[patch 084/163] mm: kmem: switch to static_branch_likely() in memcg_kmem_enabled()

Andrew Morton
2020-08-07T06:21:51Z

From: Roman Gushchin <guro@fb.com>
Subject: mm: kmem: switch to static_branch_likely() in memcg_kmem_enabled()

Currently memcg_kmem_enabled() is optimized for the kernel memory
accounting being off. It was so for a long time, and arguably the reason
behind was that the kernel memory accounting was initially an opt-in
feature. However, now it's on by default on both cgroup v1 and cgroup v2,
and it's on for all cgroups. So let's switch over to
static_branch_likely() to reflect this fact.

Unlikely there is a significant performance difference, as the cost of a
memory allocation and its accounting significantly exceeds the cost of a
jump. However, the conversion makes the code look more logically.

Link: http://lkml.kernel.org/r/20200707173612.124425-3-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/memcontrol.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/memcontrol.h~mm-kmem-switch-to-static_branch_likely-in-memcg_kmem_enabled
+++ a/include/linux/memcontrol.h
@@ -1448,7 +1448,7 @@ void memcg_put_cache_ids(void);

static inline bool memcg_kmem_enabled(void)
{
- return static_branch_unlikely(&memcg_kmem_enabled_key);
+ return static_branch_likely(&memcg_kmem_enabled_key);
}

static inline bool memcg_kmem_bypass(void)
_