From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ducrot Bruno Subject: Re: acpi_processor.c - kernel 2.6.1 Date: Mon, 19 Jan 2004 15:10:59 +0100 Sender: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Message-ID: <20040119141059.GG25416@poupinou.org> References: <1074382993.674.24.camel@dragon> <1074424728.1914.24.camel@firefly> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1074424728.1914.24.camel-YqzrDssuZYw@public.gmane.org> Errors-To: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: "Yury V. Umanets" Cc: christian graf , acpi-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-acpi@vger.kernel.org On Sun, Jan 18, 2004 at 02:18:48PM +0300, Yury V. Umanets wrote: > On Sun, 2004-01-18 at 02:43, christian graf wrote: > > Hi, > Hello, > > > > reading the /usr/src/linux-2.6.1/drivers/acpi/processor.c > > i thought the kernel should set the state dynamically, based on the > > load. Maybe it is possible to set the processor-state of my centrino > > manually. Can please anybody tell me how to get it right? > > > > There is an user-space daemon, which adjusts CPU speed basing on current > loading. And it is able to change CPU frequency if userspace cpufreq > governor is turned on. I would like to see this functionality in kernel > though. > > > The reason I'm asking is, that once I do load the processor.ko module, > > my Centrino switches immediately into C2-state. It never switches back > > to C1 state, even under heavy load like compiling the kernel. > > > I guess, that there is no code in kernel, which does watch current > loading and adjust CPU speed. Also this is job for a cpufreq governor, > not for CPU driver. > > For now, there are three governors: > (1) powersave -- setting CPU frequency statically to lowest available > frequency. > (2) performance -- setting to highest available frequency. > (3) userspace -- used for setting CPU frequency manually. > > Probably there also should be number (4), which will set it basing on > current loading. > > I think the kernel should switch back from C2 to C1 state from alone???? > > > > Please ask me whatever you need to help me swtiching back into C1 state. > > > > christian ACPI Cx states are not the same as ACPI Px states and Cx have nothing to do with cpufreq. C-states are the sleeping states for a processor. ACPI P-state will lower the voltage of the CPU and the frequency, but the processor is supposed to run, whereas ACPI C-state is a kind of replacement of the asm 'hlt' (for a 386 compatible), mostly used in the idle loop. C1 is actually this asm 'hlt', whereas C2 require a read to a IO register, and C3 require a read to a IO register plus a kind of control of the bus (on UP system). More the x in Cx is high, more you get power saving, but this have a price for the latency in order to wakeup the processor when it have to serve an interrupt. -- Ducrot Bruno -- Which is worse: ignorance or apathy? -- Don't know. Don't care. ------------------------------------------------------- The SF.Net email is sponsored by EclipseCon 2004 Premiere Conference on Open Tools Development and Integration See the breadth of Eclipse activity. February 3-5 in Anaheim, CA. http://www.eclipsecon.org/osdn