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Re: [Xen-devel] [PATCH net-next RFC 0/5] xen-netback: TX grant mapping instead of copy



On 01/11/13 19:00, Zoltan Kiss wrote:
 >> Based on my investigations the packet get only copied if it is
delivered to
 >>Dom0 stack, which is due to this patch:
 >>https://lkml.org/lkml/2012/7/20/363
 >>That's a bit unfortunate, but as far as I know for the huge majority
this use
 >>case is not too important.
Likely to be true, but it would still be interesting to know how badly
this use case suffers with this change, and any increase in CPU usage
would be interesting to know about as well.
I can't find my numbers, but as far as I remember it wasn't
significantly worse than grant copy. I will check that again.
I've measured it now: with my patch it was 5.2 Gbps, without it 5.4. Both cases iperf in Dom0 maxed out its CPU, mostly in soft interrupt context, based on top.

Zoli


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