Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933447Ab0FCAwy (ORCPT ); Wed, 2 Jun 2010 20:52:54 -0400 Received: from mail-gy0-f174.google.com ([209.85.160.174]:47978 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932771Ab0FCAwx convert rfc822-to-8bit (ORCPT ); Wed, 2 Jun 2010 20:52:53 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=W9sbL61Aww6iGG7Imq+vRy616J7TtbXijKnQe46TG4wdQ6e5wUNaYnR3GWYGLeYjXX vk69PAioIwJxnyvDSvE55i1Do2bqwEsVKehULYJY4Gea5IUQGE33i/n/QjBndM+UupZi pv6++JiyzUiKbk3J3KSgsI5X7nIJZu6fg6D04= MIME-Version: 1.0 In-Reply-To: <20100603083259.7231.A69D9226@jp.fujitsu.com> References: <20100602220429.F51E.A69D9226@jp.fujitsu.com> <20100603083259.7231.A69D9226@jp.fujitsu.com> Date: Thu, 3 Jun 2010 09:52:49 +0900 Message-ID: Subject: Re: [RFC] oom-kill: give the dying task a higher priority From: Minchan Kim To: KOSAKI Motohiro Cc: David Rientjes , "Luis Claudio R. Goncalves" , KAMEZAWA Hiroyuki , balbir@linux.vnet.ibm.com, Oleg Nesterov , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Thomas Gleixner , Peter Zijlstra , Mel Gorman , williams@redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2562 Lines: 60 On Thu, Jun 3, 2010 at 8:36 AM, KOSAKI Motohiro wrote: >> On Wed, 2 Jun 2010, KOSAKI Motohiro wrote: >> >> > > > @@ -291,9 +309,10 @@ static struct task_struct *select_bad_process(unsigned long *ppoints, >> > > >                  * Otherwise we could get an easy OOM deadlock. >> > > >                  */ >> > > >                 if (p->flags & PF_EXITING) { >> > > > -                       if (p != current) >> > > > +                       if (p != current) { >> > > > +                               boost_dying_task_prio(p, mem); >> > > >                                 return ERR_PTR(-1UL); >> > > > - >> > > > +                       } >> > > >                         chosen = p; >> > > >                         *ppoints = ULONG_MAX; >> > > >                 } >> > > >> > > This has the potential to actually make it harder to free memory if p is >> > > waiting to acquire a writelock on mm->mmap_sem in the exit path while the >> > > thread holding mm->mmap_sem is trying to run. >> > >> > if p is waiting, changing prio have no effect. It continue tol wait to release mmap_sem. >> > >> >> And that can reduce the runtime of the thread holding a writelock on >> mm->mmap_sem, making the exit actually take longer than without the patch >> if its priority is significantly higher, especially on smaller machines. > > If p need mmap_sem, p is going to sleep to wait mmap_sem. if p doesn't, > quickly exit is good thing. In other word, task fairness is not our goal > when oom occur. > Tend to agree. I didn't agree boosting of whole threads' priority. Task fairness VS system hang is trade off. task fairness is best effort but system hang is critical. Also, we have tried to it. /* * We give our sacrificial lamb high priority and access to * all the memory it needs. That way it should be able to * exit() and clear out its resources quickly... */ p->rt.time_slice = HZ; set_tsk_thread_flag(p, TIF_MEMDIE); But I think above code is meaningless unless p use SCHED_RR. So boosting of lowest RT priority with FIFO is to meet above comment's goal, I think. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/