linux-kernel - Re: [PATCH 2/2] cpuhotplug: make get_online_cpus() scalability by using percpu counter

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Message-ID: <4BC3CD24.3020400@cn.fujitsu.com>
Date:	Tue, 13 Apr 2010 09:47:16 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Oleg Nesterov <oleg@...hat.com>, Gautham R Shenoy <ego@...ibm.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Ingo Molnar <mingo@...e.hu>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Nathan Fontenot <nfont@...tin.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sachin Sant <sachinp@...ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Shane Wang <shane.wang@...el.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] cpuhotplug: make get_online_cpus() scalability by
 using percpu counter

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.
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