Re: [PATCH 10/10] vmscan: Update isolated page counters outside of main path in shrink_inactive_list()

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> When shrink_inactive_list() isolates pages, it updates a number of
> counters using temporary variables to gather them. These consume stack
> and it's in the main path that calls ->writepage(). This patch moves the
> accounting updates outside of the main path to reduce stack usage.
> 
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> ---
>  mm/vmscan.c |   63 +++++++++++++++++++++++++++++++++++-----------------------
>  1 files changed, 38 insertions(+), 25 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 2c22c83..4225319 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1061,7 +1061,8 @@ static unsigned long clear_active_flags(struct list_head *page_list,
>  			ClearPageActive(page);
>  			nr_active++;
>  		}
> -		count[lru]++;
> +		if (count)
> +			count[lru]++;
>  	}
>  
>  	return nr_active;
> @@ -1141,12 +1142,13 @@ static int too_many_isolated(struct zone *zone, int file,
>   * TODO: Try merging with migrations version of putback_lru_pages
>   */
>  static noinline void putback_lru_pages(struct zone *zone,
> -				struct zone_reclaim_stat *reclaim_stat,
> +				struct scan_control *sc,
>  				unsigned long nr_anon, unsigned long nr_file,
>   				struct list_head *page_list)
>  {
>  	struct page *page;
>  	struct pagevec pvec;
> +	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);

Seems unrelated change here.
Otherwise looks good.

 - kosaki
>  
>  	pagevec_init(&pvec, 1);
>  
> @@ -1185,6 +1187,37 @@ static noinline void putback_lru_pages(struct zone *zone,
>  	pagevec_release(&pvec);
>  }
>  
> +static noinline void update_isolated_counts(struct zone *zone, 
> +					struct scan_control *sc,
> +					unsigned long *nr_anon,
> +					unsigned long *nr_file,
> +					struct list_head *isolated_list)
> +{
> +	unsigned long nr_active;
> +	unsigned int count[NR_LRU_LISTS] = { 0, };
> +	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
> +
> +	nr_active = clear_active_flags(isolated_list, count);
> +	__count_vm_events(PGDEACTIVATE, nr_active);
> +
> +	__mod_zone_page_state(zone, NR_ACTIVE_FILE,
> +			      -count[LRU_ACTIVE_FILE]);
> +	__mod_zone_page_state(zone, NR_INACTIVE_FILE,
> +			      -count[LRU_INACTIVE_FILE]);
> +	__mod_zone_page_state(zone, NR_ACTIVE_ANON,
> +			      -count[LRU_ACTIVE_ANON]);
> +	__mod_zone_page_state(zone, NR_INACTIVE_ANON,
> +			      -count[LRU_INACTIVE_ANON]);
> +
> +	*nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
> +	*nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
> +	__mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
> +	__mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
> +
> +	reclaim_stat->recent_scanned[0] += *nr_anon;
> +	reclaim_stat->recent_scanned[1] += *nr_file;
> +}
> +
>  /*
>   * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
>   * of reclaimed pages
> @@ -1196,11 +1229,9 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
>  	LIST_HEAD(page_list);
>  	unsigned long nr_scanned;
>  	unsigned long nr_reclaimed = 0;
> -	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
>  	int lumpy_reclaim = 0;
>  	unsigned long nr_taken;
>  	unsigned long nr_active;
> -	unsigned int count[NR_LRU_LISTS] = { 0, };
>  	unsigned long nr_anon;
>  	unsigned long nr_file;
>  
> @@ -1244,25 +1275,7 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
>  		return 0;
>  	}
>  
> -	nr_active = clear_active_flags(&page_list, count);
> -	__count_vm_events(PGDEACTIVATE, nr_active);
> -
> -	__mod_zone_page_state(zone, NR_ACTIVE_FILE,
> -			      -count[LRU_ACTIVE_FILE]);
> -	__mod_zone_page_state(zone, NR_INACTIVE_FILE,
> -			      -count[LRU_INACTIVE_FILE]);
> -	__mod_zone_page_state(zone, NR_ACTIVE_ANON,
> -			      -count[LRU_ACTIVE_ANON]);
> -	__mod_zone_page_state(zone, NR_INACTIVE_ANON,
> -			      -count[LRU_INACTIVE_ANON]);
> -
> -	nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
> -	nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
> -	__mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
> -	__mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
> -
> -	reclaim_stat->recent_scanned[0] += nr_anon;
> -	reclaim_stat->recent_scanned[1] += nr_file;
> +	update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
>  
>  	spin_unlock_irq(&zone->lru_lock);
>  
> @@ -1281,7 +1294,7 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
>  		 * The attempt at page out may have made some
>  		 * of the pages active, mark them inactive again.
>  		 */
> -		nr_active = clear_active_flags(&page_list, count);
> +		nr_active = clear_active_flags(&page_list, NULL);
>  		count_vm_events(PGDEACTIVATE, nr_active);
>  
>  		nr_reclaimed += shrink_page_list(&page_list, sc,
> @@ -1293,7 +1306,7 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
>  		__count_vm_events(KSWAPD_STEAL, nr_reclaimed);
>  	__count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
>  
> -	putback_lru_pages(zone, reclaim_stat, nr_anon, nr_file, &page_list);
> +	putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
>  	return nr_reclaimed;
>  }
>  
> -- 
> 1.6.5
> 



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