Re: [RFC PATCH 4/6] mm: munlock: batch NR_MLOCK zone state updates

["Jörn Engel" <joern@logfs.org>]

On Mon, 5 August 2013 16:32:03 +0200, Vlastimil Babka wrote:
> 
> Depending on previous batch which introduced batched isolation in
> munlock_vma_range(), we can batch also the updates of NR_MLOCK
> page stats. After the whole pagevec is processed for page isolation,
> the stats are updated only once with the number of successful isolations.
> There were however no measurable perfomance gains.

Neat.  This answers a question I've had when reading patch 3/6.

> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---
>  mm/mlock.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/mlock.c b/mm/mlock.c
> index 08689b6..d112e06 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -238,6 +238,7 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
>  {
>  	int i;
>  	int nr = pagevec_count(pvec);
> +	int delta_munlocked = -nr;
>  
>  	/* Phase 1: page isolation */
>  	spin_lock_irq(&zone->lru_lock);
> @@ -248,9 +249,6 @@ static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
>  			struct lruvec *lruvec;
>  			int lru;
>  
> -			/* we have disabled interrupts */
> -			__mod_zone_page_state(zone, NR_MLOCK, -1);
> -
>  			switch (__isolate_lru_page(page,
>  						ISOLATE_UNEVICTABLE)) {
>  			case 0:
> @@ -275,8 +273,10 @@ skip_munlock:
>  			 */
>  			pvec->pages[i] = NULL;
>  			put_page(page);
> +			delta_munlocked++;
>  		}
>  	}
> +	__mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
>  	spin_unlock_irq(&zone->lru_lock);
>  
>  	/* Phase 2: page munlock and putback */
> -- 
> 1.8.1.4
> 

JA?rn

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Doubt is not a pleasant condition, but certainty is an absurd one.
-- Voltaire

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