linux-kernel - Re: [PATCH v3 02/21] memcg: make mm_match

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Date:	Tue, 28 Feb 2012 09:11:44 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH v3 02/21] memcg: make mm_match_cgroup() hirarchical

On Thu, 23 Feb 2012 17:51:46 +0400
Konstantin Khlebnikov <khlebnikov@...nvz.org> wrote:

> Check mm-owner cgroup membership hierarchically.
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>


Ack. but ... see below.

> ---
>  include/linux/memcontrol.h |   11 ++---------
>  mm/memcontrol.c            |   20 ++++++++++++++++++++
>  2 files changed, 22 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 8c4d74f..4822d53 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -87,15 +87,8 @@ extern struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm);
>  extern struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg);
>  extern struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont);
>  
> -static inline
> -int mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *cgroup)
> -{
> -	struct mem_cgroup *memcg;
> -	rcu_read_lock();
> -	memcg = mem_cgroup_from_task(rcu_dereference((mm)->owner));
> -	rcu_read_unlock();
> -	return cgroup == memcg;
> -}
> +extern int mm_match_cgroup(const struct mm_struct *mm,
> +			   const struct mem_cgroup *cgroup);
>  
>  extern struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *memcg);
>  
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index b8039d2..77f5d48 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -821,6 +821,26 @@ struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
>  				struct mem_cgroup, css);
>  }
>  
> +/**
> + * mm_match_cgroup - cgroup hierarchy mm membership test
> + * @mm		mm_struct to test
> + * @cgroup	target cgroup
> + *
> + * Returns true if mm belong this cgroup or any its child in hierarchy

belongs to ?

> + */
> +int mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *cgroup)
> +{

Please use "memcg" for representing "memory cgroup" (other function's arguments uses "memcg")

> +	struct mem_cgroup *memcg;

So, rename this as *cur_memcg or some.

> +
> +	rcu_read_lock();
> +	memcg = mem_cgroup_from_task(rcu_dereference((mm)->owner));
> +	while (memcg != cgroup && memcg && memcg->use_hierarchy)
> +		memcg = parent_mem_cgroup(memcg);

IIUC, parent_mem_cgroup() checks mem->res.parent. mem->res.parent is set only when
parent->use_hierarchy == true. Then, 

	while (memcg != cgroup)
		memcg = parent_mem_cgroup(memcg);

will be enough.

Thanks,
-Kame

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