mm: page_alloc: use jump labels to avoid checking number_of_cpusets

If cpusets are not in use then we still check a global variable on every
page allocation.  Use jump labels to avoid the overhead.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 3 deletions

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index b19d3dc2e651..ade2390ffe92 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -12,10 +12,31 @@
 #include <linux/cpumask.h>
 #include <linux/nodemask.h>
 #include <linux/mm.h>
+#include <linux/jump_label.h>
 
 #ifdef CONFIG_CPUSETS
 
-extern int number_of_cpusets;   /* How many cpusets are defined in system? */
+extern struct static_key cpusets_enabled_key;
+static inline bool cpusets_enabled(void)
+{
+        return static_key_false(&cpusets_enabled_key);
+}
+
+static inline int nr_cpusets(void)
+{
+        /* jump label reference count + the top-level cpuset */
+        return static_key_count(&cpusets_enabled_key) + 1;
+}
+
+static inline void cpuset_inc(void)
+{
+        static_key_slow_inc(&cpusets_enabled_key);
+}
+
+static inline void cpuset_dec(void)
+{
+        static_key_slow_dec(&cpusets_enabled_key);
+}
 
 extern int cpuset_init(void);
 extern void cpuset_init_smp(void);
@@ -32,13 +53,13 @@ extern int __cpuset_node_allowed_hardwall(int node, gfp_t gfp_mask);
 
 static inline int cpuset_node_allowed_softwall(int node, gfp_t gfp_mask)
 {
-        return number_of_cpusets <= 1 ||
+        return nr_cpusets() <= 1 ||
                 __cpuset_node_allowed_softwall(node, gfp_mask);
 }
 
 static inline int cpuset_node_allowed_hardwall(int node, gfp_t gfp_mask)
 {
-        return number_of_cpusets <= 1 ||
+        return nr_cpusets() <= 1 ||
                 __cpuset_node_allowed_hardwall(node, gfp_mask);
 }
 
@@ -124,6 +145,8 @@ static inline void set_mems_allowed(nodemask_t nodemask)
 
 #else /* !CONFIG_CPUSETS */
 
+static inline bool cpusets_enabled(void) { return false; }
+
 static inline int cpuset_init(void) { return 0; }
 static inline void cpuset_init_smp(void) {}