From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753844AbZJ0LbG (ORCPT ); Tue, 27 Oct 2009 07:31:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753739AbZJ0LbF (ORCPT ); Tue, 27 Oct 2009 07:31:05 -0400 Received: from lennier.cc.vt.edu ([198.82.162.213]:41334 "EHLO lennier.cc.vt.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753537AbZJ0LbF (ORCPT ); Tue, 27 Oct 2009 07:31:05 -0400 X-Mailer: exmh version 2.7.2 01/07/2005 with nmh-1.2 To: pradeep hettiarachchi Cc: linux-kernel@vger.kernel.org Subject: Re: Frequency Scaling on Intel Core 2 Duo Processors In-Reply-To: Your message of "Mon, 26 Oct 2009 11:06:23 EDT." <8fe204b0910260806l10896f9foc0568dd0b8f4b6ca@mail.gmail.com> From: Valdis.Kletnieks@vt.edu References: <8fe204b0910260806l10896f9foc0568dd0b8f4b6ca@mail.gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1256643068_9496P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Tue, 27 Oct 2009 07:31:08 -0400 Message-ID: <43501.1256643068@turing-police.cc.vt.edu> X-Mirapoint-Received-SPF: 128.173.34.98 turing-police.cc.vt.edu Valdis.Kletnieks@vt.edu 2 pass X-Mirapoint-IP-Reputation: reputation=neutral-1, source=Fixed, refid=n/a, actions=MAILHURDLE SPF TAG X-Junkmail-Info: (0) X-Junkmail-Status: score=10/50, host=vivi.cc.vt.edu X-Junkmail-SD-Raw: score=unknown, refid=str=0001.0A020205.4AE6D9FC.0295,ss=1,fgs=0, ip=0.0.0.0, so=2009-07-29 21:33:33, dmn=2009-09-10 00:05:08, mode=multiengine X-Junkmail-IWF: false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --==_Exmh_1256643068_9496P Content-Type: text/plain; charset=us-ascii On Mon, 26 Oct 2009 11:06:23 EDT, pradeep hettiarachchi said: > Hi, > > I am working on a research in real-time systems. If I want to change > the frequency of the system as rapidly as possible, what is the best > method ? At the moment I write MSR_IA32_PERF_CTL, MSR directly with > the pre-found(calculated, encoded) values** for different frequencies. > I found the entire transition (latency) takes multiple milliseconds to > complete; however, I want some faster method to change the CPU > frequency. You're going to have a hard time making it switch any faster than the value listed in /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_transition_latency though I admit I'm not awake enough yet to be sure what the units of that file are... --==_Exmh_1256643068_9496P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFK5tn8cC3lWbTT17ARAikzAJ4wNRn1a+XOwNSp9f7qH+m4wHStiQCcCr5H KvctzJn1cUtMmCcSnf2iPoM= =kPfx -----END PGP SIGNATURE----- --==_Exmh_1256643068_9496P--