From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752363Ab1JMEf4 (ORCPT ); Thu, 13 Oct 2011 00:35:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:14942 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752050Ab1JMEfz (ORCPT ); Thu, 13 Oct 2011 00:35:55 -0400 Message-ID: <4E966564.5030902@redhat.com> Date: Thu, 13 Oct 2011 00:13:24 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:6.0.2) Gecko/20110906 Thunderbird/6.0.2 MIME-Version: 1.0 To: David Rientjes CC: Satoru Moriya , Randy Dunlap , Satoru Moriya , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "lwoodman@redhat.com" , Seiji Aguchi , Andrew Morton , Hugh Dickins , "hannes@cmpxchg.org" Subject: Re: [PATCH -v2 -mm] add extra free kbytes tunable References: <20110901105208.3849a8ff@annuminas.surriel.com> <20110901100650.6d884589.rdunlap@xenotime.net> <20110901152650.7a63cb8b@annuminas.surriel.com> <65795E11DBF1E645A09CEC7EAEE94B9CB516CBBC@USINDEVS02.corp.hds.com> <4E959292.9060301@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/12/2011 04:21 PM, David Rientjes wrote: > On Wed, 12 Oct 2011, Rik van Riel wrote: > >> How would this scheme work? >> > > I suggested a patch from BFS that would raise kswapd to the same priority > of the task that triggered it (not completely up to rt, but the highest > possible in that case) and I'm waiting to hear if that helps for Satoru's > test case before looking at alternatives. We could also extend the patch > to raise the priority of an already running kswapd if a higher priority > task calls into the page allocator's slowpath. This has the distinct benefit of making kswapd most active right at the same time the application is most active, which returns us to your first objection to the extra free kbytes patch (apps will suffer from kswapd cpu use). Furthermore, I am not sure that giving kswapd more CPU time is going to help, because kswapd could be stuck on some lock, held by a lower priority (or sleeping) context. I agree that the BFS patch would be worth a try, and would be very pleasantly surprised if it worked, but I am not very optimistic about it... -- All rights reversed