From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758294Ab0E1Oga (ORCPT ); Fri, 28 May 2010 10:36:30 -0400 Received: from mail-vw0-f46.google.com ([209.85.212.46]:47827 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753661Ab0E1Og3 (ORCPT ); Fri, 28 May 2010 10:36:29 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=l6BZtj11zBk1OV/SYT5XOZUQ1+v9KtG9mZAILry4Hp6upE2nNGKGWqwlJckiLYOGgE LAJIekeGluRIA1tIFX2A8z3BFyKVvCKapCi7F8L53E4/Mcjbdp/0bRFQZ/jOSXxfHuRo VeXl0IOvL9vKe/Cs4xvKCP7LbJfFx1AEBRocM= Date: Fri, 28 May 2010 11:36:17 -0300 From: "Luis Claudio R. Goncalves" To: Minchan Kim 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: <20100528143617.GF11364@uudg.org> References: <20100528143605.7E2A.A69D9226@jp.fujitsu.com> <20100528145329.7E2D.A69D9226@jp.fujitsu.com> <20100528125305.GE11364@uudg.org> <20100528140623.GA11041@barrios-desktop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100528140623.GA11041@barrios-desktop> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Luis -- [ Luis Claudio R. Goncalves Bass - Gospel - RT ] [ Fingerprint: 4FDD B8C4 3C59 34BD 8BE9 2696 7203 D980 A448 C8F8 ]