From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754591Ab3IKPGL (ORCPT ); Wed, 11 Sep 2013 11:06:11 -0400 Received: from mail-la0-f49.google.com ([209.85.215.49]:39607 "EHLO mail-la0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754470Ab3IKPGJ (ORCPT ); Wed, 11 Sep 2013 11:06:09 -0400 Date: Wed, 11 Sep 2013 19:06:05 +0400 From: Sergey Dyasly To: David Rientjes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Michal Hocko , Rusty Russell , Sha Zhengju , Oleg Nesterov Subject: Re: [PATCH] OOM killer: wait for tasks with pending SIGKILL to exit Message-Id: <20130911190605.5528ee4563272dbea1ed56a6@gmail.com> In-Reply-To: References: <1378740624-2456-1-git-send-email-dserrg@gmail.com> X-Mailer: Sylpheed 3.3.0 (GTK+ 2.24.17; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 9 Sep 2013 13:07:08 -0700 (PDT) David Rientjes wrote: > > /* > > * If this task is not being ptraced on exit, then wait for it > > * to finish before killing some other task unnecessarily. > > */ > > - if (!(task->group_leader->ptrace & PT_TRACE_EXIT)) > > + if (!(task->group_leader->ptrace & PT_TRACE_EXIT)) { > > + set_tsk_thread_flag(task, TIF_MEMDIE); > > This does not, we do not give access to memory reserves unless the process > needs it to allocate memory. The task here, which is not current, can > call into the oom killer and be granted memory reserves if necessary. True. However, why TIF_MEMDIE is set for PF_EXITING task in oom_kill_process() then? Also, setting TIF_MEMDIE will avoid direct reclaim and memory allocation should be fast if exiting task needs it. > > @@ -412,16 +415,6 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, > > static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL, > > DEFAULT_RATELIMIT_BURST); > > > > - /* > > - * If the task is already exiting, don't alarm the sysadmin or kill > > - * its children or threads, just set TIF_MEMDIE so it can die quickly > > - */ > > - if (p->flags & PF_EXITING) { > > - set_tsk_thread_flag(p, TIF_MEMDIE); > > - put_task_struct(p); > > - return; > > - } > > I think you misunderstood the point of this; if a selected process is > already in the exit path then this is simply avoiding dumping oom kill > lines to the kernel log. We want to keep doing that. This happens in oom_kill_process() after victim has been selected by select_bad_process(). But there is already PF_EXITING check in oom_scan_process_thread() and in this case OOM code won't call oom_kill_process. There is only a slight chance that victim will become PF_EXITING between scan and kill. The only difference is in force_kill flag, and the only case where it's set is SysRq. And I think in this case OOM killer messages are a good thing to have even when victim is already exiting, instead of just silence. -- Sergey Dyasly