From: Mel Gorman <mel@csn.ul.ie>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Shaohua Li <shaohua.li@intel.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH] vmscan: make kswapd use a correct order
Date: Fri, 3 Dec 2010 12:11:53 +0000 [thread overview]
Message-ID: <20101203121153.GB13268@csn.ul.ie> (raw)
In-Reply-To: <1291305649-2405-1-git-send-email-minchan.kim@gmail.com>
On Fri, Dec 03, 2010 at 01:00:49AM +0900, Minchan Kim wrote:
> If we wake up prematurely, it means we should keep going on
> reclaiming not new order page but at old order page.
> Sometime new order can be smaller than old order by below
> race so it could make failure of old order page reclaiming.
>
> T0: Task 1 wakes up kswapd with order-3
> T1: So, kswapd starts to reclaim pages using balance_pgdat
> T2: Task 2 wakes up kswapd with order-2 because pages reclaimed
> by T1 are consumed quickly.
> T3: kswapd exits balance_pgdat and will do following:
> T4-1: In beginning of kswapd's loop, pgdat->kswapd_max_order will
> be reset with zero.
> T4-2: 'order' will be set to pgdat->kswapd_max_order(0), since it
> enters the false branch of 'if (order (3) < new_order (2))'
> T4-3: If previous balance_pgdat can't meet requirement of order-2
> free pages by high watermark, it will start reclaiming again.
> So balance_pgdat will use order-0 to do reclaim while it
> really should use order-2 at the moment.
> T4-4: At last, Task 1 can't get the any page if it wanted with
> GFP_ATOMIC.
>
> Reported-by: Shaohua Li <shaohua.li@intel.com>
> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Reviewed-by: Shaohua Li <shaohua.li@intel.com>
> Cc: Mel Gorman <mel@csn.ul.ie>
Acked-by: Mel Gorman <mel@csn.ul.ie>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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next prev parent reply other threads:[~2010-12-03 12:12 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-02 16:00 Minchan Kim
2010-12-03 12:11 ` Mel Gorman [this message]
2010-12-09 22:13 ` Andrew Morton
2010-12-10 3:53 ` Minchan Kim
2010-12-10 11:17 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2010-12-01 3:08 [patch]vmscan: " Shaohua Li
2010-12-01 4:21 ` Minchan Kim
2010-12-01 5:42 ` Shaohua Li
2010-12-01 9:44 ` KOSAKI Motohiro
2010-12-01 15:58 ` Minchan Kim
2010-12-02 0:09 ` KOSAKI Motohiro
2010-12-02 0:29 ` KOSAKI Motohiro
2010-12-02 0:58 ` Minchan Kim
2010-12-02 0:19 ` Andrew Morton
2010-12-02 9:40 ` Mel Gorman
2010-12-02 0:29 ` Shaohua Li
2010-12-02 0:54 ` Minchan Kim
2010-12-02 1:05 ` Shaohua Li
2010-12-02 1:23 ` Minchan Kim
2010-12-02 1:36 ` Minchan Kim
2010-12-02 9:42 ` Mel Gorman
2010-12-02 15:25 ` Minchan Kim
2010-12-02 2:39 ` Shaohua Li
2010-12-02 1:28 ` KOSAKI Motohiro
2010-12-02 10:12 ` Mel Gorman
2010-12-02 15:35 ` Minchan Kim
2010-12-02 15:42 ` Mel Gorman
2010-12-02 20:53 ` Simon Kirby
2010-12-03 12:00 ` Mel Gorman
2010-12-04 12:07 ` Simon Kirby
2010-12-06 12:03 ` Mel Gorman
2010-12-09 23:44 ` Simon Kirby
2010-12-10 11:32 ` Mel Gorman
2010-12-10 23:42 ` Simon Kirby
2010-12-14 9:52 ` Mel Gorman
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