From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756617Ab2IXPnn (ORCPT ); Mon, 24 Sep 2012 11:43:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32549 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756333Ab2IXPnl (ORCPT ); Mon, 24 Sep 2012 11:43:41 -0400 Message-ID: <50607F9B.7090701@redhat.com> Date: Mon, 24 Sep 2012 17:43:23 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: Peter Zijlstra CC: Raghavendra K T , "H. Peter Anvin" , Marcelo Tosatti , Ingo Molnar , Rik van Riel , Srikar , "Nikunj A. Dadhania" , KVM , Jiannan Ouyang , chegu vinod , "Andrew M. Theurer" , LKML , Srivatsa Vaddagiri , Gleb Natapov Subject: Re: [PATCH RFC 2/2] kvm: Be courteous to other VMs in overcommitted scenario in PLE handler References: <20120921115942.27611.67488.sendpatchset@codeblue> <20120921120019.27611.66093.sendpatchset@codeblue> <50607BBE.8070507@redhat.com> <1348500861.11847.72.camel@twins> In-Reply-To: <1348500861.11847.72.camel@twins> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/24/2012 05:34 PM, Peter Zijlstra wrote: > On Mon, 2012-09-24 at 17:26 +0200, Avi Kivity wrote: >> I think this is a no-op these (CFS) days. To get schedule() to do >> anything, you need to wake up a task, or let time pass, or block. >> Otherwise it will see that nothing has changed and as far as it's >> concerned you're still the best task to be running (otherwise it >> wouldn't have picked you in the first place). > > Time could have passed enough before calling this that there's now a > different/more eligible task around to schedule. Wouldn't this correspond to the scheduler interrupt firing and causing a reschedule? I thought the timer was programmed for exactly the point in time that CFS considers the right time for a switch. But I'm basing this on my mental model of CFS, not CFS itself. > Esp. for a !PREEMPT kernel this is could be significant. -- error compiling committee.c: too many arguments to function