From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755832AbXD0Nkj (ORCPT ); Fri, 27 Apr 2007 09:40:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755838AbXD0Nki (ORCPT ); Fri, 27 Apr 2007 09:40:38 -0400 Received: from [70.254.190.220] ([70.254.190.220]:36434 "EHLO server.willdawg" rhost-flags-FAIL-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1755832AbXD0NkK (ORCPT ); Fri, 27 Apr 2007 09:40:10 -0400 Date: Fri, 27 Apr 2007 13:40:08 +0000 (GMT) From: William Heimbigner X-X-Sender: icxcnika@server.thyself To: Dominik Brodowski cc: Dave Jones , Nish Aravamudan , linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [RFC] [PATCH] cpufreq: allow full selection of default governors In-Reply-To: <20070427122444.GA3714@isilmar.linta.de> Message-ID: References: <20070424211253.GG23598@redhat.com> <29495f1d0704241505p62140160o52d83e383106bf8e@mail.gmail.com> <20070425000327.GG22267@redhat.com> <20070427015410.GA9650@isilmar.linta.de> <20070427060957.GA4726@redhat.com> <20070427122444.GA3714@isilmar.linta.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 Apr 2007, Dominik Brodowski wrote: > On Fri, Apr 27, 2007 at 02:09:57AM -0400, Dave Jones wrote: >> On Thu, Apr 26, 2007 at 09:54:10PM -0400, Dominik Brodowski wrote: >> > On Tue, Apr 24, 2007 at 08:03:27PM -0400, Dave Jones wrote: >> >> On Tue, Apr 24, 2007 at 03:05:36PM -0700, Nish Aravamudan wrote: >> >> > On 4/24/07, Dave Jones wrote: >> >> >> On Tue, Apr 24, 2007 at 09:03:23PM +0000, William Heimbigner wrote: >> >> >> > The following patches should allow selection of conservative, powersave, and >> >> >> > ondemand in the kernel configuration. >> >> >> >> >> >> This has been rejected several times already. >> >> >> Ondemand and conservative isn't a viable governor for all cpufreq >> >> >> implementations (ie, ones with high switching latencies). >> >> > >> >> > This piques my curiosity -- some governors don't work with some >> >> > cpufreq implementations. Are those implementations in the kernel or in >> >> > userspace? If in the kernel, then perhaps there should be some >> >> > dependency expressed there in Kconfig between cpufreq implementation >> >> > and the available governors >> >> >> >> it can't be solved that easily. powernow-k8 for example is fine to >> >> use with ondemand on newer systems, where the latency is low. >> >> On older models however, it isn't. >> >> >> >> >> Also, see the >> >> >> comment in the Kconfig a few lines above where you are adding this. >> >> > >> >> > Are these governors unfixable? If >> >> >> >> tbh, I've forgotten the original issues that caused the comment >> >> to be placed there. Dominik ? >> > >> > Not unfixable, but: cpufreq is currently[*] built around the assumption that >> > at least one governor is correctly initialized or can be brought to work >> > when a CPU is registered with the cpufreq core. >> >> It would have to take something fairly spectacular though for performance or >> powersave to fail registration. Can you remember why we chose not to allow those? > > performance _is_ allowed; powersave would be possible -- but then those who > accidentally enable it on elanfreq might wait 100 times as long for the > system to boot, with gx-suspmod it might even be 255 times as long -- okay, > by default it's just 20 times as long, but still... > > Dominik > People should be smart enough to realize what "powersave" would imply... or at least read the help for it; again, we wouldn't have the "default default governor" be powersave, it would be performance, and they could choose powersave if they wanted to. Also, what of the conservative governor? I understand now some of the problems that could arise with ondemand, but conservative doesn't rely on low-latency transitions, and seems no riskier than performance or powersave. In fact, conservative would probably be the most useful default governor available for a laptop system. For now, I propose allowing a default governor of powersave; allowing conservative while being tagged experimental, and possibly, but not likely, allowing ondemand, tagged as experimental. William Heimbigner icxcnika@mar.tar.cc