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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 1.41 2009/08/12 02:24:57 nightmorph Exp $ -->
4
5 <guide>
6 <title>Power Management Guide</title>
7
8 <author title="Author">
9 <mail link="earthwings@gentoo.org">Dennis Nienhüser</mail>
10 </author>
11 <author title="Editor">
12 <mail link="chriswhite@gentoo.org">Chris White</mail>
13 </author>
14 <author title="Editor">
15 <mail link="nightmorph"/>
16 </author>
17
18 <abstract>
19 Power Management is the key to extend battery run time on mobile systems like
20 laptops. This guide assists you setting it up on your laptop.
21 </abstract>
22
23 <!-- The content of this document is licensed under the CC-BY-SA license -->
24 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
25 <license/>
26
27 <version>1.45</version>
28 <date>2010-01-22</date>
29
30 <chapter>
31 <title>Introduction</title>
32 <section>
33 <body>
34
35 <p>
36 Capacity and lifetime of laptop batteries have improved much in the last years.
37 Nevertheless modern processors consume much more energy than older ones and
38 each laptop generation introduces more devices hungry for energy. That's why
39 Power Management is more important than ever. Increasing battery run time
40 doesn't necessarily mean buying another battery. Much can be achieved applying
41 intelligent Power Management policies.
42 </p>
43
44 </body>
45 </section>
46 <section>
47 <title>A Quick Overview</title>
48 <body>
49
50 <p>
51 Please notice that this guide describes Power Management for <e>laptops</e>.
52 While some sections might also suite for <e>servers</e>, others do not and may
53 even cause harm. Please do not apply anything from this guide to a server
54 unless you really know what you are doing.
55 </p>
56
57 <p>
58 As this guide has become rather long, here's a short overview helping you to
59 find your way through it.
60 </p>
61
62 <p>
63 The <uri link="#doc_chap2">Prerequisites</uri> chapter talks about some
64 requirements that should be met before any of the following device individual
65 sections will work. This includes BIOS settings, kernel configuration and some
66 simplifications in user land. The following three chapters focus on devices
67 that typically consume most energy - processor, display and hard drive. Each
68 can be configured seperately. <uri link="#doc_chap3">CPU Power Management</uri>
69 shows how to adjust the processor's frequency to save a maximum of energy
70 without losing too much performance. A few different tricks prevent your hard
71 drive from working unnecessarily often in <uri link="#doc_chap5">Disk Power
72 Management</uri> (decreasing noise level as a nice side effect). Some notes on
73 graphics cards, Wireless LAN and USB finish the device section in <uri
74 link="#doc_chap6">Power Management For Other Devices</uri> while another
75 chapter is dedicated to the (rather experimental) <uri link="#doc_chap7">sleep
76 states</uri>. Last not least <uri link="#doc_chap8">Troubleshooting</uri> lists
77 common pitfalls.
78 </p>
79
80 </body>
81 </section>
82 <section>
83 <title>Power Budget For Each Component</title>
84 <body>
85
86 <figure link="/images/energy-budget.png" short="Which component consumes how
87 much energy?" caption="Power budget for each component"/>
88
89 <p>
90 Nearly every component can operate in different states - off, sleep, idle,
91 active to name a few - consuming a different amount of energy. Major parts are
92 consumed by the LCD display, CPU, chipset and hard drives. Often one is able to
93 activate OS-independent Power Management in the BIOS, but an intelligent setup
94 in the operating system adapting to different situations can achieve much more.
95 </p>
96
97 </body>
98 </section>
99 </chapter>
100
101 <chapter>
102 <title>Prerequisites</title>
103 <section>
104 <body>
105
106 <p>
107 Before discussing the details of making individual devices Power Management
108 aware, make sure certain requirements are met. After controlling BIOS settings,
109 some kernel options want to be enabled - these are in short ACPI, sleep states
110 and CPU frequency scaling. As power saving most of the time comes along with
111 performance loss or increased latency, it should only be enabled when running
112 on batteries. That's where a new runlevel <e>battery</e> comes in handy.
113 </p>
114
115 </body>
116 </section>
117 <section>
118 <title>The BIOS Part</title>
119 <body>
120
121 <p>
122 First have a look into your BIOS Power Management settings. The best way is to
123 combine BIOS and operating system policies, but for the moment it's better to
124 disable most of the BIOS part. This makes sure it doesn't interfere with your
125 policies. Don't forget to re-check BIOS settings after you configured
126 everything else.
127 </p>
128
129 </body>
130 </section>
131 <section>
132 <title>Setting USE Flags</title>
133 <body>
134
135 <p>
136 Please check that the <c>acpi</c> USE flag is set in
137 <path>/etc/make.conf</path>. Other USE flags that might be interesting for your
138 system are <c>apm</c>, <c>lm_sensors</c>, <c>nforce2</c>, <c>nvidia</c>,
139 <c>pmu</c>. See <path>/usr/portage/profiles/use*.desc</path> for details. If
140 you forgot to set one of these flags, you can recompile affected packages using
141 the <c>--newuse</c> flag in <c>emerge</c>, see <c>man emerge</c>.
142 </p>
143
144 </body>
145 </section>
146 <section>
147 <title>Configuring The Kernel</title>
148 <body>
149
150 <p>
151 ACPI (Advanced Configuration and Power Interface) support in the kernel is
152 still work in progress. Using a recent kernel will make sure you'll get the
153 most out of it.
154 </p>
155
156 <p>
157 There are different kernel sources in Portage. I'd recommend using
158 <c>gentoo-sources</c> or <c>tuxonice-sources</c>. The latter contains patches
159 for TuxOnIce, see the chapter about <uri link="#doc_chap7">sleep states</uri>
160 for more details. When configuring the kernel, activate at least these options:
161 </p>
162
163 <pre caption="Minimum kernel setup for Power Management (Kernel 2.6)">
164 Power management and ACPI options ---&gt;
165 [*] Power Management support
166 [ ] Software Suspend
167
168 ACPI( Advanced Configuration and Power Interface ) Support ---&gt;
169 [ ] Deprecated /proc/acpi/ files
170 [*] AC Adapter
171 [*] Battery
172 &lt;M&gt; Button
173 &lt;M&gt; Video
174 [ ] Generic Hotkey
175 &lt;M&gt; Fan
176 &lt;M&gt; Processor
177 &lt;M&gt; Thermal Zone
178 &lt; &gt; ASUS/Medion Laptop Extras
179 &lt; &gt; IBM ThinkPad Laptop Extras
180 &lt; &gt; Toshiba Laptop Extras
181 (0) Disable ACPI for systems before Jan 1st this year
182 [ ] Debug Statements
183 [*] Power Management Timer Support
184 &lt; &gt; ACPI0004,PNP0A05 and PNP0A06 Container Driver (EXPERIMENTAL)
185
186 CPU Frequency Scaling ---&gt;
187 [*] CPU Frequency scaling
188 [ ] Enable CPUfreq debugging
189 &lt; &gt; CPU frequency translation statistics
190 [ ] CPU frequency translation statistics details
191 Default CPUFreq governor (userspace)
192 &lt;*&gt; 'performance' governor
193 &lt;*&gt; 'powersave' governor
194 &lt;*&gt; 'ondemand' cpufreq policy governor
195 &lt;*&gt; 'conservative' cpufreq governor
196 &lt;*&gt; CPU frequency table helpers
197 &lt;M&gt; ACPI Processor P-States driver
198 &lt;*&gt; <i>CPUFreq driver for your processor</i>
199 </pre>
200
201 <p>
202 Decide yourself whether you want to enable Software Suspend, and Sleep States
203 (see below). If you own an ASUS, Medion, IBM Thinkpad or Toshiba laptop, enable
204 the appropriate section.
205 </p>
206
207 <p>
208 The kernel has to know how to enable CPU frequency scaling on your processor.
209 As each type of CPU has a different interface, you've got to choose the right
210 driver for your processor. Be careful here - enabling <c>Intel Pentium 4 clock
211 modulation</c> on a Pentium M system will lead to strange results for example.
212 Consult the kernel documentation if you're unsure which one to take.
213 </p>
214
215 <p>
216 Compile your kernel, make sure the right modules get loaded at startup and boot
217 into your new ACPI-enabled kernel. Next run <c>emerge sys-power/acpid</c> to
218 get the acpi daemon. This one informs you about events like switching from AC
219 to battery or closing the lid. Make sure the modules are loaded if you didn't
220 compile them into the kernel and start acpid by executing <c>/etc/init.d/acpid
221 start</c>. Run <c>rc-update add acpid default</c> to load it on startup. You'll
222 soon see how to use it.
223 </p>
224
225 <pre caption="Installing acpid">
226 # <i>emerge sys-power/acpid</i>
227 # <i>/etc/init.d/acpid start</i>
228 # <i>rc-update add acpid default</i>
229 </pre>
230
231 </body>
232 </section>
233 <section>
234 <title>Creating A "battery" Runlevel</title>
235 <body>
236
237 <p>
238 The default policy will be to enable Power Management only when needed -
239 running on batteries. To make the switch between AC and battery convenient,
240 create a runlevel <c>battery</c> that holds all the scripts starting and
241 stopping Power Management.
242 </p>
243
244 <note>
245 You can safely skip this section if you don't like the idea of having another
246 runlevel. However, skipping this step will make the rest a bit trickier to set
247 up. The next sections assume a runlevel <c>battery</c> exists.
248 </note>
249
250 <pre caption="Creating a battery runlevel">
251 # <i>cd /etc/runlevels</i>
252 # <i>cp -a default battery</i>
253 </pre>
254
255 <p>
256 Finished. Your new runlevel <c>battery</c> contains everything like
257 <c>default</c>, but there is no automatic switch between both yet. Time to
258 change it.
259 </p>
260
261 </body>
262 </section>
263 <section>
264 <title>Reacting On ACPI Events</title>
265 <body>
266
267 <p>
268 Typical ACPI events are closing the lid, changing the power source or pressing
269 the sleep button. An important event is changing the power source, which should
270 cause a runlevel switch. A small script will take care of it.
271 </p>
272
273 <p>
274 First you need a script which changes the runlevel to <c>default</c>
275 respectively <c>battery</c> depending on the power source. The script uses the
276 <c>on_ac_power</c> command from <c>sys-power/powermgmt-base</c> - make sure the
277 package is installed on your system.
278 </p>
279
280 <pre caption="Installing powermgt-base">
281 # <i>emerge powermgmt-base</i>
282 </pre>
283
284 <p>
285 You are now able to determine the power source by executing <c>on_ac_power
286 &amp;&amp; echo AC available || echo Running on batteries</c> in a shell. The
287 script below is responsible for changing runlevels. Save it as
288 <path>/etc/acpi/actions/pmg_switch_runlevel.sh</path>.
289 </p>
290
291 <pre caption="/etc/acpi/actions/pmg_switch_runlevel.sh">
292 #!/bin/bash
293
294 <comment># BEGIN configuration</comment>
295 RUNLEVEL_AC="default"
296 RUNLEVEL_BATTERY="battery"
297 <comment># END configuration</comment>
298
299
300 if [ ! -d "/etc/runlevels/${RUNLEVEL_AC}" ]
301 then
302 logger "${0}: Runlevel ${RUNLEVEL_AC} does not exist. Aborting."
303 exit 1
304 fi
305
306 if [ ! -d "/etc/runlevels/${RUNLEVEL_BATTERY}" ]
307 then
308 logger "${0}: Runlevel ${RUNLEVEL_BATTERY} does not exist. Aborting."
309 exit 1
310 fi
311
312 if on_ac_power
313 then
314 if [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_AC}" ]]
315 then
316 logger "Switching to ${RUNLEVEL_AC} runlevel"
317 /sbin/rc ${RUNLEVEL_AC}
318 fi
319 elif [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_BATTERY}" ]]
320 then
321 logger "Switching to ${RUNLEVEL_BATTERY} runlevel"
322 /sbin/rc ${RUNLEVEL_BATTERY}
323 fi
324 </pre>
325
326 <p>
327 Dont forget to run <c>chmod +x /etc/acpi/actions/pmg_switch_runlevel.sh</c> to
328 make the script executable. The last thing that needs to be done is calling the
329 script whenever the power source changes. That's done by catching ACPI events
330 with the help of <c>acpid</c>. First you need to know which events are
331 generated when the power source changes. The events are called
332 <c>ac_adapter</c> and <c>battery</c> on most laptops, but it might be different
333 on yours.
334 </p>
335
336 <pre caption="Determining ACPI events for changing the power source">
337 # <i>tail -f /var/log/messages | grep "ACPI event"</i>
338 </pre>
339
340 <p>
341 Run the command above and pull the power cable. You should see something like
342 this:
343 </p>
344
345 <pre caption="Sample output for power source changes">
346 [Tue Sep 20 17:39:06 2005] ACPI event "ac_adapter AC 00000080 00000000"
347 [Tue Sep 20 17:39:06 2005] ACPI event "battery BAT0 00000080 00000001"
348 </pre>
349
350 <p>
351 The interesting part is the quoted string after <c>received event</c>. It will
352 be matched by the event line in the files you are going to create below. Don't
353 worry if your system generates multiple events or always the same. As long as
354 any event is generated, runlevel changing will work.
355 </p>
356
357 <pre caption="/etc/acpi/events/pmg_ac_adapter">
358 <comment># replace "ac_adapter" below with the event generated on your laptop</comment>
359 <comment># For example, ac_adapter.* will match ac_adapter AC 00000080 00000000</comment>
360 event=ac_adapter.*
361 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
362 </pre>
363
364 <pre caption="/etc/acpi/events/pmg_battery">
365 <comment># replace "battery" below with the event generated on your laptop</comment>
366 <comment># For example, battery.* will match battery BAT0 00000080 00000001</comment>
367 event=battery.*
368 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
369 </pre>
370
371 <p>
372 Finally acpid has to be restarted to recognize the changes.
373 </p>
374
375 <pre caption="Finishing runlevel switching with acpid">
376 # <i>/etc/init.d/acpid restart</i>
377 </pre>
378
379 <p>
380 Give it a try: Plug AC in and out and watch syslog for the "Switching to AC
381 mode" or "Switching to battery mode" messages. See the <uri
382 link="#doc_chap8">Troubleshooting section</uri> if the script is not able to
383 detect the power source correctly.
384 </p>
385
386 <p>
387 Due to the nature of the event mechanism, your laptop will boot into runlevel
388 <c>default</c> regardless of the AC/battery state. This is fine when running
389 from AC, but we'd like to boot into the battery runlevel otherwise. One
390 solution would be to add another entry to the boot loader with the parameter
391 <c>softlevel=battery</c>, but it's likely to forget choosing it. A better way
392 is faking an ACPI event in the end of the boot process and letting
393 <path>pmg_switch_runlevel.sh</path> script decide whether a runlevel change is
394 necessary. Open <path>/etc/conf.d/local.start</path> in your favourite editor
395 and add these lines:
396 </p>
397
398 <pre caption="Runlevel adjustment at boot time by editing local.start">
399 <comment># Fake acpi event to switch runlevel if running on batteries</comment>
400 /etc/acpi/actions/pmg_switch_runlevel.sh "battery/battery"
401 </pre>
402
403 <p>
404 Prepared like this you can activate Power Management policies for individual
405 devices.
406 </p>
407
408 </body>
409 </section>
410 </chapter>
411
412 <chapter>
413 <title>CPU Power Management</title>
414 <section>
415 <body>
416
417 <p>
418 Mobile processors can operate at different frequencies. Some allow changing
419 voltage as well. Most of the time your CPU doesn't need to run at full speed
420 and scaling it down will save much energy - often without any performance
421 decrease.
422 </p>
423
424 </body>
425 </section>
426 <section>
427 <title>Some Technical Terms</title>
428 <body>
429
430 <p>
431 CPU frequency scaling brings up some technical terms that might be unknown to
432 you. Here's a quick introduction.
433 </p>
434
435 <p>
436 First of all, the kernel has to be able to change the processor's frequency.
437 The <b>CPUfreq processor driver</b> knows the commands to do it on your CPU.
438 Thus it's important to choose the right one in your kernel. You should already
439 have done it above. Once the kernel knows how to change frequencies, it has to
440 know which frequency it should set. This is done according to the <b>policy</b>
441 which consists of a <b>CPUfreq policy</b> and a <b>governor</b>. A CPUfreq
442 policy are just two numbers which define a range the frequency has to stay
443 between - minimal and maximal frequency. The governor now decides which of the
444 available frequencies in between minimal and maximal frequency to choose. For
445 example, the <b>powersave governor</b> always chooses the lowest frequency
446 available, the <b>performance governor</b> the highest one. The <b>userspace
447 governor</b> makes no decision but chooses whatever the user (or a program in
448 userspace) wants - which means it reads the frequency from
449 <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed</path>.
450 </p>
451
452 <p>
453 This doesn't sound like dynamic frequency changes yet and in fact it isn't.
454 Dynamics however can be accomplished with various approaches. For example, the
455 <b>ondemand governor</b> makes its decisions depending on the current CPU load.
456 The same is done by various userland tools like <c>cpudyn</c>, <c>cpufreqd</c>,
457 <c>powernowd</c> and many more. ACPI events can be used to enable or disable
458 dynamic frequency changes depending on power source.
459 </p>
460
461 </body>
462 </section>
463 <section>
464 <title>Setting The Frequency</title>
465 <body>
466
467 <p>
468 Decreasing CPU speed and voltage has two advantages: On the one hand less
469 energy is consumed, on the other hand there is thermal improvement as your
470 system doesn't get as hot as running on full speed. The main disadvantage is
471 obviously the loss of performance. Decreasing processor speed is a trade off
472 between performance loss and energy saving.
473 </p>
474
475 <note>
476 Not every laptop supports frequency scaling. If unsure, have a look at the list
477 of supported processors in the <uri link="#doc_chap8">Troubleshooting</uri>
478 section to verify yours is supported.
479 </note>
480
481 <p>
482 It's time to test whether CPU frequency changing works. Let's install another
483 tool: <c>sys-power/cpufrequtils</c>.
484 </p>
485
486 <pre caption="Checking CPU frequency">
487 # <i>emerge cpufrequtils</i>
488 # <i>cpufreq-info</i>
489 </pre>
490
491 <p>
492 Here is an example output:
493 </p>
494
495 <pre caption="Sample output from cpufreq-info">
496 cpufrequtils 0.3: cpufreq-info (C) Dominik Brodowski 2004
497 Report errors and bugs to linux@brodo.de, please.
498 analyzing CPU 0:
499 driver: centrino
500 CPUs which need to switch frequency at the same time: 0
501 hardware limits: 600 MHz - 1.40 GHz
502 available frequency steps: 600 MHz, 800 MHz, 1000 MHz, 1.20 GHz, 1.40 GHz
503 available cpufreq governors: conservative, ondemand, powersave, userspace, performance
504 current policy: frequency should be within 924 MHz and 1.40 GHz.
505 The governor "performance" may decide which speed to use
506 within this range.
507 current CPU frequency is 1.40 GHz.
508 </pre>
509
510 <p>
511 Now play around with <c>cpufreq-set</c> to make sure frequency switching works.
512 Run <c>cpufreq-set -g ondemand</c> for example to activate the ondemand
513 governor and verify the change with <c>cpufreq-info</c>. If it doesn't work as
514 expected, you might find help in the <uri link="#doc_chap8">Troubleshooting
515 section</uri> in the end of this guide.
516 </p>
517
518 <p>
519 <c>cpufrequtils</c> can operate in an automatic mode (when you use the
520 <b>ondemand</b> governor), you can also switch to the <b>userspace</b> governor
521 if you want to manually set a specific speed. You can also statically set your
522 CPU to its highest or lowest frequency by using the <b>performance</b>
523 and <b>powersave</b> governors, respectively.
524 </p>
525
526 <pre caption="Changing CPU speeds">
527 <comment>(Set the highest available frequency)</comment>
528 # <i>cpufreq-set -g performance</i>
529 <comment>(Set the lowest available frequency)</comment>
530 # <i>cpufreq-set -g powersave</i>
531 <comment>(Set a specific frequency)</comment>
532 # <i>cpufreq-set -g userspace</i>
533 # <i>cpufreq-set -f 2.00ghz</i>
534 </pre>
535
536 </body>
537 </section>
538 <section>
539 <title>Other CPU Speed Utilities</title>
540 <body>
541
542 <p>
543 While <c>cpufrequtils</c> may be the best all-around program, there are some
544 other choices available in Portage. The following table gives a quick overview
545 of available CPU speed utilities. It's roughly separated in three categories
546 <b>kernel</b> for approaches that only need kernel support, <b>daemon</b> for
547 programs that run in the background and <b>graphical</b> for programs that
548 provide a GUI for easy configuration and changes.
549 </p>
550
551 <table>
552 <tr>
553 <th>Name</th>
554 <th>Category</th>
555 <th>Switch decision</th>
556 <th>Kernel governors</th>
557 <th>Further governors</th>
558 <th>Comments</th>
559 </tr>
560 <tr>
561 <ti>'ondemand' governor</ti>
562 <ti>Kernel</ti>
563 <ti>CPU load</ti>
564 <ti>N.A.</ti>
565 <ti>N.A.</ti>
566 <ti>
567 Chooses maximal frequency on CPU load and slowly steps down when the CPU is
568 idle. 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>'conservative' governor</ti>
576 <ti>Kernel</ti>
577 <ti>CPU load</ti>
578 <ti>N.A.</ti>
579 <ti>N.A.</ti>
580 <ti>
581 Unlike the ondemand governor, conversative doesn't jump to maximum
582 frequency when CPU load is high, but increases the frequency step by step.
583 Further tuning through files in
584 <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
585 userland tools (programs, scripts) if governor switching or similar is
586 desired.
587 </ti>
588 </tr>
589 <tr>
590 <ti><uri link="http://mnm.uib.es/~gallir/cpudyn/">cpudyn</uri></ti>
591 <ti>Daemon</ti>
592 <ti>CPU load</ti>
593 <ti>Performance, powersave</ti>
594 <ti>Dynamic</ti>
595 <ti>
596 Also supports disk standby - notice however that <e>laptop mode</e> in most
597 cases will do a better job.
598 </ti>
599 </tr>
600 <tr>
601 <ti><uri link="http://sourceforge.net/projects/cpufreqd/">cpufreqd</uri></ti>
602 <ti>Daemon</ti>
603 <ti>Battery state, CPU load, temperature, running programs and more</ti>
604 <ti>All available</ti>
605 <ti>None</ti>
606 <ti>
607 Sophisticated (but somewhat complicated) setup. Extendible through plugins
608 like sensor monitoring (lm_sensors) or coordinating some NVidia based
609 graphics card memory and core. Cpufreqd is SMP aware and can optionally be
610 controlled manually at runtime.
611 </ti>
612 </tr>
613 <tr>
614 <ti>
615 <uri link="http://www.deater.net/john/powernowd.html">powernowd</uri>
616 </ti>
617 <ti>Daemon</ti>
618 <ti>CPU load</ti>
619 <ti>None</ti>
620 <ti>Passive, sine, aggressive</ti>
621 <ti>
622 Supports SMP.
623 </ti>
624 </tr>
625 <tr>
626 <ti>
627 <uri
628 link="http://projects.simpledesigns.com.pl/project/ncpufreqd/">ncpufreqd</uri>
629 </ti>
630 <ti>Daemon</ti>
631 <ti>Temperature</ti>
632 <ti>None</ti>
633 <ti>Powersave, performance</ti>
634 <ti>
635 Toggles the used governor between performance and powersave depending on
636 system temperature. Very useful on laptops with notorious heat problems.
637 </ti>
638 </tr>
639 <tr>
640 <ti><uri link="http://www.goop.org/~jeremy/speedfreq/">speedfreq</uri></ti>
641 <ti>Daemon</ti>
642 <ti>CPU load</ti>
643 <ti>None</ti>
644 <ti>Dynamic, powersave, performance, fixed speed</ti>
645 <ti>
646 Easy to configure with a nice client/server interface. Requires a 2.6
647 kernel. Unmaintained, broken and thus removed from Portage. Please switch
648 to cpufreqd if you're still using it.
649 </ti>
650 </tr>
651 <tr>
652 <ti><uri link="http://cpuspeedy.sourceforge.net/">gtk-cpuspeedy</uri></ti>
653 <ti>Graphical</ti>
654 <ti>None</ti>
655 <ti>None</ti>
656 <ti>None</ti>
657 <ti>
658 Gnome application, a graphical tool to set CPU frequency manually. It does
659 not offer any automation.
660 </ti>
661 </tr>
662 <tr>
663 <ti>klaptopdaemon</ti>
664 <ti>Graphical</ti>
665 <ti>Battery state</ti>
666 <ti>All available</ti>
667 <ti>None</ti>
668 <ti>
669 KDE only, 'ondemand' governor required for dynamic frequency scaling.
670 </ti>
671 </tr>
672 </table>
673
674 <p>
675 While adjusting the frequency to the current load looks simple at a first
676 glance, it's not such a trivial task. A bad algorithm can cause switching
677 between two frequencies all the time or wasting energy when setting frequency
678 to an unnecessary high level.
679 </p>
680
681 <p>
682 Which one to choose? If you have no idea about it, try <c>cpufreqd</c>:
683 </p>
684
685 <pre caption="Installing cpufreqd">
686 # <i>emerge cpufreqd</i>
687 </pre>
688
689 <p>
690 <c>cpufreqd</c> can be configured by editing <path>/etc/cpufreqd.conf</path>.
691 The default one that ships with cpufreqd may look a bit confusing. I recommend
692 replacing it with the one from former Gentoo developer Henrik Brix Andersen
693 (see below). Please notice that you need cpufreqd-2.0.0 or later. Earlier
694 versions have a different syntax for the config file.
695 </p>
696
697 <pre caption="/etc/cpufreqd.conf (cpufreqd-2.0.0 and later)">
698 [General]
699 pidfile=/var/run/cpufreqd.pid
700 poll_interval=3
701 enable_plugins=acpi_ac, acpi_battery
702 enable_remote=1
703 remote_group=wheel
704 verbosity=5
705 [/General]
706
707 [Profile]
708 name=ondemand
709 minfreq=0%
710 maxfreq=100%
711 policy=ondemand
712 [/Profile]
713
714 [Profile]
715 name=conservative
716 minfreq=0%
717 maxfreq=100%
718 policy=conservative
719 [/Profile]
720
721 [Profile]
722 name=powersave
723 minfreq=0%
724 maxfreq=100%
725 policy=powersave
726 [/Profile]
727
728 [Profile]
729 name=performance
730 minfreq=0%
731 maxfreq=100%
732 policy=performance
733 [/Profile]
734
735 [Rule]
736 name=battery
737 ac=off
738 profile=conservative
739 [/Rule]
740
741 [Rule]
742 name=battery_low
743 ac=off
744 battery_interval=0-10
745 profile=powersave
746 [/Rule]
747
748 [Rule]
749 name=ac
750 ac=on
751 profile=ondemand
752 [/Rule]
753 </pre>
754
755 <p>
756 Now you can start the cpufreqd daemon. Add it to the <c>default</c> and
757 <c>battery</c> runlevel as well.
758 </p>
759
760 <pre caption="Starting cpufreqd">
761 # <i>rc-update add cpufreqd default battery</i>
762 # <i>/etc/init.d/cpufreqd start</i>
763 </pre>
764
765 <p>
766 Sometimes it can be desirable to select another policy than the daemon chooses,
767 for example when battery power is low, but you know that AC will be available
768 soon. In that case you can turn on cpufreqd's manual mode with <c>cpufreqd-set
769 manual</c> and select one of your configured policies (as listed by
770 <c>cpufreqd-get</c>). You can leave manual mode by executing <c>cpufreqd-set
771 dynamic</c>.
772 </p>
773
774 <warn>
775 Do not run more than one of the above programs at the same time. It may cause
776 confusion like switching between two frequencies all the time.
777 </warn>
778
779 </body>
780 </section>
781 <section>
782 <title>Verifying the result</title>
783 <body>
784
785 <p>
786 The last thing to check is that your new policies do a good job. An easy way to
787 do so is monitoring CPU speed while working with your laptop:
788 </p>
789
790 <pre caption="Monitoring CPU speed">
791 # <i>watch grep \"cpu MHz\" /proc/cpuinfo</i>
792 </pre>
793
794 <p>
795 If <path>/proc/cpuinfo</path> doesn't get updated (see <uri
796 link="#doc_chap8">Troubleshooting</uri>), monitor the CPU frequency with
797 <c>sys-apps/x86info</c>:
798 </p>
799
800 <pre caption="Alternative CPU speed monitoring">
801 # <i>watch x86info -mhz</i>
802 </pre>
803
804 <p>
805 Depending on your setup, CPU speed should increase on heavy load, decrease on
806 no activity or just stay at the same level. When using <c>cpufreqd</c> and
807 verbosity set to 5 or higher in <path>cpufreqd.conf</path> you'll get
808 additional information about what's happening reported to <c>syslog</c>.
809 </p>
810
811 </body>
812 </section>
813 </chapter>
814
815 <chapter>
816 <title>LCD Power Management</title>
817 <section>
818 <body>
819
820 <p>
821 As you can see in <uri link="#doc_chap1_fig1">figure 1.1</uri>, the LCD
822 display consumes the biggest part of energy (might not be the case for
823 non-mobile CPU's). Thus it's quite important not only to shut the display off
824 when not needed, but also to reduce it's backlight if possible. Most laptops
825 offer the possibility to control the backlight dimming.
826 </p>
827
828 </body>
829 </section>
830 <section>
831 <title>Standby settings</title>
832 <body>
833
834 <p>
835 The first thing to check is the standby/suspend/off timings of the display. As
836 this depends heavily on your windowmanager, I'll let you figure it out
837 yourself. Just two common places: Blanking the terminal can be done with
838 <c>setterm -blank &lt;number-of-minutesM&gt;</c>, <c>setterm -powersave on</c>
839 and <c>setterm -powerdown &lt;number-of-minutesM&gt;</c>. For X.org, modify
840 <path>/etc/X11/xorg.conf</path> similar to this:
841 </p>
842
843 <pre caption="LCD suspend settings in X.org">
844 Section "ServerFlags"
845 Option "blank time" "5" <comment># Blank the screen after 5 minutes (Fake)</comment>
846 Option "standby time" "10" <comment># Turn off screen after 10 minutes (DPMS)</comment>
847 Option "suspend time" "20" <comment># Full suspend after 20 minutes</comment>
848 Option "off time" "30" <comment># Turn off after half an hour</comment>
849 [...]
850 EndSection
851
852 [...]
853
854 Section "Monitor"
855 Identifier [...]
856 Option "DPMS"
857 [...]
858 EndSection
859 </pre>
860
861 </body>
862 </section>
863 <section>
864 <title>Backlight dimming</title>
865 <body>
866
867 <p>
868 Probably more important is the backlight dimming. If you have access to the
869 dimming settings via a tool, write a small script that dims the backlight in
870 battery mode and place it in your <c>battery</c> runlevel. The following script
871 should work on most IBM Thinkpads and Toshiba laptops. You've got to enable the
872 appropriate option in your kernel (IBM Thinkpads only). For Toshiba laptops,
873 install <c>sys-power/acpitool</c> and skip configuration of <c>thinkpad_acpi</c>
874 (formerly called <c>ibm_acpi</c>) as described below.
875 </p>
876
877 <warn>
878 Support for setting brightness is marked experimental in thinkpad_acpi. It
879 accesses hardware directly and may cause severe harm to your system. Please
880 read the <uri link="http://ibm-acpi.sourceforge.net/">thinkpad_acpi
881 website</uri>
882 </warn>
883
884 <p>
885 To be able to set the brightness level, the thinkpad_acpi module has to be
886 loaded with the experimental parameter.
887 </p>
888
889 <pre caption="automatically loading the thinkpad_acpi module">
890 <comment>(Please read the warnings above before doing this!)</comment>
891 # <i>echo "options thinkpad_acpi experimental=1" >> /etc/modprobe.d/thinkpad_acpi</i>
892 # <i>update-modules</i>
893 # <i>echo thinkpad_acpi >> /etc/modules.autoload.d/kernel-2.6</i>
894 # <i>modprobe thinkpad_acpi</i>
895 </pre>
896
897 <p>
898 This should work without error messages and a file
899 <path>/proc/acpi/ibm/brightness</path> should be created after loading the
900 module. An init script will take care of choosing the brightness according to
901 the power source.
902 </p>
903
904 <pre caption="/etc/conf.d/lcd-brightness">
905 <comment># See /proc/acpi/ibm/brightness for available values</comment>
906 <comment># Please read /usr/src/linux/Documentation/thinkpad-acpi.txt</comment>
907
908 <comment># brightness level in ac mode. Default is 7.</comment>
909 BRIGHTNESS_AC=7
910
911 <comment># brightness level in battery mode. Default is 4.</comment>
912 BRIGHTNESS_BATTERY=4
913 </pre>
914
915 <pre caption="/etc/init.d/lcd-brightness">
916 #!/sbin/runscript
917
918 set_brightness() {
919 if on_ac_power
920 then
921 LEVEL=${BRIGHTNESS_AC:-7}
922 else
923 LEVEL=${BRIGHTNESS_BATTERY:-4}
924 fi
925
926 if [ -f /proc/acpi/ibm/brightness ]
927 then
928 ebegin "Setting LCD brightness"
929 echo "level ${LEVEL}" > /proc/acpi/ibm/brightness
930 eend $?
931 elif [[ -e /usr/bin/acpitool &amp;&amp; -n $(acpitool -T | grep "LCD brightness") ]]
932 then
933 ebegin "Setting LCD brightness"
934 acpitool -l $LEVEL >/dev/null || ewarn "Unable to set lcd brightness"
935 eend $?
936 else
937 ewarn "Setting LCD brightness is not supported."
938 ewarn "For IBM Thinkpads, check that thinkpad_acpi is loaded into the kernel"
939 ewarn "For Toshiba laptops, you've got to install sys-power/acpitool"
940 fi
941 }
942
943 start() {
944 set_brightness
945 }
946
947 stop () {
948 set_brightness
949 }
950 </pre>
951
952 <p>
953 When done, make sure brightness is adjusted automatically by adding it to the
954 battery runlevel.
955 </p>
956
957 <pre caption="Enabling automatic brightness adjustment">
958 # <i>chmod +x /etc/init.d/lcd-brightness</i>
959 # <i>rc-update add lcd-brightness battery</i>
960 # <i>rc</i>
961 </pre>
962
963 </body>
964 </section>
965 </chapter>
966
967 <chapter>
968 <title>Disk Power Management</title>
969 <section>
970 <body>
971
972 <p>
973 Hard disks consume less energy in sleep mode. Therefore it makes sense to
974 activate power saving features whenever the hard disk is not used for a certain
975 amount of time. I'll show you two alternative possibilities to do it. First,
976 laptop-mode will save most energy due to several measures which prevent or at
977 least delay write accesses. The drawback is that due to the delayed write
978 accesses a power outage or kernel crash will be more dangerous for data loss.
979 If you don't like this, you have to make sure that there are no processes which
980 write to your hard disk frequently. Afterwards you can enable power saving
981 features of your hard disk with <c>hdparm</c> as the second alternative.
982 </p>
983
984 </body>
985 </section>
986 <section>
987 <title>Increasing idle time - laptop-mode</title>
988 <body>
989
990 <p>
991 Recent 2.6 kernels include the so-called <c>laptop-mode</c>. When activated,
992 dirty buffers are written to disk on read calls or after 10 minutes (instead of
993 30 seconds). This minimizes the time the hard disk needs to be spun up.
994 </p>
995
996 <pre caption="Automated start of laptop-mode">
997 # <i>emerge laptop-mode-tools</i>
998 </pre>
999
1000 <p>
1001 <c>laptop-mode-tools</c> has its configuration file in
1002 <path>/etc/laptop-mode/laptop-mode.conf</path>. Adjust it the way you like it,
1003 it's well commented. Run <c>rc-update add laptop_mode battery</c> to start it
1004 automatically.
1005 </p>
1006
1007 <p>
1008 Recent versions (1.11 and later) of laptop-mode-tools include a new tool
1009 <c>lm-profiler</c>. It will monitor your system's disk usage and running
1010 network services and suggests to disable unneeded ones. You can either disable
1011 them through laptop-mode-tools builtin runlevel support (which will be reverted
1012 by Gentoo's <c>/sbin/rc</c>) or use your <c>default</c>/<c>battery</c>
1013 runlevels (recommended).
1014 </p>
1015
1016 <pre caption="Sample output from running lm-profiler">
1017 # <i>lm-profiler</i>
1018 Profiling session started.
1019 Time remaining: 600 seconds
1020 [4296896.602000] amarokapp
1021 Time remaining: 599 seconds
1022 [4296897.714000] sort
1023 [4296897.970000] mv
1024 Time remaining: 598 seconds
1025 Time remaining: 597 seconds
1026 [4296900.482000] reiserfs/0
1027 </pre>
1028
1029 <p>
1030 After profiling your system for ten minutes, lm-profiler will present a list of
1031 services which might have caused disk accesses during that time.
1032 </p>
1033
1034 <pre caption="lm-profiler suggests to disable some services">
1035 Program: "atd"
1036 Reason: standard recommendation (program may not be running)
1037 Init script: /etc/init.d/atd (GUESSED)
1038
1039 Do you want to disable this service in battery mode? [y/N]: <i>n</i>
1040 </pre>
1041
1042 <p>
1043 To disable atd as suggested in the example above, you would run <c>rc-update
1044 del atd battery</c>. Be careful not to disable services that are needed for
1045 your system to run properly - <c>lm-profiler</c> is likely to generate some
1046 false positives. Do not disable a service if you are unsure whether it's
1047 needed.
1048 </p>
1049
1050 </body>
1051 </section>
1052 <section>
1053 <title>Limiting Write Accesses</title>
1054 <body>
1055
1056 <p>
1057 If you don't want to use laptop-mode, you must take special care to disable
1058 services that write to your disk frequently - <c>syslogd</c> is a good
1059 candidate, for example. You probably don't want to shut it down completely, but
1060 it's possible to modify the config file so that "unnecessary" things don't get
1061 logged and thus don't create disk traffic. <c>Cups</c> writes to disk
1062 periodically, so consider shutting it down and only enable it manually when
1063 needed.
1064 </p>
1065
1066 <pre caption="Disabling cups in battery mode">
1067 # <i>rc-update del cupsd battery</i>
1068 </pre>
1069
1070 <p>
1071 You can also use <c>lm-profiler</c> from laptop-mode-tools (see above) to find
1072 services to disable. Once you eliminated all of them, go on with configuring
1073 hdparm.
1074 </p>
1075
1076 </body>
1077 </section>
1078 <section>
1079 <title>hdparm</title>
1080 <body>
1081
1082 <p>
1083 The second possibility is using <c>hdparm</c>. Skip this if
1084 you are using laptop-mode. Otherwise, edit <path>/etc/conf.d/hdparm</path> and
1085 add the following values to your drive entries. This example assumes your hard
1086 drive is called <b>hda</b>:
1087 </p>
1088
1089 <pre caption="Using /etc/conf.d/hdparm for disk standby">
1090 hda_args="-q -S12"
1091 </pre>
1092
1093 <p>
1094 This will activate power management for your hard drive. If you ever want to
1095 deactivate power management, you can edit <path>/etc/conf.d/hdparm</path> and
1096 change the values to <c>-q -S0</c>, or just run <c>hdparm -q -S0 /dev/hda</c>.
1097 </p>
1098
1099 <p>
1100 See <c>man hdparm</c> for the options. Though you can always start <c>hdparm</c>
1101 manually when you are on battery power by running <c>/etc/init.d/hdparm
1102 start</c>, it's much easier to automate its startup and shutdown. To do so, add
1103 <c>hdparm</c> to the battery runlevel so that it will automatically enable power
1104 management.
1105 </p>
1106
1107 <pre caption="Automate disk standby settings">
1108 # <i>rc-update add hdparm battery</i>
1109 </pre>
1110
1111 <impo>
1112 Be careful with sleep/spin down settings of your hard drive. Setting it to
1113 small values might wear out your drive and lose warranty.
1114 </impo>
1115
1116 </body>
1117 </section>
1118 <section>
1119 <title>Other tricks</title>
1120 <body>
1121
1122 <p>
1123 Another possibility is to deactivate swap in battery mode. Before writing a
1124 swapon/swapoff switcher, make sure there is enough RAM and swap isn't used
1125 heavily, otherwise you'll be in big problems.
1126 </p>
1127
1128 <p>
1129 If you don't want to use laptop-mode, it's still possible to minimize disk
1130 access by mounting certain directories as <c>tmpfs</c> - write accesses are not
1131 stored on a disk, but in main memory and get lost with unmounting. Often it's
1132 useful to mount <path>/tmp</path> like this - you don't have to pay special
1133 attention as it gets cleared on every reboot regardless whether it was mounted
1134 on disk or in RAM. Just make sure you have enough RAM and no program (like a
1135 download client or compress utility) needs extraordinary much space in
1136 <path>/tmp</path>. To activate this, enable tmpfs support in your kernel and
1137 add a line to <path>/etc/fstab</path> like this:
1138 </p>
1139
1140 <pre caption="Editing /etc/fstab to make /tmp even more volatile">
1141 none /tmp tmpfs size=32m 0 0
1142 </pre>
1143
1144 <warn>
1145 Pay attention to the size parameter and modify it for your system. If you're
1146 unsure, don't try this at all, it can become a performance bottleneck easily. In
1147 case you want to mount <path>/var/log</path> like this, make sure to merge the
1148 log files to disk before unmounting. They are essential. Don't attempt to mount
1149 <path>/var/tmp</path> like this. Portage uses it for compiling...
1150 </warn>
1151
1152 </body>
1153 </section>
1154 </chapter>
1155
1156 <chapter>
1157 <title>Power Management For Other Devices</title>
1158 <section>
1159 <title>Graphics Cards</title>
1160 <body>
1161
1162 <p>
1163 In case you own an ATI graphics card supporting PowerPlay (dynamic clock
1164 scaling for the graphics processing unit GPU), you can activate this
1165 feature in X.org. Open <path>/etc/X11/xorg.conf</path> and add (or enable) the
1166 <c>DynamicClocks</c> option in the Device section. Please notice that this
1167 feature will lead to crashes on some systems.
1168 </p>
1169
1170 <pre caption="Enabling ATI PowerPlay support in X.org">
1171 Section "Device"
1172 [...]
1173 Option "DynamicClocks" "on"
1174 EndSection
1175 </pre>
1176
1177 </body>
1178 </section>
1179 <section>
1180 <title>Wireless Power Management</title>
1181 <body>
1182
1183 <p>
1184 Wireless LAN cards consume quite a bit of energy. Put them in Power Management
1185 mode just like your hard drives.
1186 </p>
1187
1188 <note>
1189 This script assumes your wireless interface is called <c>wlan0</c>; replace
1190 this with the actual name of your interface.
1191 </note>
1192
1193 <p>
1194 Add the following option to <path>/etc/conf.d/net</path> to automatically enable
1195 power management for your wireless card:
1196 </p>
1197
1198 <pre caption="Automated WLAN Power Management">
1199 iwconfig_wlan0="power on"
1200 </pre>
1201
1202 <p>
1203 See <c>man iwconfig</c> for details and more options like the period between
1204 wakeups or timeout settings. If your driver and access point support changing
1205 the beacon time, this is a good starting point to save even more energy.
1206 </p>
1207
1208 </body>
1209 </section>
1210 <section>
1211 <title>USB Power Management</title>
1212 <body>
1213
1214 <p>
1215 There are two problems with USB devices regarding energy consumption: First,
1216 devices like USB mice, digital cameras or USB sticks consume energy while
1217 plugged in. You cannot avoid this (nevertheless remove them in case they're not
1218 needed). Second, when there are USB devices plugged in, the USB host controller
1219 periodically accesses the bus which in turn prevents the CPU from going into
1220 sleep mode. The kernel offers an experimental option to enable suspension of
1221 USB devices through driver calls or one of the <path>power/state</path> files
1222 in <path>/sys</path>.
1223 </p>
1224
1225 <pre caption="Enabling USB suspend support in the kernel">
1226 Device Drivers
1227 USB support
1228 [*] Support for Host-side USB
1229 [*] USB suspend/resume (EXPERIMENTAL)
1230 </pre>
1231
1232 </body>
1233 </section>
1234 </chapter>
1235
1236 <chapter>
1237 <title>Sleep States: sleep, standby, and suspend to disk</title>
1238 <section>
1239 <body>
1240
1241 <p>
1242 ACPI defines different sleep states. The more important ones are
1243 </p>
1244
1245 <ul>
1246 <li>S1 aka Standby</li>
1247 <li>S3 aka Suspend to RAM aka Sleep</li>
1248 <li>S4 aka Suspend to Disk aka Hibernate</li>
1249 </ul>
1250
1251 <p>
1252 They can be called whenever the system is not in use, but a shutdown is not
1253 wanted due to the long boot time.
1254 </p>
1255
1256 </body>
1257 </section>
1258 <section>
1259 <title>Sleep (S3)</title>
1260 <body>
1261
1262 <p>
1263 The ACPI support for these sleep states is marked experimental for good reason.
1264 APM sleep states seem to be more stable, however you can't use APM and ACPI
1265 together.
1266 </p>
1267
1268 <pre caption="Kernel configuration for the various suspend types">
1269 Power Management Options ---&gt;
1270 [*] Power Management support
1271 [*] Suspend to RAM and standby
1272 </pre>
1273
1274 <p>
1275 Once your kernel is properly configured, you can use the
1276 <c>hibernate-script</c> to activate suspend or sleep mode. Let's install that
1277 first.
1278 </p>
1279
1280 <pre caption="Installing the hibernate-script">
1281 # <i>emerge hibernate-script</i>
1282 </pre>
1283
1284 <p>
1285 Some configuration has to be done in <path>/etc/hibernate</path>. The default
1286 package introduces a few configuration files for each sleep state. Options that
1287 are common to all suspend methods are placed in <path>common.conf</path>; make
1288 sure this file is properly set up for your system.
1289 </p>
1290
1291 <p>
1292 To configure sleep, edit <path>sysfs-ram.conf</path> in
1293 <path>/etc/hibernate</path>. <c>UseSysfsPowerState mem</c> is already setup
1294 correctly, but if you need to make further changes to this particular sleep
1295 state (or any other sleep state) you should add them to
1296 <path>/etc/hibernate/hibernate.conf</path>. The comments and option names will
1297 guide you. If you use nfs or samba shares over the network, make sure to
1298 shutdown the appropriate init scripts to avoid timeouts.
1299 </p>
1300
1301 <note>
1302 For more information on setting up sleep states, read <c>man
1303 hibernate.conf</c>.
1304 </note>
1305
1306 <p>
1307 Ready? Now is the last chance to backup any data you want to keep after
1308 executing the next command. Notice that you probably have to hit a special key
1309 like <c>Fn</c> to resume from sleep.
1310 </p>
1311
1312 <pre caption="Calling sleep">
1313 # <i>hibernate-ram</i>
1314 </pre>
1315
1316 <p>
1317 If you're still reading, it seems to work. You can also setup standby (S1) in a
1318 similar way by editing <path>sysfs-ram.conf</path> and changing
1319 "UseSysfsPowerState mem" to "UseSysfsPowerState standby". S3 and S4 are the more
1320 interesting sleep states due to greater energy savings however.
1321 </p>
1322
1323 </body>
1324 </section>
1325 <section>
1326 <title>Hibernate (S4)</title>
1327 <body>
1328
1329 <p>
1330 This section introduces hibernation, where a snapshot of the running system is
1331 written to disk before powering off. On resume, the snapshot is loaded and you
1332 can go on working at exactly the point you called hibernate before.
1333 </p>
1334
1335 <warn>
1336 Don't exchange non hot-pluggable hardware when suspended. Don't attempt to load
1337 a snapshot with a different kernel image than the one it was created with.
1338 Shutdown any NFS or samba server/client before hibernating.
1339 </warn>
1340
1341 <p>
1342 There are two different implementations for S4. The original one is swsusp,
1343 then there is the newer tuxonice (formerly suspend2) with a nicer interface
1344 (including fbsplash support). A <uri
1345 link="http://tuxonice.net/features.html#compare">feature comparison</uri> is
1346 available at the <uri link="http://www.tuxonice.net">tuxonice homepage</uri>.
1347 There used to be Suspend-to-Disk (pmdisk), a fork of swsusp, but it has been
1348 merged back.
1349 </p>
1350
1351 <p>
1352 TuxOnIce is not included in the mainline kernel yet, therefore you either have
1353 to patch your kernel sources with the patches provided by <uri
1354 link="http://www.tuxonice.net">tuxonice.net</uri> or use
1355 <c>sys-kernel/tuxonice-sources</c>.
1356 </p>
1357
1358 <p>
1359 The kernel part for both swusp and TuxOnIce is as follows:
1360 </p>
1361
1362 <pre caption="Kernel configuration for the various suspend types">
1363 Power Management support ---&gt;
1364 <comment>(hibernate with swsusp)</comment>
1365 [*] Hibernation (aka 'suspend to disk')
1366 <comment>(replace /dev/SWAP with your swap partition)</comment>
1367 (/dev/SWAP) Default resume partition
1368
1369 <comment>(hibernate with TuxOnIce)</comment>
1370 Enhanced Hibernation (TuxOnIce)
1371 --- Image Storage (you need at least one allocator)
1372 [*] File Allocator
1373 [*] Swap Allocator
1374 --- General Options
1375 [*] Compression support
1376 [ ] Allow Keep Image Mode
1377 [*] Replace swsusp by default
1378 </pre>
1379
1380 <p>
1381 The configuration for swsusp is rather easy. If you didn't store the location
1382 of your swap partition in the kernel config, you can also pass it as a
1383 parameter with the <c>resume=/dev/SWAP</c> directive. If booting is not
1384 possible due to a broken image, use the <c>noresume</c> kernel parameter. The
1385 <c>hibernate-cleanup</c> init script invalidates swsusp images during the boot
1386 process.
1387 </p>
1388
1389 <pre caption="Invalidating swsusp images during the boot process">
1390 # <i>rc-update add hibernate-cleanup boot</i>
1391 </pre>
1392
1393 <p>
1394 To activate hibernate with swsusp, use the hibernate script and set
1395 <c>UseSysfsPowerState disk</c> in <path>/etc/hibernate/sysfs-disk</path>.
1396 </p>
1397
1398 <warn>
1399 Backup your data before doing this. Run <c>sync</c> before executing one of the
1400 commands to have cached data written to disk. First try it outside of X, then
1401 with X running, but not logged in.
1402 </warn>
1403
1404 <p>
1405 If you experience kernel panics due to uhci or similar, try to compile USB
1406 support as module and unload the modules before sending your laptop to sleep
1407 mode. There are configuration options for this in <path>common.conf</path>
1408 </p>
1409
1410 <pre caption="Hibernating with swsusp">
1411 # <i>nano -w /etc/hibernate/common.conf</i>
1412 <comment>(Make sure you have a backup of your data)</comment>
1413 # <i>hibernate</i>
1414 </pre>
1415
1416 <p>
1417 The following section discusses the setup of TuxOnIce including fbsplash support
1418 for a nice graphical progress bar during suspend and resume.
1419 </p>
1420
1421 <p>
1422 The first part of the configuration is similar to the configuration of swsusp.
1423 In case you didn't store the location of your swap partition in the kernel
1424 config, you have to pass it as a kernel parameter with the
1425 <c>resume=swap:/dev/SWAP</c> directive. If booting is not possible due to a
1426 broken image, append the <c>noresume</c> parameter. Additionally, the
1427 <c>hibernate-cleanup</c> init script invalidates TuxOnIce images during the boot
1428 process.
1429 </p>
1430
1431 <pre caption="Invalidating TuxOnIce images during the boot process">
1432 # <i>rc-update add hibernate-cleanup boot</i>
1433 </pre>
1434
1435 <p>
1436 Now edit <path>/etc/hibernate/tuxonice.conf</path>, enable the <c>TuxOnIce</c>
1437 options you need. Do not enable the <c>fbsplash</c> options in
1438 <c>common.conf</c> just yet.
1439 </p>
1440
1441 <pre caption="Hibernating with TuxOnIce">
1442 # <i>nano -w /etc/hibernate/tuxonice.conf</i>
1443 <comment>(Make sure you have a backup of your data)</comment>
1444 # <i>hibernate</i>
1445 </pre>
1446
1447 <p>
1448 Please configure <c>fbsplash</c> now if you didn't do already. To enable
1449 fbsplash support during hibernation, the <c>sys-apps/tuxonice-userui</c> package
1450 is needed. Additionally, you've got to enable the <c>fbsplash</c> USE flag.
1451 </p>
1452
1453 <pre caption="Installing tuxonice-userui">
1454 # <i>echo "sys-apps/tuxonice-userui fbsplash" >> /etc/portage/package.use</i>
1455 <comment>(It may be marked ~arch, so first it must be keyworded)</comment>
1456 # <i>echo "sys-apps/tuxonice-userui" >> /etc/portage/package.keywords</i>
1457 # <i>emerge tuxonice-userui</i>
1458 </pre>
1459
1460 <p>
1461 The ebuild tells you to make a symlink to the theme you want to use. For
1462 example, to use the <c>livecd-2005.1</c> theme, run the following command:
1463 </p>
1464
1465 <pre caption="Using the livecd-2005.1 theme during hibernation">
1466 # <i>ln -sfn /etc/splash/livecd-2005.1 /etc/splash/tuxonice</i>
1467 </pre>
1468
1469 <p>
1470 If you don't want a black screen in the first part of the resume process, you
1471 have to add the <c>tuxoniceui_fbsplash</c> tool to your initrd image. Assuming
1472 you created the initrd image with <c>splash_geninitramfs</c> and saved it as
1473 <path>/boot/fbsplash-emergence-1024x768</path>, here's how to do that.
1474 </p>
1475
1476 <pre caption="Adding tuxoniceui_fbsplash to an initrd image">
1477 # <i>mount /boot</i>
1478 # <i>mkdir ~/initrd.d</i>
1479 # <i>cp /boot/fbsplash-emergence-1024x768 ~/initrd.d/</i>
1480 # <i>cd ~/initrd.d</i>
1481 # <i>gunzip -c fbsplash-emergence-1024x768 | cpio -idm --quiet -H newc</i>
1482 # <i>rm fbsplash-emergence-1024x768</i>
1483 # <i>cp /usr/sbin/tuxoniceui_fbsplash sbin/</i>
1484 # <i>find . | cpio --quiet --dereference -o -H newc | gzip -9 > /boot/fbsplash-tuxonice-emergence-1024x768</i>
1485 </pre>
1486
1487 <p>
1488 Afterwards adjust <path>grub.conf</path> (or <path>lilo.conf</path>) so that
1489 your TuxOnIce kernel uses
1490 <path>/boot/fbsplash-tuxonice-emergence-1024x768</path> as initrd image. You can
1491 now test a dry run to see if everything is setup correctly.
1492 </p>
1493
1494 <pre caption="Test run for fbsplash hibernation">
1495 # <i>tuxoniceui_fbsplash -t</i>
1496 </pre>
1497
1498 <p>
1499 Afterwards open <path>/etc/hibernate/common.conf</path> and activate the
1500 fbsplash options. Execute <c>hibernate</c> and enjoy.
1501 </p>
1502
1503 </body>
1504 </section>
1505 </chapter>
1506
1507 <chapter>
1508 <title>Troubleshooting</title>
1509 <section>
1510 <body>
1511
1512 <p>
1513 <e>Q:</e> I'm trying to change the CPU frequency, but
1514 <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor</path> does not
1515 exist.
1516 </p>
1517
1518 <p>
1519 <e>A:</e> Make sure your processor supports CPU frequency scaling and you chose
1520 the right CPUFreq driver for your processor. Here is a list of processors that
1521 are supported by cpufreq (kernel 2.6.7): ARM Integrator, ARM-SA1100, ARM-SA1110,
1522 AMD Elan - SC400, SC410, AMD mobile K6-2+, AMD mobile K6-3+, AMD mobile Duron,
1523 AMD mobile Athlon, AMD Opteron, AMD Athlon 64, Cyrix Media GXm, Intel mobile
1524 PIII and Intel mobile PIII-M on certain chipsets, Intel Pentium 4, Intel Xeon,
1525 Intel Pentium M (Centrino), National Semiconductors Geode GX, Transmeta Crusoe,
1526 VIA Cyrix 3 / C3, UltraSPARC-III, SuperH SH-3, SH-4, several "PowerBook" and
1527 "iBook2" and various processors on some ACPI 2.0-compatible systems (only if
1528 "ACPI Processor Performance States" are available to the ACPI/BIOS interface).
1529 </p>
1530
1531 <p>
1532 <e>Q:</e> My laptop supports frequency scaling, but
1533 <path>/sys/devices/system/cpu/cpu0/cpufreq/</path> is empty.
1534 </p>
1535
1536 <p>
1537 <e>A:</e> Look for ACPI related error messages with <c>dmesg | grep ACPI</c>.
1538 Try to update the BIOS, especially if a broken DSDT is reported. You can also
1539 try to fix it yourself (which is beyond the scope of this guide).
1540 </p>
1541
1542 <p>
1543 <e>Q:</e> My laptop supports frequency scaling, but according to
1544 <path>/proc/cpuinfo</path> the speed never changes.
1545 </p>
1546
1547 <p>
1548 <e>A:</e> Probably you have activated symmetric multiprocessing support
1549 (CONFIG_SMP) in your kernel. Deactivate it and it should work. Some older
1550 kernels had a bug causing this. In that case, run <c>emerge x86info</c>, update
1551 your kernel as asked and check the current frequency with <c>x86info -mhz</c>.
1552 </p>
1553
1554 <p>
1555 <e>Q:</e> I can change the CPU frequency, but the range is not as wide as in
1556 another OS.
1557 </p>
1558
1559 <p>
1560 <e>A:</e> You can combine frequency scaling with ACPI throttling to get a lower
1561 minimum frequency. Notice that throttling doesn't save much energy and is mainly
1562 used for thermal management (keeping your laptop cool and quiet). You can read
1563 the current throttling state with <c>cat /proc/acpi/processor/CPU/throttling</c>
1564 and change it with <c>echo -n "0:x" > /proc/acpi/processor/CPU/limit</c>, where
1565 x is one of the Tx states listed in
1566 <path>/proc/acpi/processor/CPU/throttling</path>.
1567 </p>
1568
1569 <p>
1570 <e>Q:</e> When configuring the kernel, powersave, performance and userspace
1571 governors show up, but that ondemand thing is missing. Where do I get it?
1572 </p>
1573
1574 <p>
1575 <e>A:</e> The ondemand governor is only included in recent kernel sources. Try
1576 updating them.
1577 </p>
1578
1579 <p>
1580 <e>Q:</e> Battery life time seems to be worse than before.
1581 </p>
1582
1583 <p>
1584 <e>A:</e> Check your BIOS settings. Maybe you forgot to re-enable some of the
1585 settings.
1586 </p>
1587
1588 <p>
1589 <e>Q:</e> My battery is charged, but KDE reports there would be 0% left and
1590 immediately shuts down.
1591 </p>
1592
1593 <p>
1594 <e>A:</e> Check that battery support is compiled into your kernel. If you use
1595 it as a module, make sure the module is loaded.
1596 </p>
1597
1598 <p>
1599 <e>Q:</e> My system logger reports things like "logger: ACPI group battery /
1600 action battery is not defined".
1601 </p>
1602
1603 <p>
1604 <e>A:</e> This message is generated by the <path>/etc/acpi/default.sh</path>
1605 script that is shipped with acpid. You can safely ignore it. If you like to get
1606 rid of it, you can comment the appropriate line in
1607 <path>/etc/acpi/default.sh</path> as shown below:
1608 </p>
1609
1610 <pre caption="Disabling warnings about unknown acpi events">
1611 *) # logger "ACPI action $action is not defined"
1612 </pre>
1613
1614 <p>
1615 <e>Q:</e> I have a Dell Inspiron 51XX and I don't get any ACPI events.
1616 </p>
1617
1618 <p>
1619 <e>A:</e> This seems to be a kernel bug. Read on <uri
1620 link="http://bugme.osdl.org/show_bug.cgi?id=1752">here</uri>.
1621 </p>
1622
1623 <p>
1624 <e>Q:</e> I activated the <c>DynamicClocks</c> option in <path>xorg.conf</path>
1625 and now X.org crashes / the screen stays black / my laptop doesn't shutdown
1626 properly.
1627 </p>
1628
1629 <p>
1630 <e>A:</e> This happens on some systems. You have to disable
1631 <c>DynamicClocks</c>.
1632 </p>
1633
1634 <p>
1635 <e>Q:</e> I want to use TuxOnIce, but it tells me my swap partition is too
1636 small. Resizing is not an option.
1637 </p>
1638
1639 <p>
1640 <e>A:</e> If there is enough free space on your system, you can use the
1641 filewriter instead of the swapwriter. The <c>hibernate-script</c> supports it as
1642 well. More information can be found in
1643 <path>/usr/src/linux/Documentation/power/tuxonice.txt</path>.
1644 </p>
1645
1646 <p>
1647 <e>Q:</e> I just bought a brand new battery, but it only lasts for some
1648 minutes! What am I doing wrong?
1649 </p>
1650
1651 <p>
1652 <e>A:</e> First follow your manufacturer's advice on how to charge the battery
1653 correctly.
1654 </p>
1655
1656 <p>
1657 <e>Q:</e> The above didn't help. What should I do then?
1658 </p>
1659
1660 <p>
1661 <e>A:</e> Some batteries sold as "new" are in fact old ones. Try the following:
1662 </p>
1663
1664 <pre caption="Querying battery state">
1665 $ <i>grep capacity /proc/acpi/battery/BAT0/info</i>
1666 design capacity: 47520 mWh
1667 last full capacity: 41830 mWh
1668 </pre>
1669
1670 <p>
1671 If the "last full capacity" differs significantly from the design capacity,
1672 your battery is probably broken. Try to claim your warranty.
1673 </p>
1674
1675 <p>
1676 <e>Q:</e> My problem is not listed above. Where should I go next?
1677 </p>
1678
1679 <p>
1680 <e>A:</e> Don't fear to contact me, <mail link="earthwings@gentoo.org">Dennis
1681 Nienhüser</mail>, directly. The <uri link="http://forums.gentoo.org">Gentoo
1682 Forums</uri> are a good place to get help as well. If you prefer IRC, try the
1683 <c>#gentoo-laptop</c> <uri link="irc://irc.gentoo.org">channel</uri>.
1684 </p>
1685
1686 </body>
1687 </section>
1688 </chapter>
1689 </guide>

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