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

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Date:   Tue, 20 Sep 2022 10:41:29 +0800
From:   Muchun Song <muchun.song@...ux.dev>
To:     Kairui Song <kasong@...cent.com>
Cc:     cgroups@...r.kernel.org, Linux MM <linux-mm@...ck.org>,
        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
Subject: Re: [PATCH v2 1/2] mm: memcontrol: use memcg_kmem_enabled in
 count_objcg_event



> On Sep 20, 2022, at 02:06, Kairui Song <ryncsn@...il.com> 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: Muchun Song <songmuchun@...edance.com>

Thanks.