From owner-freebsd-current@FreeBSD.ORG  Thu Nov 18 14:10:49 2010
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 5B504106566C;
	Thu, 18 Nov 2010 14:10:49 +0000 (UTC) (envelope-from avg@freebsd.org)
Received: from citadel.icyb.net.ua (citadel.icyb.net.ua [212.40.38.140])
	by mx1.freebsd.org (Postfix) with ESMTP id 71EAC8FC14;
	Thu, 18 Nov 2010 14:10:48 +0000 (UTC)
Received: from odyssey.starpoint.kiev.ua (alpha-e.starpoint.kiev.ua
	[212.40.38.101])
	by citadel.icyb.net.ua (8.8.8p3/ICyb-2.3exp) with ESMTP id QAA24448;
	Thu, 18 Nov 2010 16:10:39 +0200 (EET) (envelope-from avg@freebsd.org)
Message-ID: <4CE533DE.7010401@freebsd.org>
Date: Thu, 18 Nov 2010 16:10:38 +0200
From: Andriy Gapon <avg@freebsd.org>
User-Agent: Mozilla/5.0 (X11; U; FreeBSD amd64; en-US;
	rv:1.9.2.12) Gecko/20101029 Lightning/1.0b2 Thunderbird/3.1.6
MIME-Version: 1.0
To: Daniel Nebdal <dnebdal@gmail.com>
References: <4CE29718.2050508@freebsd.org>	<D1DB20AD-779E-469B-BFFA-C0BA1A249858@neville-neil.com>	<4CE51CDA.6010202@freebsd.org>
	<AANLkTimcJFL8Y47mTznKz72w0z5+Voc9oWrz92kE+wQa@mail.gmail.com>
In-Reply-To: <AANLkTimcJFL8Y47mTznKz72w0z5+Voc9oWrz92kE+wQa@mail.gmail.com>
X-Enigmail-Version: 1.1.2
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Cc: George Neville-Neil <gnn@neville-neil.com>, freebsd-current@freebsd.org,
	freebsd-acpi@freebsd.org
Subject: Re: aperf/mperf
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 18 Nov 2010 14:10:49 -0000

on 18/11/2010 15:38 Daniel Nebdal said the following:
> Just for the sake of gathering information here:
> What they offer are two (64-bit, wrapping) counters; one that
> increases at a constant rate, and one that increases in proportion to
> the current performance of the CPU, so that APERF/MPERF = fraction of
> max possible performance the CPU has offered since the last time the
> counters were zeroed. Intel specifically suggests multiplying that
> with the observed CPU load over the same time period to get an
> absolute CPU load number, and using that to pick a suitable P-state.
> 
> On a tangent, I wonder if you can get APERF>MPERF if you're using an
> i5/i7 and their dynamic/automatic overclocking kicks in?

Yes, I believe so.
At the very least AMD explicitly documents that to be the case when Core
Performance Boost feature is activated.

> As for what to do with it, it sounds like it would make sense as an
> alternate data source for powerd?

Yes, indeed.

-- 
Andriy Gapon