Messages in this thread | | | Date | Tue, 16 Nov 2010 17:05:49 +0100 | From | Martin Schwidefsky <> | Subject | Re: [RFC][PATCH v2 4/7] taskstats: Add per task steal time accounting |
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On Tue, 16 Nov 2010 16:45:29 +0100 Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > > Except that the per-task steal time gives you lot less detail, being > > > able to profile on vcpu exit/enter gives you a much more powerfull > > > performance tool. Aside from being able to measure the steal-time it > > > allows you to instantly find hypercalls (both explicit as well as > > > implicit), so you can also measure the hypercall induced steal-time as > > > well. > > > > Yes and no. The tracepoint idea looks interesting in itself. But that does > > not completely replace the per-task steal time. The hypervisor can take > > away the cpu anytime, it is still interesting to know which task was hit > > hardest by that. You could view the cpu time lost by a hypercall as > > "synchronous" steal time for the task, the remaining delta to the total > > per-task steal time as "asynchronous" steal time. > > Right, so there is no way the guest knows about the vcpu getting > scheduled, it can only derive the fact from hardware clocks after the > fact?
Correct.
-- blue skies, Martin.
"Reality continues to ruin my life." - Calvin.
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