Re: [Qemu-devel] [RFC PATCH 1/1] ceph/rbd block driver for qemu-kvm

[Anthony Liguori]

On 05/25/2010 08:38 AM, Avi Kivity wrote:
> On 05/25/2010 04:35 PM, Anthony Liguori wrote:
> > On 05/25/2010 08:31 AM, Avi Kivity wrote:
> > > > A protocol based mechanism has the advantage of being more robust 
> > > > in the face of poorly written block backends so if it's possible to 
> > > > make it perform as well as a plugin, it's a preferable approach.
> > >
> > > May be hard due to difficulty of exposing guest memory.
> >
> > If someone did a series to add plugins, I would expect a very strong 
> > argument as to why a shared memory mechanism was not possible or at 
> > least plausible.
> >
> > I'm not sure I understand why shared memory is such a bad thing wrt 
> > KVM.  Can you elaborate?  Is it simply a matter of fork()?
>
> fork() doesn't work in the with of memory hotplug.  What else is there?

Is it that fork() doesn't work or is it that fork() is very expensive?

Regards,

Anthony Liguori