From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: Re: [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios in PLE handler Date: Mon, 24 Sep 2012 19:46:19 +0530 Message-ID: <50606B33.1040102@linux.vnet.ibm.com> References: <20120921115942.27611.67488.sendpatchset@codeblue> <1348486479.11847.46.camel@twins> <50604988.2030506@linux.vnet.ibm.com> <1348490165.11847.58.camel@twins> <50606050.309@linux.vnet.ibm.com> <1348494895.11847.64.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "H. Peter Anvin" , Marcelo Tosatti , Ingo Molnar , Avi Kivity , Rik van Riel , Srikar , "Nikunj A. Dadhania" , KVM , Jiannan Ouyang , chegu vinod , "Andrew M. Theurer" , LKML , Srivatsa Vaddagiri , Gleb Natapov , Andrew Jones To: Peter Zijlstra Return-path: In-Reply-To: <1348494895.11847.64.camel@twins> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 09/24/2012 07:24 PM, Peter Zijlstra wrote: > On Mon, 2012-09-24 at 18:59 +0530, Raghavendra K T wrote: >> However Rik had a genuine concern in the cases where runqueue is not >> equally distributed and lockholder might actually be on a different run >> queue but not running. > > Load should eventually get distributed equally -- that's what the > load-balancer is for -- so this is a temporary situation. > > We already try and favour the non running vcpu in this case, that's what > yield_to_task_fair() is about. If its still not eligible to run, tough > luck. Yes, I agree. > >> Do you think instead of using rq->nr_running, we could get a global >> sense of load using avenrun (something like avenrun/num_onlinecpus) > > To what purpose? Also, global stuff is expensive, so you should try and > stay away from it as hard as you possibly can. Yes, that concern only had made me to fall back to rq->nr_running. Will come back with the result soon.