linux-kernel - Re: [PATCH] mm: memcontrol: eliminate root memory.current

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Message-ID: <20151022090756.GB26854@dhcp22.suse.cz>
Date:	Thu, 22 Oct 2015 11:07:56 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] mm: memcontrol: eliminate root memory.current

On Wed 21-10-15 14:49:54, Johannes Weiner wrote:
> memory.current on the root level doesn't add anything that wouldn't be
> more accurate and detailed using system statistics. It already doesn't
> include slabs, and it'll be a pain to keep in sync when further memory
> types are accounted in the memory controller. Remove it.
> 
> Note that this applies to the new unified hierarchy interface only.

OK, I can understand your reasoning, other knobs are !root as well.

> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

After the bug mentioned below is fixed
Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  mm/memcontrol.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> Tejun, we should probably do this with the other controllers too.
> I don't think it makes sense anywhere to shoddily duplicate the
> system statistics on the controller root levels.
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 4f04510..c71fe40 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5022,7 +5022,7 @@ static void mem_cgroup_bind(struct cgroup_subsys_state *root_css)
>  static u64 memory_current_read(struct cgroup_subsys_state *css,
>  			       struct cftype *cft)
>  {
> -	return mem_cgroup_usage(mem_cgroup_from_css(css), false);
> +	return page_counter_read(&mem_cgroup_from_css(css)->memory);

We want that in bytes though.

>  }
>  
>  static int memory_low_show(struct seq_file *m, void *v)
> @@ -5134,6 +5134,7 @@ static int memory_events_show(struct seq_file *m, void *v)
>  static struct cftype memory_files[] = {
>  	{
>  		.name = "current",
> +		.flags = CFTYPE_NOT_ON_ROOT,
>  		.read_u64 = memory_current_read,
>  	},
>  	{
> -- 
> 2.6.1

-- 
Michal Hocko
SUSE Labs
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