linux-kernel - Re: 50 Watt idle power regression bisected to Linux-3.10

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Message-ID: <20131211231425.GD8863@pd.tnic>
Date:	Thu, 12 Dec 2013 00:14:25 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mike Galbraith <bitbucket@...ine.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Len Brown <lenb@...nel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jeremy Eder <jeder@...hat.com>, x86@...nel.org
Subject: Re: 50 Watt idle power regression bisected to Linux-3.10

On Wed, Dec 11, 2013 at 03:08:35PM -0800, H. Peter Anvin wrote:
> So I would like to propose that we switch to using a percpu variable
> which is a single cache line of nothing at all. It would only ever
> be touched by MONITOR and for explicit wakeup. Hopefully that will
> resolve this problem without the need for the CLFLUSH.

Yep, makes a lot of sense to me to have an exclusive (overloaded meaning
here :-)) cacheline only for that. And, if it works, we'll save us the
penalty from the CLFLUSH too, cool.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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