[PATCH] x86_64: group memnodemap and memnodeshift in a memnode structure

pfn_to_page() and others need to access both memnode_shift and the very
first bytes of memnodemap[]. If we force memnode_shift to be just before the
memnodemap array, we can reduce the memory footprint to one cache line
instead of two for most setups. This patch introduce a 'memnode' structure
where shift and map[] are carefully placed.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/include/asm-x86_64/mmzone.h b/include/asm-x86_64/mmzone.h
index 972c9359f7d7..937f99b26883 100644
--- a/include/asm-x86_64/mmzone.h
+++ b/include/asm-x86_64/mmzone.h
@@ -15,8 +15,13 @@
 #define NODEMAPSIZE 0xfff
 
 /* Simple perfect hash to map physical addresses to node numbers */
-extern int memnode_shift; 
-extern u8  memnodemap[NODEMAPSIZE]; 
+struct memnode {
+        int shift;
+        u8 map[NODEMAPSIZE];
+} ____cacheline_aligned;
+extern struct memnode memnode;
+#define memnode_shift memnode.shift
+#define memnodemap memnode.map
 
 extern struct pglist_data *node_data[];