linux-kernel - Re: [RFC 3/5] mm/memcontrol: do not scan anon pages if memsw limit is hit

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Message-ID: <nlnwcpezzfmq4rh7oeckrl5nmc4sszd534bo3cx34rpkadhsph@mqphvl3zyanl>
Date: Wed, 19 Mar 2025 12:36:20 -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 3/5] mm/memcontrol: do not scan anon pages if memsw limit
 is hit

On Wed, Mar 19, 2025 at 02:41:46PM +0800, Jingxiang Zeng wrote:
> From: Zeng Jingxiang <linuszeng@...cent.com>
> 
> When memory recycling is triggered by the hard watermark of

What is hard watermark?

> memsw, anonymous pages do not want to be recycled any further.
> This is consistent with the processing method of cgroup v2.
> 
> Signed-off-by: Zeng Jingxiang <linuszeng@...cent.com>

Is this patch orthogonal to the series or is it needed for v1 as well?

> ---
>  mm/memcontrol.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index c1171fb2bfd6..623ebf610946 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5072,14 +5072,21 @@ void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
>  
>  long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
>  {
> +	struct page_counter *pg_counter;
>  	long nr_swap_pages = get_nr_swap_pages();
>  
> -	if (mem_cgroup_disabled() || do_memsw_account())
> +	if (mem_cgroup_disabled())
>  		return nr_swap_pages;
> -	for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg))
> +	for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) {
> +		if (do_memsw_account())
> +			pg_counter = &memcg->memsw;
> +		else
> +			pg_counter = &memcg->swap;
> +
>  		nr_swap_pages = min_t(long, nr_swap_pages,
> -				      READ_ONCE(memcg->swap.max) -
> -				      page_counter_read(&memcg->swap));
> +				      READ_ONCE(pg_counter->max) -
> +				      page_counter_read(pg_counter));
> +	}
>  	return nr_swap_pages;
>  }
>  
> -- 
> 2.41.1
>