Messages in this thread | | | Date | Fri, 07 Aug 2009 10:46:24 -0500 | From | Anthony Liguori <> | Subject | Re: [PATCH 0/7] AlacrityVM guest drivers |
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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 :-)
> 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? 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.
> 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.
Since you're using the latest vbus bits, it makes sense to compare against the latest virtio bits.
Regards,
Anthony Liguori
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