[dm-devel] virtio_blk: fix defaults for max_hw_sectors and max_segment_size
snitzer at redhat.com
Wed Nov 26 23:00:55 UTC 2014
On Wed, Nov 26 2014 at 4:53pm -0500,
Jens Axboe <axboe at kernel.dk> wrote:
> On 11/26/2014 02:51 PM, Mike Snitzer wrote:
> > But while you're here, I wouldn't mind getting your take on virtio-blk
> > setting max_hw_sectors to -1U.
> > As I said in my original reply to mst: it only makes sense to set a
> > really high initial upper bound like that in a driver if that driver
> > goes on to stack an underlying device's limit.
> -1U should just work, IMHO, there's no reason we should need to cap it
> at some synthetic value. That said, it seems it should be one of
> those parameters that should be negotiated up and set appropriately.
I'm saying set it to the underlying device's value for max_hw_sectors --
not some synthetic value. So I think we're saying the same thing.
But it isn't immediately clear (to me) how that benefits virtio-blk
users (obviously they are getting by today). So until that is pinned
down I imagine nobody will care to extend the virtio-blk protocol to
allow stacking max_hw_sectors and max_sectors up.
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