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    SubjectRe: [PATCH V3] perf & kvm: Enhance perf to collect KVM guest os statistics from host side
    On 04/14/2010 01:14 PM, Sheng Yang wrote:
    >> I wouldn't like to depend on model specific behaviour.
    >> One option is to read all the information synchronously and store it in
    >> a per-cpu area with atomic instructions, then queue the NMI. Another
    >> option is to have another callback which tells us that the NMI is done,
    >> and have a busy loop wait until the NMI is delivered.
    > Callback seems too heavy, may affect the performance badly. Maybe a short
    > queue would help, though this one is more complex.

    The patch we're replying to adds callbacks (to read rip, etc.), so it's
    no big deal. For the queue solution, a queue of size one would probably
    be sufficient even if not guaranteed by the spec. I don't see how the
    cpu can do another guest entry without delivering the NMI.

    > But I am still curious if we extend the region, how much it would help. Would
    > get a result soon...

    Yes, interesting to see what the latency is. If it's reasonably short
    (and I expect it will be so), we can do the busy wait solution.

    If we have an NMI counter somewhere, we can simply wait until it changes.

    error compiling committee.c: too many arguments to function

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      Last update: 2010-04-14 12:23    [W:0.028 / U:128.436 seconds]
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