Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757480Ab0LMMj4 (ORCPT ); Mon, 13 Dec 2010 07:39:56 -0500 Received: from e23smtp09.au.ibm.com ([202.81.31.142]:40359 "EHLO e23smtp09.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757407Ab0LMMjx (ORCPT ); Mon, 13 Dec 2010 07:39:53 -0500 Date: Mon, 13 Dec 2010 18:09:44 +0530 From: Balbir Singh To: Avi Kivity Cc: Rik van Riel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Srivatsa Vaddagiri , Peter Zijlstra , Ingo Molnar , Anthony Liguori Subject: Re: [RFC PATCH 0/3] directed yield for Pause Loop Exiting Message-ID: <20101213123944.GA14178@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20101202144129.4357fe00@annuminas.surriel.com> <20101210050344.GR3158@balbir.in.ibm.com> <4D0328CC.1020809@redhat.com> <20101211135727.GU3158@balbir.in.ibm.com> <4D060A31.3030606@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <4D060A31.3030606@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1579 Lines: 43 * Avi Kivity [2010-12-13 13:57:37]: > On 12/11/2010 03:57 PM, Balbir Singh wrote: > >* Avi Kivity [2010-12-11 09:31:24]: > > > >> On 12/10/2010 07:03 AM, Balbir Singh wrote: > >> >> > >> >> Scheduler people, please flame me with anything I may have done > >> >> wrong, so I can do it right for a next version :) > >> >> > >> > > >> >This is a good problem statement, there are other things to consider > >> >as well > >> > > >> >1. If a hard limit feature is enabled underneath, donating the > >> >timeslice would probably not make too much sense in that case > >> > >> What's the alternative? > >> > >> Consider a two vcpu guest with a 50% hard cap. Suppose the workload > >> involves ping-ponging within the guest. If the scheduler decides to > >> schedule the vcpus without any overlap, then the throughput will be > >> dictated by the time slice. If we allow donation, throughput is > >> limited by context switch latency. > >> > > > >If the vpcu holding the lock runs more and capped, the timeslice > >transfer is a heuristic that will not help. > > Why not? as long as we shift the cap as well. > Shifting the cap would break it, no? Anyway, that is something for us to keep track of as we add additional heuristics, not a show stopper. -- Three Cheers, Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/