[dpdk-dev] [PATCH v3 0/5] vhost: optimize enqueue

[Maxime Coquelin]

On 10/13/2016 08:02 AM, Wang, Zhihong wrote:
>> > Yes, that's great effort! With your hardwork, we know what the bottleneck
>> > is and how it could be improved.
>> >
>> > However, you don't have to do code refactor (merge two code path to one)
>> > to apply those improvements. From what I know, in this patchset, there
>> > are two factors could improve the performance:
>> >
>> > - copy hdr together with packet data
>> >
>> > - shadow used ring update and update at once
>> >
>> > The overall performance boost I got with your v6 patchset with mrg-Rx
>> > code path is about 27% (in PVP case). And I have just applied the 1st
>> > optimization, it yields about 20% boosts. The left could be covered if
>> > we apply the 2nd optimization (I guess).
>> >
>> > That would be a clean way to optimize vhost mergeable Rx path:
>> >
>> > - you don't touch non-mrg Rx path (well, you may could apply the
>> >   shadow_used_ring trick to it as wel)
>> >
>> >   This would at least make sure we will have no such performance
>> >   regression issue reported by ARM guys.
>> >
>> > - you don't refactor the code
>> >
>> >   The rewrite from scratch could introduce other issues, besides the
>> >   performance regression. We may just don't know it yet.
>> >
>> >
>> > Make sense to you? If you agree, I think we could still make it in
>> > this release: they would be some small changes after all. For example,
>> > below is the patch applies the 1st optimization tip on top of
>> > dpdk-next-virtio
>
> Thanks for this great idea. I think it's a better way to do it.
> I'll start to make the patch then.
>
>

I personally find having two paths better for maintenance as it is
easier to understand (IMHO).
So if we can have the performance gain while keeping the two paths,
I definitely support the idea.

Thanks,
Maxime