Re: [Qemu-devel] [snabb-devel] Re: [PATCH v5] vhost-user: add multi queue support

[Ouyang, Changchun]

> -----Original Message-----
> From: address@hidden [mailto:snabb-
> address@hidden On Behalf Of Maxime Leroy
> Sent: Thursday, July 9, 2015 6:01 AM
> To: Michael S. Tsirkin
> Cc: Ouyang, Changchun; address@hidden; Marcel
> Apfelbaum; address@hidden; Nikolay Nikolaev; Luke Gorrie; Long,
> Thomas; address@hidden
> Subject: [snabb-devel] Re: [Qemu-devel] [PATCH v5] vhost-user: add multi
> queue support
> 
> Hi Michael,
> 
> On Wed, Jul 8, 2015 at 4:29 PM, Michael S. Tsirkin <address@hidden> wrote:
> > On Thu, May 28, 2015 at 09:23:06AM +0800, Ouyang Changchun wrote:
> >> Based on patch by Nikolay Nikolaev:
> >> Vhost-user will implement the multi queue support in a similar way to
> >> what vhost already has - a separate thread for each queue.
> >> To enable the multi queue functionality - a new command line
> >> parameter "queues" is introduced for the vhost-user netdev.
> >>
> >> Signed-off-by: Nikolay Nikolaev <address@hidden>
> >> Signed-off-by: Changchun Ouyang <address@hidden>
> >
> > So testing turned up a significant issue with the protocol extension
> > in this one.  Specifically, remote has no idea how many queues guest
> > actually wants to use (it's dynamic, guest changes this at any time).
> > We need support for enabling and disabling queues dynamically.

Do you mean we need control queue to negotiate the actual queue number between
Guest and host? Or something like that

> >
> > Given we are past hard freeze, and given no one uses this yet (dpdk
> > upstream did not merge supporting protocol), I think the best thing to
> > do is to disable this functionality for 2.4.
> > I will send a patch to do this shortly.
> 
> You are making a wrong statement, we already use multiqueue for vhost-
> user and we expected to have this support officially integrated in qemu 2.4.
> 
> Libvirt 1.2.17 has been released with multiqueue support for vhost-user.
> (http://libvirt.org/git/?p=libvirt.git;a=commit;h=366c22f2bcf1ddb8253c123f93
> fd18d1ba9eacd6)
> It checks against the version of qemu (i.e. 2.4)  to know if multiqueue is
> supported or not by qemu.
> (http://libvirt.org/git/?p=libvirt.git;a=commitdiff;h=7971723b985b9adc27122a
> 3503e7ab38ced2b57f;hp=e7f5510ef2d28ca0ae0ed5751b1fd3018130d6c1)
> 
> Dynamically enabling/disabling queue between host/guest is a nice feature
> to have.
> But it's not mandatory. You can still configure manually guest and host to use
> the same number of queues.

Same number of queues on host and guest can work normally, I have validated it 
with dpdk.

> 

Maybe we could consider still having this in 2.4,
And have an enhancement patch set to implement dynamically enabling/disabling 
in 2.5 or 2.4.x
After extending the vhost-user spec. 

Thanks
Changchun