[ovirt-devel] virtio-scsi

[Marcus White]

Hello,
Just a bump:) I am hoping this is the right list to ask the question...

MW.

On Fri, Jun 6, 2014 at 7:15 PM, Marcus White <roastedseaweed.k at gmail.com> wrote:
> Hello
> I had some basic questions, was asking them on the kvm list but it
> probably makes more sense here:)
>
> The questions are about virtio-scsi. I would appreciate any help.
>
> 1. Is virtio-scsi via QEMU a zero copy operation from guest to disk?
> The vhost-LIO as I understand it is zero copy, wasnt sure about QEMU.
> With the VM and the QEMU thread part of the same process, it would be
> good to know the flow and where the copies occur, if they do.
>
> 2. When the block layer underneath QEMU(assuming the QEMU does talk to
> the block device and not sg, for example), if an error code comes in,
> is it converted to a SCSI response before being passed to the guest?
>
> 3. Are there any other performance tweaks that would help in both the
> QEMU case and the LIO case?
>
> Thanks in advance:)
> MW