Re: vhost net: performance with ping benchmark

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Aug 24, 2009 at 09:22:47PM -0500, Anthony Liguori wrote:
> Michael S. Tsirkin wrote:
>> On Mon, Aug 24, 2009 at 11:12:41AM +0300, Michael S. Tsirkin wrote:
>>   
>>> At Rusty's suggestion, I tested vhost base performance with ping.
>>> Results below, and seem to be what you'd expect.
>>>     
>>
>> Rusty, any chance you could look at the code?  Is it in reasonable
>> shape? I think it makes sense to merge it through you. What do you
>> think?  One comment on file placement: I put files under a separate
>> vhost directory to avoid confusion with virtio-net which runs in guest.
>> Does this sound sane?  Also, can a minimal version (without TSO, tap or
>> any other features) be merged upstream first so that features can be
>> added later? Or do we have to wait until it's more full featured?
>> Finally, can it reasonably make 2.6.32, or you think it needs more time
>> out of tree?
>>   
>
> I think 2.6.32 is pushing it.  I think some time is needed to flush out  
> the userspace interface.  In particular, I don't think Mark's comments  
> have been adequately addressed.

Went over, and I thought they have. Mark, could you please comment?
Are you ok with the interface?

>  If a version were merged without GSO  
> support, some mechanism to do feature detection would be needed in the  
> userspace API.

Correct. There's already GET_FEATURES/ACK_FEATURES in place for this.

> I think this is likely going to be needed regardless.  I  
> also think the tap compatibility suggestion would simplify the  
> consumption of this in userspace.

Yes. I'll post a patch to tap showing how this can be done
without vhost changes.

> I'd like some time to look at get_state/set_state ioctl()s along with  
> dirty tracking support.  It's a much better model for live migration 
> IMHO.

That option is also available in my code, I just went for a simpler one
in my qemu patch.  I will outline how it works in a separate mail.

> I think so more thorough benchmarking would be good too.  In particular,  
> netperf/iperf runs would be nice.

I don't expect the first version to perform well in all situations and
for all users.  But it can't regress, can it? One can always fall back
to userspace ...

> Regards,
>
> Anthony Liguori
>
>> Thanks very much,
>>
>>