linux-kernel - Re: [RFC 2/5] memcontrol: add boot option to enable memsw account on dfl

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Message-ID: <m35wwnetfubjrgcikiia7aurhd4hkcguwqywjamxm4xnaximt7@cnscqcgwh4da>
Date: Wed, 19 Mar 2025 12:34:00 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Jingxiang Zeng <linuszeng@...cent.com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, cgroups@...r.kernel.org, 
	linux-kernel@...r.kernel.org, hannes@...xchg.org, mhocko@...nel.org, roman.gushchin@...ux.dev, 
	muchun.song@...ux.dev, kasong@...cent.com
Subject: Re: [RFC 2/5] memcontrol: add boot option to enable memsw account on
 dfl

On Wed, Mar 19, 2025 at 02:41:45PM +0800, Jingxiang Zeng wrote:
> From: Zeng Jingxiang <linuszeng@...cent.com>
> 
> Added cgroup.memsw_account_on_dfl startup parameter, which
> is off by default. When enabled in cgroupv2 mode, the memory
> accounting mode of swap will be reverted to cgroupv1 mode.
> 
> Signed-off-by: Zeng Jingxiang <linuszeng@...cent.com>
> ---
>  include/linux/memcontrol.h |  4 +++-
>  mm/memcontrol.c            | 11 +++++++++++
>  2 files changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index dcb087ee6e8d..96f2fad1c351 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -62,10 +62,12 @@ struct mem_cgroup_reclaim_cookie {
>  
>  #ifdef CONFIG_MEMCG
>  
> +DECLARE_STATIC_KEY_FALSE(memsw_account_on_dfl);
>  /* Whether enable memory+swap account in cgroupv2 */
>  static inline bool do_memsw_account_on_dfl(void)
>  {
> -	return IS_ENABLED(CONFIG_MEMSW_ACCOUNT_ON_DFL);
> +	return IS_ENABLED(CONFIG_MEMSW_ACCOUNT_ON_DFL)
> +				|| static_branch_unlikely(&memsw_account_on_dfl);

Why || in above condition? Shouldn't it be && ?

>  }
>  
>  #define MEM_CGROUP_ID_SHIFT	16
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 768d6b15dbfa..c1171fb2bfd6 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5478,3 +5478,14 @@ static int __init mem_cgroup_swap_init(void)
>  subsys_initcall(mem_cgroup_swap_init);
>  
>  #endif /* CONFIG_SWAP */
> +
> +DEFINE_STATIC_KEY_FALSE(memsw_account_on_dfl);
> +static int __init memsw_account_on_dfl_setup(char *s)
> +{
> +	if (!strcmp(s, "1"))
> +		static_branch_enable(&memsw_account_on_dfl);
> +	else if (!strcmp(s, "0"))
> +		static_branch_disable(&memsw_account_on_dfl);
> +	return 1;
> +}
> +__setup("cgroup.memsw_account_on_dfl=", memsw_account_on_dfl_setup);

Please keep the above in memcontrol-v1.c

> +
> \ No newline at end of file
> -- 
> 2.41.1
>