linux-kernel - Re: [patch 6/8] mm: vmscan: clean up get_scan

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Date:	Thu, 13 Dec 2012 17:18:12 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 6/8] mm: vmscan: clean up get_scan_count()

On Wed 12-12-12 16:43:38, Johannes Weiner wrote:
> Reclaim pressure balance between anon and file pages is calculated
> through a tuple of numerators and a shared denominator.
> 
> Exceptional cases that want to force-scan anon or file pages configure
> the numerators and denominator such that one list is preferred, which
> is not necessarily the most obvious way:
> 
>     fraction[0] = 1;
>     fraction[1] = 0;
>     denominator = 1;
>     goto out;
> 
> Make this easier by making the force-scan cases explicit and use the
> fractionals only in case they are calculated from reclaim history.
> 
> And bring the variable declarations/definitions in order.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

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

[...]
> @@ -1638,14 +1645,15 @@ static int vmscan_swappiness(struct scan_control *sc)
>  static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
>  			   unsigned long *nr)
>  {
> -	unsigned long anon, file, free;
> +	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
> +	u64 fraction[2], uninitialized_var(denominator);
> +	struct zone *zone = lruvec_zone(lruvec);
>  	unsigned long anon_prio, file_prio;
> +	enum scan_balance scan_balance;
> +	unsigned long anon, file, free;
> +	bool force_scan = false;
>  	unsigned long ap, fp;
> -	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
> -	u64 fraction[2], denominator;
>  	enum lru_list lru;
> -	bool force_scan = false;
> -	struct zone *zone = lruvec_zone(lruvec);

You really do love trees, don't you :P

[...]
-- 
Michal Hocko
SUSE Labs
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