linux-kernel - Re: [patch 02/11] mm: vmscan: distinguish global reclaim from global LRU scanning

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Date:	Tue, 13 Sep 2011 02:02:46 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
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>, Michal Hocko <mhocko@...e.cz>,
	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 02/11] mm: vmscan: distinguish global reclaim from global
 LRU scanning

On Mon, Sep 12, 2011 at 12:57:19PM +0200, Johannes Weiner wrote:
> The traditional zone reclaim code is scanning the per-zone LRU lists
> during direct reclaim and kswapd, and the per-zone per-memory cgroup
> LRU lists when reclaiming on behalf of a memory cgroup limit.
> 
> Subsequent patches will convert the traditional reclaim code to
> reclaim exclusively from the per-memory cgroup LRU lists.  As a
> result, using the predicate for which LRU list is scanned will no
> longer be appropriate to tell global reclaim from limit reclaim.
> 
> This patch adds a global_reclaim() predicate to tell direct/kswapd
> reclaim from memory cgroup limit reclaim and substitutes it in all
> places where currently scanning_global_lru() is used for that.
> 
> Signed-off-by: Johannes Weiner <jweiner@...hat.com>
> ---
>  mm/vmscan.c |   60 +++++++++++++++++++++++++++++++++++-----------------------
>  1 files changed, 36 insertions(+), 24 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 7502726..354f125 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -153,9 +153,25 @@ 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->mem_cgroup;
> +}
> +
> +static bool scanning_global_lru(struct scan_control *sc)
> +{
> +	return !sc->mem_cgroup;
> +}
>  #else
> -#define scanning_global_lru(sc)	(1)
> +static bool global_reclaim(struct scan_control *sc)
> +{
> +	return true;
> +}
> +
> +static bool scanning_global_lru(struct scan_control *sc)
> +{
> +	return true;
> +}
>  #endif
>  
>  static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
> @@ -1011,7 +1027,7 @@ keep_lumpy:
>  	 * back off and wait for congestion to clear because further reclaim
>  	 * will encounter the same problem
>  	 */
> -	if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
> +	if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc))
>  		zone_set_flag(zone, ZONE_CONGESTED);
>  
>  	free_page_list(&free_pages);
> @@ -1330,7 +1346,7 @@ static int too_many_isolated(struct zone *zone, int file,
>  	if (current_is_kswapd())
>  		return 0;
>  
> -	if (!scanning_global_lru(sc))
> +	if (!global_reclaim(sc))
>  		return 0;
>  
>  	if (file) {
> @@ -1508,6 +1524,12 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>  	if (scanning_global_lru(sc)) {
>  		nr_taken = isolate_pages_global(nr_to_scan, &page_list,
>  			&nr_scanned, sc->order, reclaim_mode, zone, 0, file);
> +	} else {
> +		nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list,
> +			&nr_scanned, sc->order, reclaim_mode, zone,
> +			sc->mem_cgroup, 0, file);
> +	}

Redundant braces.

> +	if (global_reclaim(sc)) {
>  		zone->pages_scanned += nr_scanned;
>  		if (current_is_kswapd())
>  			__count_zone_vm_events(PGSCAN_KSWAPD, zone,
> @@ -1515,14 +1537,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>  		else
>  			__count_zone_vm_events(PGSCAN_DIRECT, zone,
>  					       nr_scanned);
> -	} else {
> -		nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list,
> -			&nr_scanned, sc->order, reclaim_mode, zone,
> -			sc->mem_cgroup, 0, file);
> -		/*
> -		 * mem_cgroup_isolate_pages() keeps track of
> -		 * scanned pages on its own.
> -		 */
>  	}
>  
>  	if (nr_taken == 0) {
> @@ -1647,18 +1661,16 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
>  						&pgscanned, sc->order,
>  						reclaim_mode, zone,
>  						1, file);
> -		zone->pages_scanned += pgscanned;
>  	} else {
>  		nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
>  						&pgscanned, sc->order,
>  						reclaim_mode, zone,
>  						sc->mem_cgroup, 1, file);
> -		/*
> -		 * mem_cgroup_isolate_pages() keeps track of
> -		 * scanned pages on its own.
> -		 */
>  	}

Ditto.


-- 
 Kirill A. Shutemov
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