linux-kernel - Re: [rfc patch 2/6] vmscan: make distinction between memcg reclaim and LRU list selection

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Date:	Fri, 13 May 2011 08:50:27 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Ying Han <yinghan@...gle.com>, Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [rfc patch 2/6] vmscan: make distinction between memcg reclaim
 and LRU list selection

On Thu, 12 May 2011 16:53:54 +0200
Johannes Weiner <hannes@...xchg.org> wrote:

> The reclaim code has a single predicate for whether it currently
> reclaims on behalf of a memory cgroup, as well as whether it is
> reclaiming from the global LRU list or a memory cgroup LRU list.
> 
> Up to now, both cases always coincide, but subsequent patches will
> change things such that global reclaim will scan memory cgroup lists.
> 
> This patch adds a new predicate that tells global reclaim from memory
> cgroup reclaim, and then changes all callsites that are actually about
> global reclaim heuristics rather than strict LRU list selection.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>


Hmm, isn't it better to merge this to patches where the meaning of
new variable gets clearer ?

> ---
>  mm/vmscan.c |   96 ++++++++++++++++++++++++++++++++++------------------------
>  1 files changed, 56 insertions(+), 40 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index f6b435c..ceeb2a5 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -104,8 +104,12 @@ struct scan_control {
>  	 */
>  	reclaim_mode_t reclaim_mode;
>  
> -	/* Which cgroup do we reclaim from */
> -	struct mem_cgroup *mem_cgroup;
> +	/*
> +	 * The memory cgroup we reclaim on behalf of, and the one we
> +	 * are currently reclaiming from.
> +	 */
> +	struct mem_cgroup *memcg;
> +	struct mem_cgroup *current_memcg;
>  

I wonder if you avoid renaming exisiting one, the patch will
be clearer...



>  	/*
>  	 * Nodemask of nodes allowed by the caller. If NULL, all nodes
> @@ -154,16 +158,24 @@ static LIST_HEAD(shrinker_list);
>  static DECLARE_RWSEM(shrinker_rwsem);
>  
>  #ifdef CONFIG_CGROUP_MEM_RES_CTLR
> -#define scanning_global_lru(sc)	(!(sc)->mem_cgroup)
> +static bool global_reclaim(struct scan_control *sc)
> +{
> +	return !sc->memcg;
> +}
> +static bool scanning_global_lru(struct scan_control *sc)
> +{
> +	return !sc->current_memcg;
> +}


Could you add comments ?

Thanks,
-Kame

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