From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dominik Brodowski Subject: Re: [PATCH] cpufreq_ondemand Date: Wed, 20 Oct 2004 16:30:57 +0200 Sender: cpufreq-bounces@www.linux.org.uk Message-ID: <20041020143057.GA7652@dominikbrodowski.de> References: <7f800d9f04101922031be5cfe8@mail.gmail.com> <1098257735.26595.4308.camel@d845pe> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <1098257735.26595.4308.camel@d845pe> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: cpufreq-bounces+glkc-cpufreq=gmane.org@www.linux.org.uk Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Len Brown Cc: Andre Eisenbach , Alexander Clouter , linux-kernel@vger.kernel.org, Con Kolivas , "cpufreq@www.linux.org.uk" On Wed, Oct 20, 2004 at 03:35:35AM -0400, Len Brown wrote: > On Wed, 2004-10-20 at 01:03, Andre Eisenbach wrote: > > > ... If the > > speed steps down slowly but shoots up 100% quickly (as it is right > > now), even a small task (like opening a folder, or scrolling down in a > > document) will cause a tiny spike to 100% which takes a while to go > > back down. The result is that the CPU spends most of it's time at 100% > > or calming down. I wrote a small test program on my notebook which > > confirms this. > > The question is what POLICY we're trying to implement. This is why there may be DIFFERENT policies a.k.a. governors in cpufreq. > If the goal is > to to be energy efficient while the user notices no performance hit, > then fast-up/slow-down is an EXCELLENT strategy. But if the goal is to > optimize for power savings at the cost of impacting performance, then > another strategy may work better. > The point is that no strategy will be optimal for all policies. Linux > needs a global power policy manager that the rest of the system can ask > about the current policy. This way sub-systems can (automatically) > implement whatever local strategies are consistent with that global > policy. Put it in userspace, and let it ask the cpufreq core in the kernel to use a specific governor or another depending on what you want. That's what certain userspace daemons / scripts already do, btw. Dominik