linux-kernel - Re: [patch 2/2] mm: memcg: count pte references from every member of the reclaimed hierarchy

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Date:	Wed, 14 Mar 2012 15:25:19 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 2/2] mm: memcg: count pte references from every member of
 the reclaimed hierarchy

On Tue 28-02-12 15:14:49, Johannes Weiner wrote:
[...]
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index b4622fb..21004df 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1044,17 +1044,23 @@ struct lruvec *mem_cgroup_lru_move_lists(struct zone *zone,
>   * Checks whether given mem is same or in the root_mem_cgroup's
>   * hierarchy subtree
>   */
> -static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
> -		struct mem_cgroup *memcg)
> +bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
> +				  struct mem_cgroup *memcg)
>  {
> -	bool ret;
> -
>  	if (root_memcg == memcg)
>  		return true;
>  	if (!root_memcg->use_hierarchy)
>  		return false;
> +	return css_is_ancestor(&memcg->css, &root_memcg->css);
> +}
> +
> +static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
> +				       struct mem_cgroup *memcg)
> +{
> +	bool ret;
> +
>  	rcu_read_lock();
> -	ret = css_is_ancestor(&memcg->css, &root_memcg->css);
> +	ret = __mem_cgroup_same_or_subtree(root_memcg, memcg);
>  	rcu_read_unlock();
>  	return ret;
>  }
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index c631234..120646e 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -708,7 +708,8 @@ static enum page_references page_check_references(struct page *page,
>  	int referenced_ptes, referenced_page;
>  	unsigned long vm_flags;
>  
> -	referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags);
> +	referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
> +					  &vm_flags);
>  	referenced_page = TestClearPageReferenced(page);

Maybe a stupid question but isn't target_mem_cgroup NULL in the global
reclaim case? And we doesn't handle that in __mem_cgroup_same_or_subtree...

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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