linux-kernel - Re: [PATCH] mm: memcontrol: let v2 cgroups follow changes in system swappiness

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Message-ID: <20160411073117.GC23157@dhcp22.suse.cz>
Date:	Mon, 11 Apr 2016 09:31:18 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vladimir Davydov <vdavydov@...tuozzo.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...com
Subject: Re: [PATCH] mm: memcontrol: let v2 cgroups follow changes in system
 swappiness

On Fri 08-04-16 18:49:04, Johannes Weiner wrote:
> Cgroup2 currently doesn't have a per-cgroup swappiness setting. We
> might want to add one later - that's a different discussion - but
> until we do, the cgroups should always follow the system setting.
> Otherwise it will be unchangeably set to whatever the ancestor
> inherited from the system setting at the time of cgroup creation.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> Cc: stable@...r.kernel.org # 4.5

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

> ---
>  include/linux/swap.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index e58dba3..15d17c8 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -534,6 +534,10 @@ static inline swp_entry_t get_swap_page(void)
>  #ifdef CONFIG_MEMCG
>  static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
>  {
> +	/* Cgroup2 doesn't have per-cgroup swappiness */
> +	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
> +		return vm_swappiness;
> +
>  	/* root ? */
>  	if (mem_cgroup_disabled() || !memcg->css.parent)
>  		return vm_swappiness;
> -- 
> 2.8.0

-- 
Michal Hocko
SUSE Labs