[Qemu-devel] [PATCH v4 06/20] hbitmap: cache array lengths

[John Snow <jsnow@redhat.com>]

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>
Signed-off-by: John Snow <jsnow@redhat.com>
---
 util/hbitmap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/util/hbitmap.c b/util/hbitmap.c
index ab13971..5b78613 100644
--- a/util/hbitmap.c
+++ b/util/hbitmap.c
@@ -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);
     }
 
-- 
2.1.0