linux-kernel - Re: [PATCH] mutex: Introduce mutex_cpu

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Message-ID: <1287071729.29097.278.camel@twins>
Date:	Thu, 14 Oct 2010 17:55:29 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	gerald.schaefer@...ibm.com
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-s390 <linux-s390@...r.kernel.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH] mutex: Introduce mutex_cpu_relax()

On Thu, 2010-10-14 at 17:33 +0200, Gerald Schaefer wrote:
> From: Gerald Schaefer <gerald.schaefer@...ibm.com>
> 
> The spinning mutex implementation uses cpu_relax() in busy loops as a
> compiler barrier. Depending on the architecture, cpu_relax() may do more
> than needed in this specific mutex spin loops. On System z we also give
> up the time slice of the virtual cpu in cpu_relax(), which prevents
> effective spinning on the mutex.
> 
> This patch replaces cpu_relax() in the spinning mutex code with a new
> function mutex_cpu_relax(), which can be defined by each architecture
> that selects HAVE_MUTEX_CPU_RELAX. The default is still cpu_relax(), so
> this patch should not affect other architectures than System z for now.

Sure.. I'll take it.


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