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, 4 insertions, 10 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 3d54c418bd06..130017843899 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -61,12 +61,7 @@
 #include <linux/cgroup.h>
 #include <linux/wait.h>
 
-/*
- * Tracks how many cpusets are currently defined in system.
- * When there is only one cpuset (the root cpuset) we can
- * short circuit some hooks.
- */
-int number_of_cpusets __read_mostly;
+struct static_key cpusets_enabled_key __read_mostly = STATIC_KEY_INIT_FALSE;
 
 /* See "Frequency meter" comments, below. */
 
@@ -611,7 +606,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
                 goto done;
         }
 
-        csa = kmalloc(number_of_cpusets * sizeof(cp), GFP_KERNEL);
+        csa = kmalloc(nr_cpusets() * sizeof(cp), GFP_KERNEL);
         if (!csa)
                 goto done;
         csn = 0;
@@ -1888,7 +1883,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
         if (is_spread_slab(parent))
                 set_bit(CS_SPREAD_SLAB, &cs->flags);
 
-        number_of_cpusets++;
+        cpuset_inc();
 
         if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))
                 goto out_unlock;
@@ -1939,7 +1934,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
         if (is_sched_load_balance(cs))
                 update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
 
-        number_of_cpusets--;
+        cpuset_dec();
         clear_bit(CS_ONLINE, &cs->flags);
 
         mutex_unlock(&cpuset_mutex);
@@ -1992,7 +1987,6 @@ int __init cpuset_init(void)
         if (!alloc_cpumask_var(&cpus_attach, GFP_KERNEL))
                 BUG();
 
-        number_of_cpusets = 1;
         return 0;
 }