linux-kernel - Re: [PATCH] memcg: move do_memsw_account() to CONFIG_MEMCG

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Message-ID: <20250312230114.GA1247787@cmpxchg.org>
Date: Wed, 12 Mar 2025 19:01:14 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...nel.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Muchun Song <muchun.song@...ux.dev>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH] memcg: move do_memsw_account() to CONFIG_MEMCG_V1

On Wed, Mar 12, 2025 at 03:25:52PM -0700, Shakeel Butt wrote:
> The do_memsw_account() is used to enable or disable legacy memory+swap
> accounting in memory cgroup. However with disabled CONFIG_MEMCG_V1, we
> don't need to keep checking it. So, let's always return false for
> !CONFIG_MEMCG_V1 configs.
> 
> Before the patch:
> 
> $ size mm/memcontrol.o
>    text    data     bss     dec     hex filename
>   49928   10736    4172   64836    fd44 mm/memcontrol.o
> 
> After the patch:
> 
> $ size mm/memcontrol.o
>    text    data     bss     dec     hex filename
>   49430   10480    4172   64082    fa52 mm/memcontrol.o
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>

Nice. It being a jump label avoids the branch, but it's still
unnecessary text and therefor i$ burden on fairly hot paths.

Acked-by: Johannes Weiner <hannes@...xchg.org>