From owner-freebsd-current@FreeBSD.ORG  Sat Nov 20 09:54:07 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 3A163106566B;
	Sat, 20 Nov 2010 09:54:07 +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 468148FC12;
	Sat, 20 Nov 2010 09:54:05 +0000 (UTC)
Received: from porto.topspin.kiev.ua (porto-e.starpoint.kiev.ua
	[212.40.38.100])
	by citadel.icyb.net.ua (8.8.8p3/ICyb-2.3exp) with ESMTP id LAA26809;
	Sat, 20 Nov 2010 11:54:02 +0200 (EET) (envelope-from avg@freebsd.org)
Received: from localhost.topspin.kiev.ua ([127.0.0.1])
	by porto.topspin.kiev.ua with esmtp (Exim 4.34 (FreeBSD))
	id 1PJk8v-0000hl-V6; Sat, 20 Nov 2010 11:54:01 +0200
Message-ID: <4CE79AB9.1020303@freebsd.org>
Date: Sat, 20 Nov 2010 11:54:01 +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: Nate Lawson <nate@root.org>
References: <4CE29718.2050508@freebsd.org>	<D1DB20AD-779E-469B-BFFA-C0BA1A249858@neville-neil.com>	<4CE51CDA.6010202@freebsd.org>	<AANLkTimcJFL8Y47mTznKz72w0z5+Voc9oWrz92kE+wQa@mail.gmail.com>	<4CE533DE.7010401@freebsd.org>
	<4CE68C0B.1080007@freebsd.org> <4CE6CB3E.70009@root.org>
In-Reply-To: <4CE6CB3E.70009@root.org>
X-Enigmail-Version: 1.1.2
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Cc: freebsd-acpi@freebsd.org, freebsd-current@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: Sat, 20 Nov 2010 09:54:07 -0000

on 19/11/2010 21:08 Nate Lawson said the following:
> On 11/19/2010 6:39 AM, Andriy Gapon wrote:
>>
>> I am thinking about providing two APIs for this.
>>
>> 1. KPI
>> void cpu_get_a_m_perf(u_int cpu, uint64_t *aperf, uint64_t *mperf);
>>
>> 2. Userland
>> sysctl dev.cpu.N.aperf_mperf that returns two UQUAD values.
>>
>> But I am not sure where to put the code for both APIs.
>> Adding another device under cpu seems like an overkill.
> 
> These can be exported as a common interface from cpufreq
> (dev,cpu.X.perf_stats) and supplied by the child acpi_perf driver on
> each cpu.

This suggestion sounds quite appealing.
But I have some concerns.
What if hardware has the capability, but there is no cpufreq - could these MSRs
be still useful?  Or are they useful only with cpufreq?  Probably the latter...
Then, another exotic case - if a driver like est or hwpstate is attached
"directly", i.e. there is no acpi_perf/_PSS - would the MSRs be still useful?
Not sure.

-- 
Andriy Gapon