Re: [PATCH 1/3] block: add queue flag for paravirt frontend drivers

Jens Axboe
2008-11-05T09:22:08Z

On Tue, Nov 04 2008, Jeremy Fitzhardinge wrote:
> Jens Axboe wrote:
> >On Mon, Oct 27 2008, Fernando Luis Vázquez Cao wrote:
> >
> >>As is the case with SSD devices, we do not want to idle in AS/CFQ when
> >>the block device is a paravirt front-end driver. This patch adds a flag
> >>(QUEUE_FLAG_VIRT) which should be used by front-end drivers such as
> >>virtio_blk and xen-blkfront to indicate a paravirtualized device.
> >>
> >
> >All three patches look fine, although we could just reuse
> >QUEUE_FLAG_NONROT directly. But I agree it makes sense to make the
> >distinction, so I've just applied 1-3.
> >
>
> I guess in theory you could imagine that the virtual device is mapped
> directly onto a physical device, and the host OS does no scheduling, in
> which case it would be appropriate for the guest do the work. But I
> think otherwise this makes sense.

For that specific case, it should just not set the flag.

--
Jens Axboe