From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932242AbWFSX75 (ORCPT ); Mon, 19 Jun 2006 19:59:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932556AbWFSX75 (ORCPT ); Mon, 19 Jun 2006 19:59:57 -0400 Received: from omta05ps.mx.bigpond.com ([144.140.83.195]:46541 "EHLO omta05ps.mx.bigpond.com") by vger.kernel.org with ESMTP id S932242AbWFSX74 (ORCPT ); Mon, 19 Jun 2006 19:59:56 -0400 Message-ID: <44973A79.6070307@bigpond.net.au> Date: Tue, 20 Jun 2006 09:59:53 +1000 From: Peter Williams User-Agent: Thunderbird 1.5.0.2 (X11/20060501) MIME-Version: 1.0 To: Andrew Morton CC: kernel@kolivas.org, sam@vilain.net, bsingharora@gmail.com, vatsa@in.ibm.com, dev@openvz.org, linux-kernel@vger.kernel.org, efault@gmx.de, kingsley@aurema.com, ckrm-tech@lists.sourceforge.net, mingo@elte.hu, rene.herman@keyaccess.nl Subject: Re: [PATCH 0/4] sched: Add CPU rate caps References: <20060618082638.6061.20172.sendpatchset@heathwren.pw.nest> <20060618025046.77b0cecf.akpm@osdl.org> In-Reply-To: <20060618025046.77b0cecf.akpm@osdl.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Authentication-Info: Submitted using SMTP AUTH PLAIN at omta05ps.mx.bigpond.com from [147.10.133.38] using ID pwil3058@bigpond.net.au at Mon, 19 Jun 2006 23:59:54 +0000 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > > If the task can exceed its cap without impacting any other tasks (ie: there > is spare idle capacity), what happens? I trust that spare capacity gets > used? As I said in another reply, the answer to this is yes for soft caps and how good a job was demonstrated by the kernbench results that I included. Repeated here: Average Optimal -j 8 Load Run: Vanilla Patch Applied Soft Cap 0% Elapsed Time 1056.1 (1.92) 1048.2 (0.62) 1064.1 (1.59) User Time 1908.1 (1.09) 1895.2 (1.30) 1926.6 (1.39) System Time 181.7 (0.60) 177.5 (0.74) 173.8 (1.07) Total 2089.8 2072.7 2100.4 Percent CPU 197.6 (0.55) 197.0 (0) 197.0 (0) Context Switches 49253.6 (136.31) 48881.4 (92.03) 92490.8 (163.71) Sleeps 28038.8 (228.11) 28136.0 (250.65) 25769.4 (280.40) Note that the (slight) increase in the elapsed time when using a soft cap of zero can be directly attributed to the increase in CPU usage due to the cap overhead (an approximate increase of 16 seconds for elapsed time with an approximate increase of 28 seconds (for two CPUs) in CPU time consumed when comparing the "patch applied" and "soft cap 0%" numbers). I think this illustrates that (for soft caps) spare capacity is not wasted? > (Is this termed "work conserving"?) I don't know but it sounds apt. Peter PS For ordinary users, I think that the ability to run jobs in the background by using a soft cap of zero is the most useful thing that this patch provides. -- Peter Williams pwil3058@bigpond.net.au "Learning, n. The kind of ignorance distinguishing the studious." -- Ambrose Bierce