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

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.

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

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.

-Pradeep