linux-kernel - Re: [patch 08/11] mm: vmscan: convert global reclaim to per-memcg LRU lists

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Date:	Wed, 21 Sep 2011 15:10:45 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <jweiner@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Balbir Singh <bsingharora@...il.com>,
	Ying Han <yinghan@...gle.com>,
	Greg Thelen <gthelen@...gle.com>,
	Michel Lespinasse <walken@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Christoph Hellwig <hch@...radead.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 08/11] mm: vmscan: convert global reclaim to per-memcg
 LRU lists

On Mon 12-09-11 12:57:25, Johannes Weiner wrote:
> The global per-zone LRU lists are about to go away on memcg-enabled
> kernels, global reclaim must be able to find its pages on the
> per-memcg LRU lists.
> 
> Since the LRU pages of a zone are distributed over all existing memory
> cgroups, a scan target for a zone is complete when all memory cgroups
> are scanned for their proportional share of a zone's memory.
> 
> The forced scanning of small scan targets from kswapd is limited to
> zones marked unreclaimable, otherwise kswapd can quickly overreclaim
> by force-scanning the LRU lists of multiple memory cgroups.
> 
> Signed-off-by: Johannes Weiner <jweiner@...hat.com>

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

Minor nit bellow

> ---
>  mm/vmscan.c |   39 ++++++++++++++++++++++-----------------
>  1 files changed, 22 insertions(+), 17 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index bb4d8b8..053609e 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2451,13 +2445,24 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
>  static void age_active_anon(struct zone *zone, struct scan_control *sc,
>  			    int priority)
>  {
> -	struct mem_cgroup_zone mz = {
> -		.mem_cgroup = NULL,
> -		.zone = zone,
> -	};
> +	struct mem_cgroup *mem;
> +
> +	if (!total_swap_pages)
> +		return;
> +
> +	mem = mem_cgroup_iter(NULL, NULL, NULL);

Wouldn't be for_each_mem_cgroup more appropriate? Macro is not exported
but probably worth exporting? The same applies for
scan_zone_unevictable_pages from the previous patch.

> +	do {
> +		struct mem_cgroup_zone mz = {
> +			.mem_cgroup = mem,
> +			.zone = zone,
> +		};
>  
> -	if (inactive_anon_is_low(&mz))
> -		shrink_active_list(SWAP_CLUSTER_MAX, &mz, sc, priority, 0);
> +		if (inactive_anon_is_low(&mz))
> +			shrink_active_list(SWAP_CLUSTER_MAX, &mz,
> +					   sc, priority, 0);
> +
> +		mem = mem_cgroup_iter(NULL, mem, NULL);
> +	} while (mem);
>  }

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