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1 swift 1.1 <?xml version='1.0' encoding="UTF-8"?>
2     <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3 swift 1.36 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/power-management-guide.xml,v 1.35 2008/01/31 23:38:05 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 1.35 <version>1.39</version>
27     <date>2008-01-31</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 jkt 1.33 <c>gentoo-sources</c> or <c>tuxonice-sources</c>. The latter contains patches
158 jkt 1.34 for TuxOnIce, see the chapter about <uri link="#doc_chap7">sleep states</uri>
159     for more details. When configuring the kernel, activate at least these options:
160 swift 1.1 </p>
161    
162     <pre caption="Minimum kernel setup for Power Management (Kernel 2.6)">
163     Power Management Options ---&gt;
164     [*] Power Management Support
165     [ ] Software Suspend
166    
167     ACPI( Advanced Configuration and Power Interface ) Support ---&gt;
168     [*] ACPI Support
169     [ ] Sleep States
170 so 1.15 [ ] /proc/acpi/sleep (deprecated)
171 neysx 1.12 [*] AC Adapter
172     [*] Battery
173 swift 1.1 &lt;M&gt; Button
174 so 1.15 &lt;M&gt; Video
175     [ ] Generic Hotkey
176 swift 1.1 &lt;M&gt; Fan
177     &lt;M&gt; Processor
178     &lt;M&gt; Thermal Zone
179     &lt; &gt; ASUS/Medion Laptop Extras
180 so 1.15 &lt; &gt; IBM ThinkPad Laptop Extras
181 swift 1.1 &lt; &gt; Toshiba Laptop Extras
182 so 1.15 (0) Disable ACPI for systems before Jan 1st this year
183 swift 1.1 [ ] Debug Statements
184 so 1.15 [*] Power Management Timer Support
185     &lt; &gt; ACPI0004,PNP0A05 and PNP0A06 Container Driver (EXPERIMENTAL)
186 rane 1.20
187 swift 1.1 CPU Frequency Scaling ---&gt;
188     [*] CPU Frequency scaling
189 so 1.15 [ ] Enable CPUfreq debugging
190     &lt; &gt; CPU frequency translation statistics
191     [ ] CPU frequency translation statistics details
192 swift 1.1 Default CPUFreq governor (userspace)
193     &lt;*&gt; 'performance' governor
194     &lt;*&gt; 'powersave' governor
195 swift 1.8 &lt;*&gt; 'ondemand' cpufreq policy governor
196 so 1.15 &lt;*&gt; 'conservative' cpufreq governor
197 swift 1.1 &lt;*&gt; CPU frequency table helpers
198     &lt;M&gt; ACPI Processor P-States driver
199     &lt;*&gt; <i>CPUFreq driver for your processor</i>
200     </pre>
201    
202     <p>
203 so 1.15 Decide yourself whether you want to enable Software Suspend, and Sleep States
204     (see below). If you own an ASUS, Medion, IBM Thinkpad or Toshiba laptop, enable
205 neysx 1.12 the appropriate section.
206 swift 1.8 </p>
207    
208     <p>
209 rane 1.20 The kernel has to know how to enable CPU frequency scaling on your processor.
210     As each type of CPU has a different interface, you've got to choose the right
211 rane 1.19 driver for your processor. Be careful here - enabling <c>Intel Pentium 4 clock
212     modulation</c> on a Pentium M system will lead to strange results for example.
213 swift 1.8 Consult the kernel documentation if you're unsure which one to take.
214 swift 1.1 </p>
215    
216     <p>
217     Compile your kernel, make sure the right modules get loaded at startup and boot
218 rane 1.20 into your new ACPI-enabled kernel. Next run <c>emerge sys-power/acpid</c> to
219     get the acpi daemon. This one informs you about events like switching from AC
220     to battery or closing the lid. Make sure the modules are loaded if you didn't
221     compile them into the kernel and start acpid by executing <c>/etc/init.d/acpid
222     start</c>. Run <c>rc-update add acpid default</c> to load it on startup. You'll
223     soon see how to use it.
224 swift 1.1 </p>
225    
226     <pre caption="Installing acpid">
227 yoswink 1.10 # <i>emerge sys-power/acpid</i>
228 swift 1.1 # <i>/etc/init.d/acpid start</i>
229     # <i>rc-update add acpid default</i>
230     </pre>
231    
232     </body>
233     </section>
234     <section>
235 rane 1.19 <title>Creating A "battery" Runlevel</title>
236 swift 1.1 <body>
237    
238     <p>
239     The default policy will be to enable Power Management only when needed -
240     running on batteries. To make the switch between AC and battery convenient,
241 rane 1.19 create a runlevel <c>battery</c> that holds all the scripts starting and
242 swift 1.1 stopping Power Management.
243     </p>
244    
245     <note>
246     You can safely skip this section if you don't like the idea of having another
247     runlevel. However, skipping this step will make the rest a bit trickier to set
248 rane 1.19 up. The next sections assume a runlevel <c>battery</c> exists.
249 swift 1.1 </note>
250    
251     <pre caption="Creating a battery runlevel">
252     # <i>cd /etc/runlevels</i>
253     # <i>cp -a default battery</i>
254     </pre>
255    
256     <p>
257 rane 1.19 Finished. Your new runlevel <c>battery</c> contains everything like
258     <c>default</c>, but there is no automatic switch between both yet. Time to
259 swift 1.1 change it.
260     </p>
261    
262     </body>
263     </section>
264     <section>
265 rane 1.19 <title>Reacting On ACPI Events</title>
266 swift 1.1 <body>
267    
268     <p>
269     Typical ACPI events are closing the lid, changing the power source or pressing
270 swift 1.8 the sleep button. An important event is changing the power source, which should
271 so 1.15 cause a runlevel switch. A small script will take care of it.
272     </p>
273    
274     <p>
275     First you need a script which changes the runlevel to <c>default</c>
276     respectively <c>battery</c> depending on the power source. The script uses the
277     <c>on_ac_power</c> command from <c>sys-power/powermgmt-base</c> - make sure the
278     package is installed on your system.
279     </p>
280    
281     <pre caption="Installing powermgt-base">
282 rane 1.19 # <i>emerge powermgmt-base</i>
283 so 1.15 </pre>
284    
285     <p>
286 rane 1.20 You are now able to determine the power source by executing <c>on_ac_power
287     &amp;&amp; echo AC available || echo Running on batteries</c> in a shell. The
288     script below is responsible for changing runlevels. Save it as
289 so 1.15 <path>/etc/acpi/actions/pmg_switch_runlevel.sh</path>.
290 swift 1.8 </p>
291    
292 neysx 1.12 <pre caption="/etc/acpi/actions/pmg_switch_runlevel.sh">
293 swift 1.8 #!/bin/bash
294    
295 neysx 1.12 <comment># BEGIN configuration</comment>
296 swift 1.8 RUNLEVEL_AC="default"
297     RUNLEVEL_BATTERY="battery"
298 neysx 1.12 <comment># END configuration</comment>
299 swift 1.8
300 swift 1.1
301 neysx 1.12 if [ ! -d "/etc/runlevels/${RUNLEVEL_AC}" ]
302     then
303 nightmorph 1.17 logger "${0}: Runlevel ${RUNLEVEL_AC} does not exist. Aborting."
304     exit 1
305 neysx 1.12 fi
306 swift 1.8
307 neysx 1.12 if [ ! -d "/etc/runlevels/${RUNLEVEL_BATTERY}" ]
308     then
309 nightmorph 1.17 logger "${0}: Runlevel ${RUNLEVEL_BATTERY} does not exist. Aborting."
310     exit 1
311 neysx 1.12 fi
312 swift 1.1
313 neysx 1.12 if on_ac_power
314     then
315 rane 1.19 if [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_AC}" ]]
316 nightmorph 1.17 then
317     logger "Switching to ${RUNLEVEL_AC} runlevel"
318     /sbin/rc ${RUNLEVEL_AC}
319     fi
320 rane 1.19 elif [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_BATTERY}" ]]
321 neysx 1.12 then
322 nightmorph 1.17 logger "Switching to ${RUNLEVEL_BATTERY} runlevel"
323     /sbin/rc ${RUNLEVEL_BATTERY}
324 neysx 1.12 fi
325 swift 1.8 </pre>
326    
327 so 1.15 <p>
328     Dont forget to run <c>chmod +x /etc/acpi/actions/pmg_switch_runlevel.sh</c> to
329     make the script executable. The last thing that needs to be done is calling the
330     script whenever the power source changes. That's done by catching ACPI events
331     with the help of <c>acpid</c>. First you need to know which events are
332     generated when the power source changes. The events are called
333 rane 1.19 <c>ac_adapter</c> and <c>battery</c> on most laptops, but it might be different
334 so 1.15 on yours.
335     </p>
336    
337     <pre caption="Determining ACPI events for changing the power source">
338 swift 1.32 # <i>tail -f /var/log/messages | grep "received event"</i>
339 so 1.15 </pre>
340    
341     <p>
342 rane 1.20 Run the command above and pull the power cable. You should see something like
343     this:
344 so 1.15 </p>
345    
346     <pre caption="Sample output for power source changes">
347     [Tue Sep 20 17:39:06 2005] received event "ac_adapter AC 00000080 00000000"
348     [Tue Sep 20 17:39:06 2005] received event "battery BAT0 00000080 00000001"
349     </pre>
350    
351     <p>
352 rane 1.19 The interesting part is the quoted string after <c>received event</c>. It will
353 so 1.15 be matched by the event line in the files you are going to create below. Don't
354     worry if your system generates multiple events or always the same. As long as
355     any event is generated, runlevel changing will work.
356     </p>
357    
358 swift 1.8 <pre caption="/etc/acpi/events/pmg_ac_adapter">
359 neysx 1.12 <comment># replace "ac_adapter" below with the event generated on your laptop</comment>
360 so 1.15 <comment># For example, ac_adapter.* will match ac_adapter AC 00000080 00000000</comment>
361 swift 1.8 event=ac_adapter.*
362 neysx 1.12 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
363 swift 1.8 </pre>
364    
365     <pre caption="/etc/acpi/events/pmg_battery">
366 neysx 1.12 <comment># replace "battery" below with the event generated on your laptop</comment>
367 so 1.15 <comment># For example, battery.* will match battery BAT0 00000080 00000001</comment>
368 swift 1.8 event=battery.*
369 neysx 1.12 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
370 swift 1.8 </pre>
371 swift 1.1
372 swift 1.8 <p>
373 so 1.15 Finally acpid has to be restarted to recognize the changes.
374 swift 1.8 </p>
375 swift 1.1
376 swift 1.8 <pre caption="Finishing runlevel switching with acpid">
377 rane 1.19 # <i>/etc/init.d/acpid restart</i>
378 swift 1.1 </pre>
379    
380     <p>
381     Give it a try: Plug AC in and out and watch syslog for the "Switching to AC
382 rane 1.20 mode" or "Switching to battery mode" messages. See the <uri
383     link="#doc_chap8">Troubleshooting section</uri> if the script is not able to
384     detect the power source correctly.
385 swift 1.1 </p>
386    
387     <p>
388     Due to the nature of the event mechanism, your laptop will boot into runlevel
389 rane 1.19 <c>default</c> regardless of the AC/battery state. This is fine when running
390 rane 1.20 from AC, but we'd like to boot into the battery runlevel otherwise. One
391     solution would be to add another entry to the boot loader with the parameter
392 so 1.15 <c>softlevel=battery</c>, but it's likely to forget choosing it. A better way
393 rane 1.20 is faking an ACPI event in the end of the boot process and letting
394     <path>pmg_switch_runlevel.sh</path> script decide whether a runlevel change is
395     necessary. Open <path>/etc/conf.d/local.start</path> in your favourite editor
396     and add these lines:
397 swift 1.1 </p>
398    
399 so 1.15 <pre caption="Runlevel adjustment at boot time by editing local.start">
400 swift 1.1 <comment># Fake acpi event to switch runlevel if running on batteries</comment>
401 neysx 1.12 /etc/acpi/actions/pmg_switch_runlevel.sh "battery/battery"
402 swift 1.1 </pre>
403    
404     <p>
405 rane 1.20 Prepared like this you can activate Power Management policies for individual
406 swift 1.1 devices.
407     </p>
408    
409     </body>
410     </section>
411     </chapter>
412    
413     <chapter>
414     <title>CPU Power Management</title>
415     <section>
416 nightmorph 1.17 <body>
417    
418     <p>
419     Mobile processors can operate at different frequencies. Some allow changing
420     voltage as well. Most of the time your CPU doesn't need to run at full speed
421     and scaling it down will save much energy - often without any performance
422     decrease.
423     </p>
424    
425     </body>
426     </section>
427     <section>
428 rane 1.19 <title>Some Technical Terms</title>
429 swift 1.8 <body>
430    
431     <p>
432     CPU frequency scaling brings up some technical terms that might be unknown to
433     you. Here's a quick introduction.
434     </p>
435    
436     <p>
437 so 1.15 First of all, the kernel has to be able to change the processor's frequency.
438 rane 1.19 The <b>CPUfreq processor driver</b> knows the commands to do it on your CPU.
439 rane 1.20 Thus it's important to choose the right one in your kernel. You should already
440     have done it above. Once the kernel knows how to change frequencies, it has to
441     know which frequency it should set. This is done according to the <b>policy</b>
442     which consists of a <b>CPUfreq policy</b> and a <b>governor</b>. A CPUfreq
443     policy are just two numbers which define a range the frequency has to stay
444     between - minimal and maximal frequency. The governor now decides which of the
445     available frequencies in between minimal and maximal frequency to choose. For
446     example, the <b>powersave governor</b> always chooses the lowest frequency
447     available, the <b>performance governor</b> the highest one. The <b>userspace
448     governor</b> makes no decision but chooses whatever the user (or a program in
449     userspace) wants - which means it reads the frequency from
450 swift 1.8 <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed</path>.
451     </p>
452    
453     <p>
454     This doesn't sound like dynamic frequency changes yet and in fact it isn't.
455 rane 1.20 Dynamics however can be accomplished with various approaches. For example, the
456     <b>ondemand governor</b> makes its decisions depending on the current CPU load.
457     The same is done by various userland tools like <c>cpudyn</c>, <c>cpufreqd</c>,
458     <c>powernowd</c> and many more. ACPI events can be used to enable or disable
459     dynamic frequency changes depending on power source.
460 swift 1.8 </p>
461    
462     </body>
463     </section>
464     <section>
465 rane 1.19 <title>Setting The Frequency Manually</title>
466 swift 1.1 <body>
467    
468     <p>
469     Decreasing CPU speed and voltage has two advantages: On the one hand less
470     energy is consumed, on the other hand there is thermal improvement as your
471     system doesn't get as hot as running on full speed. The main disadvantage is
472     obviously the loss of performance. Decreasing processor speed is a trade off
473     between performance loss and energy saving.
474     </p>
475    
476     <note>
477     Not every laptop supports frequency scaling. If unsure, have a look at the list
478 rane 1.19 of supported processors in the <uri link="#doc_chap8">Troubleshooting</uri>
479     section to verify yours is supported.
480 swift 1.1 </note>
481    
482     <p>
483 neysx 1.12 It's time to test whether CPU frequency changing works. Let's install another
484     tool which is very handy for debugging purposes: <c>sys-power/cpufrequtils</c>
485 swift 1.1 </p>
486    
487 neysx 1.12 <pre caption="Checking CPU frequency">
488     # <i>emerge cpufrequtils</i>
489     # <i>cpufreq-info</i>
490 swift 1.1 </pre>
491    
492     <p>
493 neysx 1.12 Here is an example output:
494 swift 1.1 </p>
495    
496 neysx 1.12 <pre caption="Sample output from cpufreq-info">
497 so 1.15 cpufrequtils 0.3: cpufreq-info (C) Dominik Brodowski 2004
498 neysx 1.12 Report errors and bugs to linux@brodo.de, please.
499     analyzing CPU 0:
500     driver: centrino
501     CPUs which need to switch frequency at the same time: 0
502     hardware limits: 600 MHz - 1.40 GHz
503     available frequency steps: 600 MHz, 800 MHz, 1000 MHz, 1.20 GHz, 1.40 GHz
504 so 1.15 available cpufreq governors: conservative, ondemand, powersave, userspace, performance
505 neysx 1.12 current policy: frequency should be within 924 MHz and 1.40 GHz.
506     The governor "performance" may decide which speed to use
507     within this range.
508 so 1.15 current CPU frequency is 1.40 GHz.
509 neysx 1.12 </pre>
510    
511 swift 1.1 <p>
512 neysx 1.12 Now play around with <c>cpufreq-set</c> to make sure frequency switching works.
513     Run <c>cpufreq-set -g ondemand</c> for example to activate the ondemand
514     governor and verify the change with <c>cpufreq-info</c>. If it doesn't work as
515 rane 1.20 expected, you might find help in the <uri link="#doc_chap8">Troubleshooting
516     section</uri> in the end of this guide.
517 swift 1.1 </p>
518    
519     </body>
520     </section>
521     <section>
522     <title>Automated frequency adaption</title>
523     <body>
524    
525     <p>
526     The above is quite nice, but not doable in daily life. Better let your system
527 so 1.15 set the appropriate frequency automatically. There are many different
528     approaches to do this. The following table gives a quick overview to help you
529 rane 1.21 decide on one of them. It's roughly separated in three categories <b>kernel</b>
530 rane 1.20 for approaches that only need kernel support, <b>daemon</b> for programs that
531     run in the background and <b>graphical</b> for programs that provide a GUI for
532     easy configuration and changes.
533 swift 1.1 </p>
534    
535     <table>
536     <tr>
537     <th>Name</th>
538 swift 1.8 <th>Category</th>
539     <th>Switch decision</th>
540     <th>Kernel governors</th>
541     <th>Further governors</th>
542     <th>Comments</th>
543     </tr>
544     <tr>
545     <ti>'ondemand' governor</ti>
546     <ti>Kernel</ti>
547     <ti>CPU load</ti>
548     <ti>N.A.</ti>
549     <ti>N.A.</ti>
550     <ti>
551 so 1.15 Chooses maximal frequency on CPU load and slowly steps down when the CPU is
552     idle. Further tuning through files in
553 swift 1.8 <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
554     userland tools (programs, scripts) if governor switching or similar is
555     desired.
556     </ti>
557 swift 1.1 </tr>
558     <tr>
559 so 1.15 <ti>'conservative' governor</ti>
560     <ti>Kernel</ti>
561     <ti>CPU load</ti>
562     <ti>N.A.</ti>
563     <ti>N.A.</ti>
564     <ti>
565 neysx 1.16 Unlike the ondemand governor, conversative doesn't jump to maximum
566     frequency when CPU load is high, but increases the frequency step by step.
567     Further tuning through files in
568     <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
569     userland tools (programs, scripts) if governor switching or similar is
570     desired.
571 so 1.15 </ti>
572     </tr>
573     <tr>
574 swift 1.1 <ti><uri link="http://mnm.uib.es/~gallir/cpudyn/">cpudyn</uri></ti>
575 swift 1.8 <ti>Daemon</ti>
576     <ti>CPU load</ti>
577 neysx 1.12 <ti>Performance, powersave</ti>
578 swift 1.8 <ti>Dynamic</ti>
579     <ti>
580     Also supports disk standby - notice however that <e>laptop mode</e> in most
581     cases will do a better job.
582     </ti>
583 swift 1.1 </tr>
584     <tr>
585 swift 1.8 <ti><uri link="http://sourceforge.net/projects/cpufreqd/">cpufreqd</uri></ti>
586     <ti>Daemon</ti>
587 nightmorph 1.17 <ti>Battery state, CPU load, temperature, running programs and more</ti>
588 swift 1.8 <ti>All available</ti>
589     <ti>None</ti>
590     <ti>
591 nightmorph 1.17 Sophisticated (but somewhat complicated) setup. Extendible through plugins
592     like sensor monitoring (lm_sensors) or coordinating some NVidia based
593     graphics card memory and core. Cpufreqd is SMP aware and can optionally be
594     controlled manually at runtime.
595 swift 1.8 </ti>
596     </tr>
597     <tr>
598     <ti>
599     <uri link="http://www.deater.net/john/powernowd.html">powernowd</uri>
600     </ti>
601     <ti>Daemon</ti>
602     <ti>CPU load</ti>
603     <ti>None</ti>
604     <ti>Passive, sine, aggressive</ti>
605     <ti>
606     Supports SMP.
607     </ti>
608 swift 1.1 </tr>
609     <tr>
610 nightmorph 1.31 <ti>
611     <uri
612     link="http://projects.simpledesigns.com.pl/project/ncpufreqd/">ncpufreqd</uri>
613     </ti>
614 so 1.15 <ti>Daemon</ti>
615     <ti>Temperature</ti>
616     <ti>None</ti>
617     <ti>Powersave, performance</ti>
618     <ti>
619     Toggles the used governor between performance and powersave depending on
620     system temperature. Very useful on laptops with notorious heat problems.
621     </ti>
622     </tr>
623     <tr>
624 swift 1.1 <ti><uri link="http://www.goop.org/~jeremy/speedfreq/">speedfreq</uri></ti>
625 swift 1.8 <ti>Daemon</ti>
626     <ti>CPU load</ti>
627     <ti>None</ti>
628     <ti>Dynamic, powersave, performance, fixed speed</ti>
629     <ti>
630 so 1.15 Easy to configure with a nice client/server interface. Requires a 2.6
631     kernel. Unmaintained, broken and thus removed from Portage. Please switch
632     to cpufreqd if you're still using it.
633 swift 1.8 </ti>
634     </tr>
635     <tr>
636     <ti><uri link="http://cpuspeedy.sourceforge.net/">gtk-cpuspeedy</uri></ti>
637     <ti>Graphical</ti>
638     <ti>None</ti>
639     <ti>None</ti>
640     <ti>None</ti>
641 swift 1.1 <ti>
642 swift 1.8 Gnome application, a graphical tool to set CPU frequency manually. It does
643 neysx 1.12 not offer any automation.
644 swift 1.1 </ti>
645     </tr>
646     <tr>
647 swift 1.8 <ti>klaptopdaemon</ti>
648     <ti>Graphical</ti>
649     <ti>Battery state</ti>
650     <ti>All available</ti>
651     <ti>None</ti>
652     <ti>
653     KDE only, 'ondemand' governor required for dynamic frequency scaling.
654     </ti>
655 swift 1.1 </tr>
656     </table>
657    
658     <p>
659 so 1.15 While adjusting the frequency to the current load looks simple at a first
660     glance, it's not such a trivial task. A bad algorithm can cause switching
661     between two frequencies all the time or wasting energy when setting frequency
662 rane 1.20 to an unnecessary high level.
663 swift 1.1 </p>
664    
665     <p>
666 neysx 1.12 Which one to choose? If you have no idea about it, try <c>cpufreqd</c>:
667 swift 1.1 </p>
668    
669     <pre caption="Installing cpufreqd">
670     # <i>emerge cpufreqd</i>
671     </pre>
672    
673     <p>
674 neysx 1.12 <c>cpufreqd</c> can be configured by editing <path>/etc/cpufreqd.conf</path>.
675     The default one that ships with cpufreqd may look a bit confusing. I recommend
676 nightmorph 1.22 replacing it with the one from former Gentoo developer Henrik Brix Andersen
677     (see below). Please notice that you need cpufreqd-2.0.0 or later. Earlier
678     versions have a different syntax for the config file.
679 swift 1.1 </p>
680    
681 nightmorph 1.17 <pre caption="/etc/cpufreqd.conf (cpufreqd-2.0.0 and later)">
682 swift 1.1 [General]
683     pidfile=/var/run/cpufreqd.pid
684 nightmorph 1.17 poll_interval=3
685     enable_plugins=acpi_ac, acpi_battery
686 nightmorph 1.18 enable_remote=1
687     remote_group=wheel
688 neysx 1.12 verbosity=5
689 nightmorph 1.17 [/General]
690 swift 1.1
691     [Profile]
692 neysx 1.12 name=ondemand
693     minfreq=0%
694     maxfreq=100%
695     policy=ondemand
696 nightmorph 1.17 [/Profile]
697 swift 1.1
698     [Profile]
699 so 1.15 name=conservative
700     minfreq=0%
701     maxfreq=100%
702     policy=conservative
703 nightmorph 1.17 [/Profile]
704 so 1.15
705     [Profile]
706 neysx 1.12 name=powersave
707     minfreq=0%
708     maxfreq=100%
709 swift 1.1 policy=powersave
710 nightmorph 1.17 [/Profile]
711 swift 1.1
712     [Profile]
713 neysx 1.12 name=performance
714     minfreq=0%
715     maxfreq=100%
716     policy=performance
717 nightmorph 1.17 [/Profile]
718 swift 1.1
719     [Rule]
720 neysx 1.12 name=battery
721     ac=off
722 so 1.15 profile=conservative
723 nightmorph 1.17 [/Rule]
724 swift 1.1
725     [Rule]
726 neysx 1.12 name=battery_low
727 swift 1.1 ac=off
728 neysx 1.12 battery_interval=0-10
729     profile=powersave
730 nightmorph 1.17 [/Rule]
731 swift 1.1
732     [Rule]
733 neysx 1.12 name=ac
734     ac=on
735 so 1.15 profile=ondemand
736 nightmorph 1.17 [/Rule]
737 neysx 1.12 </pre>
738    
739     <p>
740 rane 1.19 Now you can start the cpufreqd daemon. Add it to the <c>default</c> and
741     <c>battery</c> runlevel as well.
742 swift 1.1 </p>
743    
744 neysx 1.12 <pre caption="Starting cpufreqd">
745     # <i>rc-update add cpufreqd default battery</i>
746     # <i>rc</i>
747     </pre>
748    
749 nightmorph 1.17 <p>
750     Sometimes it can be desirable to select another policy than the daemon chooses,
751     for example when battery power is low, but you know that AC will be available
752 rane 1.20 soon. In that case you can turn on cpufreqd's manual mode with <c>cpufreqd-set
753     manual</c> and select one of your configured policies (as listed by
754     <c>cpufreqd-get</c>). You can leave manual mode by executing <c>cpufreqd-set
755     dynamic</c>.
756 nightmorph 1.17 </p>
757    
758 neysx 1.12 <warn>
759     Do not run more than one of the above programs at the same time. It may cause
760     confusion like switching between two frequencies all the time.
761     </warn>
762    
763 swift 1.8 </body>
764     </section>
765     <section>
766     <title>Verifying the result</title>
767     <body>
768    
769 swift 1.1 <p>
770     The last thing to check is that your new policies do a good job. An easy way to
771 swift 1.8 do so is monitoring CPU speed while working with your laptop:
772 swift 1.1 </p>
773    
774     <pre caption="Monitoring CPU speed">
775 yoswink 1.13 # <i>watch grep \"cpu MHz\" /proc/cpuinfo</i>
776 swift 1.1 </pre>
777    
778     <p>
779 rane 1.20 If <path>/proc/cpuinfo</path> doesn't get updated (see <uri
780 swift 1.32 link="#doc_chap8">Troubleshooting</uri>), monitor the CPU frequency with
781     <c>sys-apps/x86info</c>:
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 nightmorph 1.35 <pre caption="LCD suspend settings in X.org">
828     Section "ServerFlags"
829     Option "blank time" "5" <comment># Blank the screen after 5 minutes (Fake)</comment>
830     Option "standby time" "10" <comment># Turn off screen after 10 minutes (DPMS)</comment>
831     Option "suspend time" "20" <comment># Full suspend after 20 minutes</comment>
832     Option "off time" "30" <comment># Turn off after half an hour</comment>
833 swift 1.1 [...]
834     EndSection
835    
836     [...]
837    
838     Section "Monitor"
839     Identifier [...]
840 nightmorph 1.35 Option "DPMS"
841 swift 1.1 [...]
842     EndSection
843     </pre>
844    
845 nightmorph 1.17 </body>
846     </section>
847     <section>
848     <title>Backlight dimming</title>
849     <body>
850    
851 swift 1.1 <p>
852     Probably more important is the backlight dimming. If you have access to the
853     dimming settings via a tool, write a small script that dims the backlight in
854 rane 1.19 battery mode and place it in your <c>battery</c> runlevel. The following script
855 nightmorph 1.17 should work on most IBM Thinkpads and Toshiba laptops. You've got to enable the
856 rane 1.20 appropriate option in your kernel (IBM Thinkpads only). For Toshiba laptops,
857 nightmorph 1.35 install <c>sys-power/acpitool</c> and skip configuration of <c>thinkpad_acpi</c>
858     (formerly called <c>ibm_acpi</c>) as described below.
859 neysx 1.12 </p>
860    
861     <warn>
862 swift 1.36 Support for setting brightness is marked experimental in thinkpad_acpi. It
863     accesses hardware directly and may cause severe harm to your system. Please
864     read the <uri link="http://ibm-acpi.sourceforge.net/">thinkpad_acpi
865     website</uri>
866 neysx 1.12 </warn>
867    
868     <p>
869 swift 1.36 To be able to set the brightness level, the thinkpad_acpi module has to be
870     loaded with the experimental parameter.
871 neysx 1.12 </p>
872    
873 nightmorph 1.35 <pre caption="automatically loading the thinkpad_acpi module">
874 neysx 1.12 <comment>(Please read the warnings above before doing this!)</comment>
875 nightmorph 1.35 # <i>echo "options thinkpad_acpi experimental=1" >> /etc/modules.d/thinkpad_acpi</i>
876 nightmorph 1.26 # <i>/sbin/update-modules</i>
877 nightmorph 1.35 # <i>echo thinkpad_acpi >> /etc/modules.autoload.d/kernel-2.6</i>
878     # <i>modprobe thinkpad_acpi</i>
879 neysx 1.12 </pre>
880    
881     <p>
882     This should work without error messages and a file
883     <path>/proc/acpi/ibm/brightness</path> should be created after loading the
884 rane 1.20 module. An init script will take care of choosing the brightness according to
885     the power source.
886 neysx 1.12 </p>
887    
888     <pre caption="/etc/conf.d/lcd-brightness">
889     <comment># See /proc/acpi/ibm/brightness for available values</comment>
890 nightmorph 1.35 <comment># Please read /usr/src/linux/Documentation/thinkpad-acpi.txt</comment>
891 neysx 1.12
892 nightmorph 1.23 <comment># brightness level in ac mode. Default is 7.</comment>
893 neysx 1.12 BRIGHTNESS_AC=7
894    
895     <comment># brightness level in battery mode. Default is 4.</comment>
896     BRIGHTNESS_BATTERY=4
897     </pre>
898    
899     <pre caption="/etc/init.d/lcd-brightness">
900     #!/sbin/runscript
901    
902     set_brightness() {
903     if on_ac_power
904     then
905     LEVEL=${BRIGHTNESS_AC:-7}
906     else
907     LEVEL=${BRIGHTNESS_BATTERY:-4}
908     fi
909    
910     if [ -f /proc/acpi/ibm/brightness ]
911     then
912     ebegin "Setting LCD brightness"
913     echo "level ${LEVEL}" > /proc/acpi/ibm/brightness
914     eend $?
915 nightmorph 1.17 elif [[ -e /usr/bin/acpitool &amp;&amp; -n $(acpitool -T | grep "LCD brightness") ]]
916     then
917     ebegin "Setting LCD brightness"
918     acpitool -l $LEVEL >/dev/null || ewarn "Unable to set lcd brightness"
919     eend $?
920 neysx 1.12 else
921     ewarn "Setting LCD brightness is not supported."
922 nightmorph 1.35 ewarn "For IBM Thinkpads, check that thinkpad_acpi is loaded into the kernel"
923 nightmorph 1.23 ewarn "For Toshiba laptops, you've got to install sys-power/acpitool"
924 neysx 1.12 fi
925     }
926    
927     start() {
928     set_brightness
929     }
930    
931     stop () {
932     set_brightness
933     }
934     </pre>
935    
936     <p>
937     When done, make sure brightness is adjusted automatically by adding it to the
938     battery runlevel.
939 swift 1.1 </p>
940    
941 neysx 1.12 <pre caption="Enabling automatic brightness adjustment">
942 rane 1.19 # <i>chmod +x /etc/init.d/lcd-brightness</i>
943     # <i>rc-update add lcd-brightness battery</i>
944     # <i>rc</i>
945 neysx 1.12 </pre>
946    
947 swift 1.1 </body>
948     </section>
949     </chapter>
950    
951     <chapter>
952     <title>Disk Power Management</title>
953     <section>
954 nightmorph 1.17 <body>
955 rane 1.19
956 nightmorph 1.17 <p>
957     Hard disks consume less energy in sleep mode. Therefore it makes sense to
958     activate power saving features whenever the hard disk is not used for a certain
959     amount of time. I'll show you two alternative possibilities to do it. First,
960     laptop-mode will save most energy due to several measures which prevent or at
961     least delay write accesses. The drawback is that due to the delayed write
962     accesses a power outage or kernel crash will be more dangerous for data loss.
963     If you don't like this, you have to make sure that there are no processes which
964     write to your hard disk frequently. Afterwards you can enable power saving
965 rane 1.19 features of your hard disk with <c>hdparm</c> as the second alternative.
966 nightmorph 1.17 </p>
967    
968     </body>
969     </section>
970     <section>
971     <title>Increasing idle time - laptop-mode</title>
972 swift 1.1 <body>
973    
974     <p>
975 nightmorph 1.27 Recent 2.6 kernels include the so-called <c>laptop-mode</c>. When activated,
976     dirty buffers are written to disk on read calls or after 10 minutes (instead of
977     30 seconds). This minimizes the time the hard disk needs to be spun up.
978 swift 1.1 </p>
979    
980 nightmorph 1.17 <pre caption="Automated start of laptop-mode">
981     # <i>emerge laptop-mode-tools</i>
982     </pre>
983 swift 1.1
984 nightmorph 1.17 <p>
985     <c>laptop-mode-tools</c> has its configuration file in
986     <path>/etc/laptop-mode/laptop-mode.conf</path>. Adjust it the way you like it,
987     it's well commented. Run <c>rc-update add laptop_mode battery</c> to start it
988     automatically.
989     </p>
990    
991     <p>
992     Recent versions (1.11 and later) of laptop-mode-tools include a new tool
993     <c>lm-profiler</c>. It will monitor your system's disk usage and running
994     network services and suggests to disable unneeded ones. You can either disable
995     them through laptop-mode-tools builtin runlevel support (which will be reverted
996 rane 1.19 by Gentoo's <c>/sbin/rc</c>) or use your <c>default</c>/<c>battery</c>
997 nightmorph 1.17 runlevels (recommended).
998     </p>
999    
1000     <pre caption="Sample output from running lm-profiler">
1001 rane 1.19 # <i>lm-profiler</i>
1002 nightmorph 1.17 Profiling session started.
1003     Time remaining: 600 seconds
1004     [4296896.602000] amarokapp
1005     Time remaining: 599 seconds
1006     [4296897.714000] sort
1007     [4296897.970000] mv
1008     Time remaining: 598 seconds
1009     Time remaining: 597 seconds
1010     [4296900.482000] reiserfs/0
1011     </pre>
1012    
1013     <p>
1014     After profiling your system for ten minutes, lm-profiler will present a list of
1015     services which might have caused disk accesses during that time.
1016     </p>
1017    
1018     <pre caption="lm-profiler suggests to disable some services">
1019     Program: "atd"
1020     Reason: standard recommendation (program may not be running)
1021     Init script: /etc/init.d/atd (GUESSED)
1022    
1023 rane 1.19 Do you want to disable this service in battery mode? [y/N]: <i>n</i>
1024 swift 1.1 </pre>
1025    
1026     <p>
1027 nightmorph 1.17 To disable atd as suggested in the example above, you would run <c>rc-update
1028     del atd battery</c>. Be careful not to disable services that are needed for
1029 rane 1.20 your system to run properly - <c>lm-profiler</c> is likely to generate some
1030     false positives. Do not disable a service if you are unsure whether it's
1031     needed.
1032 nightmorph 1.17 </p>
1033    
1034     </body>
1035     </section>
1036     <section>
1037 rane 1.19 <title>Limiting Write Accesses</title>
1038 nightmorph 1.17 <body>
1039    
1040     <p>
1041     If you don't want to use laptop-mode, you must take special care to disable
1042     services that write to your disk frequently - <c>syslogd</c> is a good
1043     candidate, for example. You probably don't want to shut it down completely, but
1044     it's possible to modify the config file so that "unnecessary" things don't get
1045 rane 1.20 logged and thus don't create disk traffic. <c>Cups</c> writes to disk
1046     periodically, so consider shutting it down and only enable it manually when
1047     needed.
1048 nightmorph 1.17 </p>
1049    
1050     <pre caption="Disabling cups in battery mode">
1051     # <i>rc-update del cupsd battery</i>
1052     </pre>
1053    
1054     <p>
1055     You can also use <c>lm-profiler</c> from laptop-mode-tools (see above) to find
1056     services to disable. Once you eliminated all of them, go on with configuring
1057     hdparm.
1058     </p>
1059    
1060     </body>
1061     </section>
1062     <section>
1063     <title>hdparm</title>
1064     <body>
1065    
1066     <p>
1067 nightmorph 1.28 The second possibility is using <c>hdparm</c>. Skip this if
1068     you are using laptop-mode. Otherwise, edit <path>/etc/conf.d/hdparm</path> and
1069     add the following values to your drive entries. This example assumes your hard
1070     drive is called <b>hda</b>:
1071 swift 1.1 </p>
1072    
1073 nightmorph 1.28 <pre caption="Using /etc/conf.d/hdparm for disk standby">
1074     hda_args="-q -S12"
1075     </pre>
1076 neysx 1.12
1077 nightmorph 1.28 <p>
1078     This will activate power management for your hard drive. If you ever want to
1079     deactivate power management, you can edit <path>/etc/conf.d/hdparm</path> and
1080     change the values to <c>-q -S0</c>, or just run <c>hdparm -q -S0 /dev/hda</c>.
1081     </p>
1082 swift 1.1
1083     <p>
1084 nightmorph 1.28 See <c>man hdparm</c> for the options. Though you can always start <c>hdparm</c>
1085     manually when you are on battery power by running <c>/etc/init.d/hdparm
1086     start</c>, it's much easier to automate its startup and shutdown. To do so, add
1087     <c>hdparm</c> to the battery runlevel so that it will automatically enable power
1088     management.
1089 swift 1.1 </p>
1090    
1091     <pre caption="Automate disk standby settings">
1092 nightmorph 1.28 # <i>rc-update add hdparm battery</i>
1093 swift 1.1 </pre>
1094    
1095     <impo>
1096     Be careful with sleep/spin down settings of your hard drive. Setting it to
1097     small values might wear out your drive and lose warranty.
1098     </impo>
1099    
1100     </body>
1101     </section>
1102     <section>
1103     <title>Other tricks</title>
1104     <body>
1105    
1106     <p>
1107     Another possibility is to deactivate swap in battery mode. Before writing a
1108     swapon/swapoff switcher, make sure there is enough RAM and swap isn't used
1109     heavily, otherwise you'll be in big problems.
1110     </p>
1111    
1112     <p>
1113     If you don't want to use laptop-mode, it's still possible to minimize disk
1114 rane 1.19 access by mounting certain directories as <c>tmpfs</c> - write accesses are not
1115 swift 1.1 stored on a disk, but in main memory and get lost with unmounting. Often it's
1116     useful to mount <path>/tmp</path> like this - you don't have to pay special
1117     attention as it gets cleared on every reboot regardless whether it was mounted
1118     on disk or in RAM. Just make sure you have enough RAM and no program (like a
1119     download client or compress utility) needs extraordinary much space in
1120     <path>/tmp</path>. To activate this, enable tmpfs support in your kernel and
1121     add a line to <path>/etc/fstab</path> like this:
1122     </p>
1123    
1124     <pre caption="Editing /etc/fstab to make /tmp even more volatile">
1125     none /tmp tmpfs size=32m 0 0
1126     </pre>
1127    
1128     <warn>
1129     Pay attention to the size parameter and modify it for your system. If you're
1130 rane 1.21 unsure, don't try this at all, it can become a performance bottleneck easily. In
1131 swift 1.1 case you want to mount <path>/var/log</path> like this, make sure to merge the
1132     log files to disk before unmounting. They are essential. Don't attempt to mount
1133 rane 1.19 <path>/var/tmp</path> like this. Portage uses it for compiling...
1134 swift 1.1 </warn>
1135    
1136     </body>
1137     </section>
1138     </chapter>
1139    
1140     <chapter>
1141 rane 1.19 <title>Power Management For Other Devices</title>
1142 swift 1.1 <section>
1143 rane 1.19 <title>Graphics Cards</title>
1144 so 1.15 <body>
1145    
1146     <p>
1147     In case you own an ATI graphics card supporting PowerPlay (dynamic clock
1148 nightmorph 1.25 scaling for the graphics processing unit GPU), you can activate this
1149 rane 1.20 feature in X.org. Open <path>/etc/X11/xorg.conf</path> and add (or enable) the
1150     <c>DynamicClocks</c> option in the Device section. Please notice that this
1151     feature will lead to crashes on some systems.
1152 so 1.15 </p>
1153    
1154     <pre caption="Enabling ATI PowerPlay support in X.org">
1155     Section "Device"
1156     [...]
1157     Option "DynamicClocks" "on"
1158     EndSection
1159     </pre>
1160    
1161     </body>
1162     </section>
1163     <section>
1164 swift 1.1 <title>Wireless Power Management</title>
1165     <body>
1166    
1167     <p>
1168 nightmorph 1.17 Wireless LAN cards consume quite a bit of energy. Put them in Power Management
1169 nightmorph 1.28 mode just like your hard drives.
1170 swift 1.1 </p>
1171    
1172 nightmorph 1.17 <note>
1173     This script assumes your wireless interface is called <c>wlan0</c>; replace
1174     this with the actual name of your interface.
1175     </note>
1176    
1177 nightmorph 1.28 <p>
1178 nightmorph 1.29 Add the following option to <path>/etc/conf.d/net</path> to automatically enable
1179 nightmorph 1.28 power management for your wireless card:
1180     </p>
1181 swift 1.1
1182 nightmorph 1.28 <pre caption="Automated WLAN Power Management">
1183     iwconfig_wlan0="power on"
1184 swift 1.1 </pre>
1185    
1186     <p>
1187 nightmorph 1.28 See <c>man iwconfig</c> for details and more options like the period between
1188     wakeups or timeout settings. If your driver and access point support changing
1189     the beacon time, this is a good starting point to save even more energy.
1190 swift 1.1 </p>
1191    
1192     </body>
1193     </section>
1194     <section>
1195     <title>USB Power Management</title>
1196     <body>
1197    
1198     <p>
1199     There are two problems with USB devices regarding energy consumption: First,
1200     devices like USB mice, digital cameras or USB sticks consume energy while
1201     plugged in. You cannot avoid this (nevertheless remove them in case they're not
1202     needed). Second, when there are USB devices plugged in, the USB host controller
1203     periodically accesses the bus which in turn prevents the CPU from going into
1204 rane 1.20 sleep mode. The kernel offers an experimental option to enable suspension of
1205 so 1.15 USB devices through driver calls or one of the <path>power/state</path> files
1206     in <path>/sys</path>.
1207 swift 1.1 </p>
1208    
1209 so 1.15 <pre caption="Enabling USB suspend support in the kernel">
1210     Device Drivers
1211     USB support
1212     [*] Support for Host-side USB
1213     [*] USB suspend/resume (EXPERIMENTAL)
1214     </pre>
1215    
1216 swift 1.1 </body>
1217     </section>
1218     </chapter>
1219    
1220     <chapter>
1221 rane 1.19 <title>Sleep States: sleep, standby, and suspend to disk</title>
1222 swift 1.1 <section>
1223     <body>
1224    
1225     <p>
1226     ACPI defines different sleep states. The more important ones are
1227     </p>
1228    
1229 rane 1.20 <ul>
1230 swift 1.1 <li>S1 aka Standby</li>
1231     <li>S3 aka Suspend to RAM aka Sleep</li>
1232     <li>S4 aka Suspend to Disk aka Hibernate</li>
1233     </ul>
1234    
1235     <p>
1236     They can be called whenever the system is not in use, but a shutdown is not
1237     wanted due to the long boot time.
1238     </p>
1239    
1240     </body>
1241     </section>
1242     <section>
1243 so 1.15 <title>Sleep (S3)</title>
1244 swift 1.1 <body>
1245    
1246     <p>
1247 so 1.15 The ACPI support for these sleep states is marked experimental for good reason.
1248     APM sleep states seem to be more stable, however you can't use APM and ACPI
1249     together.
1250     </p>
1251    
1252     <pre caption="Kernel configuration for the various suspend types">
1253     Power Management Options ---&gt;
1254     [*] Power Management support
1255     ACPI (Advanced Configuration and Power Interface) Support ---&gt;
1256     [*] ACPI Support
1257     [*] Sleep States
1258     </pre>
1259    
1260     <p>
1261 nightmorph 1.17 Once your kernel is properly configured, you can use the
1262 so 1.15 <c>hibernate-script</c> to activate suspend or sleep mode. Let's install that
1263     first.
1264     </p>
1265    
1266     <pre caption="Installing the hibernate-script">
1267 rane 1.19 # <i>emerge hibernate-script</i>
1268 so 1.15 </pre>
1269    
1270     <p>
1271 nightmorph 1.25 Some configuration has to be done in <path>/etc/hibernate</path>. The default
1272 nightmorph 1.24 package introduces a few configuration files for each sleep state. Options that
1273     are common to all suspend methods are placed in <path>common.conf</path>; make
1274     sure this file is properly set up for your system.
1275 so 1.15 </p>
1276    
1277     <p>
1278 nightmorph 1.24 To configure sleep, edit <path>sysfs-ram.conf</path> in
1279     <path>/etc/hibernate</path>. <c>UseSysfsPowerState mem</c> is already setup
1280 nightmorph 1.25 correctly, but if you need to make further changes to this particular sleep
1281     state (or any other sleep state) you should add them to
1282 nightmorph 1.24 <path>/etc/hibernate/hibernate.conf</path>. The comments and option names will
1283     guide you. If you use nfs or samba shares over the network, make sure to
1284     shutdown the appropriate init scripts to avoid timeouts.
1285 so 1.15 </p>
1286    
1287 nightmorph 1.24 <note>
1288     For more information on setting up sleep states, read <c>man
1289     hibernate.conf</c>.
1290     </note>
1291    
1292 so 1.15 <p>
1293     Ready? Now is the last chance to backup any data you want to keep after
1294     executing the next command. Notice that you probably have to hit a special key
1295 rane 1.19 like <c>Fn</c> to resume from sleep.
1296 so 1.15 </p>
1297    
1298     <pre caption="Calling sleep">
1299 rane 1.19 # <i>hibernate-ram</i>
1300 so 1.15 </pre>
1301    
1302     <p>
1303 rane 1.20 If you're still reading, it seems to work. You can also setup standby (S1) in a
1304 nightmorph 1.24 similar way by editing <path>sysfs-ram.conf</path> and changing
1305     "UseSysfsPowerState mem" to "UseSysfsPowerState standby". S3 and S4 are the more
1306     interesting sleep states due to greater energy savings however.
1307 so 1.15 </p>
1308    
1309     </body>
1310     </section>
1311     <section>
1312     <title>Hibernate (S4)</title>
1313     <body>
1314    
1315     <p>
1316     This section introduces hibernation, where a snapshot of the running system is
1317     written to disk before powering off. On resume, the snapshot is loaded and you
1318     can go on working at exactly the point you called hibernate before.
1319 swift 1.1 </p>
1320    
1321     <warn>
1322 so 1.15 Don't exchange non hot-pluggable hardware when suspended. Don't attempt to load
1323     a snapshot with a different kernel image than the one it was created with.
1324     Shutdown any NFS or samba server/client before hibernating.
1325 swift 1.1 </warn>
1326    
1327     <p>
1328 so 1.15 There are two different implementations for S4. The original one is swsusp,
1329 swift 1.36 then there is the newer tuxonice (former suspend2) with a nicer interface
1330     (including fbsplash support). A <uri
1331     link="http://tuxonice.net/features.html#compare"> feature comparison</uri> is
1332     available at the <uri link="http://www.tuxonice.net">tuxonice Homepage</uri>.
1333     There used to be Suspend-to-Disk (pmdisk), a fork of swsusp, but it has been
1334     merged back.
1335 swift 1.1 </p>
1336    
1337     <p>
1338 jkt 1.33 TuxOnIce is not included in the mainline kernel yet, therefore you either have
1339 rane 1.20 to patch your kernel sources with the patches provided by <uri
1340 jkt 1.33 link="http://tuxonice.net">tuxonice.net</uri> or use
1341     <c>sys-kernel/tuxonice-sources</c>.
1342 swift 1.1 </p>
1343    
1344     <p>
1345 jkt 1.33 The kernel part for both swusp and TuxOnIce is as follows:
1346 swift 1.1 </p>
1347    
1348     <pre caption="Kernel configuration for the various suspend types">
1349     Power Management Options ---&gt;
1350     <comment>(hibernate with swsusp)</comment>
1351 so 1.15 [*] Software Suspend
1352     <comment>(replace /dev/SWAP with your swap partition)</comment>
1353     (/dev/SWAP) Default resume partition
1354 rane 1.20
1355 jkt 1.33 <comment>(hibernate with TuxOnIce)</comment>
1356     Enhanced Hibernation (TuxOnIce)
1357 swift 1.1 --- Image Storage (you need at least one writer)
1358 so 1.15 [*] File Writer
1359 swift 1.1 [*] Swap Writer
1360 so 1.15 --- General Options
1361 swift 1.1 [*] LZF image compression
1362 so 1.15 <comment>(replace /dev/SWAP with your swap partition)</comment>
1363     (swap:/dev/SWAP) Default resume device name
1364     [ ] Allow Keep Image Mode
1365 swift 1.1 </pre>
1366    
1367     <p>
1368 so 1.15 The configuration for swsusp is rather easy. If you didn't store the location
1369     of your swap partition in the kernel config, you can also pass it as a
1370     parameter with the <c>resume=/dev/SWAP</c> directive. If booting is not
1371     possible due to a broken image, use the <c>noresume</c> kernel parameter. The
1372 rane 1.20 <c>hibernate-cleanup</c> init script invalidates swsusp images during the boot
1373     process.
1374 swift 1.1 </p>
1375    
1376 so 1.15 <pre caption="Invalidating swsusp images during the boot process">
1377 rane 1.19 # <i>rc-update add hibernate-cleanup boot</i>
1378 so 1.15 </pre>
1379    
1380 swift 1.1 <p>
1381 so 1.15 To activate hibernate with swsusp, use the hibernate script and set
1382 nightmorph 1.24 <c>UseSysfsPowerState disk</c> in <path>/etc/hibernate/sysfs-disk</path>.
1383 swift 1.1 </p>
1384    
1385     <warn>
1386     Backup your data before doing this. Run <c>sync</c> before executing one of the
1387     commands to have cached data written to disk. First try it outside of X, then
1388     with X running, but not logged in.
1389     </warn>
1390 rane 1.20
1391 swift 1.1 <p>
1392     If you experience kernel panics due to uhci or similar, try to compile USB
1393     support as module and unload the modules before sending your laptop to sleep
1394 nightmorph 1.24 mode. There are configuration options for this in <path>common.conf</path>
1395 swift 1.1 </p>
1396    
1397 so 1.15 <pre caption="Hibernating with swsusp">
1398 nightmorph 1.24 # <i>nano -w /etc/hibernate/common.conf</i>
1399 so 1.15 <comment>(Make sure you have a backup of your data)</comment>
1400 rane 1.19 # <i>hibernate</i>
1401 so 1.15 </pre>
1402    
1403 swift 1.1 <p>
1404 jkt 1.34 The following section discusses the setup of TuxOnIce including fbsplash support
1405     for a nice graphical progress bar during suspend and resume.
1406 so 1.15 </p>
1407    
1408     <p>
1409 rane 1.20 The first part of the configuration is similar to the configuration of swsusp.
1410     In case you didn't store the location of your swap partition in the kernel
1411     config, you have to pass it as a kernel parameter with the
1412 jkt 1.33 <c>resume=swap:/dev/SWAP</c> directive. If booting is not possible due to a
1413     broken image, append the <c>noresume</c> parameter. Additionally, the
1414 jkt 1.34 <c>hibernate-cleanup</c> init script invalidates TuxOnIce images during the boot
1415     process.
1416 so 1.15 </p>
1417    
1418 jkt 1.33 <pre caption="Invalidating TuxOnIce images during the boot process">
1419 rane 1.19 # <i>rc-update add hibernate-cleanup boot</i>
1420 so 1.15 </pre>
1421    
1422 rane 1.20 <p>
1423 jkt 1.33 Now edit <path>/etc/hibernate/suspend2.conf</path>, enable the <c>TuxOnIce</c>
1424 nightmorph 1.24 options you need. Do not enable the <c>fbsplash</c> options in
1425     <c>common.conf</c> just yet.
1426 swift 1.1 </p>
1427    
1428 jkt 1.33 <pre caption="Hibernating with TuxOnIce">
1429 nightmorph 1.24 # <i>nano -w /etc/hibernate/suspend2.conf</i>
1430 so 1.15 <comment>(Make sure you have a backup of your data)</comment>
1431 rane 1.19 # <i>hibernate</i>
1432 swift 1.8 </pre>
1433    
1434 so 1.15 <p>
1435 rane 1.20 Please configure <c>fbsplash</c> now if you didn't do already. To enable
1436 jkt 1.34 fbsplash support during hibernation, the <c>sys-apps/tuxonice-userui</c> package
1437     is needed. Additionally, you've got to enable the <c>fbsplash</c> USE flag.
1438 so 1.15 </p>
1439    
1440 jkt 1.33 <pre caption="Installing tuxonice-userui">
1441     # <i>echo "sys-apps/tuxonice-userui fbsplash" >> /etc/portage/package.use</i>
1442 nightmorph 1.24 <comment>(It may be marked ~arch, so first it must be keyworded)</comment>
1443 jkt 1.33 # <i>echo "sys-apps/tuxonice-userui" >> /etc/portage/package.keywords</i>
1444     # <i>emerge tuxonice-userui</i>
1445 so 1.15 </pre>
1446    
1447     <p>
1448     The ebuild tells you to make a symlink to the theme you want to use. For
1449     example, to use the <c>livecd-2005.1</c> theme, run the following command:
1450     </p>
1451    
1452     <pre caption="Using the livecd-2005.1 theme during hibernation">
1453 rane 1.19 # <i>ln -sfn /etc/splash/livecd-2005.1 /etc/splash/suspend2</i>
1454 so 1.15 </pre>
1455    
1456     <p>
1457     If you don't want a black screen in the first part of the resume process, you
1458 jkt 1.33 have to add the <c>tuxoniceui_fbsplash</c> tool to your initrd image. Assuming
1459 so 1.15 you created the initrd image with <c>splash_geninitramfs</c> and saved it as
1460 rane 1.20 <path>/boot/fbsplash-emergence-1024x768</path>, here's how to do that.
1461 so 1.15 </p>
1462    
1463 jkt 1.33 <pre caption="Adding tuxoniceui_fbsplash to an initrd image">
1464 rane 1.19 # <i>mount /boot</i>
1465     # <i>mkdir ~/initrd.d</i>
1466     # <i>cp /boot/fbsplash-emergence-1024x768 ~/initrd.d/</i>
1467     # <i>cd ~/initrd.d</i>
1468     # <i>gunzip -c fbsplash-emergence-1024x768 | cpio -idm --quiet -H newc</i>
1469     # <i>rm fbsplash-emergence-1024x768</i>
1470 jkt 1.33 # <i>cp /usr/sbin/tuxoniceui_fbsplash sbin/</i>
1471     # <i>find . | cpio --quiet --dereference -o -H newc | gzip -9 > /boot/fbsplash-tuxonice-emergence-1024x768</i>
1472 so 1.15 </pre>
1473    
1474     <p>
1475 nightmorph 1.24 Afterwards adjust <path>grub.conf</path> (or <path>lilo.conf</path>) so that
1476 jkt 1.33 your TuxOnIce kernel uses
1477     <path>/boot/fbsplash-tuxonice-emergence-1024x768</path> as initrd image. You can
1478 nightmorph 1.24 now test a dry run to see if everything is setup correctly.
1479 so 1.15 </p>
1480    
1481     <pre caption="Test run for fbsplash hibernation">
1482 jkt 1.33 # <i>tuxoniceui_fbsplash -t</i>
1483 so 1.15 </pre>
1484    
1485     <p>
1486 nightmorph 1.24 Afterwards open <path>/etc/hibernate/common.conf</path> and activate the
1487     fbsplash options. Execute <c>hibernate</c> and enjoy.
1488 so 1.15 </p>
1489    
1490 swift 1.1 </body>
1491     </section>
1492     </chapter>
1493    
1494     <chapter>
1495     <title>Troubleshooting</title>
1496     <section>
1497     <body>
1498    
1499     <p>
1500     <e>Q:</e> I'm trying to change the CPU frequency, but
1501     <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor</path> does not
1502     exist.
1503     </p>
1504    
1505     <p>
1506     <e>A:</e> Make sure your processor supports CPU frequency scaling and you chose
1507     the right CPUFreq driver for your processor. Here is a list of processors that
1508 jkt 1.34 are supported by cpufreq (kernel 2.6.7): ARM Integrator, ARM-SA1100, ARM-SA1110,
1509     AMD Elan - SC400, SC410, AMD mobile K6-2+, AMD mobile K6-3+, AMD mobile Duron,
1510     AMD mobile Athlon, AMD Opteron, AMD Athlon 64, Cyrix Media GXm, Intel mobile
1511     PIII and Intel mobile PIII-M on certain chipsets, Intel Pentium 4, Intel Xeon,
1512     Intel Pentium M (Centrino), National Semiconductors Geode GX, Transmeta Crusoe,
1513     VIA Cyrix 3 / C3, UltraSPARC-III, SuperH SH-3, SH-4, several "PowerBook" and
1514     "iBook2" and various processors on some ACPI 2.0-compatible systems (only if
1515     "ACPI Processor Performance States" are available to the ACPI/BIOS interface).
1516 swift 1.1 </p>
1517    
1518     <p>
1519     <e>Q:</e> My laptop supports frequency scaling, but
1520     <path>/sys/devices/system/cpu/cpu0/cpufreq/</path> is empty.
1521     </p>
1522    
1523     <p>
1524     <e>A:</e> Look for ACPI related error messages with <c>dmesg | grep ACPI</c>.
1525     Try to update the BIOS, especially if a broken DSDT is reported. You can also
1526     try to fix it yourself (which is beyond the scope of this guide).
1527     </p>
1528    
1529     <p>
1530 rane 1.19 <e>Q:</e> My laptop supports frequency scaling, but according to
1531     <path>/proc/cpuinfo</path> the speed never changes.
1532 swift 1.1 </p>
1533    
1534     <p>
1535 swift 1.8 <e>A:</e> Probably you have activated symmetric multiprocessing support
1536     (CONFIG_SMP) in your kernel. Deactivate it and it should work. Some older
1537 rane 1.20 kernels had a bug causing this. In that case, run <c>emerge x86info</c>, update
1538 jkt 1.34 your kernel as asked and check the current frequency with <c>x86info -mhz</c>.
1539 swift 1.1 </p>
1540    
1541     <p>
1542     <e>Q:</e> I can change the CPU frequency, but the range is not as wide as in
1543     another OS.
1544     </p>
1545    
1546     <p>
1547     <e>A:</e> You can combine frequency scaling with ACPI throttling to get a lower
1548 jkt 1.34 minimum frequency. Notice that throttling doesn't save much energy and is mainly
1549     used for thermal management (keeping your laptop cool and quiet). You can read
1550     the current throttling state with <c>cat /proc/acpi/processor/CPU/throttling</c>
1551     and change it with <c>echo -n "0:x" > /proc/acpi/processor/CPU/limit</c>, where
1552     x is one of the Tx states listed in
1553 swift 1.1 <path>/proc/acpi/processor/CPU/throttling</path>.
1554     </p>
1555    
1556     <p>
1557 swift 1.8 <e>Q:</e> When configuring the kernel, powersave, performance and userspace
1558     governors show up, but that ondemand thing is missing. Where do I get it?
1559     </p>
1560    
1561     <p>
1562     <e>A:</e> The ondemand governor is only included in recent kernel sources. Try
1563     updating them.
1564     </p>
1565    
1566     <p>
1567 swift 1.1 <e>Q:</e> Battery life time seems to be worse than before.
1568     </p>
1569    
1570     <p>
1571     <e>A:</e> Check your BIOS settings. Maybe you forgot to re-enable some of the
1572     settings.
1573     </p>
1574    
1575     <p>
1576     <e>Q:</e> My battery is charged, but KDE reports there would be 0% left and
1577     immediately shuts down.
1578     </p>
1579    
1580     <p>
1581     <e>A:</e> Check that battery support is compiled into your kernel. If you use
1582     it as a module, make sure the module is loaded.
1583     </p>
1584    
1585     <p>
1586 rane 1.20 <e>Q:</e> My system logger reports things like "logger: ACPI group battery /
1587     action battery is not defined".
1588 nightmorph 1.17 </p>
1589    
1590     <p>
1591 rane 1.20 <e>A:</e> This message is generated by the <path>/etc/acpi/default.sh</path>
1592     script that is shipped with acpid. You can safely ignore it. If you like to get
1593     rid of it, you can comment the appropriate line in
1594     <path>/etc/acpi/default.sh</path> as shown below:
1595 nightmorph 1.17 </p>
1596    
1597     <pre caption="Disabling warnings about unknown acpi events">
1598     *) # logger "ACPI action $action is not defined"
1599     </pre>
1600    
1601     <p>
1602 swift 1.1 <e>Q:</e> I have a Dell Inspiron 51XX and I don't get any ACPI events.
1603     </p>
1604    
1605     <p>
1606     <e>A:</e> This seems to be a kernel bug. Read on <uri
1607     link="http://bugme.osdl.org/show_bug.cgi?id=1752">here</uri>.
1608     </p>
1609    
1610     <p>
1611 rane 1.20 <e>Q:</e> I activated the <c>DynamicClocks</c> option in <path>xorg.conf</path>
1612     and now X.org crashes / the screen stays black / my laptop doesn't shutdown
1613 so 1.15 properly.
1614     </p>
1615    
1616     <p>
1617 rane 1.20 <e>A:</e> This happens on some systems. You have to disable
1618     <c>DynamicClocks</c>.
1619 so 1.15 </p>
1620    
1621     <p>
1622 jkt 1.33 <e>Q:</e> I want to use TuxOnIce, but it tells me my swap partition is too
1623 so 1.15 small. Resizing is not an option.
1624     </p>
1625    
1626     <p>
1627 rane 1.20 <e>A:</e> If there is enough free space on your system, you can use the
1628 jkt 1.34 filewriter instead of the swapwriter. The <c>hibernate-script</c> supports it as
1629     well. More information can be found in
1630 jkt 1.33 <path>/usr/src/linux/Documentation/power/tuxonice.txt</path>.
1631 so 1.15 </p>
1632    
1633     <p>
1634 swift 1.1 <e>Q:</e> I just bought a brand new battery, but it only lasts for some
1635     minutes! What am I doing wrong?
1636     </p>
1637    
1638     <p>
1639     <e>A:</e> First follow your manufacturer's advice on how to charge the battery
1640 rane 1.20 correctly.
1641 swift 1.1 </p>
1642    
1643     <p>
1644     <e>Q:</e> The above didn't help. What should I do then?
1645     </p>
1646    
1647     <p>
1648     <e>A:</e> Some batteries sold as "new" are in fact old ones. Try the following:
1649     </p>
1650    
1651     <pre caption="Querying battery state">
1652     $ <i>grep capacity /proc/acpi/battery/BAT0/info</i>
1653     design capacity: 47520 mWh
1654     last full capacity: 41830 mWh
1655     </pre>
1656    
1657     <p>
1658     If the "last full capacity" differs significantly from the design capacity,
1659     your battery is probably broken. Try to claim your warranty.
1660     </p>
1661    
1662 swift 1.8 <p>
1663     <e>Q:</e> My problem is not listed above. Where should I go next?
1664     </p>
1665    
1666     <p>
1667 nightmorph 1.17 <e>A:</e> Don't fear to contact me, <mail link="earthwings@gentoo.org">Dennis
1668 rane 1.20 Nienhüser</mail>, directly. The <uri link="http://forums.gentoo.org">Gentoo
1669     Forums</uri> are a good place to get help as well. If you prefer IRC, try the
1670     <c>#gentoo-laptop</c> channel at <uri
1671     link="irc://irc.freenode.net">irc.freenode.net</uri>.
1672 swift 1.8 </p>
1673    
1674 swift 1.1 </body>
1675     </section>
1676     </chapter>
1677     </guide>

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