linux-kernel - Re: Swappiness vs. mmap() and interactive response

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Message-Id: <20090430135100.D21A.A69D9226@jp.fujitsu.com>
Date:	Thu, 30 Apr 2009 13:55:10 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	kosaki.motohiro@...fujitsu.com, Elladan <elladan@...imo.com>,
	Theodore Tso <tytso@....edu>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, linux-mm <linux-mm@...ck.org>,
	Rik van Riel <riel@...hat.com>
Subject: Re: Swappiness vs. mmap() and interactive response

> On Wed, 29 Apr 2009 21:14:39 -0700 Elladan <elladan@...imo.com> wrote:
> 
> > > Elladan, have you checked to see whether the Mapped: number in
> > > /proc/meminfo is decreasing?
> > 
> > Yes, Mapped decreases while a large file copy is ongoing.  It increases again
> > if I use the GUI.
> 
> OK.  If that's still happening to an appreciable extent after you've
> increased /proc/sys/vm/swappiness then I'd wager that we have a
> bug/regression in that area.
> 
> Local variable `scan' in shrink_zone() is vulnerable to multiplicative
> overflows on large zones, but I doubt if you have enough memory to
> trigger that bug.
> 
> 
> From: Andrew Morton <akpm@...ux-foundation.org>
> 
> Local variable `scan' can overflow on zones which are larger than
> 
> 	(2G * 4k) / 100 = 80GB.
> 
> Making it 64-bit on 64-bit will fix that up.

Agghh, thanks bugfix.

Note: His meminfo indicate his machine has 3.5GB ram. then this
patch don't fix his problem.



> 
> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: Wu Fengguang <fengguang.wu@...el.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: Lee Schermerhorn <lee.schermerhorn@...com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
> 
>  mm/vmscan.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff -puN mm/vmscan.c~vmscan-avoid-multiplication-overflow-in-shrink_zone mm/vmscan.c
> --- a/mm/vmscan.c~vmscan-avoid-multiplication-overflow-in-shrink_zone
> +++ a/mm/vmscan.c
> @@ -1479,7 +1479,7 @@ static void shrink_zone(int priority, st
>  
>  	for_each_evictable_lru(l) {
>  		int file = is_file_lru(l);
> -		int scan;
> +		unsigned long scan;
>  
>  		scan = zone_nr_pages(zone, sc, l);
>  		if (priority) {
> _
> 
> 



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