linux-kernel - Re: Why Semaphore Hardware-Dependent?

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Message-Id: <200608272339.08092.ak@suse.de>
Date:	Sun, 27 Aug 2006 23:39:08 +0200
From:	Andi Kleen <ak@...e.de>
To:	Christoph Lameter <clameter@....com>
Cc:	Dong Feng <middle.fengdong@...il.com>,
	Paul Mackerras <paulus@...ba.org>, linux-kernel@...r.kernel.org
Subject: Re: Why Semaphore Hardware-Dependent?

On Sunday 27 August 2006 23:05, Christoph Lameter wrote:
> On Sun, 27 Aug 2006, Andi Kleen wrote:
> 
> > rwsems don't -- there are two flavours: a generic spinlock'ed one and a 
> > complicated atomic based one that only works on some architectures. 
> > As far as I know nobody has demonstrated a clear performance increase
> > from the first so it might be possible to switch all to the generic
> > implementation.
> 
> Yup that would be the major issue.I'd be interested to see some tests in 
> that area.

x86-64 always uses the spinlocked version (vs i386 using the atomic one)
and I haven't heard of anybody complaining.

-Andi
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