From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rik van Riel Subject: Re: Stolen and degraded time and schedulers Date: Wed, 14 Mar 2007 15:45:03 -0400 Message-ID: <45F850BF.5030702@redhat.com> References: <45F6D1D0.6080905@goop.org> <1173816769.22180.14.camel@localhost> <45F70A71.9090205@goop.org> <1173821224.1416.24.camel@dwalker1> <45F71EA5.2090203@goop.org> <45F74515.7010808@vmware.com> <45F77C27.8090604@goop.org> <45F846AB.6060200@vmware.com> <45F84E39.7030507@goop.org> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <45F84E39.7030507@goop.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.osdl.org Errors-To: virtualization-bounces@lists.osdl.org Content-Type: text/plain; charset="us-ascii" To: Jeremy Fitzhardinge Cc: dwalker@mvista.com, john stultz , paulus@au.ibm.com, Linux Kernel Mailing List , Con Kolivas , Chris Wright , Virtualization Mailing List , cpufreq@lists.linux.org.uk, schwidefsky@de.ibm.com, Thomas Gleixner , Ingo Molnar Jeremy Fitzhardinge wrote: >> How is time quantum getting stolen less important? Time quantum >> getting stolen results directly in more unnecessary context switches >> since we might steal the entire timeslice before the process even ran. > = > It doesn't matter why you didn't get the time; = Oh, but it does. System administrators can use steal time the same way they use iowait time: to spot bottlenecks on their systems. If you have a lot of iowait time, you know you want either faster IO or more memory. If you have a lot of steal time, you know you need to spread your virtual machines over more CPUs. Steal time allows you to see the difference between a busy system and an overloaded system. -- = Politics is the struggle between those who want to make their country the best in the world, and those who believe it already is. Each group calls the other unpatriotic. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030866AbXCNTxd (ORCPT ); Wed, 14 Mar 2007 15:53:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030872AbXCNTxd (ORCPT ); Wed, 14 Mar 2007 15:53:33 -0400 Received: from mx1.redhat.com ([66.187.233.31]:56238 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030866AbXCNTxc (ORCPT ); Wed, 14 Mar 2007 15:53:32 -0400 Message-ID: <45F850BF.5030702@redhat.com> Date: Wed, 14 Mar 2007 15:45:03 -0400 From: Rik van Riel Organization: Red Hat, Inc User-Agent: Thunderbird 1.5.0.7 (X11/20061008) MIME-Version: 1.0 To: Jeremy Fitzhardinge CC: Dan Hecht , dwalker@mvista.com, cpufreq@lists.linux.org.uk, Linux Kernel Mailing List , Con Kolivas , Chris Wright , Virtualization Mailing List , john stultz , Ingo Molnar , Thomas Gleixner , paulus@au.ibm.com, schwidefsky@de.ibm.com Subject: Re: Stolen and degraded time and schedulers References: <45F6D1D0.6080905@goop.org> <1173816769.22180.14.camel@localhost> <45F70A71.9090205@goop.org> <1173821224.1416.24.camel@dwalker1> <45F71EA5.2090203@goop.org> <45F74515.7010808@vmware.com> <45F77C27.8090604@goop.org> <45F846AB.6060200@vmware.com> <45F84E39.7030507@goop.org> In-Reply-To: <45F84E39.7030507@goop.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jeremy Fitzhardinge wrote: >> How is time quantum getting stolen less important? Time quantum >> getting stolen results directly in more unnecessary context switches >> since we might steal the entire timeslice before the process even ran. > > It doesn't matter why you didn't get the time; Oh, but it does. System administrators can use steal time the same way they use iowait time: to spot bottlenecks on their systems. If you have a lot of iowait time, you know you want either faster IO or more memory. If you have a lot of steal time, you know you need to spread your virtual machines over more CPUs. Steal time allows you to see the difference between a busy system and an overloaded system. -- Politics is the struggle between those who want to make their country the best in the world, and those who believe it already is. Each group calls the other unpatriotic.