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    SubjectRe: [PATCH 0/7] AlacrityVM guest drivers
    Anthony Liguori wrote:
    > Gregory Haskins wrote:
    >> That said, note that the graphs were from earlier kernel runs (2.6.28,
    >> 29-rc8). The most recent data I can find that I published is for
    >> 2.6.29, announced with the vbus-v3 release back in April:
    >>
    >> http://lkml.org/lkml/2009/4/21/408
    >>
    >> In it, the virtio-net throughput numbers are substantially higher and
    >> possibly more in line with your expectations (4.5gb/s) (though notably
    >> still lagging venet, which weighed in at 5.6gb/s).
    >>
    >
    > Okay, that makes more sense. Would be nice to update the graphs as they
    > make virtio look really, really bad :-)

    Yeah, they are certainly ripe for an update. (Note that I was
    unilaterally stale on venet numbers, too) ;)

    >
    >> Generally, I find that the virtio-net exhibits non-deterministic results
    >> from release to release. I suspect (as we have discussed) the
    >> tx-mitigation scheme. Some releases buffer the daylights out of the
    >> stream, and virtio gets close(r) throughput (e.g. 4.5g vs 5.8g, but
    >> absolutely terrible latency (4000us vs 65us). Other releases it seems
    >> to operate with more of a compromise (1.3gb/s vs 3.8gb/s, but 350us vs
    >> 85us).
    >>
    >
    > Are you using kvm modules or a new kernel?

    I just build the entire kernel from git.

    > There was some timer
    > infrastructure changes around 28/29 and it's possible that the system
    > your on is now detecting an hpet which will result in a better time
    > source. That could have an affect on mitigation.

    Yeah, I suspect you are right. I always kept the .config and machine
    constant, but I *do* bounce around kernel versions so perhaps I got
    hosed by a make-oldconfig cycle somewhere along the way.

    >
    >> If there is another patch-series/tree I should be using for comparison,
    >> please point me at it.
    >>
    >
    > No, I think it's fair to look at upstream Linux. Looking at the latest
    > bits would be nice though because there are some virtio friendly changes
    > recently like MSI-x and GRO.

    Yeah, I will definitely include kvm.git in addition to whatever is
    current from Linus. I already have adopted using the latest
    qemu-kvm.git into my workflow.

    Regards,
    -Greg

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