[PATCH] s390: add read_mostly optimization

Add a read_mostly section and define __read_mostly to prevent cache line
pollution due to writes for mostly read variables.  In addition fix the
incorrect alignment of the cache_line_aligned data section.  s390 has a
cacheline size of 256 bytes.

Signed-off-by: Christian Borntraeger <cborntra@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/s390/kernel/vmlinux.lds.S

@@ -58,9 +58,11 @@ SECTIONS
   . = ALIGN(4096);
   .data.page_aligned : { *(.data.idt) }
 
-  . = ALIGN(32);
+  . = ALIGN(256);
   .data.cacheline_aligned : { *(.data.cacheline_aligned) }
 
+  . = ALIGN(256);
+  .data.read_mostly : { *(.data.read_mostly) }
   _edata = .;			/* End of data section */
 
   . = ALIGN(8192);		/* init_task */

include/asm-s390/cache.h

@@ -16,4 +16,6 @@
 
 #define ARCH_KMALLOC_MINALIGN	8
 
+#define __read_mostly __attribute__((__section__(".data.read_mostly")))
+
 #endif