7ld %8lu %5hd %s\n", > > > > > > for 1024 times? I think one SysRq-f per one process is sufficient. > > > > I am not following you here. If we kill the process the whole process > > group (aka all threads) will get killed which ever thread we happen to > > send the sigkill to. > > Please distinguish "sending SIGKILL to a process" and "all threads in that > process terminate". I didn't say anything about termination if your read my response again. [...] > > > How can we guarantee that find_lock_task_mm() from oom_kill_process() > > > chooses !TIF_MEMDIE thread when try_to_sacrifice_child() somehow chose > > > !TIF_MEMDIE thread? I think choosing !TIF_MEMDIE thread at > > > find_lock_task_mm() is the simplest way. > > > > find_lock_task_mm chosing TIF_MEMDIE thread shouldn't change anything > > because the whole thread group will go down anyway. If you want to > > guarantee that the sysrq+f never choses a task which has a TIF_MEMDIE > > thread then we would have to check for fatal_signal_pending as well > > AFAIU. Fiddling with find find_lock_task_mm will not help you though > > unless I am missing something. > > I do want to guarantee that the SysRq-f (and timeout based next victim > selection) never chooses a process which has a TIF_MEMDIE thread. Sigh... see what I have written in the paragraph you are replying to... > I don't like current "oom: clear TIF_MEMDIE after oom_reaper managed to unmap > the address space" patch unless both "mm,oom: exclude TIF_MEMDIE processes from > candidates." patch and "mm,oom: Re-enable OOM killer using timers." Those patches are definitely not a prerequisite from the functional point of view and putting them together as a prerequisite sounds like blocking a useful feature without technical grounds to me. -- Michal Hocko SUSE Labs -- 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