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    SubjectRe: [RFC PATCH 0/3] generic hypercall support
    Marcelo Tosatti wrote:
    > On Thu, May 07, 2009 at 08:35:03PM -0300, Marcelo Tosatti wrote:
    >
    >> Also for PIO/MMIO you're adding this unoptimized lookup to the
    >> measurement:
    >>
    >> pio_dev = vcpu_find_pio_dev(vcpu, port, size, !in);
    >> if (pio_dev) {
    >> kernel_pio(pio_dev, vcpu, vcpu->arch.pio_data);
    >> complete_pio(vcpu);
    >> return 1;
    >> }
    >>
    >> Whereas for hypercall measurement you don't. I believe a fair comparison
    >> would be have a shared guest/host memory area where you store guest/host
    >> TSC values and then do, on guest:
    >>
    >> rdtscll(&shared_area->guest_tsc);
    >> pio/mmio/hypercall
    >> ... back to host
    >> rdtscll(&shared_area->host_tsc);
    >>
    >> And then calculate the difference (minus guests TSC_OFFSET of course)?
    >>
    >
    > Test Machine: Dell Precision 490 - 4-way SMP (2x2) x86_64 "Woodcrest"
    > Core2 Xeon 5130 @2.00Ghz, 4GB RAM.
    >
    > Also it would be interesting to see the MMIO comparison with EPT/NPT,
    > it probably sucks much less than what you're seeing.
    >
    >

    Agreed. If you or someone on this thread has such a beast, please fire
    up my test and post the numbers.

    -Greg

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