From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752594Ab1FTGCt (ORCPT ); Mon, 20 Jun 2011 02:02:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51911 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751951Ab1FTGCr (ORCPT ); Mon, 20 Jun 2011 02:02:47 -0400 Message-ID: <4DFEE276.9020403@redhat.com> Date: Mon, 20 Jun 2011 09:02:30 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10 MIME-Version: 1.0 To: Glauber Costa CC: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Rik van Riel , Jeremy Fitzhardinge , Peter Zijlstra , Anthony Liguori , Eric B Munson Subject: Re: [PATCH v2 3/7] KVM-HV: KVM Steal time implementation References: <1308262856-5779-1-git-send-email-glommer@redhat.com> <1308262856-5779-4-git-send-email-glommer@redhat.com> <4DFDC821.2090905@redhat.com> <4DFEB61A.4070204@redhat.com> In-Reply-To: <4DFEB61A.4070204@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/20/2011 05:53 AM, Glauber Costa wrote: > >> >>> +static void record_steal_time(struct kvm_vcpu *vcpu) >>> +{ >>> + u64 delta; >>> + >>> + if (vcpu->arch.st.stime&& vcpu->arch.st.this_time_out) { >> >> 0 is a valid value for stime. > > > how exactly? stime is a guest physical address... 0 is a valid physical address. >>> >>> @@ -2158,6 +2206,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, >>> int cpu) >>> kvm_migrate_timers(vcpu); >>> vcpu->cpu = cpu; >>> } >>> + >>> + record_steal_time(vcpu); >>> } >> >> This records time spent in userspace in the vcpu thread as steal time. >> Is this what we want? Or just time preempted away? > > There are arguments either way. > > Right now, the way it is, it does account our iothread as steal time, > which is not 100 % accurate if we think steal time as "whatever takes > time away from our VM". I tend to think it as "whatever takes time > away from this CPU", which includes other cpus in the same VM. So > thinking this way, in a 1-1 phys-to-virt cpu mapping, if the iothread > is taking 80 % cpu for whatever reason, we have 80 % steal time the > cpu that is sharing the physical cpu with the iothread. I'm not talking about the iothread, rather the vcpu thread while running in userspace. > > Maybe we could account that as iotime ? > Questions like that are one of the reasons behind me leaving extra > fields in the steal time structure. We could do a more fine grained > accounting and differentiate between the multiple entities that can do > work (of various kinds) in our behalf. > What do other architectures do (xen, s390)? -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.