linux-kernel - Re: [PATCH 3/3] mm: kmem: switch to static_branch_likely() in memcg_kmem

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Date:   Tue, 7 Jul 2020 10:52:36 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Roman Gushchin <guro@...com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Linux MM <linux-mm@...ck.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Kernel Team <kernel-team@...com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] mm: kmem: switch to static_branch_likely() in memcg_kmem_enabled()

On Tue, Jul 7, 2020 at 10:36 AM Roman Gushchin <guro@...com> wrote:
>
> Currently memcg_kmem_enabled() is optimized for the kernel memory
> accounting being off. It was so for a long time, and arguably the
> reason behind was that the kernel memory accounting was initially an
> opt-in feature. However, now it's on by default on both cgroup v1
> and cgroup v2, and it's on for all cgroups. So let's switch over
> to static_branch_likely() to reflect this fact.
>
> Unlikely there is a significant performance difference, as the cost
> of a memory allocation and its accounting significantly exceeds the
> cost of a jump. However, the conversion makes the code look more
> logically.
>
> Signed-off-by: Roman Gushchin <guro@...com>

Reviewed-by: Shakeel Butt <shakeelb@...gle.com>