Re: [PATCH] mm: memcontrol: treat disabled memcg as kmem accounting disabled

[Michal Hocko <mhocko@suse.com>]

On Thu 27-08-26 17:17:50, Hao Li wrote:
> mem_cgroup_kmem_disabled() currently only checks whether the
> "cgroup.memory=nokmem" option is specified. However, kmem accounting is
> also unavailable when memcg itself is disabled.
> 
> Check both conditions to ensure the function accurately reflects the
> kmem accounting state.

It would be really great if you could describe how we could end up with
the inconsistent memcg enabled but kmem enabled and what kind of effect
does this have.

AFAICS the inconsistency is possible and it would lead some wastage but
no functional problems but the changelog should be more descriptive.

> Signed-off-by: Hao Li <hao.li@linux.dev>
> ---
>  mm/memcontrol.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 1ebceade4021..b28f6165c354 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -132,7 +132,7 @@ static DEFINE_SPINLOCK(objcg_lock);
>  
>  bool mem_cgroup_kmem_disabled(void)
>  {
> -	return cgroup_memory_nokmem;
> +	return cgroup_memory_nokmem || mem_cgroup_disabled();
>  }
>  
>  static void memcg_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages);
> -- 
> 2.54.0

-- 
Michal Hocko
SUSE Labs