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

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Message-ID: <Z9KKXF-CSYuGKSXW@tiehlicka>
Date: Thu, 13 Mar 2025 08:33:48 +0100
From: Michal Hocko <mhocko@...e.com>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.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 12-03-25 15:25:52, 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>

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

> ---
>  mm/memcontrol-v1.h | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h
> index 653ff1bad244..6358464bb416 100644
> --- a/mm/memcontrol-v1.h
> +++ b/mm/memcontrol-v1.h
> @@ -22,12 +22,6 @@
>  	     iter != NULL;				\
>  	     iter = mem_cgroup_iter(NULL, iter, NULL))
>  
> -/* Whether legacy memory+swap accounting is active */
> -static inline bool do_memsw_account(void)
> -{
> -	return !cgroup_subsys_on_dfl(memory_cgrp_subsys);
> -}
> -
>  unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap);
>  
>  void drain_all_stock(struct mem_cgroup *root_memcg);
> @@ -42,6 +36,12 @@ struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg);
>  /* Cgroup v1-specific declarations */
>  #ifdef CONFIG_MEMCG_V1
>  
> +/* Whether legacy memory+swap accounting is active */
> +static inline bool do_memsw_account(void)
> +{
> +	return !cgroup_subsys_on_dfl(memory_cgrp_subsys);
> +}
> +
>  unsigned long memcg_events_local(struct mem_cgroup *memcg, int event);
>  unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx);
>  unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item);
> @@ -94,6 +94,7 @@ extern struct cftype mem_cgroup_legacy_files[];
>  
>  #else	/* CONFIG_MEMCG_V1 */
>  
> +static inline bool do_memsw_account(void) { return false; }
>  static inline bool memcg1_alloc_events(struct mem_cgroup *memcg) { return true; }
>  static inline void memcg1_free_events(struct mem_cgroup *memcg) {}
>  
> -- 
> 2.47.1

-- 
Michal Hocko
SUSE Labs