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Re: [Qemu-devel] [PATCH 0/3] info blockstats (block-qcow2): show highest
Re: [Qemu-devel] [PATCH 0/3] info blockstats (block-qcow2): show highest allocated offset (bytes)
Sun, 11 Jan 2009 11:31:53 +0200
Thunderbird 126.96.36.199 (X11/20081119)
Kevin Wolf wrote:
Uri Lublin schrieb:
Although there may be many free blocks below that number (allocated and
the file system can not deallocate those blocks, and they have to be reused
by qemu. Also note that due to fragmentation those free blocks may not
be used on next allocations.
Any idea what would it mean to performance if we changed the behaviour
so that s->free_cluster_index always points to lowest free cluster? Then
most of the fragmentation should be gone.
I don't know, it has to be implemented and measured.
If the impact would be too big we could still change the code to use two
free_cluster_indexes, one for single cluster allocation and one for
larger blocks. This was suggested earlier and I think there were even
patches for it, but I don't seem to remember who exactly suggested this.
That should make qcow2 images less defragmented.