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

[Michal Hocko]

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@xxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # 4.5

Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> ---
>  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