From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH RFC 2/2] kvm: Be courteous to other VMs in overcommitted scenario in PLE handler Date: Mon, 24 Sep 2012 17:43:23 +0200 Message-ID: <50607F9B.7090701@redhat.com> References: <20120921115942.27611.67488.sendpatchset@codeblue> <20120921120019.27611.66093.sendpatchset@codeblue> <50607BBE.8070507@redhat.com> <1348500861.11847.72.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit 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 To: Peter Zijlstra Return-path: In-Reply-To: <1348500861.11847.72.camel@twins> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.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