linux-kernel - Re: [PATCHv2] x86: add kconfig options for newer 64-bit processors

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Message-ID: <20131021105401.GA5019@nazgul.tnic>
Date:	Mon, 21 Oct 2013 12:54:01 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Austin S Hemmelgarn <ahferroin7@...il.com>
Cc:	Linux-Kernel mailing list <linux-kernel@...r.kernel.org>,
	x86@...nel.org, Linux Torvalds <torvalds@...l.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCHv2] x86: add kconfig options for newer 64-bit processors

On Sun, Oct 20, 2013 at 07:58:06PM -0400, Austin S Hemmelgarn wrote:
> I am not trying to say that this provides any improvement in speed (or
> at least the AMD options, the one for Intel Ivy Bridge processors does
> appear to do better in this respect).

"Does appear" is not a very good answer - you need to give concrete
benchmark results which people can repeat on their own and confirm your
observations.

> As I stated in the comments just before the patch itself, "...testing
> of MPILEDRIVER seems to indicate an improvement to energy efficiency
> over GENERIC_CPU as it causes the on cpu power sensor to consistently
> read an average of 1.5 watts lower under idle load than when
> using GENERIC_CPU (this corresponds to about 5% decrease in power
> consumption on a idle-tickless system, and about 2% on a non-dynticks
> system.).". While this result is dependent on a large number of
> factors (not the least of which being that I have my CPU over-clocked
> to the point that the lowest C-state runs at 1.4GHz, which really
> hurts energy efficiency) it is still a positive result, and most of
> the equivalent options primarily improve energy efficiency.

Again, how exactly do I reproduce your observations on my boxes? I need
a step-by-step walk through please.

> Also, you have to understand that my target audience isn't the
> mainstream distros,...

Well, if your target audience is only a very small fraction of the linux
users, then we don't need this in the mainline kernel in the first
place, do we?

Thanks.
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