Il 17/12/2012 18:14, Eric Blake ha scritto:
> 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?
Right, I should add such a pass.
Paolo
>> +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.
>
