2010-05-13 00:41:28 +02:00
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Overview:
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2010-05-12 23:33:46 +02:00
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This is a very simple program that will adjust the speed of your CPU
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depending on system load. It works as a client of the CPUFreq driver.
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2010-05-13 00:41:28 +02:00
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It is designed for use with CPU's supporting AMD's PowerNow power management
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scheme, as it's algorithm works better if there are more then two CPU
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speeds available. (aka, ARM, AMD K6/K7, Via C3, and Crusoe as opposed to
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traditional Intel and Ultrasparc).
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2010-05-12 23:33:46 +02:00
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2010-05-13 00:41:28 +02:00
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This program is essentially a simple client to the CPUFreq sysfs interface.
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This means that you -need- to be running Linux v2.5 or later that includes
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the sysfs interface. This daemon will -not- work with the CPUFreq driver
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interface included in Linux v2.4. Feel free to write your own daemon
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to support that if you like; you can even use this as a starting point.
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If there's enough clamoring for it, then maybe I'll whip up something.
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You also need a CPU that supports frequency scaling and supports the CPUFreq
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interface. This code has been tested on various AMD and PPC processors
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2010-05-12 23:33:46 +02:00
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2010-05-13 00:41:28 +02:00
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I have been running this daemon on my AMD laptop for over 2 years with no
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problems to report, and it's nice that my laptop remains cool unless I'm
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really doing something intensive, like watching DivX movies, without me
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having to manually intervene and set the speed. I just recently bought an
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Apple iBook G3, and powernowd-0.80 worked flawlessly on it right out of
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the box.
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Features:
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This daemon's goal is simplicity and speed. It doesn't try and make
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too many decisions for you. That's its beauty, but it may not be what
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everyone's looking for. Some of the features this daemon has:
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One, simple heuristic to determine CPU load: "user + sys" time.
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Ignore "niced" programs (setiathome, itself, etc). In my mind this is
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consistent with what is meant when someone 'nice's a program to begin
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with. (configurable in v0.85+) Designed for CPU's that support more
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then two speed states, but works well with anything. Very fast, low
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overhead /proc/stat gathering (method stolen from procps). Supports SMP
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Will automatically switch to 'userspace' governor. Care taken to make
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the code non-root exploitable (but please audit for yourself first!)
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Frequency step size is configurable (default to 100MHz/step) 4 different
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behavioral modes to choose from (SINE, AGGRESSIVE, PASSIVE, LEAPS),
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which determine the behavior when the load changes. Configurable from the
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command line. Written in C for speed and simplicity. Logging to stdout
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or syslog Configurable Polling frequency in milliseconds (defaults to 1s)
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Configurable highwater/lowwater marks for CPU usage. (defaults 80/20%)
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Many similar daemons use other methods to determine what speed to use,
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such as battery status, AC status, temperature, fan status, etc. They all
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have their place. I however feel that in the grand scheme of things none
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of the above matters. When I'm not using my CPU, I don't care if it's
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running at a slower speed. When I -am- using my CPU, I only need it to
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be fast enough to handle the task at hand without hiccuping. And when I'm
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taxing my CPU, I want it running full speed. That's all this daemon does,
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monitor CPU load and adjust the speed accordingly. Since in all reality
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my CPU is idle 99% of the time (or playing mp3's which it can easily do
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at it's lowest speed rating), this by definition leads to low power usage,
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low temperatures, low speed fans, and better battery life.
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