linux-kernel - Re: [PATCH] x86: Add clflush before monitor for Intel 7400 series

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Message-ID: <20090207140245.1e91a88f@lxorguk.ukuu.org.uk>
Date:	Sat, 7 Feb 2009 14:02:45 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Cc:	H Peter Anvin <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	thomas@...ux-os.sc.intel.com,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: Add clflush before monitor for Intel 7400 series -
 v2

On Fri, 6 Feb 2009 16:47:29 -0800
"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com> wrote:

> 
> 
> For Intel 7400 series CPUs, the recommendation is to use a clflush on the
> monitored address just before monitor and mwait pair [1]. This clflush makes
> sure that there are no false wakeups from mwait when the monitored address
> was recently written to.

Given our mwait usages will very quickly go back to sleep in such a case
and it would almost certainly be one sleep only is this really worth the
effort ?
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