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    SubjectRe: [PATCH v2 3/6] KVM-GST: KVM Steal time accounting
    On Sun, 2011-01-30 at 16:04 +0200, Avi Kivity wrote:
    > On 01/28/2011 09:52 PM, Glauber Costa wrote:
    > > This patch accounts steal time time in kernel/sched.
    > > I kept it from last proposal, because I still see advantages
    > > in it: Doing it here will give us easier access from scheduler
    > > variables such as the cpu rq. The next patch shows an example of
    > > usage for it.
    > >
    > > Since functions like account_idle_time() can be called from
    > > multiple places, not only account_process_tick(), steal time
    > > grabbing is repeated in each account function separatedely.
    > >
    > I accept that steal time is worthwhile, but do you have some way to
    > demonstrate that the implementation actually works and is beneficial?
    > Perhaps run two cpu-bound compute processes on one vcpu, overcommit that
    > vcpu, and see what happens to the processing rate with and without steal
    > time accounting. I'd expect a fairer response with steal time accounting.


    There are two things here:
    One of them, which is solely the accounting of steal time, (patches 1 to
    4) has absolutely nothing to do with what you said. Its sole purpose is
    to provide the user with information about "why is my process slow if I
    am using 100 % of my cpu?")

    The last patch is the only one that actually tries to rebalance cpus
    according to steal time information. For that, I do have some
    experiments I did here to see if it is working, will try to provide more
    precise data in the next submission.

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