From: Feng Tang <feng.tang@intel.com>
Date: Sun, 3 Jul 2022 19:44:50 +0800
Subject: iommu/iova: change IOVA_MAG_SIZE to 127 to save memory
Git-commit: b4c9bf178ace26c52c9cac36f265ba95132a221d
Patch-mainline: v6.0-rc1
References: bsc#1205701

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@intel.com>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20220703114450.15184-1-feng.tang@intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 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 db77aa675145..e44f565c5319 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 {