linux-kernel - Re: [patch 07/19] (NEW) add some sanity checks to get_scan

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Message-Id: <20080109131642.56b3fa91.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 9 Jan 2008 13:16:42 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch 07/19] (NEW) add some sanity checks to get_scan_ratio

On Tue, 08 Jan 2008 15:59:46 -0500
Rik van Riel <riel@...hat.com> wrote:

> The access ratio based scan rate determination in get_scan_ratio
> works ok in most situations, but needs to be corrected in some
> corner cases:
> - if we run out of swap space, do not bother scanning the anon LRUs
> - if we have already freed all of the page cache, we need to scan
>   the anon LRUs
> 
> Signed-off-by: Rik van Riel <riel@...hat.com>
> 
> Index: linux-2.6.24-rc6-mm1/mm/vmscan.c
> ===================================================================
> --- linux-2.6.24-rc6-mm1.orig/mm/vmscan.c	2008-01-07 17:33:50.000000000 -0500
> +++ linux-2.6.24-rc6-mm1/mm/vmscan.c	2008-01-07 17:57:49.000000000 -0500
> @@ -1182,7 +1182,7 @@ static unsigned long shrink_list(enum lr
>  static void get_scan_ratio(struct zone *zone, struct scan_control * sc,
>  					unsigned long *percent)
>  {
> -	unsigned long anon, file;
> +	unsigned long anon, file, free;
>  	unsigned long anon_prio, file_prio;
>  	unsigned long rotate_sum;
>  	unsigned long ap, fp;
> @@ -1230,6 +1230,20 @@ static void get_scan_ratio(struct zone *
>  	else if (fp > 100)
>  		fp = 100;
>  	percent[1] = fp;
> +
> +	free = zone_page_state(zone, NR_FREE_PAGES);
> +
> +	/*
> +	 * If we have no swap space, do not bother scanning anon pages
> +	 */
> +	if (nr_swap_pages <= 0)
> +		percent[0] = 0;
Doesn't this mean that swap-cache in ACTIVE_ANON_LIST is not scanned ?
Or swap-cache is in File-Cache list ?

Thanks,
-Kame

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