Re: [libvirt PATCH 2/3] virbitmap: remove redundant mem_alloc
On Mon, Aug 03, 2020 at 19:18:52 +0200, Ján Tomko wrote:
We have two variables tracking the size of the map:
map_len and mem_alloc.
Remove mem_alloc as well as code keeping them in sync.
Signed-off-by: Ján Tomko <jtomko(a)redhat.com>
Fixes: 917426c8d7dd26f13142fc4c5c1a8a19137ac647
---
src/util/virbitmap.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)
diff --git a/src/util/virbitmap.c b/src/util/virbitmap.c
index 60fd8491dd..4c205016ff 100644
--- a/src/util/virbitmap.c
+++ b/src/util/virbitmap.c
[...]
@@ -197,13 +195,12 @@ virBitmapExpand(virBitmapPtr map,
/* resize the memory if necessary */
if (map->map_len < new_len) {
- if (VIR_RESIZE_N(map->map, map->map_alloc, map->map_len,
+ if (VIR_RESIZE_N(map->map, map->map_len, map->map_len,
new_len - map->map_len) < 0)
return -1;
* VIR_RESIZE_N:
* @ptr: pointer to hold address of allocated memory
* @alloc: variable tracking number of elements currently allocated
* @count: number of elements currently in use
* @add: minimum number of elements to additionally support
*
* Blindly using VIR_EXPAND_N(array, alloc, 1) in a loop scales
* quadratically, because every iteration must copy contents from
* all prior iterations. But amortized linear scaling can be achieved
* by tracking allocation size separately from the number of used
* elements, and growing geometrically only as needed.
*
* If 'count' + 'add' is larger than 'alloc', then geometrically
reallocate
* the array of 'alloc' elements, each sizeof(*ptr) bytes long, and store
* the address of allocated memory in 'ptr' and the new size in 'alloc'.
* The new elements are filled with zero.