linux-kernel - [PATCH v2 1/2] mm: memcontrol: use memcg_kmem_enabled in count_objcg

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Date:   Tue, 20 Sep 2022 02:06:33 +0800
From:   Kairui Song <ryncsn@...il.com>
To:     cgroups@...r.kernel.org, linux-mm@...ck.org
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Kairui Song <kasong@...cent.com>
Subject: [PATCH v2 1/2] mm: memcontrol: use memcg_kmem_enabled in count_objcg_event

From: Kairui Song <kasong@...cent.com>

There are currently two helpers for checking if cgroup kmem
accounting is enabled:

- mem_cgroup_kmem_disabled
- memcg_kmem_enabled

mem_cgroup_kmem_disabled is a simple helper that returns true
if cgroup.memory=nokmem is specified, otherwise returns false.

memcg_kmem_enabled is a bit different, it returns true if
cgroup.memory=nokmem is not specified and there was at least one
non-root memory control enabled cgroup ever created. This help improve
performance when kmem accounting was not actually activated. And it's
optimized with static branch.

The usage of mem_cgroup_kmem_disabled is for sub-systems that need to
preallocate data for kmem accounting since they could be initialized
before kmem accounting is activated. But count_objcg_event doesn't
need that, so using memcg_kmem_enabled is better here.

Signed-off-by: Kairui Song <kasong@...cent.com>
---
 include/linux/memcontrol.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 6257867fbf95..e6d3d5870d6f 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1779,7 +1779,7 @@ static inline void count_objcg_event(struct obj_cgroup *objcg,
 {
 	struct mem_cgroup *memcg;

-	if (mem_cgroup_kmem_disabled())
+	if (!memcg_kmem_enabled())
 		return;

 	rcu_read_lock();
-- 
2.35.2