From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [PATCH v1 1/2] intel_pstate: Use the cpu load to determine the PercentPerformance
Date: Sat, 07 Nov 2015 02:09:31 +0100
Message-ID: <1546343.Y03T7q8XC6@vostro.rjw.lan>
References: <1446542840-14982-1-git-send-email-philippe.longepe@linux.intel.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7Bit
Return-path: <linux-pm-owner@vger.kernel.org>
Received: from v094114.home.net.pl ([79.96.170.134]:46100 "HELO
	v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with SMTP id S1753326AbbKGAkS (ORCPT
	<rfc822;linux-pm@vger.kernel.org>); Fri, 6 Nov 2015 19:40:18 -0500
In-Reply-To: <1446542840-14982-1-git-send-email-philippe.longepe@linux.intel.com>
Sender: linux-pm-owner@vger.kernel.org
List-Id: linux-pm@vger.kernel.org
To: Philippe Longepe <philippe.longepe@linux.intel.com>, srinivas.pandruvada@linux.intel.com
Cc: linux-pm@vger.kernel.org, Stephane Gasparini <stephane.gasparini@linux.intel.com>

On Tuesday, November 03, 2015 10:27:19 AM Philippe Longepe wrote:
> Aperf and Mperf counter are not enough to determine the Target P-state
> because they measure performance only when the targeted processor is
> in the C0 state (active state).
> Because of that, we were computing the average P-state during the last
> period which can be very different from the average frequency
> (or percentage of performance).
> 
> As defined in the SDM (section 14.2), the PercentPerformance is defined by:
> 
> PercentPerformance = PercentBusy * (delta_aperf / delta_mperf);
> 
> The PercentBusy (or load) can be estimated as the ratio of the mperf
> counter running at a constant frequency only during active periods (C0)
> and the time stamp counter running at the same frequency but also
> during idle.
> 
> So, PercentBusy = 100 * (delta_mperf / delta_tsc)
> 
> and, PercentPerformance = 100 * (delta_mperf / delta_tsc) *
> 				(delta_aperf / delta_mperf)
> That can be simplified with:
> PercentPerformance = 100 * (delta_aperf / delta_tsc)
> 
> Signed-off-by: Philippe Longepe <philippe.longepe@linux.intel.com>
> Signed-off-by: Stephane Gasparini <stephane.gasparini@linux.intel.com>

Srinivas, I need your ACK here and for the [2/2].

Thanks,
Rafael