Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755804AbZJ0Aok (ORCPT ); Mon, 26 Oct 2009 20:44:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755522AbZJ0Aoj (ORCPT ); Mon, 26 Oct 2009 20:44:39 -0400 Received: from mail-yw0-f202.google.com ([209.85.211.202]:61311 "EHLO mail-yw0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755506AbZJ0Aoj (ORCPT ); Mon, 26 Oct 2009 20:44:39 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; b=PQVhRu67EnaUWnm4hhfj9g9uIaqQ0qHjH+OxEsvqpHPk6PG1Qcbopem6Pi9wPsJ8Ma tS3/l+jV+zPg7carVAo1JAJwQ2cXwo2x9AFuLfX23x4x5jAz1bHZEll4jBckSozzTCH0 LppvyNZNDiA+t06tv3MMf/Rd462NWYTIEUXO4= Message-ID: <4AE64279.4080902@gmail.com> Date: Mon, 26 Oct 2009 18:44:41 -0600 From: Robert Hancock User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20091014 Fedora/3.0-2.8.b4.fc11 Thunderbird/3.0b4 MIME-Version: 1.0 To: Robert Bradbury CC: linux-kernel@vger.kernel.org Subject: Re: Broken ondemand scheduler in Linux 2.6.30+ on Pentium IVs References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1544 Lines: 31 On 10/25/2009 04:46 PM, Robert Bradbury wrote: > Somewhere in the Linux 2.6.30+ patches was a change to > "arch/x86/kernel/cpu/cpufreq/ > p4-clockmod.c" which changed (around line 253) such that > policy->cpuinfo.transition_latency = 1000000; /* assumed */ > became > policy->cpuinfo.transition_latency = 10000001; > > This prevents the ondemand scheduler from being adopted and working > correctly (on a system with the Gnome CPU Frequency Monitor). The > reports I have received regarding *why* this change was made are > cryptic at best. p4-clockmod is NOT true CPU frequency scaling, it just forces the CPU to idle on a periodic duty cycle and has no effect on CPU frequency. The clock modulation feature is basically just engaging the same mechanism the CPU uses to reduce heat output when it gets too hot, and which is not meant as a power saving mechanism. When engaged, it does reduce heat output and power usage, but not as much as it reduces system performance, and means the system will simply take longer to return to idle. In short, using p4-clockmod can only increase power usage in any real workload. If your system and CPU actually support CPU frequency scaling then p4-clockmod isn't the driver that should be being used, acpi-cpufreq is the one on most systems. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/