[libvirt] [PATCH] Support for qemu aio drive option

[Chris Lalancette]

On 05/12/2010 11:26 PM, Eric Blake wrote:
> From: Matthias Dahl <mdvirt at designassembly.de>
> 
> qemu allows the user to choose what io storage api should be used, either the
> default (threads) or native (linux aio) which in the latter case can result in
> better performance.
> 
> Thanks a lot to Eric Blake and Matthias Bolte for their comments.

(sorry, I reviewed the one big patch instead of the split up patches.  It seems
to be the same except for the addition of the symbols to libvirt_private.syms)

The implementation looks perfectly reasonable.  I'm just concerned that the
concept of what we are doing is too qemu specific, though.  Basically, I think
what we are trying to model here is the concept of an I/O backend implementation,
correct?  Should we maybe change this to be "<iobackend type='%s'/>", and then
have available enums like:

aiothreads
aionative
...

That way, for other hypervisors that do something different (like VirtualBox,
which just has AIO on/off), we can have additional enums to describe their
behavior.  Even further, if a given hypervisor wanted to do something like
"Direct I/O" for the I/O backend (as an example), we could also use this element
to specify that.  What do you think?

-- 
Chris Lalancette