Re: [Qemu-devel] [PATCH v2 8/8] virtio-blk: add x-data-plane=on|off performance feature

[Daniel P. Berrange]

On Tue, Nov 20, 2012 at 02:50:02PM +0100, Stefan Hajnoczi wrote:
> On Tue, Nov 20, 2012 at 12:37:08PM +0000, Daniel P. Berrange wrote:
> > On Tue, Nov 20, 2012 at 01:31:52PM +0100, Stefan Hajnoczi wrote:
> > > The virtio-blk-data-plane feature is easy to integrate into
> > > hw/virtio-blk.c.  The data plane can be started and stopped similar to
> > > vhost-net.
> > > 
> > > Users can take advantage of the virtio-blk-data-plane feature using the
> > > new -device virtio-blk-pci,x-data-plane=on property.
> > > 
> > > The x-data-plane name was chosen because at this stage the feature is
> > > experimental and likely to see changes in the future.
> > 
> > Can you give some indication of how it is likely to change, since
> > this has a bearing on any libvirt use of this feature ?
> 
> The following expectations:
> 
> 1. This is an experimental feature.  It can be enabled through libvirt
>    using <qemu:commandline>.
> 
> 2. There is ongoing work to break down the global mutex in QEMU, which
>    will allow virtio-blk-data-plane functionality to become the
>    virtio-blk emulation default.  At that point no command-line options
>    will be necessary (migration and image formats will be supported).
> 
> So I think there's no need for libvirt to do anything here.

Thanks for clarifying, Kevin / Stefan. Based on this info, we'll do nothing
with this in libvirt, in the expection that it'll become the default when
QEMU is ready for it.

Daniel
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