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#1 2004-07-21 04:46:41

forn4x
Member
Registered: 2004-06-23
Posts: 13

Arch on laptop - acpi, acpid, etc

Hi everybody,

I installed Arch 0.6 Base on my Compaq Presario 2100 notebook some time ago and I decided to kill some time making ACPI to work...
At first I couldn't start without the option acpi=off, since the ACPI was freezing kernel during bootup. After disabling APIC (noapic and nolapic parameters) I managed to start it. Now shutdown turns the laptop off and the fans are not running all the time like crazy. Actually that is everything I need, but from curiosity, and because I have some free time I decided to investigate a little bit further... and here are my questions:

1. To what degree ACPI in the kernel is controlling my hardware? It is controlling only fans or something else too? Can I manually turn on/off the fun? Can it change the speed of my processor by itself?

I am asking that because I like to control my computer. One reason why I don't like win is because it always assumes what is best for you and does it without asking you (ah, my experiences)...

2. What is acpid for? Since I couldn't find any other scripts than for powerbutton, is there any reason I should install it? What can you do with it?

3. What cpufreqd is for? Is it doing something that acpid cannot do?

Ok, that's preety much it for today. Besides, I am really happy with Arch on board ;D
Thanks in advance
Wojciech Szlachta


"Earth is the cradle of humanity, but one cannot live
in a cradle forever."     Konstantin E. Tsiolkovsky

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#2 2004-07-21 08:12:35

Mr Green
Forum Fellow
From: U.K.
Registered: 2003-12-21
Posts: 5,746

Re: Arch on laptop - acpi, acpid, etc

http://www.acpi.info/

HTH

Mr Green


Mr Green

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#3 2004-07-21 09:32:14

Bobonov
Member
From: Roma - Italy
Registered: 2003-05-07
Posts: 295

Re: Arch on laptop - acpi, acpid, etc

forn4x wrote:

1. To what degree ACPI in the kernel is controlling my hardware? It is controlling only fans or something else too? Can I manually turn on/off the fun? Can it change the speed of my processor by itself?

2. What is acpid for? Since I couldn't find any other scripts than for powerbutton, is there any reason I should install it? What can you do with it?

3. What cpufreqd is for? Is it doing something that acpid cannot do?

1/2) ACPID can do more, but this depends on you hardware support/possibility. There are not many info on acpid http://acpid.sourceforge.net/ as you can see. Generally speaking it execute command on events.
Anyway acpid allow you to monitor the charge of your battery and let linux to know if the laptop is plugged or not. I this way you can chose particular action to do when not plugged and command/advise to execute when battery is running out. ie if you have brigthness controll you can lover it and speed down the processor to save the battery by executing/sending command to one of the following.

3) cpufreqd allow you to speed up/down the processor clock in this way you can save battery charge. Not allprocessor support this, ie my ADM xp has it.
You can configure it to speed up/down on events, like low battery or laptop not plugged.
There is also cpudyn, I didn't try it, it seem is able to speed up/down the processor dynamically.
Tha means if you use just openoffice to write a letter  it speed down the processor, if compile a program it speed up. If you use gimp untill you wiev an image the speed is low once you apply a filter and more CPU power is required it speed up. I think it check the CPU usage and if it goes over a certain % it speed up, if it goes down a certain % it speed down.
Speed down processor --> less heating ---> fan starts rarely
To use them you need kernel 2.6 or 2.4 patched , ACPID is not necessary for this functionality.

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#4 2004-07-21 16:26:24

forn4x
Member
Registered: 2004-06-23
Posts: 13

Re: Arch on laptop - acpi, acpid, etc

Ok, I did some more reading... and I found out that cpufreqd and cpudynd are actually using the cpufreq option in the kernel - they are not using acpi to control the speed of your processor... (cpudynd can use acpi instead with -acpi option)

What will happen if we decide to slow down processor in both acpi and cpufreq???

I am just trying to find a best way to set up my notebook so that it will be doing what I want it to do... when ac adaptor is plugged I like it to work on a full speed, but when it is unplugged I'd like to use cpudynd, therefore, I think the best way would be to set up an acpi script, that would start cpudynd on the event of plugging in the ac adaptor and stop it, when ac adaptor is unplugged. Is that correct?
Since my acpi doesn't see the throttling options, due to wrong dsdt table, can I use cpudynd without using the correct dsdt table (by cpufreq) - it would require patching the kernel?

But I still don't know what cpufreqd is for? Is it something like cpudynd that automatically changes the frequency of your processor based on a system load?

Thanks
Wojciech Szlachta


"Earth is the cradle of humanity, but one cannot live
in a cradle forever."     Konstantin E. Tsiolkovsky

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#5 2004-07-22 00:16:58

forn4x
Member
Registered: 2004-06-23
Posts: 13

Re: Arch on laptop - acpi, acpid, etc

Ok, I spent most of the day investigating acpi and cpufreq in kernel and after all I will answer my own questions by myself... maybe somebody will find these helpful:

acpi offers 3 possible options to control the processor speed:

- power management
CPU power management allows the ACPI system to put the CPU into a sleep state when the computer is not using 100% of the CPU's capabilities

- throttling control
throttling is sort of enforced CPU power management, even when the system is highly active, the CPU is "put to sleep" for short amounts of time, so that power can be saved

- performance management
your processor can run on (at least) two different frequencies and voltage ranges
performance management is much more effective than throttling control and it is the same thing that cpufreq in kernels form 2.6 series, and therefore should be controlled by cpufreq

acpid is the deamon controlling events from /proc/acpi/events and executing scripts based on that events
cpufreqd is similiar to cpudynd and they dynamically change the processor frequence (look performance management) based on a system load

Wojciech Szlachta


"Earth is the cradle of humanity, but one cannot live
in a cradle forever."     Konstantin E. Tsiolkovsky

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