From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758555Ab0E1PM7 (ORCPT ); Fri, 28 May 2010 11:12:59 -0400 Received: from mail-px0-f174.google.com ([209.85.212.174]:60542 "EHLO mail-px0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751691Ab0E1PM6 (ORCPT ); Fri, 28 May 2010 11:12:58 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=lLcPd6KOWwwOdI9wg+ZG9HQKJxAttF3EvXCFr0XSYhLrX3EqYUNMD+Yg/t5bu0pptZ p+ckiFQ0RDhS4MGixvTHkOeQHGKPOxpE/gbtXG32xMED9mSsdhYn8U7CaJYNnHHXUi+i mF+8D2vnlN7ssyzkTHKWRWUinXQs1Yx1ICK4Q= Date: Sat, 29 May 2010 00:12:49 +0900 From: Minchan Kim To: "Luis Claudio R. Goncalves" Cc: KOSAKI Motohiro , balbir@linux.vnet.ibm.com, Oleg Nesterov , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Thomas Gleixner , Peter Zijlstra , David Rientjes , Mel Gorman , williams@redhat.com Subject: Re: [RFC] oom-kill: give the dying task a higher priority Message-ID: <20100528151249.GB12035@barrios-desktop> References: <20100528143605.7E2A.A69D9226@jp.fujitsu.com> <20100528145329.7E2D.A69D9226@jp.fujitsu.com> <20100528125305.GE11364@uudg.org> <20100528140623.GA11041@barrios-desktop> <20100528143617.GF11364@uudg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100528143617.GF11364@uudg.org> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 28, 2010 at 11:36:17AM -0300, Luis Claudio R. Goncalves wrote: > On Fri, May 28, 2010 at 11:06:23PM +0900, Minchan Kim wrote: > | On Fri, May 28, 2010 at 09:53:05AM -0300, Luis Claudio R. Goncalves wrote: > | > On Fri, May 28, 2010 at 02:59:02PM +0900, KOSAKI Motohiro wrote: > ... > | > | As far as my observation, RT-function always have some syscall. because pure > | > | calculation doesn't need deterministic guarantee. But _if_ you are really > | > | using such priority design. I'm ok maximum NonRT priority instead maximum > | > | RT priority too. > | > > | > I confess I failed to distinguish memcg OOM and system OOM and used "in > | > case of OOM kill the selected task the faster you can" as the guideline. > | > If the exit code path is short that shouldn't be a problem. > | > > | > Maybe the right way to go would be giving the dying task the biggest > | > priority inside that memcg to be sure that it will be the next process from > | > that memcg to be scheduled. Would that be reasonable? > | > | Hmm. I can't understand your point. > | What do you mean failing distinguish memcg and system OOM? > | > | We already have been distinguish it by mem_cgroup_out_of_memory. > | (but we have to enable CONFIG_CGROUP_MEM_RES_CTLR). > | So task selected in select_bad_process is one out of memcg's tasks when > | memcg have a memory pressure. > > The approach of giving the highest priority to the dying task makes sense > in a system wide OOM situation. I though that would also be good for the > memcg OOM case. > > After Balbir Singh's comment, I understand that in a memcg OOM the dying > task should have a priority just above the priority of the main task of > that memcg, in order to avoid interfering in the rest of the system. > > That is the point where I failed to distinguish between memcg and system OOM. > > Should I pursue that new idea of looking for the right priority inside the > memcg or is it overkill? I really don't have a clear view of the impact of > a memcg OOM on system performance - don't know if it is better to solve the > issue sooner (highest RT priority) or leave it to be solved later (highest > prio on the memcg). I have the impression the general case points to the > simpler solution. I think highest RT proirity ins't good solution. As I mentiond, Some RT functions don't want to be preempted by other processes which cause memory pressure. It makes RT task broken. On the other hand, normal processes don't have a requirement of RT. But it isn't a big problem that it lost little time slice, I think. So how about raising max normal priority? but I am not sure this is right solution. Let's listen other's opinion. I believe Peter have a good idea. > > Luis > -- > [ Luis Claudio R. Goncalves Bass - Gospel - RT ] > [ Fingerprint: 4FDD B8C4 3C59 34BD 8BE9 2696 7203 D980 A448 C8F8 ] > -- Kind regards, Minchan Kim