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

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Message-ID: <20131219154557.GC26289@pd.tnic>
Date:	Thu, 19 Dec 2013 16:45:57 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.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>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH] x86 idle: repair large-server 50-watt idle-power
 regression

On Thu, Dec 19, 2013 at 06:40:41AM -0800, H. Peter Anvin wrote:
> ... or just use static_cpu_has() maybe?

Right, if we can get the compiler to generate the shortest CLFLUSH of 3
bytes with register indirect addressing for the operand, then stomping
over those 3 bytes with the alternatives would be the fastest solution.

If, of course, three NOPs which get discarded in the front end are
cheaper than the near JMP from static_cpu_has.

-- 
Regards/Gruss,
    Boris.

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