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Date: Tue, 13 Apr 2010 09:47:16 +0800
From: Lai Jiangshan <laijs@cn.fujitsu.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Oleg Nesterov <oleg@redhat.com>, Gautham R Shenoy <ego@in.ibm.com>,
       Rusty Russell <rusty@rustcorp.com.au>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
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       Nathan Fontenot <nfont@austin.ibm.com>,
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       Thomas Gleixner <tglx@linutronix.de>, Sachin Sant <sachinp@in.ibm.com>,
       "H. Peter Anvin" <hpa@zytor.com>, Shane Wang <shane.wang@intel.com>,
       Roland McGrath <roland@redhat.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] cpuhotplug: make get_online_cpus() scalability by
 using percpu counter
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Peter Zijlstra wrote:
> On Mon, 2010-04-12 at 20:30 +0800, Lai Jiangshan wrote:
>> Because read-preference RWL will cause write site starvation.
> 
> Sure, but why is that a problem? Hotplug should be a rare event,


> who cares if it takes a while to come through.

It is totally starvation, hotplug can not complete.
I think it is a kind of DOS attack.