linux-kernel - Re: [PATCH 1/3] mm: kswapd: Stop high-order balancing when any suitable zone is balanced

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20101201112354.ABA8.A69D9226@jp.fujitsu.com>
Date:	Wed,  1 Dec 2010 11:23:11 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Shaohua Li <shaohua.li@...el.com>
Cc:	kosaki.motohiro@...fujitsu.com, Mel Gorman <mel@....ul.ie>,
	Simon Kirby <sim@...tway.ca>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] mm: kswapd: Stop high-order balancing when any suitable zone is balanced

> 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.



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/