linux-kernel - Re: [PATCH 2/4] vmscan: get_scan

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Date:	Tue, 29 Dec 2009 13:04:12 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 2/4] vmscan: get_scan_ratio cleanup

* KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> [2009-12-28 16:48:06]:

> The get_scan_ratio() should have all scan-ratio related calculations.
> Thus, this patch move some calculation into get_scan_ratio.
> 
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> ---
>  mm/vmscan.c |   23 ++++++++++++++---------
>  1 files changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 2bbee91..640486b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1501,6 +1501,13 @@ static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
>  	unsigned long ap, fp;
>  	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
> 
> +	/* If we have no swap space, do not bother scanning anon pages. */
> +	if (!sc->may_swap || (nr_swap_pages <= 0)) {
> +		percent[0] = 0;
> +		percent[1] = 100;
> +		return;
> +	}
> +


>  	anon  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
>  		zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
>  	file  = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
> @@ -1598,22 +1605,20 @@ static void shrink_zone(int priority, struct zone *zone,
>  	unsigned long nr_reclaimed = sc->nr_reclaimed;
>  	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
>  	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
> -	int noswap = 0;
> 
> -	/* If we have no swap space, do not bother scanning anon pages. */
> -	if (!sc->may_swap || (nr_swap_pages <= 0)) {
> -		noswap = 1;
> -		percent[0] = 0;
> -		percent[1] = 100;
> -	} else
> -		get_scan_ratio(zone, sc, percent);
> +	get_scan_ratio(zone, sc, percent);

Where do we set noswap? Is percent[0] == 0 used to indicate noswap =
1?

> 
>  	for_each_evictable_lru(l) {
>  		int file = is_file_lru(l);
>  		unsigned long scan;
> 
> +		if (percent[file] == 0) {
> +			nr[l] = 0;
> +			continue;
> +		}
> +

Is this really needed? Won't nr_scan_try_batch handle it correctly?

>  		scan = zone_nr_lru_pages(zone, sc, l);
> -		if (priority || noswap) {
> +		if (priority) {
>  			scan >>= priority;
>  			scan = (scan * percent[file]) / 100;
>  		}

-- 
	Balbir
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