On 06/05/2013 05:15 PM, Waiman Long wrote:
Currently, the ebitmap_node structure has a fixed size of 32 bytes. On
a 32-bit system, the overhead is 8 bytes, leaving 24 bytes for being
used as bitmaps. The overhead ratio is 1/4.
On a 64-bit system, the overhead is 16 bytes. Therefore, only 16 bytes
are left for bitmap purpose and the overhead ratio is 1/2. With a
3.8.2 kernel, a boot-up operation will cause the ebitmap_get_bit()
function to be called about 9 million times. The average number of
ebitmap_node traversal is about 3.7.
This patch increases the size of the ebitmap_node structure to 64
bytes for 64-bit system to keep the overhead ratio at 1/4. This may
also improve performance a little bit by making node to node traversal
less frequent (< 2) as more bits are available in each node.
Signed-off-by: Waiman Long <waiman.l...@hp.com>
Acked-by: Stephen Smalley <s...@tycho.nsa.gov>
---
security/selinux/ss/ebitmap.h | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/security/selinux/ss/ebitmap.h b/security/selinux/ss/ebitmap.h
index e7eb3a9..712c8a7 100644
--- a/security/selinux/ss/ebitmap.h
+++ b/security/selinux/ss/ebitmap.h
@@ -16,7 +16,13 @@
#include <net/netlabel.h>
-#define EBITMAP_UNIT_NUMS ((32 - sizeof(void *) - sizeof(u32)) \
+#ifdef CONFIG_64BIT
+#define EBITMAP_NODE_SIZE 64
+#else
+#define EBITMAP_NODE_SIZE 32
+#endif
+
+#define EBITMAP_UNIT_NUMS ((EBITMAP_NODE_SIZE-sizeof(void *)-sizeof(u32))\
/ sizeof(unsigned long))
#define EBITMAP_UNIT_SIZE BITS_PER_LONG
#define EBITMAP_SIZE (EBITMAP_UNIT_NUMS * EBITMAP_UNIT_SIZE)
--
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