linux-kernel - Re: [RFC PATCH] x86 alternatives : fix LOCK_PREFIX race with preemptible kernel and CPU hotplug

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Message-ID: <48A468F5.4050308@zytor.com>
Date:	Thu, 14 Aug 2008 10:18:45 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Steven Rostedt <srostedt@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Roland McGrath <roland@...hat.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Gregory Haskins <ghaskins@...ell.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	Clark Williams <williams@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [RFC PATCH] x86 alternatives : fix LOCK_PREFIX race with	preemptible
 kernel and CPU hotplug

Jeremy Fitzhardinge wrote:
> 
>> Xeon 2.0GHz
>>
>>
>> Summary
>>
>>                   no lock prefix (s)   with lock prefix (s)    Speedup
>> make -j1 kernel/      33.94 +/- 0.07         34.91 +/- 0.27      2.8 %
>> hackbench 50           2.99 +/- 0.01          3.74 +/- 0.01     25.1 %
>>   
> 
> Yeah, that's more severe than I would have expected.  Perhaps I have AMD 
> numbers in my head.
> 

He doesn't specify what kind of Xeon it is (there are three completely 
different CPUs under the Xeon brand name: P3 Xeon, P4 Xeon, and Core 2 
Xeon), but I think it's a P4 Xeon.

Netburst sucked in so many ways, and this is one of them.

	-hpa


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