linux-kernel - Re: [patch 10/11] mm: make per-memcg LRU lists exclusive

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Date:	Wed, 21 Sep 2011 17:24:58 +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 10/11] mm: make per-memcg LRU lists exclusive

On Mon 12-09-11 12:57:27, Johannes Weiner wrote:
> Now that all code that operated on global per-zone LRU lists is
> converted to operate on per-memory cgroup LRU lists instead, there is
> no reason to keep the double-LRU scheme around any longer.
> 
> The pc->lru member is removed and page->lru is linked directly to the
> per-memory cgroup LRU lists, which removes two pointers from a
> descriptor that exists for every page frame in the system.
> 
> Signed-off-by: Johannes Weiner <jweiner@...hat.com>
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: Ying Han <yinghan@...gle.com>

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

Minor comments/questions bellow.
> ---
>  include/linux/memcontrol.h  |   54 +++-----
>  include/linux/mm_inline.h   |   21 +--
>  include/linux/page_cgroup.h |    1 -
>  mm/memcontrol.c             |  319 ++++++++++++++++++++-----------------------
>  mm/page_cgroup.c            |    1 -
>  mm/swap.c                   |   23 ++-
>  mm/vmscan.c                 |   81 +++++-------
>  7 files changed, 228 insertions(+), 272 deletions(-)
> 
[...]
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 465001c..a7d14a5 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
[...]
> @@ -934,115 +954,123 @@ EXPORT_SYMBOL(mem_cgroup_count_vm_event);
>   * When moving account, the page is not on LRU. It's isolated.
>   */
>  
> -struct page *mem_cgroup_lru_to_page(struct zone *zone, struct mem_cgroup *mem,
> -				    enum lru_list lru)
> +/**
> + * mem_cgroup_lru_add_list - account for adding an lru page and return lruvec
> + * @zone: zone of the page
> + * @page: the page
> + * @lru: current lru
> + *
> + * This function accounts for @page being added to @lru, and returns
> + * the lruvec for the given @zone and the memcg @page is charged to.
> + *
> + * The callsite is then responsible for physically linking the page to
> + * the returned lruvec->lists[@lru].
> + */
> +struct lruvec *mem_cgroup_lru_add_list(struct zone *zone, struct page *page,
> +				       enum lru_list lru)

I know that names are alway tricky but what about mem_cgroup_acct_lru_add?
Analogously for mem_cgroup_lru_del_list, mem_cgroup_lru_del and
mem_cgroup_lru_move_lists.

[...]
> @@ -3615,11 +3593,11 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
>  static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
>  				int node, int zid, enum lru_list lru)
>  {
> -	struct zone *zone;
>  	struct mem_cgroup_per_zone *mz;
> -	struct page_cgroup *pc, *busy;
>  	unsigned long flags, loop;
>  	struct list_head *list;
> +	struct page *busy;
> +	struct zone *zone;

Any specific reason to move zone declaration down here? Not that it
matters much. Just curious.

>  	int ret = 0;
>  
>  	zone = &NODE_DATA(node)->node_zones[zid];
> @@ -3639,16 +3618,16 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
>  			spin_unlock_irqrestore(&zone->lru_lock, flags);
>  			break;
>  		}
> -		pc = list_entry(list->prev, struct page_cgroup, lru);
> -		if (busy == pc) {
> -			list_move(&pc->lru, list);
> +		page = list_entry(list->prev, struct page, lru);
> +		if (busy == page) {
> +			list_move(&page->lru, list);
>  			busy = NULL;
>  			spin_unlock_irqrestore(&zone->lru_lock, flags);
>  			continue;
>  		}
>  		spin_unlock_irqrestore(&zone->lru_lock, flags);
>  
> -		page = lookup_cgroup_page(pc);
> +		pc = lookup_page_cgroup(page);

lookup_page_cgroup might return NULL so we probably want BUG_ON(!pc)
here. We are not very consistent about checking the return value,
though.

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