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1 <?xml version='1.0' encoding="UTF-8"?>
2 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/power-management-guide.xml,v 1.28 2007/07/08 07:48:12 nightmorph Exp $ -->
4 <guide link="/doc/en/power-management-guide.xml">
5 <title>Power Management Guide</title>
6
7 <author title="Author">
8 <mail link="earthwings@gentoo.org">Dennis Nienhüser</mail>
9 </author>
10 <author title="Editor">
11 <mail link="chriswhite@gentoo.org">Chris White</mail>
12 </author>
13 <author title="Editor">
14 <mail link="nightmorph@gentoo.org">Joshua Saddler</mail>
15 </author>
16
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 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
24 <license/>
25
26 <version>1.34</version>
27 <date>2007-07-08</date>
28
29 <chapter>
30 <title>Introduction</title>
31 <section>
32 <body>
33
34 <p>
35 Capacity and lifetime of laptop batteries have improved much in the last years.
36 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 <title>A Quick Overview</title>
47 <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 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 without losing too much performance. A few different tricks prevent your hard
70 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 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 chapter is dedicated to the (rather experimental) <uri link="#doc_chap7">sleep
75 states</uri>. Last not least <uri link="#doc_chap8">Troubleshooting</uri> lists
76 common pitfalls.
77 </p>
78
79 </body>
80 </section>
81 <section>
82 <title>Power Budget For Each Component</title>
83 <body>
84
85 <figure link="/images/energy-budget.png" short="Which component consumes how
86 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 Before discussing the details of making individual devices Power Management
107 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 </p>
113
114 </body>
115 </section>
116 <section>
117 <title>The BIOS Part</title>
118 <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 <title>Setting USE Flags</title>
132 <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 the <c>--newuse</c> flag in <c>emerge</c>, see <c>man emerge</c>.
141 </p>
142
143 </body>
144 </section>
145 <section>
146 <title>Configuring The Kernel</title>
147 <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 There are different kernel sources in Portage. I'd recommend using
157 <c>gentoo-sources</c> or <c>suspend2-sources</c>. The latter contains patches
158 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 </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 [ ] /proc/acpi/sleep (deprecated)
172 [*] AC Adapter
173 [*] Battery
174 &lt;M&gt; Button
175 &lt;M&gt; Video
176 [ ] Generic Hotkey
177 &lt;M&gt; Fan
178 &lt;M&gt; Processor
179 &lt;M&gt; Thermal Zone
180 &lt; &gt; ASUS/Medion Laptop Extras
181 &lt; &gt; IBM ThinkPad Laptop Extras
182 &lt; &gt; Toshiba Laptop Extras
183 (0) Disable ACPI for systems before Jan 1st this year
184 [ ] Debug Statements
185 [*] Power Management Timer Support
186 &lt; &gt; ACPI0004,PNP0A05 and PNP0A06 Container Driver (EXPERIMENTAL)
187
188 CPU Frequency Scaling ---&gt;
189 [*] CPU Frequency scaling
190 [ ] Enable CPUfreq debugging
191 &lt; &gt; CPU frequency translation statistics
192 [ ] CPU frequency translation statistics details
193 Default CPUFreq governor (userspace)
194 &lt;*&gt; 'performance' governor
195 &lt;*&gt; 'powersave' governor
196 &lt;*&gt; 'ondemand' cpufreq policy governor
197 &lt;*&gt; 'conservative' cpufreq governor
198 &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 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 the appropriate section.
207 </p>
208
209 <p>
210 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 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 Consult the kernel documentation if you're unsure which one to take.
215 </p>
216
217 <p>
218 Compile your kernel, make sure the right modules get loaded at startup and boot
219 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 </p>
226
227 <pre caption="Installing acpid">
228 # <i>emerge sys-power/acpid</i>
229 # <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 <title>Creating A "battery" Runlevel</title>
237 <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 create a runlevel <c>battery</c> that holds all the scripts starting and
243 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 up. The next sections assume a runlevel <c>battery</c> exists.
250 </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 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 change it.
261 </p>
262
263 </body>
264 </section>
265 <section>
266 <title>Reacting On ACPI Events</title>
267 <body>
268
269 <p>
270 Typical ACPI events are closing the lid, changing the power source or pressing
271 the sleep button. An important event is changing the power source, which should
272 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 # <i>emerge powermgmt-base</i>
284 </pre>
285
286 <p>
287 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 <path>/etc/acpi/actions/pmg_switch_runlevel.sh</path>.
291 </p>
292
293 <pre caption="/etc/acpi/actions/pmg_switch_runlevel.sh">
294 #!/bin/bash
295
296 <comment># BEGIN configuration</comment>
297 RUNLEVEL_AC="default"
298 RUNLEVEL_BATTERY="battery"
299 <comment># END configuration</comment>
300
301
302 if [ ! -d "/etc/runlevels/${RUNLEVEL_AC}" ]
303 then
304 logger "${0}: Runlevel ${RUNLEVEL_AC} does not exist. Aborting."
305 exit 1
306 fi
307
308 if [ ! -d "/etc/runlevels/${RUNLEVEL_BATTERY}" ]
309 then
310 logger "${0}: Runlevel ${RUNLEVEL_BATTERY} does not exist. Aborting."
311 exit 1
312 fi
313
314 if on_ac_power
315 then
316 if [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_AC}" ]]
317 then
318 logger "Switching to ${RUNLEVEL_AC} runlevel"
319 /sbin/rc ${RUNLEVEL_AC}
320 fi
321 elif [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_BATTERY}" ]]
322 then
323 logger "Switching to ${RUNLEVEL_BATTERY} runlevel"
324 /sbin/rc ${RUNLEVEL_BATTERY}
325 fi
326 </pre>
327
328 <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 <c>ac_adapter</c> and <c>battery</c> on most laptops, but it might be different
335 on yours.
336 </p>
337
338 <pre caption="Determining ACPI events for changing the power source">
339 # <i>tail -f /var/log/acpid | grep "received event"</i>
340 </pre>
341
342 <p>
343 Run the command above and pull the power cable. You should see something like
344 this:
345 </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 The interesting part is the quoted string after <c>received event</c>. It will
354 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 <pre caption="/etc/acpi/events/pmg_ac_adapter">
360 <comment># replace "ac_adapter" below with the event generated on your laptop</comment>
361 <comment># For example, ac_adapter.* will match ac_adapter AC 00000080 00000000</comment>
362 event=ac_adapter.*
363 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
364 </pre>
365
366 <pre caption="/etc/acpi/events/pmg_battery">
367 <comment># replace "battery" below with the event generated on your laptop</comment>
368 <comment># For example, battery.* will match battery BAT0 00000080 00000001</comment>
369 event=battery.*
370 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
371 </pre>
372
373 <p>
374 Finally acpid has to be restarted to recognize the changes.
375 </p>
376
377 <pre caption="Finishing runlevel switching with acpid">
378 # <i>/etc/init.d/acpid restart</i>
379 </pre>
380
381 <p>
382 Give it a try: Plug AC in and out and watch syslog for the "Switching to AC
383 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 </p>
387
388 <p>
389 Due to the nature of the event mechanism, your laptop will boot into runlevel
390 <c>default</c> regardless of the AC/battery state. This is fine when running
391 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 <c>softlevel=battery</c>, but it's likely to forget choosing it. A better way
394 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 </p>
399
400 <pre caption="Runlevel adjustment at boot time by editing local.start">
401 <comment># Fake acpi event to switch runlevel if running on batteries</comment>
402 /etc/acpi/actions/pmg_switch_runlevel.sh "battery/battery"
403 </pre>
404
405 <p>
406 Prepared like this you can activate Power Management policies for individual
407 devices.
408 </p>
409
410 </body>
411 </section>
412 </chapter>
413
414 <chapter>
415 <title>CPU Power Management</title>
416 <section>
417 <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 <title>Some Technical Terms</title>
430 <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 First of all, the kernel has to be able to change the processor's frequency.
439 The <b>CPUfreq processor driver</b> knows the commands to do it on your CPU.
440 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 <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 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 </p>
462
463 </body>
464 </section>
465 <section>
466 <title>Setting The Frequency Manually</title>
467 <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 of supported processors in the <uri link="#doc_chap8">Troubleshooting</uri>
480 section to verify yours is supported.
481 </note>
482
483 <p>
484 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 </p>
487
488 <pre caption="Checking CPU frequency">
489 # <i>emerge cpufrequtils</i>
490 # <i>cpufreq-info</i>
491 </pre>
492
493 <p>
494 Here is an example output:
495 </p>
496
497 <pre caption="Sample output from cpufreq-info">
498 cpufrequtils 0.3: cpufreq-info (C) Dominik Brodowski 2004
499 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 available cpufreq governors: conservative, ondemand, powersave, userspace, performance
506 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 current CPU frequency is 1.40 GHz.
510 </pre>
511
512 <p>
513 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 expected, you might find help in the <uri link="#doc_chap8">Troubleshooting
517 section</uri> in the end of this guide.
518 </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 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 decide on one of them. It's roughly separated in three categories <b>kernel</b>
531 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 </p>
535
536 <table>
537 <tr>
538 <th>Name</th>
539 <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 Chooses maximal frequency on CPU load and slowly steps down when the CPU is
553 idle. Further tuning through files in
554 <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 </tr>
559 <tr>
560 <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 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 </ti>
573 </tr>
574 <tr>
575 <ti><uri link="http://mnm.uib.es/~gallir/cpudyn/">cpudyn</uri></ti>
576 <ti>Daemon</ti>
577 <ti>CPU load</ti>
578 <ti>Performance, powersave</ti>
579 <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 </tr>
585 <tr>
586 <ti><uri link="http://sourceforge.net/projects/cpufreqd/">cpufreqd</uri></ti>
587 <ti>Daemon</ti>
588 <ti>Battery state, CPU load, temperature, running programs and more</ti>
589 <ti>All available</ti>
590 <ti>None</ti>
591 <ti>
592 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 </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 </tr>
610 <tr>
611 <ti>
612 <uri
613 link="http://fatcat.ftj.agh.edu.pl/~nelchael/index.php?cat=projs&amp;subcat=ncpufreqd&amp;language=en">ncpufreqd</uri>
614 </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 <ti><uri link="http://www.goop.org/~jeremy/speedfreq/">speedfreq</uri></ti>
626 <ti>Daemon</ti>
627 <ti>CPU load</ti>
628 <ti>None</ti>
629 <ti>Dynamic, powersave, performance, fixed speed</ti>
630 <ti>
631 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 </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 <ti>
643 Gnome application, a graphical tool to set CPU frequency manually. It does
644 not offer any automation.
645 </ti>
646 </tr>
647 <tr>
648 <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 </tr>
657 </table>
658
659 <p>
660 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 to an unnecessary high level.
664 </p>
665
666 <p>
667 Which one to choose? If you have no idea about it, try <c>cpufreqd</c>:
668 </p>
669
670 <pre caption="Installing cpufreqd">
671 # <i>emerge cpufreqd</i>
672 </pre>
673
674 <p>
675 <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 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 </p>
681
682 <pre caption="/etc/cpufreqd.conf (cpufreqd-2.0.0 and later)">
683 [General]
684 pidfile=/var/run/cpufreqd.pid
685 poll_interval=3
686 enable_plugins=acpi_ac, acpi_battery
687 enable_remote=1
688 remote_group=wheel
689 verbosity=5
690 [/General]
691
692 [Profile]
693 name=ondemand
694 minfreq=0%
695 maxfreq=100%
696 policy=ondemand
697 [/Profile]
698
699 [Profile]
700 name=conservative
701 minfreq=0%
702 maxfreq=100%
703 policy=conservative
704 [/Profile]
705
706 [Profile]
707 name=powersave
708 minfreq=0%
709 maxfreq=100%
710 policy=powersave
711 [/Profile]
712
713 [Profile]
714 name=performance
715 minfreq=0%
716 maxfreq=100%
717 policy=performance
718 [/Profile]
719
720 [Rule]
721 name=battery
722 ac=off
723 profile=conservative
724 [/Rule]
725
726 [Rule]
727 name=battery_low
728 ac=off
729 battery_interval=0-10
730 profile=powersave
731 [/Rule]
732
733 [Rule]
734 name=ac
735 ac=on
736 profile=ondemand
737 [/Rule]
738 </pre>
739
740 <p>
741 Now you can start the cpufreqd daemon. Add it to the <c>default</c> and
742 <c>battery</c> runlevel as well.
743 </p>
744
745 <pre caption="Starting cpufreqd">
746 # <i>rc-update add cpufreqd default battery</i>
747 # <i>rc</i>
748 </pre>
749
750 <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 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 </p>
758
759 <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 </body>
765 </section>
766 <section>
767 <title>Verifying the result</title>
768 <body>
769
770 <p>
771 The last thing to check is that your new policies do a good job. An easy way to
772 do so is monitoring CPU speed while working with your laptop:
773 </p>
774
775 <pre caption="Monitoring CPU speed">
776 # <i>watch grep \"cpu MHz\" /proc/cpuinfo</i>
777 </pre>
778
779 <p>
780 If <path>/proc/cpuinfo</path> doesn't get updated (see <uri
781 link="#doc_chap8">Troubleshooting</uri>), monitor the CPU frequency with:
782 </p>
783
784 <pre caption="Alternative CPU speed monitoring">
785 # <i>watch x86info -mhz</i>
786 </pre>
787
788 <p>
789 Depending on your setup, CPU speed should increase on heavy load, decrease on
790 no activity or just stay at the same level. When using <c>cpufreqd</c> and
791 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 </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 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 </p>
811
812 </body>
813 </section>
814 <section>
815 <title>Standby settings</title>
816 <body>
817
818 <p>
819 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 yourself. Just two common places: Blanking the terminal can be done with
822 <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 </p>
826
827 <pre caption="LCD suspend settings in X.org and XFree86">
828 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 </body>
852 </section>
853 <section>
854 <title>Backlight dimming</title>
855 <body>
856
857 <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 battery mode and place it in your <c>battery</c> runlevel. The following script
861 should work on most IBM Thinkpads and Toshiba laptops. You've got to enable the
862 appropriate option in your kernel (IBM Thinkpads only). For Toshiba laptops,
863 install <c>sys-power/acpitool</c> and skip configuration of <c>ibm_acpi</c> as
864 described below.
865 </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 # <i>echo "options ibm_acpi experimental=1" >> /etc/modules.d/ibm_acpi</i>
881 # <i>/sbin/update-modules</i>
882 # <i>echo ibm_acpi >> /etc/modules.autoload.d/kernel-2.6</i>
883 # <i>modprobe ibm_acpi</i>
884 </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 module. An init script will take care of choosing the brightness according to
890 the power source.
891 </p>
892
893 <pre caption="/etc/conf.d/lcd-brightness">
894 <comment># See /proc/acpi/ibm/brightness for available values</comment>
895 <comment># Please read /usr/src/linux/Documentation/ibm-acpi.txt</comment>
896
897 <comment># brightness level in ac mode. Default is 7.</comment>
898 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 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 else
926 ewarn "Setting LCD brightness is not supported."
927 ewarn "For IBM Thinkpads, check that ibm_acpi is loaded into the kernel"
928 ewarn "For Toshiba laptops, you've got to install sys-power/acpitool"
929 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 </p>
945
946 <pre caption="Enabling automatic brightness adjustment">
947 # <i>chmod +x /etc/init.d/lcd-brightness</i>
948 # <i>rc-update add lcd-brightness battery</i>
949 # <i>rc</i>
950 </pre>
951
952 </body>
953 </section>
954 </chapter>
955
956 <chapter>
957 <title>Disk Power Management</title>
958 <section>
959 <body>
960
961 <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 features of your hard disk with <c>hdparm</c> as the second alternative.
971 </p>
972
973 </body>
974 </section>
975 <section>
976 <title>Increasing idle time - laptop-mode</title>
977 <body>
978
979 <p>
980 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 </p>
984
985 <pre caption="Automated start of laptop-mode">
986 # <i>emerge laptop-mode-tools</i>
987 </pre>
988
989 <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 by Gentoo's <c>/sbin/rc</c>) or use your <c>default</c>/<c>battery</c>
1002 runlevels (recommended).
1003 </p>
1004
1005 <pre caption="Sample output from running lm-profiler">
1006 # <i>lm-profiler</i>
1007 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 Do you want to disable this service in battery mode? [y/N]: <i>n</i>
1029 </pre>
1030
1031 <p>
1032 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 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 </p>
1038
1039 </body>
1040 </section>
1041 <section>
1042 <title>Limiting Write Accesses</title>
1043 <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 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 </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 The second possibility is using <c>hdparm</c>. Skip this if
1073 you are using laptop-mode. Otherwise, edit <path>/etc/conf.d/hdparm</path> and
1074 add the following values to your drive entries. This example assumes your hard
1075 drive is called <b>hda</b>:
1076 </p>
1077
1078 <pre caption="Using /etc/conf.d/hdparm for disk standby">
1079 hda_args="-q -S12"
1080 </pre>
1081
1082 <p>
1083 This will activate power management for your hard drive. If you ever want to
1084 deactivate power management, you can edit <path>/etc/conf.d/hdparm</path> and
1085 change the values to <c>-q -S0</c>, or just run <c>hdparm -q -S0 /dev/hda</c>.
1086 </p>
1087
1088 <p>
1089 See <c>man hdparm</c> for the options. Though you can always start <c>hdparm</c>
1090 manually when you are on battery power by running <c>/etc/init.d/hdparm
1091 start</c>, it's much easier to automate its startup and shutdown. To do so, add
1092 <c>hdparm</c> to the battery runlevel so that it will automatically enable power
1093 management.
1094 </p>
1095
1096 <pre caption="Automate disk standby settings">
1097 # <i>rc-update add hdparm battery</i>
1098 </pre>
1099
1100 <impo>
1101 Be careful with sleep/spin down settings of your hard drive. Setting it to
1102 small values might wear out your drive and lose warranty.
1103 </impo>
1104
1105 </body>
1106 </section>
1107 <section>
1108 <title>Other tricks</title>
1109 <body>
1110
1111 <p>
1112 Another possibility is to deactivate swap in battery mode. Before writing a
1113 swapon/swapoff switcher, make sure there is enough RAM and swap isn't used
1114 heavily, otherwise you'll be in big problems.
1115 </p>
1116
1117 <p>
1118 If you don't want to use laptop-mode, it's still possible to minimize disk
1119 access by mounting certain directories as <c>tmpfs</c> - write accesses are not
1120 stored on a disk, but in main memory and get lost with unmounting. Often it's
1121 useful to mount <path>/tmp</path> like this - you don't have to pay special
1122 attention as it gets cleared on every reboot regardless whether it was mounted
1123 on disk or in RAM. Just make sure you have enough RAM and no program (like a
1124 download client or compress utility) needs extraordinary much space in
1125 <path>/tmp</path>. To activate this, enable tmpfs support in your kernel and
1126 add a line to <path>/etc/fstab</path> like this:
1127 </p>
1128
1129 <pre caption="Editing /etc/fstab to make /tmp even more volatile">
1130 none /tmp tmpfs size=32m 0 0
1131 </pre>
1132
1133 <warn>
1134 Pay attention to the size parameter and modify it for your system. If you're
1135 unsure, don't try this at all, it can become a performance bottleneck easily. In
1136 case you want to mount <path>/var/log</path> like this, make sure to merge the
1137 log files to disk before unmounting. They are essential. Don't attempt to mount
1138 <path>/var/tmp</path> like this. Portage uses it for compiling...
1139 </warn>
1140
1141 </body>
1142 </section>
1143 </chapter>
1144
1145 <chapter>
1146 <title>Power Management For Other Devices</title>
1147 <section>
1148 <title>Graphics Cards</title>
1149 <body>
1150
1151 <p>
1152 In case you own an ATI graphics card supporting PowerPlay (dynamic clock
1153 scaling for the graphics processing unit GPU), you can activate this
1154 feature in X.org. Open <path>/etc/X11/xorg.conf</path> and add (or enable) the
1155 <c>DynamicClocks</c> option in the Device section. Please notice that this
1156 feature will lead to crashes on some systems.
1157 </p>
1158
1159 <pre caption="Enabling ATI PowerPlay support in X.org">
1160 Section "Device"
1161 [...]
1162 Option "DynamicClocks" "on"
1163 EndSection
1164 </pre>
1165
1166 </body>
1167 </section>
1168 <section>
1169 <title>Wireless Power Management</title>
1170 <body>
1171
1172 <p>
1173 Wireless LAN cards consume quite a bit of energy. Put them in Power Management
1174 mode just like your hard drives.
1175 </p>
1176
1177 <note>
1178 This script assumes your wireless interface is called <c>wlan0</c>; replace
1179 this with the actual name of your interface.
1180 </note>
1181
1182 <p>
1183 Add the following option to <path>/etc/conf.d/net</path> to automatically enable
1184 power management for your wireless card:
1185 </p>
1186
1187 <pre caption="Automated WLAN Power Management">
1188 iwconfig_wlan0="power on"
1189 </pre>
1190
1191 <p>
1192 See <c>man iwconfig</c> for details and more options like the period between
1193 wakeups or timeout settings. If your driver and access point support changing
1194 the beacon time, this is a good starting point to save even more energy.
1195 </p>
1196
1197 </body>
1198 </section>
1199 <section>
1200 <title>USB Power Management</title>
1201 <body>
1202
1203 <p>
1204 There are two problems with USB devices regarding energy consumption: First,
1205 devices like USB mice, digital cameras or USB sticks consume energy while
1206 plugged in. You cannot avoid this (nevertheless remove them in case they're not
1207 needed). Second, when there are USB devices plugged in, the USB host controller
1208 periodically accesses the bus which in turn prevents the CPU from going into
1209 sleep mode. The kernel offers an experimental option to enable suspension of
1210 USB devices through driver calls or one of the <path>power/state</path> files
1211 in <path>/sys</path>.
1212 </p>
1213
1214 <pre caption="Enabling USB suspend support in the kernel">
1215 Device Drivers
1216 USB support
1217 [*] Support for Host-side USB
1218 [*] USB suspend/resume (EXPERIMENTAL)
1219 </pre>
1220
1221 </body>
1222 </section>
1223 </chapter>
1224
1225 <chapter>
1226 <title>Sleep States: sleep, standby, and suspend to disk</title>
1227 <section>
1228 <body>
1229
1230 <p>
1231 ACPI defines different sleep states. The more important ones are
1232 </p>
1233
1234 <ul>
1235 <li>S1 aka Standby</li>
1236 <li>S3 aka Suspend to RAM aka Sleep</li>
1237 <li>S4 aka Suspend to Disk aka Hibernate</li>
1238 </ul>
1239
1240 <p>
1241 They can be called whenever the system is not in use, but a shutdown is not
1242 wanted due to the long boot time.
1243 </p>
1244
1245 </body>
1246 </section>
1247 <section>
1248 <title>Sleep (S3)</title>
1249 <body>
1250
1251 <p>
1252 The ACPI support for these sleep states is marked experimental for good reason.
1253 APM sleep states seem to be more stable, however you can't use APM and ACPI
1254 together.
1255 </p>
1256
1257 <pre caption="Kernel configuration for the various suspend types">
1258 Power Management Options ---&gt;
1259 [*] Power Management support
1260 ACPI (Advanced Configuration and Power Interface) Support ---&gt;
1261 [*] ACPI Support
1262 [*] Sleep States
1263 </pre>
1264
1265 <p>
1266 Once your kernel is properly configured, you can use the
1267 <c>hibernate-script</c> to activate suspend or sleep mode. Let's install that
1268 first.
1269 </p>
1270
1271 <pre caption="Installing the hibernate-script">
1272 # <i>emerge hibernate-script</i>
1273 </pre>
1274
1275 <p>
1276 Some configuration has to be done in <path>/etc/hibernate</path>. The default
1277 package introduces a few configuration files for each sleep state. Options that
1278 are common to all suspend methods are placed in <path>common.conf</path>; make
1279 sure this file is properly set up for your system.
1280 </p>
1281
1282 <p>
1283 To configure sleep, edit <path>sysfs-ram.conf</path> in
1284 <path>/etc/hibernate</path>. <c>UseSysfsPowerState mem</c> is already setup
1285 correctly, but if you need to make further changes to this particular sleep
1286 state (or any other sleep state) you should add them to
1287 <path>/etc/hibernate/hibernate.conf</path>. The comments and option names will
1288 guide you. If you use nfs or samba shares over the network, make sure to
1289 shutdown the appropriate init scripts to avoid timeouts.
1290 </p>
1291
1292 <note>
1293 For more information on setting up sleep states, read <c>man
1294 hibernate.conf</c>.
1295 </note>
1296
1297 <p>
1298 Ready? Now is the last chance to backup any data you want to keep after
1299 executing the next command. Notice that you probably have to hit a special key
1300 like <c>Fn</c> to resume from sleep.
1301 </p>
1302
1303 <pre caption="Calling sleep">
1304 # <i>hibernate-ram</i>
1305 </pre>
1306
1307 <p>
1308 If you're still reading, it seems to work. You can also setup standby (S1) in a
1309 similar way by editing <path>sysfs-ram.conf</path> and changing
1310 "UseSysfsPowerState mem" to "UseSysfsPowerState standby". S3 and S4 are the more
1311 interesting sleep states due to greater energy savings however.
1312 </p>
1313
1314 </body>
1315 </section>
1316 <section>
1317 <title>Hibernate (S4)</title>
1318 <body>
1319
1320 <p>
1321 This section introduces hibernation, where a snapshot of the running system is
1322 written to disk before powering off. On resume, the snapshot is loaded and you
1323 can go on working at exactly the point you called hibernate before.
1324 </p>
1325
1326 <warn>
1327 Don't exchange non hot-pluggable hardware when suspended. Don't attempt to load
1328 a snapshot with a different kernel image than the one it was created with.
1329 Shutdown any NFS or samba server/client before hibernating.
1330 </warn>
1331
1332 <p>
1333 There are two different implementations for S4. The original one is swsusp,
1334 then there is the newer suspend2 with a nicer interface (including fbsplash
1335 support). A <uri link="http://suspend2.net/features.html#compare"> feature
1336 comparison</uri> is available at the <uri link="http://suspend2.net"> suspend2
1337 Homepage</uri>. There used to be Suspend-to-Disk (pmdisk), a fork of swsusp,
1338 but it has been merged back.
1339 </p>
1340
1341 <p>
1342 Suspend2 is not included in the mainline kernel yet, therefore you either have
1343 to patch your kernel sources with the patches provided by <uri
1344 link="http://suspend2.net">suspend2.net</uri> or use
1345 <c>sys-kernel/suspend2-sources</c>.
1346 </p>
1347
1348 <p>
1349 The kernel part for both swusp and suspend2 is as follows:
1350 </p>
1351
1352 <pre caption="Kernel configuration for the various suspend types">
1353 Power Management Options ---&gt;
1354 <comment>(hibernate with swsusp)</comment>
1355 [*] Software Suspend
1356 <comment>(replace /dev/SWAP with your swap partition)</comment>
1357 (/dev/SWAP) Default resume partition
1358
1359 <comment>(hibernate with suspend2)</comment>
1360 Software Suspend 2
1361 --- Image Storage (you need at least one writer)
1362 [*] File Writer
1363 [*] Swap Writer
1364 --- General Options
1365 [*] LZF image compression
1366 <comment>(replace /dev/SWAP with your swap partition)</comment>
1367 (swap:/dev/SWAP) Default resume device name
1368 [ ] Allow Keep Image Mode
1369 </pre>
1370
1371 <p>
1372 The configuration for swsusp is rather easy. If you didn't store the location
1373 of your swap partition in the kernel config, you can also pass it as a
1374 parameter with the <c>resume=/dev/SWAP</c> directive. If booting is not
1375 possible due to a broken image, use the <c>noresume</c> kernel parameter. The
1376 <c>hibernate-cleanup</c> init script invalidates swsusp images during the boot
1377 process.
1378 </p>
1379
1380 <pre caption="Invalidating swsusp images during the boot process">
1381 # <i>rc-update add hibernate-cleanup boot</i>
1382 </pre>
1383
1384 <p>
1385 To activate hibernate with swsusp, use the hibernate script and set
1386 <c>UseSysfsPowerState disk</c> in <path>/etc/hibernate/sysfs-disk</path>.
1387 </p>
1388
1389 <warn>
1390 Backup your data before doing this. Run <c>sync</c> before executing one of the
1391 commands to have cached data written to disk. First try it outside of X, then
1392 with X running, but not logged in.
1393 </warn>
1394
1395 <p>
1396 If you experience kernel panics due to uhci or similar, try to compile USB
1397 support as module and unload the modules before sending your laptop to sleep
1398 mode. There are configuration options for this in <path>common.conf</path>
1399 </p>
1400
1401 <pre caption="Hibernating with swsusp">
1402 # <i>nano -w /etc/hibernate/common.conf</i>
1403 <comment>(Make sure you have a backup of your data)</comment>
1404 # <i>hibernate</i>
1405 </pre>
1406
1407 <p>
1408 The following section discusses the setup of suspend2 including fbsplash
1409 support for a nice graphical progress bar during suspend and resume.
1410 </p>
1411
1412 <p>
1413 The first part of the configuration is similar to the configuration of swsusp.
1414 In case you didn't store the location of your swap partition in the kernel
1415 config, you have to pass it as a kernel parameter with the
1416 <c>resume2=swap:/dev/SWAP</c> directive. If booting is not possible due to a
1417 broken image, append the <c>noresume2</c> parameter. Additionally, the
1418 <c>hibernate-cleanup</c> init script invalidates suspend2 images during the
1419 boot process.
1420 </p>
1421
1422 <pre caption="Invalidating suspend2 images during the boot process">
1423 # <i>rc-update add hibernate-cleanup boot</i>
1424 </pre>
1425
1426 <p>
1427 Now edit <path>/etc/hibernate/suspend2.conf</path>, enable the <c>suspend2</c>
1428 options you need. Do not enable the <c>fbsplash</c> options in
1429 <c>common.conf</c> just yet.
1430 </p>
1431
1432 <pre caption="Hibernating with suspend2">
1433 # <i>nano -w /etc/hibernate/suspend2.conf</i>
1434 <comment>(Make sure you have a backup of your data)</comment>
1435 # <i>hibernate</i>
1436 </pre>
1437
1438 <p>
1439 Please configure <c>fbsplash</c> now if you didn't do already. To enable
1440 fbsplash support during hibernation, the <c>sys-apps/suspend2-userui</c>
1441 package is needed. Additionally, you've got to enable the <c>fbsplash</c> USE
1442 flag.
1443 </p>
1444
1445 <pre caption="Installing suspend2-userui">
1446 # <i>echo "sys-apps/suspend2-userui fbsplash" >> /etc/portage/package.use</i>
1447 <comment>(It may be marked ~arch, so first it must be keyworded)</comment>
1448 # <i>echo "sys-apps/suspend2-userui" >> /etc/portage/package.keywords</i>
1449 # <i>emerge suspend2-userui</i>
1450 </pre>
1451
1452 <p>
1453 The ebuild tells you to make a symlink to the theme you want to use. For
1454 example, to use the <c>livecd-2005.1</c> theme, run the following command:
1455 </p>
1456
1457 <pre caption="Using the livecd-2005.1 theme during hibernation">
1458 # <i>ln -sfn /etc/splash/livecd-2005.1 /etc/splash/suspend2</i>
1459 </pre>
1460
1461 <p>
1462 If you don't want a black screen in the first part of the resume process, you
1463 have to add the <c>suspend2ui_fbsplash</c> tool to your initrd image. Assuming
1464 you created the initrd image with <c>splash_geninitramfs</c> and saved it as
1465 <path>/boot/fbsplash-emergence-1024x768</path>, here's how to do that.
1466 </p>
1467
1468 <pre caption="Adding suspend2ui_fbsplash to an initrd image">
1469 # <i>mount /boot</i>
1470 # <i>mkdir ~/initrd.d</i>
1471 # <i>cp /boot/fbsplash-emergence-1024x768 ~/initrd.d/</i>
1472 # <i>cd ~/initrd.d</i>
1473 # <i>gunzip -c fbsplash-emergence-1024x768 | cpio -idm --quiet -H newc</i>
1474 # <i>rm fbsplash-emergence-1024x768</i>
1475 # <i>cp /usr/sbin/suspend2ui_fbsplash sbin/</i>
1476 # <i>find . | cpio --quiet --dereference -o -H newc | gzip -9 > /boot/fbsplash-suspend2-emergence-1024x768</i>
1477 </pre>
1478
1479 <p>
1480 Afterwards adjust <path>grub.conf</path> (or <path>lilo.conf</path>) so that
1481 your suspend2 kernel uses
1482 <path>/boot/fbsplash-suspend2-emergence-1024x768</path> as initrd image. You can
1483 now test a dry run to see if everything is setup correctly.
1484 </p>
1485
1486 <pre caption="Test run for fbsplash hibernation">
1487 # <i>suspend2ui_fbsplash -t</i>
1488 </pre>
1489
1490 <p>
1491 Afterwards open <path>/etc/hibernate/common.conf</path> and activate the
1492 fbsplash options. Execute <c>hibernate</c> and enjoy.
1493 </p>
1494
1495 </body>
1496 </section>
1497 </chapter>
1498
1499 <chapter>
1500 <title>Troubleshooting</title>
1501 <section>
1502 <body>
1503
1504 <p>
1505 <e>Q:</e> I'm trying to change the CPU frequency, but
1506 <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor</path> does not
1507 exist.
1508 </p>
1509
1510 <p>
1511 <e>A:</e> Make sure your processor supports CPU frequency scaling and you chose
1512 the right CPUFreq driver for your processor. Here is a list of processors that
1513 are supported by cpufreq (kernel 2.6.7): ARM Integrator, ARM-SA1100,
1514 ARM-SA1110, AMD Elan - SC400, SC410, AMD mobile K6-2+, AMD mobile K6-3+, AMD
1515 mobile Duron, AMD mobile Athlon, AMD Opteron, AMD Athlon 64, Cyrix Media GXm,
1516 Intel mobile PIII and Intel mobile PIII-M on certain chipsets, Intel Pentium 4,
1517 Intel Xeon, Intel Pentium M (Centrino), National Semiconductors Geode GX,
1518 Transmeta Crusoe, VIA Cyrix 3 / C3, UltraSPARC-III, SuperH SH-3, SH-4, several
1519 "PowerBook" and "iBook2" and various processors on some ACPI 2.0-compatible
1520 systems (only if "ACPI Processor Performance States" are available to the
1521 ACPI/BIOS interface).
1522 </p>
1523
1524 <p>
1525 <e>Q:</e> My laptop supports frequency scaling, but
1526 <path>/sys/devices/system/cpu/cpu0/cpufreq/</path> is empty.
1527 </p>
1528
1529 <p>
1530 <e>A:</e> Look for ACPI related error messages with <c>dmesg | grep ACPI</c>.
1531 Try to update the BIOS, especially if a broken DSDT is reported. You can also
1532 try to fix it yourself (which is beyond the scope of this guide).
1533 </p>
1534
1535 <p>
1536 <e>Q:</e> My laptop supports frequency scaling, but according to
1537 <path>/proc/cpuinfo</path> the speed never changes.
1538 </p>
1539
1540 <p>
1541 <e>A:</e> Probably you have activated symmetric multiprocessing support
1542 (CONFIG_SMP) in your kernel. Deactivate it and it should work. Some older
1543 kernels had a bug causing this. In that case, run <c>emerge x86info</c>, update
1544 your kernel as asked and check the current frequency with
1545 <c>x86info -mhz</c>.
1546 </p>
1547
1548 <p>
1549 <e>Q:</e> I can change the CPU frequency, but the range is not as wide as in
1550 another OS.
1551 </p>
1552
1553 <p>
1554 <e>A:</e> You can combine frequency scaling with ACPI throttling to get a lower
1555 minimum frequency. Notice that throttling doesn't save much energy and is
1556 mainly used for thermal management (keeping your laptop cool and quiet). You
1557 can read the current throttling state with <c>cat
1558 /proc/acpi/processor/CPU/throttling</c> and change it with <c>echo -n "0:x" >
1559 /proc/acpi/processor/CPU/limit</c>, where x is one of the Tx states listed in
1560 <path>/proc/acpi/processor/CPU/throttling</path>.
1561 </p>
1562
1563 <p>
1564 <e>Q:</e> When configuring the kernel, powersave, performance and userspace
1565 governors show up, but that ondemand thing is missing. Where do I get it?
1566 </p>
1567
1568 <p>
1569 <e>A:</e> The ondemand governor is only included in recent kernel sources. Try
1570 updating them.
1571 </p>
1572
1573 <p>
1574 <e>Q:</e> Battery life time seems to be worse than before.
1575 </p>
1576
1577 <p>
1578 <e>A:</e> Check your BIOS settings. Maybe you forgot to re-enable some of the
1579 settings.
1580 </p>
1581
1582 <p>
1583 <e>Q:</e> My battery is charged, but KDE reports there would be 0% left and
1584 immediately shuts down.
1585 </p>
1586
1587 <p>
1588 <e>A:</e> Check that battery support is compiled into your kernel. If you use
1589 it as a module, make sure the module is loaded.
1590 </p>
1591
1592 <p>
1593 <e>Q:</e> My system logger reports things like "logger: ACPI group battery /
1594 action battery is not defined".
1595 </p>
1596
1597 <p>
1598 <e>A:</e> This message is generated by the <path>/etc/acpi/default.sh</path>
1599 script that is shipped with acpid. You can safely ignore it. If you like to get
1600 rid of it, you can comment the appropriate line in
1601 <path>/etc/acpi/default.sh</path> as shown below:
1602 </p>
1603
1604 <pre caption="Disabling warnings about unknown acpi events">
1605 *) # logger "ACPI action $action is not defined"
1606 </pre>
1607
1608 <p>
1609 <e>Q:</e> I have a Dell Inspiron 51XX and I don't get any ACPI events.
1610 </p>
1611
1612 <p>
1613 <e>A:</e> This seems to be a kernel bug. Read on <uri
1614 link="http://bugme.osdl.org/show_bug.cgi?id=1752">here</uri>.
1615 </p>
1616
1617 <p>
1618 <e>Q:</e> I activated the <c>DynamicClocks</c> option in <path>xorg.conf</path>
1619 and now X.org crashes / the screen stays black / my laptop doesn't shutdown
1620 properly.
1621 </p>
1622
1623 <p>
1624 <e>A:</e> This happens on some systems. You have to disable
1625 <c>DynamicClocks</c>.
1626 </p>
1627
1628 <p>
1629 <e>Q:</e> I want to use suspend2, but it tells me my swap partition is too
1630 small. Resizing is not an option.
1631 </p>
1632
1633 <p>
1634 <e>A:</e> If there is enough free space on your system, you can use the
1635 filewriter instead of the swapwriter. The <c>hibernate-script</c> supports it
1636 as well. More information can be found in
1637 <path>/usr/src/linux/Documentation/power/suspend2.txt</path>.
1638 </p>
1639
1640 <p>
1641 <e>Q:</e> I just bought a brand new battery, but it only lasts for some
1642 minutes! What am I doing wrong?
1643 </p>
1644
1645 <p>
1646 <e>A:</e> First follow your manufacturer's advice on how to charge the battery
1647 correctly.
1648 </p>
1649
1650 <p>
1651 <e>Q:</e> The above didn't help. What should I do then?
1652 </p>
1653
1654 <p>
1655 <e>A:</e> Some batteries sold as "new" are in fact old ones. Try the following:
1656 </p>
1657
1658 <pre caption="Querying battery state">
1659 $ <i>grep capacity /proc/acpi/battery/BAT0/info</i>
1660 design capacity: 47520 mWh
1661 last full capacity: 41830 mWh
1662 </pre>
1663
1664 <p>
1665 If the "last full capacity" differs significantly from the design capacity,
1666 your battery is probably broken. Try to claim your warranty.
1667 </p>
1668
1669 <p>
1670 <e>Q:</e> My problem is not listed above. Where should I go next?
1671 </p>
1672
1673 <p>
1674 <e>A:</e> Don't fear to contact me, <mail link="earthwings@gentoo.org">Dennis
1675 Nienhüser</mail>, directly. The <uri link="http://forums.gentoo.org">Gentoo
1676 Forums</uri> are a good place to get help as well. If you prefer IRC, try the
1677 <c>#gentoo-laptop</c> channel at <uri
1678 link="irc://irc.freenode.net">irc.freenode.net</uri>.
1679 </p>
1680
1681 </body>
1682 </section>
1683 </chapter>
1684 </guide>

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