On 2012-12-03 16:53, Osier wrote:
>On 2012年12月03日 11:39, hzguanqiang wrote:
>> On 2012-12-03 10:33, Osier wrote:
>> >On 2012年11月28日 16:34, hzguanqiang wrote:
>> >> Hi, guys.
>> >> I want to change block I/O throttle using 'virsh blkdeviotune' with vm
>> >> not running, it reported an error:
>> >> # virsh blkdeviotune instance-000000dc /dev/loop0 --total-bytes-sec
>> >> 20000000 --total-iops-sec 20 --config
>> >> error: Unable to change block I/O throttle
>> >> error: unsupported configuration: block I/O throttling not supported
>> >> with this QEMU binary
>> >> I can do this when the vm is running. Is it a bug? How can I fix this
>> >> problem.
>> >
>> >It just looks strange, as you can tune when the VM is active. Because
>> >the qemu capabilities is collected during the qemu driver starts up,
>> >which is independant with the domain states.
>> >
>> >Probably you will want to debug the qemu capabilities collecting
>> >process.
>> >
>> >Osier
>> Osier, Firstly, thanks for your reply.
>> The situation is that I want to resize the disk and meanwhile reset the
>> block I/O throttle. And during the whole process, The vm is stopped.
>> I've found this was directly caused by the patch "qemu: reject
>> blockiotune if qemu too old" post by Eric Blake long before. I've sent
>> an email to ask him the reason. Maybe, People think you can't set I/O
>> throtting if vm not started, I guess.
>
>Eric's path is good, because it makes no sense to set block IO tune
>for inactive guest if the qemu doesn't support it, otherwise the guest
>will fails to start.
>
>The key point is why the IO tuning can be set when the guest is active,
>while fails when it's inactive. Because the qemu caps is not related
>with the domain states.