Re: [Qemu-devel] [PATCH 1/2] Make cow_co_is_allocated and cow_update_bitmap more efficient

[Charlie Shepherd]

On 21/08/2013 09:14, Paolo Bonzini wrote:
> Il 21/08/2013 00:53, Charlie Shepherd ha scritto:
> > What if nb_sectors > 512 * 8?
> For cow_co_is_allocated, you have the luxury of returning information
> only for the fewer than nb_sectors.  That is, you can set *num_same to a
> smaller value than nb_sectors, even if sector_num + *num_same has the
> same state as the [sector_num, sector_num + *num_same) range.  It will
> cause extra calls to is_allocated in the callers, but that's it.
So we can report a conservative estimate of *num_same? It still seems 
worthwhile to me to be as efficient as possible, I guess that means 
processing a sector's worth of metadata at a time?

Charlie