Date: Thu, 30 Apr 2009 11:44:54 -0400 (EDT)
From: Christoph Lameter <cl@linux.com>
To: Ingo Molnar <mingo@elte.hu>
cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Nick Piggin <nickpiggin@yahoo.com.au>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, thomas.pi@arcor.dea,
       Yuriy Lalym <ylalym@gmail.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       ltt-dev@lists.casi.polymtl.ca, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH] Fix dirty page accounting in
 redirty_page_for_writepage()
In-Reply-To: <20090430154255.GA3714@elte.hu>
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On Thu, 30 Apr 2009, Ingo Molnar wrote:

> nice. Do these all get called with irqs off, all the time?

In most cases yes. The VMstat patch includes an example were we may not
care too much about a event counter missing a beat once in a while for
platforms not supporting atomic per cpu ops. I know this affects IA64. The
cost of an atomic operations for an event counter update (which would have
avoided the potential of a concurrent update) was not justifiable.


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