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Re: [Xen-devel] [PATCH] Network Checksum Removal

On 23 May 2005, at 20:55, Bin Ren wrote:

I've added the support for ethtools. By turning on and off netfront
checksum offloading, I'm getting the following throughput numbers,
using iperf. Each test was run three times. CPU usages are quite
similar in two cases ('top' output). Looks like checksum computation
is not a major overhead in domU networking.

dom0/1/2 all have 128M memory. dom0 has e1000 tx checksum offloading turned on.

What happens to CPU usage in dom1 when tx checksumming is disabled?

Overall though these are the kind of results I would expect. Linux usually does csumming at the same time as it has to do a copy anyway, and it ends up being limited by memory/L2-cache bandwidth, not the extra computation. But the offload extensions haven't cost much to implement and there are probably cases where it helps a little.

Maybe I'm being pessimistic though: Can you reproduce the rather more impressive speedups that you previously saw, Jon?

 -- Keir

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