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hbitmap: cache array lengths 

As a convenience: between incremental backups, bitmap migrations
and bitmap persistence we seem to need to recalculate these a lot.

Because the lengths are a little bit-twiddly, let's just solidly
cache them and be done with it.

Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1429314609-29776-7-git-send-email-jsnow@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
John Snow 2015-04-17 19:49:54 -04:00 committed by Kevin Wolf
parent 592fdd02ae
commit 8515efbef1
1 changed files with 4 additions and 0 deletions
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4
util/hbitmap.c
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@ -90,6 +90,9 @@ struct HBitmap {
* bitmap will still allocate HBITMAP_LEVELS arrays.
*/
unsigned long *levels[HBITMAP_LEVELS];
/* The length of each levels[] array. */
uint64_t sizes[HBITMAP_LEVELS];
};
/* Advance hbi to the next nonzero word and return it. hbi->pos
@ -384,6 +387,7 @@ HBitmap *hbitmap_alloc(uint64_t size, int granularity)
hb->granularity = granularity;
for (i = HBITMAP_LEVELS; i-- > 0; ) {
size = MAX((size + BITS_PER_LONG - 1) >> BITS_PER_LEVEL, 1);
hb->sizes[i] = size;
hb->levels[i] = g_new0(unsigned long, size);
}