mm, memcg: avoid unnecessary function call when memcg is disabled

While profiling numa/core v16 with cgroup_disable=memory on the command
line, I noticed mem_cgroup_count_vm_event() still showed up as high as
0.60% in perftop.

This occurs because the function is called extremely often even when memcg
is disabled.

To fix this, inline the check for mem_cgroup_disabled() so we avoid the
unnecessary function call if memcg is disabled.

Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Glauber Costa <glommer@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 48eddec2ff029c1c5d44ffc7d7c35c5a9f3a5faa..095d2b4266a3d3200b56f8193f06953d671f0791 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -184,7 +184,14 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
                                                gfp_t gfp_mask,
                                                unsigned long *total_scanned);
 
-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx);
+static inline void mem_cgroup_count_vm_event(struct mm_struct *mm,
+                                            enum vm_event_item idx)
+{
+       if (mem_cgroup_disabled() || !mm)
+               return;
+       __mem_cgroup_count_vm_event(mm, idx);
+}
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 void mem_cgroup_split_huge_fixup(struct page *head);
 #endif

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a164c8bbffe76a9eba47c3df48eeb4be05326931..f3009b4bae510bdf5eced41a429aa1476519df2f 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -63,6 +63,8 @@
 #include <trace/events/vmscan.h>
 
 struct cgroup_subsys mem_cgroup_subsys __read_mostly;
+EXPORT_SYMBOL(mem_cgroup_subsys);
+
 #define MEM_CGROUP_RECLAIM_RETRIES     5
 static struct mem_cgroup *root_mem_cgroup __read_mostly;
 
@@ -1150,13 +1152,10 @@ void mem_cgroup_iter_break(struct mem_cgroup *root,
             iter != NULL;                              \
             iter = mem_cgroup_iter(NULL, iter, NULL))
 
-void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
+void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
 {
        struct mem_cgroup *memcg;
 
-       if (!mm)
-               return;
-
        rcu_read_lock();
        memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
        if (unlikely(!memcg))
@@ -1175,7 +1174,7 @@ void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
 out:
        rcu_read_unlock();
 }
-EXPORT_SYMBOL(mem_cgroup_count_vm_event);
+EXPORT_SYMBOL(__mem_cgroup_count_vm_event);
 
 /**
  * mem_cgroup_zone_lruvec - get the lru list vector for a zone and memcg