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

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Date:   Mon, 19 Sep 2022 19:27:38 -0700
From:   Roman Gushchin <roman.gushchin@...ux.dev>
To:     Kairui Song <kasong@...cent.com>
Cc:     cgroups@...r.kernel.org, linux-mm@...ck.org,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] mm: memcontrol: use memcg_kmem_enabled in
 count_objcg_event

On Tue, Sep 20, 2022 at 02:06:33AM +0800, Kairui Song wrote:
> 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>

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

Thanks, Kairui!