[libvirt] [RFC PATCH 0/8 v3] Summary on block IO throttle

Eric Blake eblake at redhat.com
Thu Nov 10 22:04:59 UTC 2011


On 11/10/2011 02:50 PM, Adam Litke wrote:
> Hi Lei,
>
> I've tested this and found that it works well except for one small thing.
>
> When the domain is running and I change one of the throttle settings using the
> --config option in virsh, the on-disk domain xml file is properly updated, but
> the command 'virsh dumpxml' returns the old version.  Is this how it is supposed
> to work?

Yes:

virsh blkdeviotune --config => on-disk only (takes effect next boot; 
fails if transient)

virsh blkdeviotune --live => running only (takes effect now, and lost on 
next boot; fails if offline persistent)

virsh blkdeviotune --config --live => on-disk and current (takes effect 
now and persists to next boot; fails if not running persistent)

virsh blkdeviotune --current => either --config or --live


Also, in thinking about this, I can't help wonder if for extensibility 
of ALL the virTypedParameter commands, we might be better off with 
exposing a long-hand option for raw control of virTypedParameter, so 
that an older virsh can still set options in a newer server without 
having to recompile virsh to add a new named option to match every new 
hypervisor named option.  Something like:

virsh blkdeviotune --set-long total_bytes_sec=number

as long-hand for:

virsh blkdeviotune --total_bytes_sec number

We still need a v4 respinning this to use virTypedParameter; I can help 
by posting a patch 1/8 that shows the changes that I think we need in 
the public interface, but I don't want to spend the time rebasing the 
entire series.

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org




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