On 02/05/2013 11:54 AM, Stefan Hajnoczi wrote: > The qemu-img check command can display fragmentation statistics: > * Total number of clusters in virtual disk > * Number of allocated clusters > * Number of fragmented clusters > > This patch adds fragmentation statistics support to qcow2. > > Compressed and normal clusters count as allocated. Zero clusters are > not counted as allocated unless their L2 entry has a non-zero offset > (e.g. preallocation). > > Only the current L1 table counts towards the statistics - snapshots are > ignored. > > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> > --- > block/qcow2-refcount.c | 25 ++++++++++++++++++++++++- > 1 file changed, 24 insertions(+), 1 deletion(-)
Reviewed-by: Eric Blake <ebl...@redhat.com>
> @@ -963,6 +965,17 @@ static int check_refcounts_l2(BlockDriverState *bs,
> BdrvCheckResult *res,
> l2_entry &= s->cluster_offset_mask;
> inc_refcounts(bs, res, refcount_table, refcount_table_size,
> l2_entry & ~511, nb_csectors * 512);
> +
> + if (flags & CHECK_FRAG_INFO) {
> + res->bfi.allocated_clusters++;
> + if (next_contiguous_offset &&
> + (l2_entry & ~511) != next_contiguous_offset) {
> + res->bfi.fragmented_clusters++;
> + }
> + /* Round down again, see nb_sectors above */
> + next_contiguous_offset = (l2_entry & ~511) +
That's a lot of repetition of (l2_entry & ~511), which feels somewhat
magic; is it worth a dedicated temporary variable better named to
explain why l2_entry is being rounded down to a 512-byte boundary?
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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