From: Kairui Song <kasong@tencent.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@tencent.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

> On Sep 20, 2022, at 02:06, Kairui Song <ryncsn@gmail.com> wrote:
> 
> From: Kairui Song <kasong@tencent.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@tencent.com>

Acked-by: Muchun Song <songmuchun@bytedance.com>

Thanks.

On Tue, Sep 20, 2022 at 02:06:33AM +0800, Kairui Song wrote:
> From: Kairui Song <kasong@tencent.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@tencent.com>

Acked-by: Roman Gushchin <roman.gushchin@linux.dev>

Thanks, Kairui!

On Tue, Sep 20, 2022 at 02:06:33AM +0800, Kairui Song wrote:
> From: Kairui Song <kasong@tencent.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@tencent.com>

Acked-by: Shakeel Butt <shakeelb@google.com>