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Is CPU overhead really independent of packet size in Xen?
Hi,
I'm reading some Xen performance slides which is published on XenSummit
(www.xensource.com/files/summit_3/perf-isolation-gupta.pdf). The presenter
claims the CPU overhead is independent of network packet size in Xen VM
domains. I haven't done much research on network I/O on Xen, but I have done
many experiments on disk I/O.

Based on my disk I/O experimental results, I found out, generally the CPU
utilization decrease as the I/O packet size increase which is consistent
with the IPv4 forwarding experiments I did before (not on Xen, on plain IA32
Linux). The only exception I noticed is DomainUF. For both small size and
large size sequential I/O, the CPU utilization in DomainUF remains almost
constant (100%) while CPU utilization drops for 4k and 8K random I/O.

If anyone in this mailing list has done similar experiments, please adivse
the difference when considering CPU utilization for network I/O and disk
I/O? or should both network I/O and disk I/O have the same curve of CPU
utilization vs. Packet Size?

Thanks,

Liang


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