On Mon, 1 Dec 2014 13:46:45 +0200
"Michael S. Tsirkin" [off-list ref] wrote:

On Mon, Dec 01, 2014 at 12:33:15PM +0100, Cornelia Huck wrote:

quoted

On Mon, 1 Dec 2014 11:26:58 +0200
"Michael S. Tsirkin" [off-list ref] wrote:

quoted

For some places on data path, it might be worth it
to cache the correct value e.g. as part of device
structure. This replaces a branch with a memory load,
so the gain would have to be measured, best done
separately?

I think we'll want to do some measuring once the basic structure is
in place anyway.

What's meant by in place here?

That this patchset is ready :)

quoted

We should make sure that e.g. s390 only takes minor
hit due to all that swapping that is needed for standard-compliant
devices. Caching the value might certainly help in some paths.

Well, this is queued in linux-next for 3.19, so
now's the time to do it :)

So much to do, so little time...

I'm still feeling a bit uncomfortable with some of the changes
(virtio-scsi etc.) as I have not been able to test them yet (as there's
no converted qemu for these yet). The virtio-net and virtio-blk changes
seem sane, though, and virtio-ccw should be fine as well.

OTOH, it's not like we're introducing new external interfaces, so later
rework should be fine.