[libvirt-users] Getting libvirt Error when setting IO tune read_bytes_sec value using libvirt API virDomainSetBlockIotune

[vikrant verma]

Hi Michal,

Thanks for the reply.

But i want to keep this setting, my intention is to set IO throttling (IO
tunning) over the block storage which is attached to the VM.

As per my understanding there are 2 ways to do it.

1. Using Cgroup - we can put the IO throttling on the device using
cgroup command (this i have tried and it is working)

2. Using Libvirt API virDomainSetBlockIoTune() - But i am not able to
achieve the IO throttling using it, please suggest how to do it.

Please let me know how to do it using Libvirt.

Regards,
Vikrant




On Thu, May 9, 2013 at 5:42 PM, Michal Privoznik <mprivozn at redhat.com>wrote:

> On 09.05.2013 14:02, vikrant verma wrote:
> > Hi All,
> >
> >  I am setting the value for  "read_bytes_sec"  using the following API
> code
> >
> > virDomainSetBlockIoTune(dom, "/mnt/tmpsdb/FileVM1", parainfoPtr,
> > nparams, 2);
> >
> > I am succesfully able to set this value and i can read it back using the
> API
> >
> >
> >
> virDomainGetBlockIoTune(dom,"/mnt/tmpsdb/FileVM1",parainfoPtr,&nparams,2);
> >
> > But after setting this value when i shutdown my VM and start it again I
> > am getting following error -
> >
> > ibvirtError: internal error Process exited while reading console log
> > output: qemu-system-x86_64: -drive
> >
> file=/mnt/tmpsdb/FileVM1,if=none,id=drive-ide0-1-1,format=raw,bps_rd=1048576:
> > Invalid parameter 'bps_rd'
>
> Interesting. What's the qemu version? bps_rs has been introduced in
> qemu-1.1 IIRC.
>
> >
> >
> > Note - when i see dumpxml of the VM following lines are got added after
> > setting the iotunes for read_bytes_sec
> >
> >  <iotune>
> >         <read_bytes_sec>1048576</read_bytes_sec>
> >       </iotune>
> >
>
> Yep, that's correct. If you don't need this setting anymore, just delete
> it (e.g. by using virsh edit) and you should be able to start the domain
> up again.
>
> >
> > Please help me. Also i wanted to know whether we can set block IO tune
> > for a VM using the above API. Is it same as the IO throttling provided
> > by cgroup?
> >
> >
> >
>
> Michal
>
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