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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