Re: [Qemu-discuss] How to use IO throttling and IO burst

[Alexandre LAURENT]

I see, but I am still wondering how "burst" option was thought ? I mean, ok, it will not work on local block devices/files since I am starting two VMs. Will it work with NFS ? I don't see why it would work better in this case.

Moreover, what are the recommanded options to use with drive to get cgroups working ? Is there a need to remove caching or use special caching mode ?

Thank you,

Best regards,

Alexandre

2014-04-03 11:20 GMT+02:00 Fam Zheng <address@hidden>:

On Thu, 04/03 11:06, Alexandre LAURENT wrote:
> Hi,
>
> I am using QEMU 1.7.1 and I would like to know how to use the 'drive'
> options :
> - bps_wr
> - bps_wr_max
> - bps_rd
> - bps_rd_max
>
> Can you explain me how to limit IO access between two VMs, where one would
> be limited and the second one have full IO access. My point is to give full
> IO access to the limited one when the second is doing nothing.
>

QEMU's block IO throttling cannot do this because one QEMU process doesn't know
about other QEMU instances. However if you use local block devices or files as
drive backend, it's possible to configure Linux cgroups on two backends with
different weights:

https://www.kernel.org/doc/Documentation/cgroups/blkio-controller.txt

Fam