Re: [Qemu-devel] [Qemu-discuss] iolimits for virtio-9p

[Greg Kurz <gkurz@linux.vnet.ibm.com>]

On Wed, 27 Apr 2016 16:39:58 +0200
Pradeep Kiruvale <pradeepkiruvale@gmail.com> wrote:

> On 27 April 2016 at 10:38, Alberto Garcia <berto@igalia.com> wrote:
> 
> > On Wed, Apr 27, 2016 at 09:29:02AM +0200, Pradeep Kiruvale wrote:
> >
> > > Thanks for the reply. I am still in the early phase, I will let you
> > > know if any changes are needed for the APIs.
> > >
> > > We might also have to implement throttle-group.c for 9p devices, if
> > > we want to apply throttle for group of devices.
> >
> > Fair enough, but again please note that:
> >
> > - throttle-group.c is not meant to be generic, but it's tied to
> >   BlockDriverState / BlockBackend.
> > - it is currently being rewritten:
> >   https://lists.gnu.org/archive/html/qemu-block/2016-04/msg00645.html
> >
> > If you can explain your use case with a bit more detail we can try to
> > see what can be done about it.
> >
> >
> We want to use  virtio-9p for block io instead of virtio-blk-pci. But in
> case of

9p is mostly aimed at sharing files... why would you want to use it for
block io instead of a true block device ? And how would you do that ?

> virtio-9p we can just use fsdev devices, so we want to apply throttling
> (QoS)
> on these devices and as of now the io throttling only possible with the
> -drive option.
> 

Indeed.

> As a work around we are doing the throttling using cgroup. It has its own
> costs.

Can you elaborate ?

> So, we want to have throttling for fsdev devices inside the qemu itself. I
> am just
> trying to understand and estimate time required for implementing it for the
> fsdevices.
> 

I still don't clearly understand what you are trying to do... maybe provide
a more detailed scenario.

> 
> -Pradeep

Cheers.

--
Greg