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hbitmap: enable merging across granularities

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Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190709232550.10724-9-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
This commit is contained in:
John Snow 2019-07-29 16:35:53 -04:00
parent 3bde4b010e
commit c5b40c1f9c
1 changed files with 35 additions and 1 deletions
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36
util/hbitmap.c
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@ -781,7 +781,27 @@ void hbitmap_truncate(HBitmap *hb, uint64_t size)
bool hbitmap_can_merge(const HBitmap *a, const HBitmap *b)
{
return (a->size == b->size) && (a->granularity == b->granularity);
return (a->orig_size == b->orig_size);
}
/**
* hbitmap_sparse_merge: performs dst = dst | src
* works with differing granularities.
* best used when src is sparsely populated.
*/
static void hbitmap_sparse_merge(HBitmap *dst, const HBitmap *src)
{
uint64_t offset = 0;
uint64_t count = src->orig_size;
while (hbitmap_next_dirty_area(src, &offset, &count)) {
hbitmap_set(dst, offset, count);
offset += count;
if (offset >= src->orig_size) {
break;
}
count = src->orig_size - offset;
}
}
/**
@ -812,10 +832,24 @@ bool hbitmap_merge(const HBitmap *a, const HBitmap *b, HBitmap *result)
return true;
}
if (a->granularity != b->granularity) {
if ((a != result) && (b != result)) {
hbitmap_reset_all(result);
}
if (a != result) {
hbitmap_sparse_merge(result, a);
}
if (b != result) {
hbitmap_sparse_merge(result, b);
}
return true;
}
/* This merge is O(size), as BITS_PER_LONG and HBITMAP_LEVELS are constant.
* It may be possible to improve running times for sparsely populated maps
* by using hbitmap_iter_next, but this is suboptimal for dense maps.
*/
assert(a->size == b->size);
for (i = HBITMAP_LEVELS - 1; i >= 0; i--) {
for (j = 0; j < a->sizes[i]; j++) {
result->levels[i][j] = a->levels[i][j] | b->levels[i][j];