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[Xen-devel] Direct I/O performance: direct interrupts to running domU?



Hi,

I'm testing performance of a NIC assigned directly to a domU. (xen-3.0.3 x86_64)

After your help straightening out the problems with my test environment, my netperf throughput numbers were close to base Linux (generally with 0.5%); however, when I did the netperf transaction tests, the numbers on Xen (either dom0 and domU) were 10-20% lower than the base Linux depending on the test parameters. Since this linear transaction test would be very sensitive to the latency/path-length involved in the interrupt delivery, I'm making the assumption, for the moment, that this is the problem without cranking up xenoprof/oprofile to prove it.

One of the questions that came up in a discussion was whether it might be technically possible to have interrupts delivered directly to a running domain without the hypervisor overhead. This would presumably involve some additional overhead at the time the hypervisor switched domains, but it might be a worthwhile trade-off.

Thanks,

John Byrne









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