linux-kernel - Re: [patch 05/11] mm: memcg: only check for PageSwapCache when uncharging anon

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Date:	Mon, 9 Jul 2012 17:05:33 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 05/11] mm: memcg: only check for PageSwapCache when
 uncharging anon

On Thu 05-07-12 02:44:57, Johannes Weiner wrote:
> Only anon pages that are uncharged at the time of the last page table
> mapping vanishing may be in swapcache.
> 
> When shmem pages, file pages, swap-freed anon pages, or just migrated
> pages are uncharged, they are known for sure to be not in swapcache.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: Michal Hocko <mhocko@...e.cz>

> ---
>  mm/memcontrol.c |   13 ++++---------
>  1 files changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a3bf414..3d56b4e 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3026,8 +3026,6 @@ void mem_cgroup_uncharge_cache_page(struct page *page)
>  {
>  	VM_BUG_ON(page_mapped(page));
>  	VM_BUG_ON(page->mapping);
> -	if (PageSwapCache(page))
> -		return;
>  	__mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE, false);
>  }
>  
> @@ -3092,8 +3090,6 @@ mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
>  	if (!swapout) /* this was a swap cache but the swap is unused ! */
>  		ctype = MEM_CGROUP_CHARGE_TYPE_DROP;
>  
> -	if (PageSwapCache(page))
> -		return;
>  	memcg = __mem_cgroup_uncharge_common(page, ctype, false);
>  
>  	/*
> @@ -3283,11 +3279,10 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg,
>  		unused = oldpage;
>  	}
>  	anon = PageAnon(used);
> -	if (!PageSwapCache(page))
> -		__mem_cgroup_uncharge_common(unused,
> -					     anon ? MEM_CGROUP_CHARGE_TYPE_ANON
> -					     : MEM_CGROUP_CHARGE_TYPE_CACHE,
> -					     true);
> +	__mem_cgroup_uncharge_common(unused,
> +				     anon ? MEM_CGROUP_CHARGE_TYPE_ANON
> +				     : MEM_CGROUP_CHARGE_TYPE_CACHE,
> +				     true);
>  	css_put(&memcg->css);
>  	/*
>  	 * We disallowed uncharge of pages under migration because mapcount
> -- 
> 1.7.7.6
> 

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