On 12/12/2012 06:46 AM, Paolo Bonzini wrote: > Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> > --- > hbitmap.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++---------- > hbitmap.h | 25 +++++++++++++++++++++++++ > 2 files changed, 72 insertions(+), 10 deletions(-)
When using hbitmap_alloc_with_data, must the user pass in all 0 data, or
do you do a one-time slow pass over the passed-in data to populate the
remaining layers of the hbitmap to allow faster traversal later?
> +HBitmap *hbitmap_alloc_with_data(uint64_t size, int granularity, void *data)
> +{
> + HBitmap *hb = g_malloc0(sizeof(struct HBitmap));
> + unsigned i;
> +
> + hb->size = hbitmap_round_size(size, granularity);
> hb->granularity = granularity;
> + hb->last_level_allocated = (data == NULL);
> +
> for (i = HBITMAP_LEVELS; i-- > 0; ) {
> - size = MAX((size + BITS_PER_LONG - 1) >> BITS_PER_LEVEL, 1);
> - hb->levels[i] = g_malloc0(size * sizeof(unsigned long));
> + if (data == NULL) {
> + data = g_malloc0(hbitmap_required_size(size, granularity));
> + }
> + hb->levels[i] = data;
> + data = NULL;
> + granularity += BITS_PER_LEVEL;
> }
>
> /* We necessarily have free bits in level 0 due to the definition
> * of HBITMAP_LEVELS, so use one for a sentinel. This speeds up
> * hbitmap_iter_skip_words.
> */
> - assert(size == 1);
> + assert(hbitmap_required_size(size, granularity) == sizeof(unsigned
> long));
> hb->levels[0][0] |= 1UL << (BITS_PER_LONG - 1);
> return hb;
> }
Based on the implementation, you aren't inspecting the contents of data.
> +/**
> + * hbitmap_alloc_with_data:
> + * @size: Number of bits in the bitmap.
> + * @granularity: Granularity of the bitmap.
> + * @data: Pointer to a data block that will be used for the bottom level
> + * of the HBitmap.
> + *
> + * Allocate a new HBitmap, using a client-provided data block for the
> + * actual bitmap and allocating memory only for the compressed levels.
> + * If @data is NULL, this function is equivalent to @hbitmap_alloc.
> + */
> +HBitmap *hbitmap_alloc_with_data(uint64_t size, int granularity, void *data);
But this documentation didn't mention that the caller must pass in all 0s.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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