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

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Message-Id: <20090429214332.a2b5b469.akpm@linux-foundation.org>
Date:	Wed, 29 Apr 2009 21:43:32 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Elladan <elladan@...imo.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.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.

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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