kmalloc will round up the request size to power of 2, and current
iova_magazine's size is 1032 (1024+8) bytes, so each instance
allocated will get 2048 bytes from kmalloc, causing around 1KB
waste.
Change IOVA_MAG_SIZE from 128 to 127 to make size of 'iova_magazine'
1024 bytes so that no memory will be wasted.
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
Acked-by: Robin Murphy <robin.murphy@xxxxxxx>
---
Changelog:
since v1:
* update commit log per the comments from Robin and John
drivers/iommu/iova.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index db77aa675145b..27634ddd9b904 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -614,7 +614,12 @@ EXPORT_SYMBOL_GPL(reserve_iova);
* dynamic size tuning described in the paper.
*/
-#define IOVA_MAG_SIZE 128
+/*
+ * As kmalloc's buffer size is fixed to power of 2, 127 is chosen to
+ * assure size of 'iova_magazine' to be 1024 bytes, so that no memory
+ * will be wasted.
+ */
+#define IOVA_MAG_SIZE 127
#define MAX_GLOBAL_MAGS 32 /* magazines per bin */
struct iova_magazine {
--
2.27.0
