Re: [Qemu-devel] [PATCH 2/2] Virtio block device support

Hollis Blanchard
2008-11-26T18:24:22Z

On Tue, 2008-11-25 at 15:57 -0600, Anthony Liguori wrote:
> This has been posted before but I believe it now has addressed all outstanding
> concerns. I'd like to apply it if there are no objections.
>
> This patch adds virtio-blk support to QEMU. virtio-blk is a paravirtual disk
> controller that can achieve good performance when using KVM.
>
> Since virtio is based on a scatter/gather API, we don't have a linear buffer
> for each request. This forces us to allocate a linear buffer since the current
> block driver API does not have a scatter/gather operation. This allocation
> can never exceed the maximum data limit on the ring queue so it isn't
> unbounded.
>
> posix-aio cannot support a scatter/gather asynchronous operation so we'll need
> to introduce our own thread pool to eliminate this limitation. There is work
> underway to do this.
>
> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Tested and working (in conjunction with the virtio page size patch I
just posted).

--
Hollis Blanchard
IBM Linux Technology Center