linux-kernel - Re: [PATCH] x86 idle: repair large-server 50-watt idle-power regression

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Date:	Thu, 19 Dec 2013 22:17:01 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Len Brown <lenb@...nel.org>,
	x86@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
	stable@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86 idle: repair large-server 50-watt idle-power
 regression


* H. Peter Anvin <hpa@...or.com> wrote:

> CLFLUSH is only (guaranteed to be) ordered with respect to MFENCE 
> according to the SDM.

Yes, I quoted the relevant text a couple of hours ago, CLFLUSH is 
pretty special, so it's not ordered against atomics or serializing 
instructions for example - only ordered against explict MFENCE calls, 
which on x86 is mb()/smp_mb().

Thanks,

	Ingo
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