[PATCH] cpuset: mark number_of_cpusets read_mostly

Mark cpuset global 'number_of_cpusets' as __read_mostly.

This global is accessed everytime a zone is considered in the zonelist loops
beneath __alloc_pages, looking for a free memory page.  If number_of_cpusets
is just one, then we can short circuit the mems_allowed check.

Since this global is read alot on a hot path, and written rarely, it is an
excellent candidate for __read_mostly.

Thanks to Christoph Lameter for the suggestion.
Signed-off-by: NPaul Jackson <pj@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

kernel/cpuset.c

@@ -62,7 +62,7 @@
  * When there is only one cpuset (the root cpuset) we can
  * short circuit some hooks.
  */
-int number_of_cpusets;
+int number_of_cpusets __read_mostly;
 
 /* See "Frequency meter" comments, below. */