From: Shaohua Li <shaohua.li@intel.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>, Simon Kirby <sim@hostway.ca>,
Dave Hansen <dave@linux.vnet.ibm.com>,
linux-mm <linux-mm@kvack.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/3] mm: kswapd: Stop high-order balancing when any suitable zone is balanced
Date: Wed, 01 Dec 2010 10:47:47 +0800 [thread overview]
Message-ID: <1291171667.12777.51.camel@sli10-conroe> (raw)
In-Reply-To: <20101201112354.ABA8.A69D9226@jp.fujitsu.com>
On Wed, 2010-12-01 at 10:23 +0800, KOSAKI Motohiro wrote:
> > On Wed, 2010-12-01 at 01:15 +0800, Mel Gorman wrote:
> > > When the allocator enters its slow path, kswapd is woken up to balance the
> > > node. It continues working until all zones within the node are balanced. For
> > > order-0 allocations, this makes perfect sense but for higher orders it can
> > > have unintended side-effects. If the zone sizes are imbalanced, kswapd
> > > may reclaim heavily on a smaller zone discarding an excessive number of
> > > pages. The user-visible behaviour is that kswapd is awake and reclaiming
> > > even though plenty of pages are free from a suitable zone.
> > >
> > > This patch alters the "balance" logic to stop kswapd if any suitable zone
> > > becomes balanced to reduce the number of pages it reclaims from other zones.
> > from my understanding, the patch will break reclaim high zone if a low
> > zone meets the high order allocation, even the high zone doesn't meet
> > the high order allocation. This, for example, will make a high order
> > allocation from a high zone fallback to low zone and quickly exhaust low
> > zone, for example DMA. This will break some drivers.
>
> Have you seen patch [3/3]? I think it migigate your pointed issue.
yes, it improves a lot, but still possible for small systems.
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next prev parent reply other threads:[~2010-12-01 2:47 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-30 17:15 [RFC PATCH 0/3] Prevent kswapd dumping excessive amounts of memory in response to high-order allocations Mel Gorman
2010-11-30 17:15 ` [PATCH 1/3] mm: kswapd: Stop high-order balancing when any suitable zone is balanced Mel Gorman
2010-12-01 2:13 ` Shaohua Li
2010-12-01 2:23 ` KOSAKI Motohiro
2010-12-01 2:47 ` Shaohua Li [this message]
2010-12-01 2:59 ` KOSAKI Motohiro
2010-12-01 3:20 ` Shaohua Li
2010-12-01 3:28 ` KOSAKI Motohiro
2010-12-01 7:40 ` Shaohua Li
2010-12-01 7:52 ` KOSAKI Motohiro
2010-12-01 8:24 ` Shaohua Li
2010-12-01 11:07 ` Mel Gorman
2010-11-30 17:15 ` [PATCH 2/3] mm: kswapd: Use the order that kswapd was reclaiming at for sleeping_prematurely() Mel Gorman
2010-11-30 17:15 ` [PATCH 3/3] mm: kswapd: Keep kswapd awake for high-order allocations until a percentage of the node is balanced Mel Gorman
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