[PATCH] radix-tree: small

Reduce radix tree node memory usage by about a factor of 4 for small files
(< 64K).  There are pointer traversal and memory usage costs for large
files with dense pagecache.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 35a2d93..7cbdada 100644 (file)
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -33,7 +33,7 @@
 
 
 #ifdef __KERNEL__
-#define RADIX_TREE_MAP_SHIFT   6
+#define RADIX_TREE_MAP_SHIFT   (CONFIG_BASE_SMALL ? 4 : 6)
 #else
 #define RADIX_TREE_MAP_SHIFT   3       /* For more stressful testing */
 #endif