On 27 April 2016 at 19:12, Greg Kurz <gk...@linux.vnet.ibm.com> wrote:
> On Wed, 27 Apr 2016 16:39:58 +0200 > Pradeep Kiruvale <pradeepkiruv...@gmail.com> wrote: > > > On 27 April 2016 at 10:38, Alberto Garcia <be...@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 ? > *Yes, we want to share the files itself. So we are using the virtio-9p.* *We want to have QoS on these files access for every VM.* > > > 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 ? > *We saw that we need to create cgroups and set it and also we observed lot of iowaits * *compared to implementing the throttling inside the qemu.* *This we did observe by using the virtio-blk-pci devices. (Using cgroups Vs qemu throttling)* Thanks, Pradeep
