linux-kernel - Re: [PATCH] mm: memcontrol: rename memcg_kmem

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Message-ID: <Y+tG5NopD5DTZSSh@dhcp22.suse.cz>
Date:   Tue, 14 Feb 2023 09:31:32 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Roman Gushchin <roman.gushchin@...ux.dev>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Dennis Zhou <dennis@...nel.org>, linux-mm@...ck.org
Subject: Re: [PATCH] mm: memcontrol: rename memcg_kmem_enabled()

On Mon 13-02-23 11:29:22, Roman Gushchin wrote:
> Currently there are two kmem-related helper functions with a confusing
> semantics: memcg_kmem_enabled() and mem_cgroup_kmem_disabled().
> 
> The problem is that an obvious expectation
> memcg_kmem_enabled() == !mem_cgroup_kmem_disabled(),
> can be false.
> 
> mem_cgroup_kmem_disabled() is similar to mem_cgroup_disabled(): it
> returns true only if CONFIG_MEMCG_KMEM is not set or the kmem
> accounting is disabled using a boot time kernel option
> "cgroup.memory=nokmem". It never changes the value dynamically.
> 
> memcg_kmem_enabled() is different: it always returns false until
> the first non-root memory cgroup will get online (assuming the kernel
> memory accounting is enabled). It's goal is to improve the performance
> on systems without the cgroupfs mounted/memory controller enabled or
> on the systems with only the root memory cgroup.
> 
> To make things more obvious and avoid potential bugs, let's rename
> memcg_kmem_enabled() to memcg_kmem_online().
> 
> Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Shakeel Butt <shakeelb@...gle.com>
> Cc: Muchun Song <muchun.song@...ux.dev>
> Cc: Dennis Zhou <dennis@...nel.org>
> Cc: linux-mm@...ck.org

Makes sense
Acked-by: Michal Hocko <mhocko@...e.com>
Thanks!

-- 
Michal Hocko
SUSE Labs