From b4c9bf178ace26c52c9cac36f265ba95132a221d Mon Sep 17 00:00:00 2001 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 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(-) (limited to 'drivers/iommu/iova.c') 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 { -- cgit v1.2.3