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1 swift 1.1 <?xml version='1.0' encoding="UTF-8"?>
2     <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3 nightmorph 1.27 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/power-management-guide.xml,v 1.26 2007/04/16 05:39:54 nightmorph Exp $ -->
4 so 1.15 <guide link="/doc/en/power-management-guide.xml">
5 swift 1.1 <title>Power Management Guide</title>
6    
7 swift 1.4 <author title="Author">
8 nightmorph 1.17 <mail link="earthwings@gentoo.org">Dennis Nienhüser</mail>
9 swift 1.1 </author>
10 rane 1.19 <author title="Editor">
11     <mail link="chriswhite@gentoo.org">Chris White</mail>
12     </author>
13 nightmorph 1.26 <author title="Editor">
14     <mail link="nightmorph@gentoo.org">Joshua Saddler</mail>
15     </author>
16 swift 1.1
17     <abstract>
18     Power Management is the key to extend battery run time on mobile systems like
19     laptops. This guide assists you setting it up on your laptop.
20     </abstract>
21    
22     <!-- The content of this document is licensed under the CC-BY-SA license -->
23 so 1.15 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
24 swift 1.1 <license/>
25    
26 nightmorph 1.27 <version>1.33</version>
27     <date>2007-05-30</date>
28 swift 1.1
29     <chapter>
30     <title>Introduction</title>
31     <section>
32     <body>
33    
34     <p>
35 so 1.15 Capacity and lifetime of laptop batteries have improved much in the last years.
36 swift 1.1 Nevertheless modern processors consume much more energy than older ones and
37     each laptop generation introduces more devices hungry for energy. That's why
38     Power Management is more important than ever. Increasing battery run time
39     doesn't necessarily mean buying another battery. Much can be achieved applying
40     intelligent Power Management policies.
41     </p>
42    
43     </body>
44     </section>
45     <section>
46 rane 1.19 <title>A Quick Overview</title>
47 swift 1.1 <body>
48    
49     <p>
50     Please notice that this guide describes Power Management for <e>laptops</e>.
51     While some sections might also suite for <e>servers</e>, others do not and may
52     even cause harm. Please do not apply anything from this guide to a server
53     unless you really know what you are doing.
54     </p>
55    
56     <p>
57     As this guide has become rather long, here's a short overview helping you to
58     find your way through it.
59     </p>
60    
61     <p>
62 rane 1.19 The <uri link="#doc_chap2">Prerequisites</uri> chapter talks about some
63     requirements that should be met before any of the following device individual
64     sections will work. This includes BIOS settings, kernel configuration and some
65     simplifications in user land. The following three chapters focus on devices
66     that typically consume most energy - processor, display and hard drive. Each
67     can be configured seperately. <uri link="#doc_chap3">CPU Power Management</uri>
68     shows how to adjust the processor's frequency to save a maximum of energy
69 rane 1.21 without losing too much performance. A few different tricks prevent your hard
70 rane 1.19 drive from working unnecessarily often in <uri link="#doc_chap5">Disk Power
71     Management</uri> (decreasing noise level as a nice side effect). Some notes on
72 rane 1.20 graphics cards, Wireless LAN and USB finish the device section in <uri
73     link="#doc_chap6">Power Management For Other Devices</uri> while another
74 rane 1.19 chapter is dedicated to the (rather experimental) <uri link="#doc_chap7">sleep
75 rane 1.20 states</uri>. Last not least <uri link="#doc_chap8">Troubleshooting</uri> lists
76     common pitfalls.
77 swift 1.1 </p>
78    
79     </body>
80     </section>
81     <section>
82 rane 1.19 <title>Power Budget For Each Component</title>
83 swift 1.1 <body>
84    
85 swift 1.2 <figure link="/images/energy-budget.png" short="Which component consumes how
86 swift 1.1 much energy?" caption="Power budget for each component"/>
87    
88     <p>
89     Nearly every component can operate in different states - off, sleep, idle,
90     active to name a few - consuming a different amount of energy. Major parts are
91     consumed by the LCD display, CPU, chipset and hard drives. Often one is able to
92     activate OS-independent Power Management in the BIOS, but an intelligent setup
93     in the operating system adapting to different situations can achieve much more.
94     </p>
95    
96     </body>
97     </section>
98     </chapter>
99    
100     <chapter>
101     <title>Prerequisites</title>
102     <section>
103     <body>
104    
105     <p>
106 nightmorph 1.17 Before discussing the details of making individual devices Power Management
107 rane 1.20 aware, make sure certain requirements are met. After controlling BIOS settings,
108     some kernel options want to be enabled - these are in short ACPI, sleep states
109     and CPU frequency scaling. As power saving most of the time comes along with
110     performance loss or increased latency, it should only be enabled when running
111     on batteries. That's where a new runlevel <e>battery</e> comes in handy.
112 swift 1.1 </p>
113    
114     </body>
115     </section>
116     <section>
117 rane 1.19 <title>The BIOS Part</title>
118 swift 1.1 <body>
119    
120     <p>
121     First have a look into your BIOS Power Management settings. The best way is to
122     combine BIOS and operating system policies, but for the moment it's better to
123     disable most of the BIOS part. This makes sure it doesn't interfere with your
124     policies. Don't forget to re-check BIOS settings after you configured
125     everything else.
126     </p>
127    
128     </body>
129     </section>
130     <section>
131 rane 1.19 <title>Setting USE Flags</title>
132 nightmorph 1.17 <body>
133    
134     <p>
135     Please check that the <c>acpi</c> USE flag is set in
136     <path>/etc/make.conf</path>. Other USE flags that might be interesting for your
137     system are <c>apm</c>, <c>lm_sensors</c>, <c>nforce2</c>, <c>nvidia</c>,
138     <c>pmu</c>. See <path>/usr/portage/profiles/use*.desc</path> for details. If
139     you forgot to set one of these flags, you can recompile affected packages using
140 rane 1.19 the <c>--newuse</c> flag in <c>emerge</c>, see <c>man emerge</c>.
141 nightmorph 1.17 </p>
142    
143     </body>
144     </section>
145     <section>
146 rane 1.19 <title>Configuring The Kernel</title>
147 swift 1.1 <body>
148    
149     <p>
150     ACPI (Advanced Configuration and Power Interface) support in the kernel is
151     still work in progress. Using a recent kernel will make sure you'll get the
152     most out of it.
153     </p>
154    
155     <p>
156 rane 1.20 There are different kernel sources in Portage. I'd recommend using
157 so 1.15 <c>gentoo-sources</c> or <c>suspend2-sources</c>. The latter contains patches
158 rane 1.19 for Software Suspend 2, see the chapter about <uri link="#doc_chap7">sleep
159     states</uri> for more details. When configuring the kernel, activate at least
160     these options:
161 swift 1.1 </p>
162    
163     <pre caption="Minimum kernel setup for Power Management (Kernel 2.6)">
164     Power Management Options ---&gt;
165     [*] Power Management Support
166     [ ] Software Suspend
167    
168     ACPI( Advanced Configuration and Power Interface ) Support ---&gt;
169     [*] ACPI Support
170     [ ] Sleep States
171 so 1.15 [ ] /proc/acpi/sleep (deprecated)
172 neysx 1.12 [*] AC Adapter
173     [*] Battery
174 swift 1.1 &lt;M&gt; Button
175 so 1.15 &lt;M&gt; Video
176     [ ] Generic Hotkey
177 swift 1.1 &lt;M&gt; Fan
178     &lt;M&gt; Processor
179     &lt;M&gt; Thermal Zone
180     &lt; &gt; ASUS/Medion Laptop Extras
181 so 1.15 &lt; &gt; IBM ThinkPad Laptop Extras
182 swift 1.1 &lt; &gt; Toshiba Laptop Extras
183 so 1.15 (0) Disable ACPI for systems before Jan 1st this year
184 swift 1.1 [ ] Debug Statements
185 so 1.15 [*] Power Management Timer Support
186     &lt; &gt; ACPI0004,PNP0A05 and PNP0A06 Container Driver (EXPERIMENTAL)
187 rane 1.20
188 swift 1.1 CPU Frequency Scaling ---&gt;
189     [*] CPU Frequency scaling
190 so 1.15 [ ] Enable CPUfreq debugging
191     &lt; &gt; CPU frequency translation statistics
192     [ ] CPU frequency translation statistics details
193 swift 1.1 Default CPUFreq governor (userspace)
194     &lt;*&gt; 'performance' governor
195     &lt;*&gt; 'powersave' governor
196 swift 1.8 &lt;*&gt; 'ondemand' cpufreq policy governor
197 so 1.15 &lt;*&gt; 'conservative' cpufreq governor
198 swift 1.1 &lt;*&gt; CPU frequency table helpers
199     &lt;M&gt; ACPI Processor P-States driver
200     &lt;*&gt; <i>CPUFreq driver for your processor</i>
201     </pre>
202    
203     <p>
204 so 1.15 Decide yourself whether you want to enable Software Suspend, and Sleep States
205     (see below). If you own an ASUS, Medion, IBM Thinkpad or Toshiba laptop, enable
206 neysx 1.12 the appropriate section.
207 swift 1.8 </p>
208    
209     <p>
210 rane 1.20 The kernel has to know how to enable CPU frequency scaling on your processor.
211     As each type of CPU has a different interface, you've got to choose the right
212 rane 1.19 driver for your processor. Be careful here - enabling <c>Intel Pentium 4 clock
213     modulation</c> on a Pentium M system will lead to strange results for example.
214 swift 1.8 Consult the kernel documentation if you're unsure which one to take.
215 swift 1.1 </p>
216    
217     <p>
218     Compile your kernel, make sure the right modules get loaded at startup and boot
219 rane 1.20 into your new ACPI-enabled kernel. Next run <c>emerge sys-power/acpid</c> to
220     get the acpi daemon. This one informs you about events like switching from AC
221     to battery or closing the lid. Make sure the modules are loaded if you didn't
222     compile them into the kernel and start acpid by executing <c>/etc/init.d/acpid
223     start</c>. Run <c>rc-update add acpid default</c> to load it on startup. You'll
224     soon see how to use it.
225 swift 1.1 </p>
226    
227     <pre caption="Installing acpid">
228 yoswink 1.10 # <i>emerge sys-power/acpid</i>
229 swift 1.1 # <i>/etc/init.d/acpid start</i>
230     # <i>rc-update add acpid default</i>
231     </pre>
232    
233     </body>
234     </section>
235     <section>
236 rane 1.19 <title>Creating A "battery" Runlevel</title>
237 swift 1.1 <body>
238    
239     <p>
240     The default policy will be to enable Power Management only when needed -
241     running on batteries. To make the switch between AC and battery convenient,
242 rane 1.19 create a runlevel <c>battery</c> that holds all the scripts starting and
243 swift 1.1 stopping Power Management.
244     </p>
245    
246     <note>
247     You can safely skip this section if you don't like the idea of having another
248     runlevel. However, skipping this step will make the rest a bit trickier to set
249 rane 1.19 up. The next sections assume a runlevel <c>battery</c> exists.
250 swift 1.1 </note>
251    
252     <pre caption="Creating a battery runlevel">
253     # <i>cd /etc/runlevels</i>
254     # <i>cp -a default battery</i>
255     </pre>
256    
257     <p>
258 rane 1.19 Finished. Your new runlevel <c>battery</c> contains everything like
259     <c>default</c>, but there is no automatic switch between both yet. Time to
260 swift 1.1 change it.
261     </p>
262    
263     </body>
264     </section>
265     <section>
266 rane 1.19 <title>Reacting On ACPI Events</title>
267 swift 1.1 <body>
268    
269     <p>
270     Typical ACPI events are closing the lid, changing the power source or pressing
271 swift 1.8 the sleep button. An important event is changing the power source, which should
272 so 1.15 cause a runlevel switch. A small script will take care of it.
273     </p>
274    
275     <p>
276     First you need a script which changes the runlevel to <c>default</c>
277     respectively <c>battery</c> depending on the power source. The script uses the
278     <c>on_ac_power</c> command from <c>sys-power/powermgmt-base</c> - make sure the
279     package is installed on your system.
280     </p>
281    
282     <pre caption="Installing powermgt-base">
283 rane 1.19 # <i>emerge powermgmt-base</i>
284 so 1.15 </pre>
285    
286     <p>
287 rane 1.20 You are now able to determine the power source by executing <c>on_ac_power
288     &amp;&amp; echo AC available || echo Running on batteries</c> in a shell. The
289     script below is responsible for changing runlevels. Save it as
290 so 1.15 <path>/etc/acpi/actions/pmg_switch_runlevel.sh</path>.
291 swift 1.8 </p>
292    
293 neysx 1.12 <pre caption="/etc/acpi/actions/pmg_switch_runlevel.sh">
294 swift 1.8 #!/bin/bash
295    
296 neysx 1.12 <comment># BEGIN configuration</comment>
297 swift 1.8 RUNLEVEL_AC="default"
298     RUNLEVEL_BATTERY="battery"
299 neysx 1.12 <comment># END configuration</comment>
300 swift 1.8
301 swift 1.1
302 neysx 1.12 if [ ! -d "/etc/runlevels/${RUNLEVEL_AC}" ]
303     then
304 nightmorph 1.17 logger "${0}: Runlevel ${RUNLEVEL_AC} does not exist. Aborting."
305     exit 1
306 neysx 1.12 fi
307 swift 1.8
308 neysx 1.12 if [ ! -d "/etc/runlevels/${RUNLEVEL_BATTERY}" ]
309     then
310 nightmorph 1.17 logger "${0}: Runlevel ${RUNLEVEL_BATTERY} does not exist. Aborting."
311     exit 1
312 neysx 1.12 fi
313 swift 1.1
314 neysx 1.12 if on_ac_power
315     then
316 rane 1.19 if [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_AC}" ]]
317 nightmorph 1.17 then
318     logger "Switching to ${RUNLEVEL_AC} runlevel"
319     /sbin/rc ${RUNLEVEL_AC}
320     fi
321 rane 1.19 elif [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_BATTERY}" ]]
322 neysx 1.12 then
323 nightmorph 1.17 logger "Switching to ${RUNLEVEL_BATTERY} runlevel"
324     /sbin/rc ${RUNLEVEL_BATTERY}
325 neysx 1.12 fi
326 swift 1.8 </pre>
327    
328 so 1.15 <p>
329     Dont forget to run <c>chmod +x /etc/acpi/actions/pmg_switch_runlevel.sh</c> to
330     make the script executable. The last thing that needs to be done is calling the
331     script whenever the power source changes. That's done by catching ACPI events
332     with the help of <c>acpid</c>. First you need to know which events are
333     generated when the power source changes. The events are called
334 rane 1.19 <c>ac_adapter</c> and <c>battery</c> on most laptops, but it might be different
335 so 1.15 on yours.
336     </p>
337    
338     <pre caption="Determining ACPI events for changing the power source">
339 rane 1.19 # <i>tail -f /var/log/acpid | grep "received event"</i>
340 so 1.15 </pre>
341    
342     <p>
343 rane 1.20 Run the command above and pull the power cable. You should see something like
344     this:
345 so 1.15 </p>
346    
347     <pre caption="Sample output for power source changes">
348     [Tue Sep 20 17:39:06 2005] received event "ac_adapter AC 00000080 00000000"
349     [Tue Sep 20 17:39:06 2005] received event "battery BAT0 00000080 00000001"
350     </pre>
351    
352     <p>
353 rane 1.19 The interesting part is the quoted string after <c>received event</c>. It will
354 so 1.15 be matched by the event line in the files you are going to create below. Don't
355     worry if your system generates multiple events or always the same. As long as
356     any event is generated, runlevel changing will work.
357     </p>
358    
359 swift 1.8 <pre caption="/etc/acpi/events/pmg_ac_adapter">
360 neysx 1.12 <comment># replace "ac_adapter" below with the event generated on your laptop</comment>
361 so 1.15 <comment># For example, ac_adapter.* will match ac_adapter AC 00000080 00000000</comment>
362 swift 1.8 event=ac_adapter.*
363 neysx 1.12 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
364 swift 1.8 </pre>
365    
366     <pre caption="/etc/acpi/events/pmg_battery">
367 neysx 1.12 <comment># replace "battery" below with the event generated on your laptop</comment>
368 so 1.15 <comment># For example, battery.* will match battery BAT0 00000080 00000001</comment>
369 swift 1.8 event=battery.*
370 neysx 1.12 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
371 swift 1.8 </pre>
372 swift 1.1
373 swift 1.8 <p>
374 so 1.15 Finally acpid has to be restarted to recognize the changes.
375 swift 1.8 </p>
376 swift 1.1
377 swift 1.8 <pre caption="Finishing runlevel switching with acpid">
378 rane 1.19 # <i>/etc/init.d/acpid restart</i>
379 swift 1.1 </pre>
380    
381     <p>
382     Give it a try: Plug AC in and out and watch syslog for the "Switching to AC
383 rane 1.20 mode" or "Switching to battery mode" messages. See the <uri
384     link="#doc_chap8">Troubleshooting section</uri> if the script is not able to
385     detect the power source correctly.
386 swift 1.1 </p>
387    
388     <p>
389     Due to the nature of the event mechanism, your laptop will boot into runlevel
390 rane 1.19 <c>default</c> regardless of the AC/battery state. This is fine when running
391 rane 1.20 from AC, but we'd like to boot into the battery runlevel otherwise. One
392     solution would be to add another entry to the boot loader with the parameter
393 so 1.15 <c>softlevel=battery</c>, but it's likely to forget choosing it. A better way
394 rane 1.20 is faking an ACPI event in the end of the boot process and letting
395     <path>pmg_switch_runlevel.sh</path> script decide whether a runlevel change is
396     necessary. Open <path>/etc/conf.d/local.start</path> in your favourite editor
397     and add these lines:
398 swift 1.1 </p>
399    
400 so 1.15 <pre caption="Runlevel adjustment at boot time by editing local.start">
401 swift 1.1 <comment># Fake acpi event to switch runlevel if running on batteries</comment>
402 neysx 1.12 /etc/acpi/actions/pmg_switch_runlevel.sh "battery/battery"
403 swift 1.1 </pre>
404    
405     <p>
406 rane 1.20 Prepared like this you can activate Power Management policies for individual
407 swift 1.1 devices.
408     </p>
409    
410     </body>
411     </section>
412     </chapter>
413    
414     <chapter>
415     <title>CPU Power Management</title>
416     <section>
417 nightmorph 1.17 <body>
418    
419     <p>
420     Mobile processors can operate at different frequencies. Some allow changing
421     voltage as well. Most of the time your CPU doesn't need to run at full speed
422     and scaling it down will save much energy - often without any performance
423     decrease.
424     </p>
425    
426     </body>
427     </section>
428     <section>
429 rane 1.19 <title>Some Technical Terms</title>
430 swift 1.8 <body>
431    
432     <p>
433     CPU frequency scaling brings up some technical terms that might be unknown to
434     you. Here's a quick introduction.
435     </p>
436    
437     <p>
438 so 1.15 First of all, the kernel has to be able to change the processor's frequency.
439 rane 1.19 The <b>CPUfreq processor driver</b> knows the commands to do it on your CPU.
440 rane 1.20 Thus it's important to choose the right one in your kernel. You should already
441     have done it above. Once the kernel knows how to change frequencies, it has to
442     know which frequency it should set. This is done according to the <b>policy</b>
443     which consists of a <b>CPUfreq policy</b> and a <b>governor</b>. A CPUfreq
444     policy are just two numbers which define a range the frequency has to stay
445     between - minimal and maximal frequency. The governor now decides which of the
446     available frequencies in between minimal and maximal frequency to choose. For
447     example, the <b>powersave governor</b> always chooses the lowest frequency
448     available, the <b>performance governor</b> the highest one. The <b>userspace
449     governor</b> makes no decision but chooses whatever the user (or a program in
450     userspace) wants - which means it reads the frequency from
451 swift 1.8 <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed</path>.
452     </p>
453    
454     <p>
455     This doesn't sound like dynamic frequency changes yet and in fact it isn't.
456 rane 1.20 Dynamics however can be accomplished with various approaches. For example, the
457     <b>ondemand governor</b> makes its decisions depending on the current CPU load.
458     The same is done by various userland tools like <c>cpudyn</c>, <c>cpufreqd</c>,
459     <c>powernowd</c> and many more. ACPI events can be used to enable or disable
460     dynamic frequency changes depending on power source.
461 swift 1.8 </p>
462    
463     </body>
464     </section>
465     <section>
466 rane 1.19 <title>Setting The Frequency Manually</title>
467 swift 1.1 <body>
468    
469     <p>
470     Decreasing CPU speed and voltage has two advantages: On the one hand less
471     energy is consumed, on the other hand there is thermal improvement as your
472     system doesn't get as hot as running on full speed. The main disadvantage is
473     obviously the loss of performance. Decreasing processor speed is a trade off
474     between performance loss and energy saving.
475     </p>
476    
477     <note>
478     Not every laptop supports frequency scaling. If unsure, have a look at the list
479 rane 1.19 of supported processors in the <uri link="#doc_chap8">Troubleshooting</uri>
480     section to verify yours is supported.
481 swift 1.1 </note>
482    
483     <p>
484 neysx 1.12 It's time to test whether CPU frequency changing works. Let's install another
485     tool which is very handy for debugging purposes: <c>sys-power/cpufrequtils</c>
486 swift 1.1 </p>
487    
488 neysx 1.12 <pre caption="Checking CPU frequency">
489     # <i>emerge cpufrequtils</i>
490     # <i>cpufreq-info</i>
491 swift 1.1 </pre>
492    
493     <p>
494 neysx 1.12 Here is an example output:
495 swift 1.1 </p>
496    
497 neysx 1.12 <pre caption="Sample output from cpufreq-info">
498 so 1.15 cpufrequtils 0.3: cpufreq-info (C) Dominik Brodowski 2004
499 neysx 1.12 Report errors and bugs to linux@brodo.de, please.
500     analyzing CPU 0:
501     driver: centrino
502     CPUs which need to switch frequency at the same time: 0
503     hardware limits: 600 MHz - 1.40 GHz
504     available frequency steps: 600 MHz, 800 MHz, 1000 MHz, 1.20 GHz, 1.40 GHz
505 so 1.15 available cpufreq governors: conservative, ondemand, powersave, userspace, performance
506 neysx 1.12 current policy: frequency should be within 924 MHz and 1.40 GHz.
507     The governor "performance" may decide which speed to use
508     within this range.
509 so 1.15 current CPU frequency is 1.40 GHz.
510 neysx 1.12 </pre>
511    
512 swift 1.1 <p>
513 neysx 1.12 Now play around with <c>cpufreq-set</c> to make sure frequency switching works.
514     Run <c>cpufreq-set -g ondemand</c> for example to activate the ondemand
515     governor and verify the change with <c>cpufreq-info</c>. If it doesn't work as
516 rane 1.20 expected, you might find help in the <uri link="#doc_chap8">Troubleshooting
517     section</uri> in the end of this guide.
518 swift 1.1 </p>
519    
520     </body>
521     </section>
522     <section>
523     <title>Automated frequency adaption</title>
524     <body>
525    
526     <p>
527     The above is quite nice, but not doable in daily life. Better let your system
528 so 1.15 set the appropriate frequency automatically. There are many different
529     approaches to do this. The following table gives a quick overview to help you
530 rane 1.21 decide on one of them. It's roughly separated in three categories <b>kernel</b>
531 rane 1.20 for approaches that only need kernel support, <b>daemon</b> for programs that
532     run in the background and <b>graphical</b> for programs that provide a GUI for
533     easy configuration and changes.
534 swift 1.1 </p>
535    
536     <table>
537     <tr>
538     <th>Name</th>
539 swift 1.8 <th>Category</th>
540     <th>Switch decision</th>
541     <th>Kernel governors</th>
542     <th>Further governors</th>
543     <th>Comments</th>
544     </tr>
545     <tr>
546     <ti>'ondemand' governor</ti>
547     <ti>Kernel</ti>
548     <ti>CPU load</ti>
549     <ti>N.A.</ti>
550     <ti>N.A.</ti>
551     <ti>
552 so 1.15 Chooses maximal frequency on CPU load and slowly steps down when the CPU is
553     idle. Further tuning through files in
554 swift 1.8 <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
555     userland tools (programs, scripts) if governor switching or similar is
556     desired.
557     </ti>
558 swift 1.1 </tr>
559     <tr>
560 so 1.15 <ti>'conservative' governor</ti>
561     <ti>Kernel</ti>
562     <ti>CPU load</ti>
563     <ti>N.A.</ti>
564     <ti>N.A.</ti>
565     <ti>
566 neysx 1.16 Unlike the ondemand governor, conversative doesn't jump to maximum
567     frequency when CPU load is high, but increases the frequency step by step.
568     Further tuning through files in
569     <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
570     userland tools (programs, scripts) if governor switching or similar is
571     desired.
572 so 1.15 </ti>
573     </tr>
574     <tr>
575 swift 1.1 <ti><uri link="http://mnm.uib.es/~gallir/cpudyn/">cpudyn</uri></ti>
576 swift 1.8 <ti>Daemon</ti>
577     <ti>CPU load</ti>
578 neysx 1.12 <ti>Performance, powersave</ti>
579 swift 1.8 <ti>Dynamic</ti>
580     <ti>
581     Also supports disk standby - notice however that <e>laptop mode</e> in most
582     cases will do a better job.
583     </ti>
584 swift 1.1 </tr>
585     <tr>
586 swift 1.8 <ti><uri link="http://sourceforge.net/projects/cpufreqd/">cpufreqd</uri></ti>
587     <ti>Daemon</ti>
588 nightmorph 1.17 <ti>Battery state, CPU load, temperature, running programs and more</ti>
589 swift 1.8 <ti>All available</ti>
590     <ti>None</ti>
591     <ti>
592 nightmorph 1.17 Sophisticated (but somewhat complicated) setup. Extendible through plugins
593     like sensor monitoring (lm_sensors) or coordinating some NVidia based
594     graphics card memory and core. Cpufreqd is SMP aware and can optionally be
595     controlled manually at runtime.
596 swift 1.8 </ti>
597     </tr>
598     <tr>
599     <ti>
600     <uri link="http://www.deater.net/john/powernowd.html">powernowd</uri>
601     </ti>
602     <ti>Daemon</ti>
603     <ti>CPU load</ti>
604     <ti>None</ti>
605     <ti>Passive, sine, aggressive</ti>
606     <ti>
607     Supports SMP.
608     </ti>
609 swift 1.1 </tr>
610     <tr>
611 so 1.15 <ti>
612 rane 1.20 <uri
613     link="http://fatcat.ftj.agh.edu.pl/~nelchael/index.php?cat=projs&amp;subcat=ncpufreqd&amp;language=en">ncpufreqd</uri>
614 so 1.15 </ti>
615     <ti>Daemon</ti>
616     <ti>Temperature</ti>
617     <ti>None</ti>
618     <ti>Powersave, performance</ti>
619     <ti>
620     Toggles the used governor between performance and powersave depending on
621     system temperature. Very useful on laptops with notorious heat problems.
622     </ti>
623     </tr>
624     <tr>
625 swift 1.1 <ti><uri link="http://www.goop.org/~jeremy/speedfreq/">speedfreq</uri></ti>
626 swift 1.8 <ti>Daemon</ti>
627     <ti>CPU load</ti>
628     <ti>None</ti>
629     <ti>Dynamic, powersave, performance, fixed speed</ti>
630     <ti>
631 so 1.15 Easy to configure with a nice client/server interface. Requires a 2.6
632     kernel. Unmaintained, broken and thus removed from Portage. Please switch
633     to cpufreqd if you're still using it.
634 swift 1.8 </ti>
635     </tr>
636     <tr>
637     <ti><uri link="http://cpuspeedy.sourceforge.net/">gtk-cpuspeedy</uri></ti>
638     <ti>Graphical</ti>
639     <ti>None</ti>
640     <ti>None</ti>
641     <ti>None</ti>
642 swift 1.1 <ti>
643 swift 1.8 Gnome application, a graphical tool to set CPU frequency manually. It does
644 neysx 1.12 not offer any automation.
645 swift 1.1 </ti>
646     </tr>
647     <tr>
648 swift 1.8 <ti>klaptopdaemon</ti>
649     <ti>Graphical</ti>
650     <ti>Battery state</ti>
651     <ti>All available</ti>
652     <ti>None</ti>
653     <ti>
654     KDE only, 'ondemand' governor required for dynamic frequency scaling.
655     </ti>
656 swift 1.1 </tr>
657     </table>
658    
659     <p>
660 so 1.15 While adjusting the frequency to the current load looks simple at a first
661     glance, it's not such a trivial task. A bad algorithm can cause switching
662     between two frequencies all the time or wasting energy when setting frequency
663 rane 1.20 to an unnecessary high level.
664 swift 1.1 </p>
665    
666     <p>
667 neysx 1.12 Which one to choose? If you have no idea about it, try <c>cpufreqd</c>:
668 swift 1.1 </p>
669    
670     <pre caption="Installing cpufreqd">
671     # <i>emerge cpufreqd</i>
672     </pre>
673    
674     <p>
675 neysx 1.12 <c>cpufreqd</c> can be configured by editing <path>/etc/cpufreqd.conf</path>.
676     The default one that ships with cpufreqd may look a bit confusing. I recommend
677 nightmorph 1.22 replacing it with the one from former Gentoo developer Henrik Brix Andersen
678     (see below). Please notice that you need cpufreqd-2.0.0 or later. Earlier
679     versions have a different syntax for the config file.
680 swift 1.1 </p>
681    
682 nightmorph 1.17 <pre caption="/etc/cpufreqd.conf (cpufreqd-2.0.0 and later)">
683 swift 1.1 [General]
684     pidfile=/var/run/cpufreqd.pid
685 nightmorph 1.17 poll_interval=3
686     enable_plugins=acpi_ac, acpi_battery
687 nightmorph 1.18 enable_remote=1
688     remote_group=wheel
689 neysx 1.12 verbosity=5
690 nightmorph 1.17 [/General]
691 swift 1.1
692     [Profile]
693 neysx 1.12 name=ondemand
694     minfreq=0%
695     maxfreq=100%
696     policy=ondemand
697 nightmorph 1.17 [/Profile]
698 swift 1.1
699     [Profile]
700 so 1.15 name=conservative
701     minfreq=0%
702     maxfreq=100%
703     policy=conservative
704 nightmorph 1.17 [/Profile]
705 so 1.15
706     [Profile]
707 neysx 1.12 name=powersave
708     minfreq=0%
709     maxfreq=100%
710 swift 1.1 policy=powersave
711 nightmorph 1.17 [/Profile]
712 swift 1.1
713     [Profile]
714 neysx 1.12 name=performance
715     minfreq=0%
716     maxfreq=100%
717     policy=performance
718 nightmorph 1.17 [/Profile]
719 swift 1.1
720     [Rule]
721 neysx 1.12 name=battery
722     ac=off
723 so 1.15 profile=conservative
724 nightmorph 1.17 [/Rule]
725 swift 1.1
726     [Rule]
727 neysx 1.12 name=battery_low
728 swift 1.1 ac=off
729 neysx 1.12 battery_interval=0-10
730     profile=powersave
731 nightmorph 1.17 [/Rule]
732 swift 1.1
733     [Rule]
734 neysx 1.12 name=ac
735     ac=on
736 so 1.15 profile=ondemand
737 nightmorph 1.17 [/Rule]
738 neysx 1.12 </pre>
739    
740     <p>
741 rane 1.19 Now you can start the cpufreqd daemon. Add it to the <c>default</c> and
742     <c>battery</c> runlevel as well.
743 swift 1.1 </p>
744    
745 neysx 1.12 <pre caption="Starting cpufreqd">
746     # <i>rc-update add cpufreqd default battery</i>
747     # <i>rc</i>
748     </pre>
749    
750 nightmorph 1.17 <p>
751     Sometimes it can be desirable to select another policy than the daemon chooses,
752     for example when battery power is low, but you know that AC will be available
753 rane 1.20 soon. In that case you can turn on cpufreqd's manual mode with <c>cpufreqd-set
754     manual</c> and select one of your configured policies (as listed by
755     <c>cpufreqd-get</c>). You can leave manual mode by executing <c>cpufreqd-set
756     dynamic</c>.
757 nightmorph 1.17 </p>
758    
759 neysx 1.12 <warn>
760     Do not run more than one of the above programs at the same time. It may cause
761     confusion like switching between two frequencies all the time.
762     </warn>
763    
764 swift 1.8 </body>
765     </section>
766     <section>
767     <title>Verifying the result</title>
768     <body>
769    
770 swift 1.1 <p>
771     The last thing to check is that your new policies do a good job. An easy way to
772 swift 1.8 do so is monitoring CPU speed while working with your laptop:
773 swift 1.1 </p>
774    
775     <pre caption="Monitoring CPU speed">
776 yoswink 1.13 # <i>watch grep \"cpu MHz\" /proc/cpuinfo</i>
777 swift 1.1 </pre>
778    
779     <p>
780 rane 1.20 If <path>/proc/cpuinfo</path> doesn't get updated (see <uri
781     link="#doc_chap8">Troubleshooting</uri>), monitor the CPU frequency with:
782 swift 1.1 </p>
783    
784     <pre caption="Alternative CPU speed monitoring">
785 neysx 1.12 # <i>watch x86info -mhz</i>
786 swift 1.1 </pre>
787    
788     <p>
789     Depending on your setup, CPU speed should increase on heavy load, decrease on
790 rane 1.19 no activity or just stay at the same level. When using <c>cpufreqd</c> and
791 rane 1.20 verbosity set to 5 or higher in <path>cpufreqd.conf</path> you'll get
792     additional information about what's happening reported to <c>syslog</c>.
793 swift 1.1 </p>
794    
795     </body>
796     </section>
797     </chapter>
798    
799     <chapter>
800     <title>LCD Power Management</title>
801     <section>
802     <body>
803    
804     <p>
805 rane 1.20 As you can see in <uri link="#doc_chap1_fig1">figure 1.1</uri>, the LCD
806     display consumes the biggest part of energy (might not be the case for
807     non-mobile CPU's). Thus it's quite important not only to shut the display off
808     when not needed, but also to reduce it's backlight if possible. Most laptops
809     offer the possibility to control the backlight dimming.
810 swift 1.1 </p>
811    
812 nightmorph 1.17 </body>
813     </section>
814     <section>
815     <title>Standby settings</title>
816     <body>
817    
818 swift 1.1 <p>
819 nightmorph 1.17 The first thing to check is the standby/suspend/off timings of the display. As
820     this depends heavily on your windowmanager, I'll let you figure it out
821 rane 1.20 yourself. Just two common places: Blanking the terminal can be done with
822 nightmorph 1.17 <c>setterm -blank &lt;number-of-minutesM&gt;</c>, <c>setterm -powersave on</c>
823     and <c>setterm -powerdown &lt;number-of-minutesM&gt;</c>. For X.org, modify
824     <path>/etc/X11/xorg.conf</path> similar to this:
825 swift 1.1 </p>
826    
827 so 1.15 <pre caption="LCD suspend settings in X.org and XFree86">
828 swift 1.1 Section "ServerLayout"
829     Identifier [...]
830     [...]
831     Option "BlankTime" "5" <comment># Blank the screen after 5 minutes (Fake)</comment>
832     Option "StandbyTime" "10" <comment># Turn off screen after 10 minutes (DPMS)</comment>
833     Option "SuspendTime" "20" <comment># Full suspend after 20 minutes</comment>
834     Option "OffTime" "30" <comment># Turn off after half an hour</comment>
835     [...]
836     EndSection
837    
838     [...]
839    
840     Section "Monitor"
841     Identifier [...]
842     Option "DPMS" "true"
843     [...]
844     EndSection
845     </pre>
846    
847     <p>
848     This is the same for XFree86 and <path>/etc/X11/XF86Config</path>.
849     </p>
850    
851 nightmorph 1.17 </body>
852     </section>
853     <section>
854     <title>Backlight dimming</title>
855     <body>
856    
857 swift 1.1 <p>
858     Probably more important is the backlight dimming. If you have access to the
859     dimming settings via a tool, write a small script that dims the backlight in
860 rane 1.19 battery mode and place it in your <c>battery</c> runlevel. The following script
861 nightmorph 1.17 should work on most IBM Thinkpads and Toshiba laptops. You've got to enable the
862 rane 1.20 appropriate option in your kernel (IBM Thinkpads only). For Toshiba laptops,
863 nightmorph 1.23 install <c>sys-power/acpitool</c> and skip configuration of <c>ibm_acpi</c> as
864 rane 1.20 described below.
865 neysx 1.12 </p>
866    
867     <warn>
868     Support for setting brightness is marked experimental in ibm-acpi. It accesses
869     hardware directly and may cause severe harm to your system. Please read the
870     <uri link="http://ibm-acpi.sourceforge.net/">ibm-acpi website</uri>
871     </warn>
872    
873     <p>
874     To be able to set the brightness level, the ibm_acpi module has to be loaded
875     with the experimental parameter.
876     </p>
877    
878     <pre caption="automatically loading the ibm_acpi module">
879     <comment>(Please read the warnings above before doing this!)</comment>
880 rane 1.19 # <i>echo "options ibm_acpi experimental=1" >> /etc/modules.d/ibm_acpi</i>
881 nightmorph 1.26 # <i>/sbin/update-modules</i>
882 rane 1.19 # <i>echo ibm_acpi >> /etc/modules.autoload.d/kernel-2.6</i>
883     # <i>modprobe ibm_acpi</i>
884 neysx 1.12 </pre>
885    
886     <p>
887     This should work without error messages and a file
888     <path>/proc/acpi/ibm/brightness</path> should be created after loading the
889 rane 1.20 module. An init script will take care of choosing the brightness according to
890     the power source.
891 neysx 1.12 </p>
892    
893     <pre caption="/etc/conf.d/lcd-brightness">
894     <comment># See /proc/acpi/ibm/brightness for available values</comment>
895 nightmorph 1.17 <comment># Please read /usr/src/linux/Documentation/ibm-acpi.txt</comment>
896 neysx 1.12
897 nightmorph 1.23 <comment># brightness level in ac mode. Default is 7.</comment>
898 neysx 1.12 BRIGHTNESS_AC=7
899    
900     <comment># brightness level in battery mode. Default is 4.</comment>
901     BRIGHTNESS_BATTERY=4
902     </pre>
903    
904     <pre caption="/etc/init.d/lcd-brightness">
905     #!/sbin/runscript
906    
907     set_brightness() {
908     if on_ac_power
909     then
910     LEVEL=${BRIGHTNESS_AC:-7}
911     else
912     LEVEL=${BRIGHTNESS_BATTERY:-4}
913     fi
914    
915     if [ -f /proc/acpi/ibm/brightness ]
916     then
917     ebegin "Setting LCD brightness"
918     echo "level ${LEVEL}" > /proc/acpi/ibm/brightness
919     eend $?
920 nightmorph 1.17 elif [[ -e /usr/bin/acpitool &amp;&amp; -n $(acpitool -T | grep "LCD brightness") ]]
921     then
922     ebegin "Setting LCD brightness"
923     acpitool -l $LEVEL >/dev/null || ewarn "Unable to set lcd brightness"
924     eend $?
925 neysx 1.12 else
926     ewarn "Setting LCD brightness is not supported."
927 nightmorph 1.17 ewarn "For IBM Thinkpads, check that ibm_acpi is loaded into the kernel"
928 nightmorph 1.23 ewarn "For Toshiba laptops, you've got to install sys-power/acpitool"
929 neysx 1.12 fi
930     }
931    
932     start() {
933     set_brightness
934     }
935    
936     stop () {
937     set_brightness
938     }
939     </pre>
940    
941     <p>
942     When done, make sure brightness is adjusted automatically by adding it to the
943     battery runlevel.
944 swift 1.1 </p>
945    
946 neysx 1.12 <pre caption="Enabling automatic brightness adjustment">
947 rane 1.19 # <i>chmod +x /etc/init.d/lcd-brightness</i>
948     # <i>rc-update add lcd-brightness battery</i>
949     # <i>rc</i>
950 neysx 1.12 </pre>
951    
952 swift 1.1 </body>
953     </section>
954     </chapter>
955    
956     <chapter>
957     <title>Disk Power Management</title>
958     <section>
959 nightmorph 1.17 <body>
960 rane 1.19
961 nightmorph 1.17 <p>
962     Hard disks consume less energy in sleep mode. Therefore it makes sense to
963     activate power saving features whenever the hard disk is not used for a certain
964     amount of time. I'll show you two alternative possibilities to do it. First,
965     laptop-mode will save most energy due to several measures which prevent or at
966     least delay write accesses. The drawback is that due to the delayed write
967     accesses a power outage or kernel crash will be more dangerous for data loss.
968     If you don't like this, you have to make sure that there are no processes which
969     write to your hard disk frequently. Afterwards you can enable power saving
970 rane 1.19 features of your hard disk with <c>hdparm</c> as the second alternative.
971 nightmorph 1.17 </p>
972    
973     </body>
974     </section>
975     <section>
976     <title>Increasing idle time - laptop-mode</title>
977 swift 1.1 <body>
978    
979     <p>
980 nightmorph 1.27 Recent 2.6 kernels include the so-called <c>laptop-mode</c>. When activated,
981     dirty buffers are written to disk on read calls or after 10 minutes (instead of
982     30 seconds). This minimizes the time the hard disk needs to be spun up.
983 swift 1.1 </p>
984    
985 nightmorph 1.17 <pre caption="Automated start of laptop-mode">
986     # <i>emerge laptop-mode-tools</i>
987     </pre>
988 swift 1.1
989 nightmorph 1.17 <p>
990     <c>laptop-mode-tools</c> has its configuration file in
991     <path>/etc/laptop-mode/laptop-mode.conf</path>. Adjust it the way you like it,
992     it's well commented. Run <c>rc-update add laptop_mode battery</c> to start it
993     automatically.
994     </p>
995    
996     <p>
997     Recent versions (1.11 and later) of laptop-mode-tools include a new tool
998     <c>lm-profiler</c>. It will monitor your system's disk usage and running
999     network services and suggests to disable unneeded ones. You can either disable
1000     them through laptop-mode-tools builtin runlevel support (which will be reverted
1001 rane 1.19 by Gentoo's <c>/sbin/rc</c>) or use your <c>default</c>/<c>battery</c>
1002 nightmorph 1.17 runlevels (recommended).
1003     </p>
1004    
1005     <pre caption="Sample output from running lm-profiler">
1006 rane 1.19 # <i>lm-profiler</i>
1007 nightmorph 1.17 Profiling session started.
1008     Time remaining: 600 seconds
1009     [4296896.602000] amarokapp
1010     Time remaining: 599 seconds
1011     [4296897.714000] sort
1012     [4296897.970000] mv
1013     Time remaining: 598 seconds
1014     Time remaining: 597 seconds
1015     [4296900.482000] reiserfs/0
1016     </pre>
1017    
1018     <p>
1019     After profiling your system for ten minutes, lm-profiler will present a list of
1020     services which might have caused disk accesses during that time.
1021     </p>
1022    
1023     <pre caption="lm-profiler suggests to disable some services">
1024     Program: "atd"
1025     Reason: standard recommendation (program may not be running)
1026     Init script: /etc/init.d/atd (GUESSED)
1027    
1028 rane 1.19 Do you want to disable this service in battery mode? [y/N]: <i>n</i>
1029 swift 1.1 </pre>
1030    
1031     <p>
1032 nightmorph 1.17 To disable atd as suggested in the example above, you would run <c>rc-update
1033     del atd battery</c>. Be careful not to disable services that are needed for
1034 rane 1.20 your system to run properly - <c>lm-profiler</c> is likely to generate some
1035     false positives. Do not disable a service if you are unsure whether it's
1036     needed.
1037 nightmorph 1.17 </p>
1038    
1039     </body>
1040     </section>
1041     <section>
1042 rane 1.19 <title>Limiting Write Accesses</title>
1043 nightmorph 1.17 <body>
1044    
1045     <p>
1046     If you don't want to use laptop-mode, you must take special care to disable
1047     services that write to your disk frequently - <c>syslogd</c> is a good
1048     candidate, for example. You probably don't want to shut it down completely, but
1049     it's possible to modify the config file so that "unnecessary" things don't get
1050 rane 1.20 logged and thus don't create disk traffic. <c>Cups</c> writes to disk
1051     periodically, so consider shutting it down and only enable it manually when
1052     needed.
1053 nightmorph 1.17 </p>
1054    
1055     <pre caption="Disabling cups in battery mode">
1056     # <i>rc-update del cupsd battery</i>
1057     </pre>
1058    
1059     <p>
1060     You can also use <c>lm-profiler</c> from laptop-mode-tools (see above) to find
1061     services to disable. Once you eliminated all of them, go on with configuring
1062     hdparm.
1063     </p>
1064    
1065     </body>
1066     </section>
1067     <section>
1068     <title>hdparm</title>
1069     <body>
1070    
1071     <p>
1072 rane 1.20 The second possibility is using a small script and <c>hdparm</c>. Skip this if
1073     you are using laptop-mode. Otherwise, create <path>/etc/init.d/pmg_hda</path>:
1074 swift 1.1 </p>
1075    
1076     <pre caption="Using hdparm for disk standby">
1077     #!/sbin/runscript
1078 neysx 1.12
1079     depend() {
1080 nightmorph 1.17 after hdparm
1081 neysx 1.12 }
1082    
1083 swift 1.1 start() {
1084 nightmorph 1.17 ebegin "Activating Power Management for Hard Drives"
1085     hdparm -q -S12 /dev/hda
1086     eend $?
1087 swift 1.1 }
1088    
1089     stop () {
1090 nightmorph 1.17 ebegin "Deactivating Power Management for Hard Drives"
1091     hdparm -q -S253 /dev/hda
1092     eend $?
1093 swift 1.1 }
1094     </pre>
1095    
1096     <p>
1097     See <c>man hdparm</c> for the options. If your script is ready, add it to the
1098     battery runlevel.
1099     </p>
1100    
1101     <pre caption="Automate disk standby settings">
1102 nightmorph 1.17 # <i>chmod +x /etc/init.d/pmg_hda</i>
1103 swift 1.1 # <i>/sbin/depscan.sh</i>
1104 nightmorph 1.17 # <i>rc-update add pmg_hda battery</i>
1105 swift 1.1 </pre>
1106    
1107     <impo>
1108     Be careful with sleep/spin down settings of your hard drive. Setting it to
1109     small values might wear out your drive and lose warranty.
1110     </impo>
1111    
1112     </body>
1113     </section>
1114     <section>
1115     <title>Other tricks</title>
1116     <body>
1117    
1118     <p>
1119     Another possibility is to deactivate swap in battery mode. Before writing a
1120     swapon/swapoff switcher, make sure there is enough RAM and swap isn't used
1121     heavily, otherwise you'll be in big problems.
1122     </p>
1123    
1124     <p>
1125     If you don't want to use laptop-mode, it's still possible to minimize disk
1126 rane 1.19 access by mounting certain directories as <c>tmpfs</c> - write accesses are not
1127 swift 1.1 stored on a disk, but in main memory and get lost with unmounting. Often it's
1128     useful to mount <path>/tmp</path> like this - you don't have to pay special
1129     attention as it gets cleared on every reboot regardless whether it was mounted
1130     on disk or in RAM. Just make sure you have enough RAM and no program (like a
1131     download client or compress utility) needs extraordinary much space in
1132     <path>/tmp</path>. To activate this, enable tmpfs support in your kernel and
1133     add a line to <path>/etc/fstab</path> like this:
1134     </p>
1135    
1136     <pre caption="Editing /etc/fstab to make /tmp even more volatile">
1137     none /tmp tmpfs size=32m 0 0
1138     </pre>
1139    
1140     <warn>
1141     Pay attention to the size parameter and modify it for your system. If you're
1142 rane 1.21 unsure, don't try this at all, it can become a performance bottleneck easily. In
1143 swift 1.1 case you want to mount <path>/var/log</path> like this, make sure to merge the
1144     log files to disk before unmounting. They are essential. Don't attempt to mount
1145 rane 1.19 <path>/var/tmp</path> like this. Portage uses it for compiling...
1146 swift 1.1 </warn>
1147    
1148     </body>
1149     </section>
1150     </chapter>
1151    
1152     <chapter>
1153 rane 1.19 <title>Power Management For Other Devices</title>
1154 swift 1.1 <section>
1155 rane 1.19 <title>Graphics Cards</title>
1156 so 1.15 <body>
1157    
1158     <p>
1159     In case you own an ATI graphics card supporting PowerPlay (dynamic clock
1160 nightmorph 1.25 scaling for the graphics processing unit GPU), you can activate this
1161 rane 1.20 feature in X.org. Open <path>/etc/X11/xorg.conf</path> and add (or enable) the
1162     <c>DynamicClocks</c> option in the Device section. Please notice that this
1163     feature will lead to crashes on some systems.
1164 so 1.15 </p>
1165    
1166     <pre caption="Enabling ATI PowerPlay support in X.org">
1167     Section "Device"
1168     [...]
1169     Option "DynamicClocks" "on"
1170     EndSection
1171     </pre>
1172    
1173     </body>
1174     </section>
1175     <section>
1176 swift 1.1 <title>Wireless Power Management</title>
1177     <body>
1178    
1179     <p>
1180 nightmorph 1.17 Wireless LAN cards consume quite a bit of energy. Put them in Power Management
1181 rane 1.19 mode in analogy to the <c>pmg_hda</c> script.
1182 swift 1.1 </p>
1183    
1184 nightmorph 1.17 <note>
1185     This script assumes your wireless interface is called <c>wlan0</c>; replace
1186     this with the actual name of your interface.
1187     </note>
1188    
1189 swift 1.1 <pre caption="WLAN Power Management automated">
1190     #!/sbin/runscript
1191     start() {
1192     ebegin "Activating Power Management for Wireless LAN"
1193 nightmorph 1.17 iwconfig wlan0 power on
1194 swift 1.1 eend $?
1195     }
1196    
1197     stop () {
1198     ebegin "Deactivating Power Management for Wireless LAN"
1199     iwconfig wlan0 power off
1200     eend $?
1201     }
1202     </pre>
1203    
1204     <p>
1205 nightmorph 1.17 Starting this script will activate power saving features for wlan0. Save it as
1206     <path>/etc/init.d/pmg_wlan0</path> and add it to the battery runlevel like the
1207     disk script above. See <c>man iwconfig</c> for details and more options like
1208     the period between wakeups or timeout settings. If your driver and access point
1209     support changing the beacon time, this is a good starting point to save even
1210     more energy.
1211 swift 1.1 </p>
1212    
1213 swift 1.8 <pre caption="Power Management for WLAN">
1214 nightmorph 1.17 # <i>chmod +x /etc/init.d/pmg_wlan0</i>
1215 swift 1.8 # <i>/sbin/depscan.sh</i>
1216 nightmorph 1.17 # <i>rc-update add pmg_wlan0 battery</i>
1217 swift 1.8 </pre>
1218    
1219 swift 1.1 </body>
1220     </section>
1221     <section>
1222     <title>USB Power Management</title>
1223     <body>
1224    
1225     <p>
1226     There are two problems with USB devices regarding energy consumption: First,
1227     devices like USB mice, digital cameras or USB sticks consume energy while
1228     plugged in. You cannot avoid this (nevertheless remove them in case they're not
1229     needed). Second, when there are USB devices plugged in, the USB host controller
1230     periodically accesses the bus which in turn prevents the CPU from going into
1231 rane 1.20 sleep mode. The kernel offers an experimental option to enable suspension of
1232 so 1.15 USB devices through driver calls or one of the <path>power/state</path> files
1233     in <path>/sys</path>.
1234 swift 1.1 </p>
1235    
1236 so 1.15 <pre caption="Enabling USB suspend support in the kernel">
1237     Device Drivers
1238     USB support
1239     [*] Support for Host-side USB
1240     [*] USB suspend/resume (EXPERIMENTAL)
1241     </pre>
1242    
1243 swift 1.1 </body>
1244     </section>
1245     </chapter>
1246    
1247     <chapter>
1248 rane 1.19 <title>Sleep States: sleep, standby, and suspend to disk</title>
1249 swift 1.1 <section>
1250     <body>
1251    
1252     <p>
1253     ACPI defines different sleep states. The more important ones are
1254     </p>
1255    
1256 rane 1.20 <ul>
1257 swift 1.1 <li>S1 aka Standby</li>
1258     <li>S3 aka Suspend to RAM aka Sleep</li>
1259     <li>S4 aka Suspend to Disk aka Hibernate</li>
1260     </ul>
1261    
1262     <p>
1263     They can be called whenever the system is not in use, but a shutdown is not
1264     wanted due to the long boot time.
1265     </p>
1266    
1267     </body>
1268     </section>
1269     <section>
1270 so 1.15 <title>Sleep (S3)</title>
1271 swift 1.1 <body>
1272    
1273     <p>
1274 so 1.15 The ACPI support for these sleep states is marked experimental for good reason.
1275     APM sleep states seem to be more stable, however you can't use APM and ACPI
1276     together.
1277     </p>
1278    
1279     <pre caption="Kernel configuration for the various suspend types">
1280     Power Management Options ---&gt;
1281     [*] Power Management support
1282     ACPI (Advanced Configuration and Power Interface) Support ---&gt;
1283     [*] ACPI Support
1284     [*] Sleep States
1285     </pre>
1286    
1287     <p>
1288 nightmorph 1.17 Once your kernel is properly configured, you can use the
1289 so 1.15 <c>hibernate-script</c> to activate suspend or sleep mode. Let's install that
1290     first.
1291     </p>
1292    
1293     <pre caption="Installing the hibernate-script">
1294 rane 1.19 # <i>emerge hibernate-script</i>
1295 so 1.15 </pre>
1296    
1297     <p>
1298 nightmorph 1.25 Some configuration has to be done in <path>/etc/hibernate</path>. The default
1299 nightmorph 1.24 package introduces a few configuration files for each sleep state. Options that
1300     are common to all suspend methods are placed in <path>common.conf</path>; make
1301     sure this file is properly set up for your system.
1302 so 1.15 </p>
1303    
1304     <p>
1305 nightmorph 1.24 To configure sleep, edit <path>sysfs-ram.conf</path> in
1306     <path>/etc/hibernate</path>. <c>UseSysfsPowerState mem</c> is already setup
1307 nightmorph 1.25 correctly, but if you need to make further changes to this particular sleep
1308     state (or any other sleep state) you should add them to
1309 nightmorph 1.24 <path>/etc/hibernate/hibernate.conf</path>. The comments and option names will
1310     guide you. If you use nfs or samba shares over the network, make sure to
1311     shutdown the appropriate init scripts to avoid timeouts.
1312 so 1.15 </p>
1313    
1314 nightmorph 1.24 <note>
1315     For more information on setting up sleep states, read <c>man
1316     hibernate.conf</c>.
1317     </note>
1318    
1319 so 1.15 <p>
1320     Ready? Now is the last chance to backup any data you want to keep after
1321     executing the next command. Notice that you probably have to hit a special key
1322 rane 1.19 like <c>Fn</c> to resume from sleep.
1323 so 1.15 </p>
1324    
1325     <pre caption="Calling sleep">
1326 rane 1.19 # <i>hibernate-ram</i>
1327 so 1.15 </pre>
1328    
1329     <p>
1330 rane 1.20 If you're still reading, it seems to work. You can also setup standby (S1) in a
1331 nightmorph 1.24 similar way by editing <path>sysfs-ram.conf</path> and changing
1332     "UseSysfsPowerState mem" to "UseSysfsPowerState standby". S3 and S4 are the more
1333     interesting sleep states due to greater energy savings however.
1334 so 1.15 </p>
1335    
1336     </body>
1337     </section>
1338     <section>
1339     <title>Hibernate (S4)</title>
1340     <body>
1341    
1342     <p>
1343     This section introduces hibernation, where a snapshot of the running system is
1344     written to disk before powering off. On resume, the snapshot is loaded and you
1345     can go on working at exactly the point you called hibernate before.
1346 swift 1.1 </p>
1347    
1348     <warn>
1349 so 1.15 Don't exchange non hot-pluggable hardware when suspended. Don't attempt to load
1350     a snapshot with a different kernel image than the one it was created with.
1351     Shutdown any NFS or samba server/client before hibernating.
1352 swift 1.1 </warn>
1353    
1354     <p>
1355 so 1.15 There are two different implementations for S4. The original one is swsusp,
1356 rane 1.20 then there is the newer suspend2 with a nicer interface (including fbsplash
1357     support). A <uri link="http://suspend2.net/features.html#compare"> feature
1358     comparison</uri> is available at the <uri link="http://suspend2.net"> suspend2
1359     Homepage</uri>. There used to be Suspend-to-Disk (pmdisk), a fork of swsusp,
1360     but it has been merged back.
1361 swift 1.1 </p>
1362    
1363     <p>
1364 so 1.15 Suspend2 is not included in the mainline kernel yet, therefore you either have
1365 rane 1.20 to patch your kernel sources with the patches provided by <uri
1366     link="http://suspend2.net">suspend2.net</uri> or use
1367 so 1.15 <c>sys-kernel/suspend2-sources</c>.
1368 swift 1.1 </p>
1369    
1370     <p>
1371 so 1.15 The kernel part for both swusp and suspend2 is as follows:
1372 swift 1.1 </p>
1373    
1374     <pre caption="Kernel configuration for the various suspend types">
1375     Power Management Options ---&gt;
1376     <comment>(hibernate with swsusp)</comment>
1377 so 1.15 [*] Software Suspend
1378     <comment>(replace /dev/SWAP with your swap partition)</comment>
1379     (/dev/SWAP) Default resume partition
1380 rane 1.20
1381 so 1.15 <comment>(hibernate with suspend2)</comment>
1382 swift 1.1 Software Suspend 2
1383     --- Image Storage (you need at least one writer)
1384 so 1.15 [*] File Writer
1385 swift 1.1 [*] Swap Writer
1386 so 1.15 --- General Options
1387 swift 1.1 [*] LZF image compression
1388 so 1.15 <comment>(replace /dev/SWAP with your swap partition)</comment>
1389     (swap:/dev/SWAP) Default resume device name
1390     [ ] Allow Keep Image Mode
1391 swift 1.1 </pre>
1392    
1393     <p>
1394 so 1.15 The configuration for swsusp is rather easy. If you didn't store the location
1395     of your swap partition in the kernel config, you can also pass it as a
1396     parameter with the <c>resume=/dev/SWAP</c> directive. If booting is not
1397     possible due to a broken image, use the <c>noresume</c> kernel parameter. The
1398 rane 1.20 <c>hibernate-cleanup</c> init script invalidates swsusp images during the boot
1399     process.
1400 swift 1.1 </p>
1401    
1402 so 1.15 <pre caption="Invalidating swsusp images during the boot process">
1403 rane 1.19 # <i>rc-update add hibernate-cleanup boot</i>
1404 so 1.15 </pre>
1405    
1406 swift 1.1 <p>
1407 so 1.15 To activate hibernate with swsusp, use the hibernate script and set
1408 nightmorph 1.24 <c>UseSysfsPowerState disk</c> in <path>/etc/hibernate/sysfs-disk</path>.
1409 swift 1.1 </p>
1410    
1411     <warn>
1412     Backup your data before doing this. Run <c>sync</c> before executing one of the
1413     commands to have cached data written to disk. First try it outside of X, then
1414     with X running, but not logged in.
1415     </warn>
1416 rane 1.20
1417 swift 1.1 <p>
1418     If you experience kernel panics due to uhci or similar, try to compile USB
1419     support as module and unload the modules before sending your laptop to sleep
1420 nightmorph 1.24 mode. There are configuration options for this in <path>common.conf</path>
1421 swift 1.1 </p>
1422    
1423 so 1.15 <pre caption="Hibernating with swsusp">
1424 nightmorph 1.24 # <i>nano -w /etc/hibernate/common.conf</i>
1425 so 1.15 <comment>(Make sure you have a backup of your data)</comment>
1426 rane 1.19 # <i>hibernate</i>
1427 so 1.15 </pre>
1428    
1429 swift 1.1 <p>
1430 so 1.15 The following section discusses the setup of suspend2 including fbsplash
1431     support for a nice graphical progress bar during suspend and resume.
1432     </p>
1433    
1434     <p>
1435 rane 1.20 The first part of the configuration is similar to the configuration of swsusp.
1436     In case you didn't store the location of your swap partition in the kernel
1437     config, you have to pass it as a kernel parameter with the
1438 so 1.15 <c>resume2=swap:/dev/SWAP</c> directive. If booting is not possible due to a
1439     broken image, append the <c>noresume2</c> parameter. Additionally, the
1440     <c>hibernate-cleanup</c> init script invalidates suspend2 images during the
1441     boot process.
1442     </p>
1443    
1444     <pre caption="Invalidating suspend2 images during the boot process">
1445 rane 1.19 # <i>rc-update add hibernate-cleanup boot</i>
1446 so 1.15 </pre>
1447    
1448 rane 1.20 <p>
1449 nightmorph 1.24 Now edit <path>/etc/hibernate/suspend2.conf</path>, enable the <c>suspend2</c>
1450     options you need. Do not enable the <c>fbsplash</c> options in
1451     <c>common.conf</c> just yet.
1452 swift 1.1 </p>
1453    
1454 so 1.15 <pre caption="Hibernating with suspend2">
1455 nightmorph 1.24 # <i>nano -w /etc/hibernate/suspend2.conf</i>
1456 so 1.15 <comment>(Make sure you have a backup of your data)</comment>
1457 rane 1.19 # <i>hibernate</i>
1458 swift 1.8 </pre>
1459    
1460 so 1.15 <p>
1461 rane 1.20 Please configure <c>fbsplash</c> now if you didn't do already. To enable
1462     fbsplash support during hibernation, the <c>sys-apps/suspend2-userui</c>
1463     package is needed. Additionally, you've got to enable the <c>fbsplash</c> USE
1464     flag.
1465 so 1.15 </p>
1466    
1467     <pre caption="Installing suspend2-userui">
1468 rane 1.19 # <i>echo "sys-apps/suspend2-userui fbsplash" >> /etc/portage/package.use</i>
1469 nightmorph 1.24 <comment>(It may be marked ~arch, so first it must be keyworded)</comment>
1470     # <i>echo "sys-apps/suspend2-userui" >> /etc/portage/package.keywords</i>
1471 rane 1.19 # <i>emerge suspend2-userui</i>
1472 so 1.15 </pre>
1473    
1474     <p>
1475     The ebuild tells you to make a symlink to the theme you want to use. For
1476     example, to use the <c>livecd-2005.1</c> theme, run the following command:
1477     </p>
1478    
1479     <pre caption="Using the livecd-2005.1 theme during hibernation">
1480 rane 1.19 # <i>ln -sfn /etc/splash/livecd-2005.1 /etc/splash/suspend2</i>
1481 so 1.15 </pre>
1482    
1483     <p>
1484     If you don't want a black screen in the first part of the resume process, you
1485     have to add the <c>suspend2ui_fbsplash</c> tool to your initrd image. Assuming
1486     you created the initrd image with <c>splash_geninitramfs</c> and saved it as
1487 rane 1.20 <path>/boot/fbsplash-emergence-1024x768</path>, here's how to do that.
1488 so 1.15 </p>
1489    
1490     <pre caption="Adding suspend2ui_fbsplash to an initrd image">
1491 rane 1.19 # <i>mount /boot</i>
1492     # <i>mkdir ~/initrd.d</i>
1493     # <i>cp /boot/fbsplash-emergence-1024x768 ~/initrd.d/</i>
1494     # <i>cd ~/initrd.d</i>
1495     # <i>gunzip -c fbsplash-emergence-1024x768 | cpio -idm --quiet -H newc</i>
1496     # <i>rm fbsplash-emergence-1024x768</i>
1497     # <i>cp /usr/sbin/suspend2ui_fbsplash sbin/</i>
1498     # <i>find . | cpio --quiet --dereference -o -H newc | gzip -9 > /boot/fbsplash-suspend2-emergence-1024x768</i>
1499 so 1.15 </pre>
1500    
1501     <p>
1502 nightmorph 1.24 Afterwards adjust <path>grub.conf</path> (or <path>lilo.conf</path>) so that
1503     your suspend2 kernel uses
1504     <path>/boot/fbsplash-suspend2-emergence-1024x768</path> as initrd image. You can
1505     now test a dry run to see if everything is setup correctly.
1506 so 1.15 </p>
1507    
1508     <pre caption="Test run for fbsplash hibernation">
1509 rane 1.19 # <i>suspend2ui_fbsplash -t</i>
1510 so 1.15 </pre>
1511    
1512     <p>
1513 nightmorph 1.24 Afterwards open <path>/etc/hibernate/common.conf</path> and activate the
1514     fbsplash options. Execute <c>hibernate</c> and enjoy.
1515 so 1.15 </p>
1516    
1517 swift 1.1 </body>
1518     </section>
1519     </chapter>
1520    
1521     <chapter>
1522     <title>Troubleshooting</title>
1523     <section>
1524     <body>
1525    
1526     <p>
1527     <e>Q:</e> I'm trying to change the CPU frequency, but
1528     <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor</path> does not
1529     exist.
1530     </p>
1531    
1532     <p>
1533     <e>A:</e> Make sure your processor supports CPU frequency scaling and you chose
1534     the right CPUFreq driver for your processor. Here is a list of processors that
1535     are supported by cpufreq (kernel 2.6.7): ARM Integrator, ARM-SA1100,
1536     ARM-SA1110, AMD Elan - SC400, SC410, AMD mobile K6-2+, AMD mobile K6-3+, AMD
1537     mobile Duron, AMD mobile Athlon, AMD Opteron, AMD Athlon 64, Cyrix Media GXm,
1538     Intel mobile PIII and Intel mobile PIII-M on certain chipsets, Intel Pentium 4,
1539     Intel Xeon, Intel Pentium M (Centrino), National Semiconductors Geode GX,
1540     Transmeta Crusoe, VIA Cyrix 3 / C3, UltraSPARC-III, SuperH SH-3, SH-4, several
1541     "PowerBook" and "iBook2" and various processors on some ACPI 2.0-compatible
1542     systems (only if "ACPI Processor Performance States" are available to the
1543     ACPI/BIOS interface).
1544     </p>
1545    
1546     <p>
1547     <e>Q:</e> My laptop supports frequency scaling, but
1548     <path>/sys/devices/system/cpu/cpu0/cpufreq/</path> is empty.
1549     </p>
1550    
1551     <p>
1552     <e>A:</e> Look for ACPI related error messages with <c>dmesg | grep ACPI</c>.
1553     Try to update the BIOS, especially if a broken DSDT is reported. You can also
1554     try to fix it yourself (which is beyond the scope of this guide).
1555     </p>
1556    
1557     <p>
1558 rane 1.19 <e>Q:</e> My laptop supports frequency scaling, but according to
1559     <path>/proc/cpuinfo</path> the speed never changes.
1560 swift 1.1 </p>
1561    
1562     <p>
1563 swift 1.8 <e>A:</e> Probably you have activated symmetric multiprocessing support
1564     (CONFIG_SMP) in your kernel. Deactivate it and it should work. Some older
1565 rane 1.20 kernels had a bug causing this. In that case, run <c>emerge x86info</c>, update
1566     your kernel as asked and check the current frequency with
1567 swift 1.8 <c>x86info -mhz</c>.
1568 swift 1.1 </p>
1569    
1570     <p>
1571     <e>Q:</e> I can change the CPU frequency, but the range is not as wide as in
1572     another OS.
1573     </p>
1574    
1575     <p>
1576     <e>A:</e> You can combine frequency scaling with ACPI throttling to get a lower
1577     minimum frequency. Notice that throttling doesn't save much energy and is
1578     mainly used for thermal management (keeping your laptop cool and quiet). You
1579     can read the current throttling state with <c>cat
1580     /proc/acpi/processor/CPU/throttling</c> and change it with <c>echo -n "0:x" >
1581     /proc/acpi/processor/CPU/limit</c>, where x is one of the Tx states listed in
1582     <path>/proc/acpi/processor/CPU/throttling</path>.
1583     </p>
1584    
1585     <p>
1586 swift 1.8 <e>Q:</e> When configuring the kernel, powersave, performance and userspace
1587     governors show up, but that ondemand thing is missing. Where do I get it?
1588     </p>
1589    
1590     <p>
1591     <e>A:</e> The ondemand governor is only included in recent kernel sources. Try
1592     updating them.
1593     </p>
1594    
1595     <p>
1596 swift 1.1 <e>Q:</e> Battery life time seems to be worse than before.
1597     </p>
1598    
1599     <p>
1600     <e>A:</e> Check your BIOS settings. Maybe you forgot to re-enable some of the
1601     settings.
1602     </p>
1603    
1604     <p>
1605     <e>Q:</e> My battery is charged, but KDE reports there would be 0% left and
1606     immediately shuts down.
1607     </p>
1608    
1609     <p>
1610     <e>A:</e> Check that battery support is compiled into your kernel. If you use
1611     it as a module, make sure the module is loaded.
1612     </p>
1613    
1614     <p>
1615 rane 1.20 <e>Q:</e> My system logger reports things like "logger: ACPI group battery /
1616     action battery is not defined".
1617 nightmorph 1.17 </p>
1618    
1619     <p>
1620 rane 1.20 <e>A:</e> This message is generated by the <path>/etc/acpi/default.sh</path>
1621     script that is shipped with acpid. You can safely ignore it. If you like to get
1622     rid of it, you can comment the appropriate line in
1623     <path>/etc/acpi/default.sh</path> as shown below:
1624 nightmorph 1.17 </p>
1625    
1626     <pre caption="Disabling warnings about unknown acpi events">
1627     *) # logger "ACPI action $action is not defined"
1628     </pre>
1629    
1630     <p>
1631 swift 1.1 <e>Q:</e> I have a Dell Inspiron 51XX and I don't get any ACPI events.
1632     </p>
1633    
1634     <p>
1635     <e>A:</e> This seems to be a kernel bug. Read on <uri
1636     link="http://bugme.osdl.org/show_bug.cgi?id=1752">here</uri>.
1637     </p>
1638    
1639     <p>
1640 rane 1.20 <e>Q:</e> I activated the <c>DynamicClocks</c> option in <path>xorg.conf</path>
1641     and now X.org crashes / the screen stays black / my laptop doesn't shutdown
1642 so 1.15 properly.
1643     </p>
1644    
1645     <p>
1646 rane 1.20 <e>A:</e> This happens on some systems. You have to disable
1647     <c>DynamicClocks</c>.
1648 so 1.15 </p>
1649    
1650     <p>
1651     <e>Q:</e> I want to use suspend2, but it tells me my swap partition is too
1652     small. Resizing is not an option.
1653     </p>
1654    
1655     <p>
1656 rane 1.20 <e>A:</e> If there is enough free space on your system, you can use the
1657 so 1.15 filewriter instead of the swapwriter. The <c>hibernate-script</c> supports it
1658     as well. More information can be found in
1659     <path>/usr/src/linux/Documentation/power/suspend2.txt</path>.
1660     </p>
1661    
1662     <p>
1663 swift 1.1 <e>Q:</e> I just bought a brand new battery, but it only lasts for some
1664     minutes! What am I doing wrong?
1665     </p>
1666    
1667     <p>
1668     <e>A:</e> First follow your manufacturer's advice on how to charge the battery
1669 rane 1.20 correctly.
1670 swift 1.1 </p>
1671    
1672     <p>
1673     <e>Q:</e> The above didn't help. What should I do then?
1674     </p>
1675    
1676     <p>
1677     <e>A:</e> Some batteries sold as "new" are in fact old ones. Try the following:
1678     </p>
1679    
1680     <pre caption="Querying battery state">
1681     $ <i>grep capacity /proc/acpi/battery/BAT0/info</i>
1682     design capacity: 47520 mWh
1683     last full capacity: 41830 mWh
1684     </pre>
1685    
1686     <p>
1687     If the "last full capacity" differs significantly from the design capacity,
1688     your battery is probably broken. Try to claim your warranty.
1689     </p>
1690    
1691 swift 1.8 <p>
1692     <e>Q:</e> My problem is not listed above. Where should I go next?
1693     </p>
1694    
1695     <p>
1696 nightmorph 1.17 <e>A:</e> Don't fear to contact me, <mail link="earthwings@gentoo.org">Dennis
1697 rane 1.20 Nienhüser</mail>, directly. The <uri link="http://forums.gentoo.org">Gentoo
1698     Forums</uri> are a good place to get help as well. If you prefer IRC, try the
1699     <c>#gentoo-laptop</c> channel at <uri
1700     link="irc://irc.freenode.net">irc.freenode.net</uri>.
1701 swift 1.8 </p>
1702    
1703 swift 1.1 </body>
1704     </section>
1705     </chapter>
1706     </guide>

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