Re: [Xen-devel] [PATCH 0/3 V2] xen-netback: switch to NAPI + kthread 1:1 model

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Jul 03, 2013 at 01:45:13PM +0100, Andrew Bennieston wrote:
[...]
> >If you have time, could you try my third series? In the third series,
> >the only possible performance impact is the new model, which should
> >narrow the problem down.
> 
> Wei, I finally have the results from testing your V3 patches. They
> are available at:
> 
> http://wiki.xenproject.org/wiki/Xen-netback_NAPI_%2B_kThread_V3_performance_testing
> 

Thanks, Andrew.

> This time, the base for the tests was linux-next, rather than
> v3.6.11 (mostly to reduce the effort in backporting patches) so the
> results can't be directly compared to the V1, but I still ran tests
> without, then with, your patches, so you should be able to see the
> direct effect of those patches.
> 
> The summary is that there is (as expected) no impact on the dom0 ->
> VM measurements, and the VM -> dom0 measurements are identical with
> and without the patches up to 4 concurrently transmitting VMs or so,
> after which the original version outperforms the patched version.
> The difference becomes less pronounced as the number of TCP streams
> is increased, though.
> 
> My conclusion from these results would be that your V3 patches have
> fairly minimal performance impact, although they should improve
> _fairness_ (due to the kthread per VIF) on the transmit (into VM)
> pathway, and simplify the handling of the receive (out of VM)
> scenario too.
> 

I'm happy to know at least my patches don't have significant negative
impact. :-)

> In other news, it looks like the throughput in general has improved
> between 3.6 and -next :)
> 

Agreed.


Wei.

> Cheers,
> Andrew

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