On Sat, 2012-03-24 at 16:30 +0100, Christoph Hellwig wrote:
> On Wed, Mar 14, 2012 at 01:14:18PM +0100, Paolo Bonzini wrote:
> >
> > Note that the discard granularity is only a hint, so it's really more a
> > maximum suggested value than a granularity. Outside of a cluster
> > boundary the format
On Sat, 2012-03-24 at 16:27 +0100, Christoph Hellwig wrote:
> > has_discard = !fallocate(s->fd, FALLOC_FL_PUNCH_HOLE |
> > FALLOC_FL_KEEP_SIZE,
>
> There is no point in using FALLOC_FL_KEEP_SIZE together with
> FALLOC_FL_PUNCH_HOLE.
It's *required*. From the man page [0], "The FALLOC_FL_
On Thu, 2012-03-15 at 10:36 +0100, Paolo Bonzini wrote:
> Changing across guest boots is a minor problem, but changing across
> migration must be avoided at all costs.
>
> BTW, after this discussion I think we can instead report
> discard_granularity = 512 and discard_zeroes_data=0 and get most of
On Wed, 2012-03-14 at 08:41 +0100, Paolo Bonzini wrote:
> Il 13/03/2012 20:13, Richard Laager ha scritto:
> >>> > > * For SCSI, report an unmap_granularity to the guest as follows:
> >>> > > max(logical_block_size, discard_granu
U.
On Mon, 2012-03-12 at 13:27 +0100, Paolo Bonzini wrote:
> Il 10/03/2012 19:02, Richard Laager ha scritto:
> > I propose adding the following behaviors in any event:
> > * If a QEMU block device reports a discard_granularity > 0, it
> > must be equ
I'm believe your patch set provides these behaviors now:
* QEMU block drivers report discard_granularity.
* discard_granularity = 0 means no discard
* The guest is told there's no discard support.
* discard_granularity < 0 is undefined.
I was just working on this as well, though your implementation is *far*
more complete than mine. (I was only looking at making changes to the
discard implementation in block/raw-posix.c.)
I've got several comments, which I've separated by logical topic...
BLKDISCARD
fallocate(
