linux-kernel - Re: [PATCH 8/5] llist: Remove cpu

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Date:	Mon, 12 Sep 2011 17:26:27 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Huang Ying <ying.huang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH 8/5] llist: Remove cpu_relax() usage in cmpxchg loops

On 09/12/2011 05:05 PM, Peter Zijlstra wrote:
> Subject: llist: Remove cpu_relax() usage in cmpxchg loops
> From: Peter Zijlstra<a.p.zijlstra@...llo.nl>
> Date: Mon Sep 12 15:50:49 CEST 2011
>
> Initial benchmarks show they're a net loss (2 socket wsm):
>
>   $ for i in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor ; do echo performance>  $i; done
>   $ echo 4096 32000 64 128>  /proc/sys/kernel/sem
>   $ ./sembench -t 2048 -w 1900 -o 0
>

We hyperthreading enabled, and were all threads loaded?  cpu_relax 
allows the other thread to make more progress while the spinner relaxes.

-- 
error compiling committee.c: too many arguments to function

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