[libvirt] Virt io blk buffer

Eric Blake eblake at redhat.com
Fri Feb 24 18:49:54 UTC 2012

On 02/23/2012 11:53 PM, Pankaj Rawat wrote:
> Hi all 
> Can any one tell what is the default Vitio blk IO Buffer size 

You'll probably get better response on the qemu lists, since virtio is
part of qemu.

> And can we change it ? if yes how?

Libvirt does not currently expose anything to change this, other than
the fact that _if_ qemu supports a way to change it on the command line,
you can use <qemu:command> in your XML to add the extra arguments; or if
qemu supports it via a monitor command, you can use 'virsh
qemu-monitor-command' to change it at runtime.  But again, I don't know
enough about the situation to know if qemu even exposes a
parameterizable block size for virtio, since no one has previously asked
for libvirt to start encoding it into its XML as a formal feature.

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Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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