From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757761Ab1F1MbK (ORCPT ); Tue, 28 Jun 2011 08:31:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10246 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757735Ab1F1Maq (ORCPT ); Tue, 28 Jun 2011 08:30:46 -0400 Message-ID: <4E09C965.9040200@redhat.com> Date: Tue, 28 Jun 2011 09:30:29 -0300 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc14 Thunderbird/3.1.10 MIME-Version: 1.0 To: Marcelo Tosatti CC: Avi Kivity , 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> <20110620205619.GA3971@amt.cnet> In-Reply-To: <20110620205619.GA3971@amt.cnet> 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 05:56 PM, Marcelo Tosatti wrote: > On Sun, Jun 19, 2011 at 12:57:53PM +0300, Avi Kivity wrote: >> On 06/17/2011 01:20 AM, Glauber Costa wrote: >>> To implement steal time, we need the hypervisor to pass the guest information >>> about how much time was spent running other processes outside the VM. >>> This is per-vcpu, and using the kvmclock structure for that is an abuse >>> we decided not to make. >>> >>> In this patchset, I am introducing a new msr, KVM_MSR_STEAL_TIME, that >>> holds the memory area address containing information about steal time >>> >>> This patch contains the hypervisor part for it. I am keeping it separate from >>> the headers to facilitate backports to people who wants to backport the kernel >>> part but not the hypervisor, or the other way around. >>> >>> >>> >>> +#define KVM_STEAL_ALIGNMENT_BITS 5 >>> +#define KVM_STEAL_VALID_BITS ((-1ULL<< (KVM_STEAL_ALIGNMENT_BITS + 1))) >>> +#define KVM_STEAL_RESERVED_MASK (((1<< KVM_STEAL_ALIGNMENT_BITS) - 1 )<< 1) >> >> Clumsy, but okay. >> >>> +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. >> >>> + >>> + if (unlikely(kvm_read_guest(vcpu->kvm, vcpu->arch.st.stime, >>> + &vcpu->arch.st.steal, sizeof(struct kvm_steal_time)))) { >>> + >>> + vcpu->arch.st.stime = 0; >>> + return; >>> + } >>> + >>> + delta = (get_kernel_ns() - vcpu->arch.st.this_time_out); >>> + >>> + vcpu->arch.st.steal.steal += delta; >>> + vcpu->arch.st.steal.version += 2; >>> + >>> + if (unlikely(kvm_write_guest(vcpu->kvm, vcpu->arch.st.stime, >>> + &vcpu->arch.st.steal, sizeof(struct kvm_steal_time)))) { >>> + >>> + vcpu->arch.st.stime = 0; >>> + return; >>> + } >>> + } >>> + >>> +} >>> + >>> >>> @@ -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? > > It also accounts halt time (kvm_vcpu_block) as steal time. Glauber, you > could instead use the "runnable-state-but-waiting-in-runqueue" field of > SCHEDSTATS, i forgot the exact name. > I thought about it in the past. I let the idea aside because I didn't want to introduce a dependency on SCHEDSTATS. But thinking about it again now (and after some days of experimentations with it), I think we could have both. use run_delay (the field you were thinking of) when schedstats are available, and fallback to an estimate method like the one we're doing when it is not. Objections ?