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

[David Vrabel <david.vrabel@citrix.com>]

On 27/05/13 12:29, Wei Liu wrote:
> * This is a xen-devel only post, since we have not reached concesus on
>   what to add / remove in this new model. This series tries to be
>   conservative about adding in new feature compared to V1.
> 
> This series implements NAPI + kthread 1:1 model for Xen netback.
> 
> This model
>  - provides better scheduling fairness among vifs
>  - is prerequisite for implementing multiqueue for Xen network driver
> 
> The first two patches are ground work for the third patch. First one
> simplifies code in netback, second one can reduce memory footprint if we
> switch to 1:1 model.
> 
> The third patch has the real meat:
>  - make use of NAPI to mitigate interrupt 
>  - kthreads are not bound to CPUs any more, so that we can take
>    advantage of backend scheduler and trust it to do the right thing
> 
> Change since V1:
>  - No page pool in this version. Instead page tracking facility is
>    removed.

Andrew Bennieston has done some performance measurements with (I think)
the V1 series and it shows a significant decrease in performance of
from-guest traffic even with only two VIFs.

Andrew will be able to comment more on this.

Andrew, can you also make available your results for others to review?

David