/[gentoo]/xml/htdocs/doc/en/power-management-guide.xml
Gentoo

Contents of /xml/htdocs/doc/en/power-management-guide.xml

Parent Directory Parent Directory | Revision Log Revision Log


Revision 1.21 - (show annotations) (download) (as text)
Thu Aug 17 00:45:29 2006 UTC (8 years ago) by rane
Branch: MAIN
Changes since 1.20: +4 -4 lines
File MIME type: application/xml
#144153, typos

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 1.20 2006/07/27 08:23:01 rane 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
14 <abstract>
15 Power Management is the key to extend battery run time on mobile systems like
16 laptops. This guide assists you setting it up on your laptop.
17 </abstract>
18
19 <!-- The content of this document is licensed under the CC-BY-SA license -->
20 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
21 <license/>
22
23 <version>1.28</version>
24 <date>2006-07-26</date>
25
26 <chapter>
27 <title>Introduction</title>
28 <section>
29 <body>
30
31 <p>
32 Capacity and lifetime of laptop batteries have improved much in the last years.
33 Nevertheless modern processors consume much more energy than older ones and
34 each laptop generation introduces more devices hungry for energy. That's why
35 Power Management is more important than ever. Increasing battery run time
36 doesn't necessarily mean buying another battery. Much can be achieved applying
37 intelligent Power Management policies.
38 </p>
39
40 </body>
41 </section>
42 <section>
43 <title>A Quick Overview</title>
44 <body>
45
46 <p>
47 Please notice that this guide describes Power Management for <e>laptops</e>.
48 While some sections might also suite for <e>servers</e>, others do not and may
49 even cause harm. Please do not apply anything from this guide to a server
50 unless you really know what you are doing.
51 </p>
52
53 <p>
54 As this guide has become rather long, here's a short overview helping you to
55 find your way through it.
56 </p>
57
58 <p>
59 The <uri link="#doc_chap2">Prerequisites</uri> chapter talks about some
60 requirements that should be met before any of the following device individual
61 sections will work. This includes BIOS settings, kernel configuration and some
62 simplifications in user land. The following three chapters focus on devices
63 that typically consume most energy - processor, display and hard drive. Each
64 can be configured seperately. <uri link="#doc_chap3">CPU Power Management</uri>
65 shows how to adjust the processor's frequency to save a maximum of energy
66 without losing too much performance. A few different tricks prevent your hard
67 drive from working unnecessarily often in <uri link="#doc_chap5">Disk Power
68 Management</uri> (decreasing noise level as a nice side effect). Some notes on
69 graphics cards, Wireless LAN and USB finish the device section in <uri
70 link="#doc_chap6">Power Management For Other Devices</uri> while another
71 chapter is dedicated to the (rather experimental) <uri link="#doc_chap7">sleep
72 states</uri>. Last not least <uri link="#doc_chap8">Troubleshooting</uri> lists
73 common pitfalls.
74 </p>
75
76 </body>
77 </section>
78 <section>
79 <title>Power Budget For Each Component</title>
80 <body>
81
82 <figure link="/images/energy-budget.png" short="Which component consumes how
83 much energy?" caption="Power budget for each component"/>
84
85 <p>
86 Nearly every component can operate in different states - off, sleep, idle,
87 active to name a few - consuming a different amount of energy. Major parts are
88 consumed by the LCD display, CPU, chipset and hard drives. Often one is able to
89 activate OS-independent Power Management in the BIOS, but an intelligent setup
90 in the operating system adapting to different situations can achieve much more.
91 </p>
92
93 </body>
94 </section>
95 </chapter>
96
97 <chapter>
98 <title>Prerequisites</title>
99 <section>
100 <body>
101
102 <p>
103 Before discussing the details of making individual devices Power Management
104 aware, make sure certain requirements are met. After controlling BIOS settings,
105 some kernel options want to be enabled - these are in short ACPI, sleep states
106 and CPU frequency scaling. As power saving most of the time comes along with
107 performance loss or increased latency, it should only be enabled when running
108 on batteries. That's where a new runlevel <e>battery</e> comes in handy.
109 </p>
110
111 </body>
112 </section>
113 <section>
114 <title>The BIOS Part</title>
115 <body>
116
117 <p>
118 First have a look into your BIOS Power Management settings. The best way is to
119 combine BIOS and operating system policies, but for the moment it's better to
120 disable most of the BIOS part. This makes sure it doesn't interfere with your
121 policies. Don't forget to re-check BIOS settings after you configured
122 everything else.
123 </p>
124
125 </body>
126 </section>
127 <section>
128 <title>Setting USE Flags</title>
129 <body>
130
131 <p>
132 Please check that the <c>acpi</c> USE flag is set in
133 <path>/etc/make.conf</path>. Other USE flags that might be interesting for your
134 system are <c>apm</c>, <c>lm_sensors</c>, <c>nforce2</c>, <c>nvidia</c>,
135 <c>pmu</c>. See <path>/usr/portage/profiles/use*.desc</path> for details. If
136 you forgot to set one of these flags, you can recompile affected packages using
137 the <c>--newuse</c> flag in <c>emerge</c>, see <c>man emerge</c>.
138 </p>
139
140 </body>
141 </section>
142 <section>
143 <title>Configuring The Kernel</title>
144 <body>
145
146 <p>
147 ACPI (Advanced Configuration and Power Interface) support in the kernel is
148 still work in progress. Using a recent kernel will make sure you'll get the
149 most out of it.
150 </p>
151
152 <p>
153 There are different kernel sources in Portage. I'd recommend using
154 <c>gentoo-sources</c> or <c>suspend2-sources</c>. The latter contains patches
155 for Software Suspend 2, see the chapter about <uri link="#doc_chap7">sleep
156 states</uri> for more details. When configuring the kernel, activate at least
157 these options:
158 </p>
159
160 <pre caption="Minimum kernel setup for Power Management (Kernel 2.6)">
161 Power Management Options ---&gt;
162 [*] Power Management Support
163 [ ] Software Suspend
164
165 ACPI( Advanced Configuration and Power Interface ) Support ---&gt;
166 [*] ACPI Support
167 [ ] Sleep States
168 [ ] /proc/acpi/sleep (deprecated)
169 [*] AC Adapter
170 [*] Battery
171 &lt;M&gt; Button
172 &lt;M&gt; Video
173 [ ] Generic Hotkey
174 &lt;M&gt; Fan
175 &lt;M&gt; Processor
176 &lt;M&gt; Thermal Zone
177 &lt; &gt; ASUS/Medion Laptop Extras
178 &lt; &gt; IBM ThinkPad Laptop Extras
179 &lt; &gt; Toshiba Laptop Extras
180 (0) Disable ACPI for systems before Jan 1st this year
181 [ ] Debug Statements
182 [*] Power Management Timer Support
183 &lt; &gt; ACPI0004,PNP0A05 and PNP0A06 Container Driver (EXPERIMENTAL)
184
185 CPU Frequency Scaling ---&gt;
186 [*] CPU Frequency scaling
187 [ ] Enable CPUfreq debugging
188 &lt; &gt; CPU frequency translation statistics
189 [ ] CPU frequency translation statistics details
190 Default CPUFreq governor (userspace)
191 &lt;*&gt; 'performance' governor
192 &lt;*&gt; 'powersave' governor
193 &lt;*&gt; 'ondemand' cpufreq policy governor
194 &lt;*&gt; 'conservative' cpufreq governor
195 &lt;*&gt; CPU frequency table helpers
196 &lt;M&gt; ACPI Processor P-States driver
197 &lt;*&gt; <i>CPUFreq driver for your processor</i>
198 </pre>
199
200 <p>
201 Decide yourself whether you want to enable Software Suspend, and Sleep States
202 (see below). If you own an ASUS, Medion, IBM Thinkpad or Toshiba laptop, enable
203 the appropriate section.
204 </p>
205
206 <p>
207 The kernel has to know how to enable CPU frequency scaling on your processor.
208 As each type of CPU has a different interface, you've got to choose the right
209 driver for your processor. Be careful here - enabling <c>Intel Pentium 4 clock
210 modulation</c> on a Pentium M system will lead to strange results for example.
211 Consult the kernel documentation if you're unsure which one to take.
212 </p>
213
214 <p>
215 Compile your kernel, make sure the right modules get loaded at startup and boot
216 into your new ACPI-enabled kernel. Next run <c>emerge sys-power/acpid</c> to
217 get the acpi daemon. This one informs you about events like switching from AC
218 to battery or closing the lid. Make sure the modules are loaded if you didn't
219 compile them into the kernel and start acpid by executing <c>/etc/init.d/acpid
220 start</c>. Run <c>rc-update add acpid default</c> to load it on startup. You'll
221 soon see how to use it.
222 </p>
223
224 <pre caption="Installing acpid">
225 # <i>emerge sys-power/acpid</i>
226 # <i>/etc/init.d/acpid start</i>
227 # <i>rc-update add acpid default</i>
228 </pre>
229
230 </body>
231 </section>
232 <section>
233 <title>Creating A "battery" Runlevel</title>
234 <body>
235
236 <p>
237 The default policy will be to enable Power Management only when needed -
238 running on batteries. To make the switch between AC and battery convenient,
239 create a runlevel <c>battery</c> that holds all the scripts starting and
240 stopping Power Management.
241 </p>
242
243 <note>
244 You can safely skip this section if you don't like the idea of having another
245 runlevel. However, skipping this step will make the rest a bit trickier to set
246 up. The next sections assume a runlevel <c>battery</c> exists.
247 </note>
248
249 <pre caption="Creating a battery runlevel">
250 # <i>cd /etc/runlevels</i>
251 # <i>cp -a default battery</i>
252 </pre>
253
254 <p>
255 Finished. Your new runlevel <c>battery</c> contains everything like
256 <c>default</c>, but there is no automatic switch between both yet. Time to
257 change it.
258 </p>
259
260 </body>
261 </section>
262 <section>
263 <title>Reacting On ACPI Events</title>
264 <body>
265
266 <p>
267 Typical ACPI events are closing the lid, changing the power source or pressing
268 the sleep button. An important event is changing the power source, which should
269 cause a runlevel switch. A small script will take care of it.
270 </p>
271
272 <p>
273 First you need a script which changes the runlevel to <c>default</c>
274 respectively <c>battery</c> depending on the power source. The script uses the
275 <c>on_ac_power</c> command from <c>sys-power/powermgmt-base</c> - make sure the
276 package is installed on your system.
277 </p>
278
279 <pre caption="Installing powermgt-base">
280 # <i>emerge powermgmt-base</i>
281 </pre>
282
283 <p>
284 You are now able to determine the power source by executing <c>on_ac_power
285 &amp;&amp; echo AC available || echo Running on batteries</c> in a shell. The
286 script below is responsible for changing runlevels. Save it as
287 <path>/etc/acpi/actions/pmg_switch_runlevel.sh</path>.
288 </p>
289
290 <pre caption="/etc/acpi/actions/pmg_switch_runlevel.sh">
291 #!/bin/bash
292
293 <comment># BEGIN configuration</comment>
294 RUNLEVEL_AC="default"
295 RUNLEVEL_BATTERY="battery"
296 <comment># END configuration</comment>
297
298
299 if [ ! -d "/etc/runlevels/${RUNLEVEL_AC}" ]
300 then
301 logger "${0}: Runlevel ${RUNLEVEL_AC} does not exist. Aborting."
302 exit 1
303 fi
304
305 if [ ! -d "/etc/runlevels/${RUNLEVEL_BATTERY}" ]
306 then
307 logger "${0}: Runlevel ${RUNLEVEL_BATTERY} does not exist. Aborting."
308 exit 1
309 fi
310
311 if on_ac_power
312 then
313 if [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_AC}" ]]
314 then
315 logger "Switching to ${RUNLEVEL_AC} runlevel"
316 /sbin/rc ${RUNLEVEL_AC}
317 fi
318 elif [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_BATTERY}" ]]
319 then
320 logger "Switching to ${RUNLEVEL_BATTERY} runlevel"
321 /sbin/rc ${RUNLEVEL_BATTERY}
322 fi
323 </pre>
324
325 <p>
326 Dont forget to run <c>chmod +x /etc/acpi/actions/pmg_switch_runlevel.sh</c> to
327 make the script executable. The last thing that needs to be done is calling the
328 script whenever the power source changes. That's done by catching ACPI events
329 with the help of <c>acpid</c>. First you need to know which events are
330 generated when the power source changes. The events are called
331 <c>ac_adapter</c> and <c>battery</c> on most laptops, but it might be different
332 on yours.
333 </p>
334
335 <pre caption="Determining ACPI events for changing the power source">
336 # <i>tail -f /var/log/acpid | grep "received event"</i>
337 </pre>
338
339 <p>
340 Run the command above and pull the power cable. You should see something like
341 this:
342 </p>
343
344 <pre caption="Sample output for power source changes">
345 [Tue Sep 20 17:39:06 2005] received event "ac_adapter AC 00000080 00000000"
346 [Tue Sep 20 17:39:06 2005] received event "battery BAT0 00000080 00000001"
347 </pre>
348
349 <p>
350 The interesting part is the quoted string after <c>received event</c>. It will
351 be matched by the event line in the files you are going to create below. Don't
352 worry if your system generates multiple events or always the same. As long as
353 any event is generated, runlevel changing will work.
354 </p>
355
356 <pre caption="/etc/acpi/events/pmg_ac_adapter">
357 <comment># replace "ac_adapter" below with the event generated on your laptop</comment>
358 <comment># For example, ac_adapter.* will match ac_adapter AC 00000080 00000000</comment>
359 event=ac_adapter.*
360 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
361 </pre>
362
363 <pre caption="/etc/acpi/events/pmg_battery">
364 <comment># replace "battery" below with the event generated on your laptop</comment>
365 <comment># For example, battery.* will match battery BAT0 00000080 00000001</comment>
366 event=battery.*
367 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
368 </pre>
369
370 <p>
371 Finally acpid has to be restarted to recognize the changes.
372 </p>
373
374 <pre caption="Finishing runlevel switching with acpid">
375 # <i>/etc/init.d/acpid restart</i>
376 </pre>
377
378 <p>
379 Give it a try: Plug AC in and out and watch syslog for the "Switching to AC
380 mode" or "Switching to battery mode" messages. See the <uri
381 link="#doc_chap8">Troubleshooting section</uri> if the script is not able to
382 detect the power source correctly.
383 </p>
384
385 <p>
386 Due to the nature of the event mechanism, your laptop will boot into runlevel
387 <c>default</c> regardless of the AC/battery state. This is fine when running
388 from AC, but we'd like to boot into the battery runlevel otherwise. One
389 solution would be to add another entry to the boot loader with the parameter
390 <c>softlevel=battery</c>, but it's likely to forget choosing it. A better way
391 is faking an ACPI event in the end of the boot process and letting
392 <path>pmg_switch_runlevel.sh</path> script decide whether a runlevel change is
393 necessary. Open <path>/etc/conf.d/local.start</path> in your favourite editor
394 and add these lines:
395 </p>
396
397 <pre caption="Runlevel adjustment at boot time by editing local.start">
398 <comment># Fake acpi event to switch runlevel if running on batteries</comment>
399 /etc/acpi/actions/pmg_switch_runlevel.sh "battery/battery"
400 </pre>
401
402 <p>
403 Prepared like this you can activate Power Management policies for individual
404 devices.
405 </p>
406
407 </body>
408 </section>
409 </chapter>
410
411 <chapter>
412 <title>CPU Power Management</title>
413 <section>
414 <body>
415
416 <p>
417 Mobile processors can operate at different frequencies. Some allow changing
418 voltage as well. Most of the time your CPU doesn't need to run at full speed
419 and scaling it down will save much energy - often without any performance
420 decrease.
421 </p>
422
423 </body>
424 </section>
425 <section>
426 <title>Some Technical Terms</title>
427 <body>
428
429 <p>
430 CPU frequency scaling brings up some technical terms that might be unknown to
431 you. Here's a quick introduction.
432 </p>
433
434 <p>
435 First of all, the kernel has to be able to change the processor's frequency.
436 The <b>CPUfreq processor driver</b> knows the commands to do it on your CPU.
437 Thus it's important to choose the right one in your kernel. You should already
438 have done it above. Once the kernel knows how to change frequencies, it has to
439 know which frequency it should set. This is done according to the <b>policy</b>
440 which consists of a <b>CPUfreq policy</b> and a <b>governor</b>. A CPUfreq
441 policy are just two numbers which define a range the frequency has to stay
442 between - minimal and maximal frequency. The governor now decides which of the
443 available frequencies in between minimal and maximal frequency to choose. For
444 example, the <b>powersave governor</b> always chooses the lowest frequency
445 available, the <b>performance governor</b> the highest one. The <b>userspace
446 governor</b> makes no decision but chooses whatever the user (or a program in
447 userspace) wants - which means it reads the frequency from
448 <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed</path>.
449 </p>
450
451 <p>
452 This doesn't sound like dynamic frequency changes yet and in fact it isn't.
453 Dynamics however can be accomplished with various approaches. For example, the
454 <b>ondemand governor</b> makes its decisions depending on the current CPU load.
455 The same is done by various userland tools like <c>cpudyn</c>, <c>cpufreqd</c>,
456 <c>powernowd</c> and many more. ACPI events can be used to enable or disable
457 dynamic frequency changes depending on power source.
458 </p>
459
460 </body>
461 </section>
462 <section>
463 <title>Setting The Frequency Manually</title>
464 <body>
465
466 <p>
467 Decreasing CPU speed and voltage has two advantages: On the one hand less
468 energy is consumed, on the other hand there is thermal improvement as your
469 system doesn't get as hot as running on full speed. The main disadvantage is
470 obviously the loss of performance. Decreasing processor speed is a trade off
471 between performance loss and energy saving.
472 </p>
473
474 <note>
475 Not every laptop supports frequency scaling. If unsure, have a look at the list
476 of supported processors in the <uri link="#doc_chap8">Troubleshooting</uri>
477 section to verify yours is supported.
478 </note>
479
480 <p>
481 It's time to test whether CPU frequency changing works. Let's install another
482 tool which is very handy for debugging purposes: <c>sys-power/cpufrequtils</c>
483 </p>
484
485 <pre caption="Checking CPU frequency">
486 # <i>emerge cpufrequtils</i>
487 # <i>cpufreq-info</i>
488 </pre>
489
490 <p>
491 Here is an example output:
492 </p>
493
494 <pre caption="Sample output from cpufreq-info">
495 cpufrequtils 0.3: cpufreq-info (C) Dominik Brodowski 2004
496 Report errors and bugs to linux@brodo.de, please.
497 analyzing CPU 0:
498 driver: centrino
499 CPUs which need to switch frequency at the same time: 0
500 hardware limits: 600 MHz - 1.40 GHz
501 available frequency steps: 600 MHz, 800 MHz, 1000 MHz, 1.20 GHz, 1.40 GHz
502 available cpufreq governors: conservative, ondemand, powersave, userspace, performance
503 current policy: frequency should be within 924 MHz and 1.40 GHz.
504 The governor "performance" may decide which speed to use
505 within this range.
506 current CPU frequency is 1.40 GHz.
507 </pre>
508
509 <p>
510 Now play around with <c>cpufreq-set</c> to make sure frequency switching works.
511 Run <c>cpufreq-set -g ondemand</c> for example to activate the ondemand
512 governor and verify the change with <c>cpufreq-info</c>. If it doesn't work as
513 expected, you might find help in the <uri link="#doc_chap8">Troubleshooting
514 section</uri> in the end of this guide.
515 </p>
516
517 </body>
518 </section>
519 <section>
520 <title>Automated frequency adaption</title>
521 <body>
522
523 <p>
524 The above is quite nice, but not doable in daily life. Better let your system
525 set the appropriate frequency automatically. There are many different
526 approaches to do this. The following table gives a quick overview to help you
527 decide on one of them. It's roughly separated in three categories <b>kernel</b>
528 for approaches that only need kernel support, <b>daemon</b> for programs that
529 run in the background and <b>graphical</b> for programs that provide a GUI for
530 easy configuration and changes.
531 </p>
532
533 <table>
534 <tr>
535 <th>Name</th>
536 <th>Category</th>
537 <th>Switch decision</th>
538 <th>Kernel governors</th>
539 <th>Further governors</th>
540 <th>Comments</th>
541 </tr>
542 <tr>
543 <ti>'ondemand' governor</ti>
544 <ti>Kernel</ti>
545 <ti>CPU load</ti>
546 <ti>N.A.</ti>
547 <ti>N.A.</ti>
548 <ti>
549 Chooses maximal frequency on CPU load and slowly steps down when the CPU is
550 idle. Further tuning through files in
551 <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
552 userland tools (programs, scripts) if governor switching or similar is
553 desired.
554 </ti>
555 </tr>
556 <tr>
557 <ti>'conservative' governor</ti>
558 <ti>Kernel</ti>
559 <ti>CPU load</ti>
560 <ti>N.A.</ti>
561 <ti>N.A.</ti>
562 <ti>
563 Unlike the ondemand governor, conversative doesn't jump to maximum
564 frequency when CPU load is high, but increases the frequency step by step.
565 Further tuning through files in
566 <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
567 userland tools (programs, scripts) if governor switching or similar is
568 desired.
569 </ti>
570 </tr>
571 <tr>
572 <ti><uri link="http://mnm.uib.es/~gallir/cpudyn/">cpudyn</uri></ti>
573 <ti>Daemon</ti>
574 <ti>CPU load</ti>
575 <ti>Performance, powersave</ti>
576 <ti>Dynamic</ti>
577 <ti>
578 Also supports disk standby - notice however that <e>laptop mode</e> in most
579 cases will do a better job.
580 </ti>
581 </tr>
582 <tr>
583 <ti><uri link="http://sourceforge.net/projects/cpufreqd/">cpufreqd</uri></ti>
584 <ti>Daemon</ti>
585 <ti>Battery state, CPU load, temperature, running programs and more</ti>
586 <ti>All available</ti>
587 <ti>None</ti>
588 <ti>
589 Sophisticated (but somewhat complicated) setup. Extendible through plugins
590 like sensor monitoring (lm_sensors) or coordinating some NVidia based
591 graphics card memory and core. Cpufreqd is SMP aware and can optionally be
592 controlled manually at runtime.
593 </ti>
594 </tr>
595 <tr>
596 <ti>
597 <uri link="http://www.deater.net/john/powernowd.html">powernowd</uri>
598 </ti>
599 <ti>Daemon</ti>
600 <ti>CPU load</ti>
601 <ti>None</ti>
602 <ti>Passive, sine, aggressive</ti>
603 <ti>
604 Supports SMP.
605 </ti>
606 </tr>
607 <tr>
608 <ti>
609 <uri
610 link="http://fatcat.ftj.agh.edu.pl/~nelchael/index.php?cat=projs&amp;subcat=ncpufreqd&amp;language=en">ncpufreqd</uri>
611 </ti>
612 <ti>Daemon</ti>
613 <ti>Temperature</ti>
614 <ti>None</ti>
615 <ti>Powersave, performance</ti>
616 <ti>
617 Toggles the used governor between performance and powersave depending on
618 system temperature. Very useful on laptops with notorious heat problems.
619 </ti>
620 </tr>
621 <tr>
622 <ti><uri link="http://www.goop.org/~jeremy/speedfreq/">speedfreq</uri></ti>
623 <ti>Daemon</ti>
624 <ti>CPU load</ti>
625 <ti>None</ti>
626 <ti>Dynamic, powersave, performance, fixed speed</ti>
627 <ti>
628 Easy to configure with a nice client/server interface. Requires a 2.6
629 kernel. Unmaintained, broken and thus removed from Portage. Please switch
630 to cpufreqd if you're still using it.
631 </ti>
632 </tr>
633 <tr>
634 <ti><uri link="http://cpuspeedy.sourceforge.net/">gtk-cpuspeedy</uri></ti>
635 <ti>Graphical</ti>
636 <ti>None</ti>
637 <ti>None</ti>
638 <ti>None</ti>
639 <ti>
640 Gnome application, a graphical tool to set CPU frequency manually. It does
641 not offer any automation.
642 </ti>
643 </tr>
644 <tr>
645 <ti>klaptopdaemon</ti>
646 <ti>Graphical</ti>
647 <ti>Battery state</ti>
648 <ti>All available</ti>
649 <ti>None</ti>
650 <ti>
651 KDE only, 'ondemand' governor required for dynamic frequency scaling.
652 </ti>
653 </tr>
654 </table>
655
656 <p>
657 While adjusting the frequency to the current load looks simple at a first
658 glance, it's not such a trivial task. A bad algorithm can cause switching
659 between two frequencies all the time or wasting energy when setting frequency
660 to an unnecessary high level.
661 </p>
662
663 <p>
664 Which one to choose? If you have no idea about it, try <c>cpufreqd</c>:
665 </p>
666
667 <pre caption="Installing cpufreqd">
668 # <i>emerge cpufreqd</i>
669 </pre>
670
671 <p>
672 <c>cpufreqd</c> can be configured by editing <path>/etc/cpufreqd.conf</path>.
673 The default one that ships with cpufreqd may look a bit confusing. I recommend
674 replacing it with the one from Gentoo developer Henrik Brix Andersen (see
675 below). Please notice that you need cpufreqd-2.0.0 or later. Earlier versions
676 have a different syntax for the config file.
677 </p>
678
679 <pre caption="/etc/cpufreqd.conf (cpufreqd-2.0.0 and later)">
680 [General]
681 pidfile=/var/run/cpufreqd.pid
682 poll_interval=3
683 enable_plugins=acpi_ac, acpi_battery
684 enable_remote=1
685 remote_group=wheel
686 verbosity=5
687 [/General]
688
689 [Profile]
690 name=ondemand
691 minfreq=0%
692 maxfreq=100%
693 policy=ondemand
694 [/Profile]
695
696 [Profile]
697 name=conservative
698 minfreq=0%
699 maxfreq=100%
700 policy=conservative
701 [/Profile]
702
703 [Profile]
704 name=powersave
705 minfreq=0%
706 maxfreq=100%
707 policy=powersave
708 [/Profile]
709
710 [Profile]
711 name=performance
712 minfreq=0%
713 maxfreq=100%
714 policy=performance
715 [/Profile]
716
717 [Rule]
718 name=battery
719 ac=off
720 profile=conservative
721 [/Rule]
722
723 [Rule]
724 name=battery_low
725 ac=off
726 battery_interval=0-10
727 profile=powersave
728 [/Rule]
729
730 [Rule]
731 name=ac
732 ac=on
733 profile=ondemand
734 [/Rule]
735 </pre>
736
737 <p>
738 Now you can start the cpufreqd daemon. Add it to the <c>default</c> and
739 <c>battery</c> runlevel as well.
740 </p>
741
742 <pre caption="Starting cpufreqd">
743 # <i>rc-update add cpufreqd default battery</i>
744 # <i>rc</i>
745 </pre>
746
747 <p>
748 Sometimes it can be desirable to select another policy than the daemon chooses,
749 for example when battery power is low, but you know that AC will be available
750 soon. In that case you can turn on cpufreqd's manual mode with <c>cpufreqd-set
751 manual</c> and select one of your configured policies (as listed by
752 <c>cpufreqd-get</c>). You can leave manual mode by executing <c>cpufreqd-set
753 dynamic</c>.
754 </p>
755
756 <warn>
757 Do not run more than one of the above programs at the same time. It may cause
758 confusion like switching between two frequencies all the time.
759 </warn>
760
761 </body>
762 </section>
763 <section>
764 <title>Verifying the result</title>
765 <body>
766
767 <p>
768 The last thing to check is that your new policies do a good job. An easy way to
769 do so is monitoring CPU speed while working with your laptop:
770 </p>
771
772 <pre caption="Monitoring CPU speed">
773 # <i>watch grep \"cpu MHz\" /proc/cpuinfo</i>
774 </pre>
775
776 <p>
777 If <path>/proc/cpuinfo</path> doesn't get updated (see <uri
778 link="#doc_chap8">Troubleshooting</uri>), monitor the CPU frequency with:
779 </p>
780
781 <pre caption="Alternative CPU speed monitoring">
782 # <i>watch x86info -mhz</i>
783 </pre>
784
785 <p>
786 Depending on your setup, CPU speed should increase on heavy load, decrease on
787 no activity or just stay at the same level. When using <c>cpufreqd</c> and
788 verbosity set to 5 or higher in <path>cpufreqd.conf</path> you'll get
789 additional information about what's happening reported to <c>syslog</c>.
790 </p>
791
792 </body>
793 </section>
794 </chapter>
795
796 <chapter>
797 <title>LCD Power Management</title>
798 <section>
799 <body>
800
801 <p>
802 As you can see in <uri link="#doc_chap1_fig1">figure 1.1</uri>, the LCD
803 display consumes the biggest part of energy (might not be the case for
804 non-mobile CPU's). Thus it's quite important not only to shut the display off
805 when not needed, but also to reduce it's backlight if possible. Most laptops
806 offer the possibility to control the backlight dimming.
807 </p>
808
809 </body>
810 </section>
811 <section>
812 <title>Standby settings</title>
813 <body>
814
815 <p>
816 The first thing to check is the standby/suspend/off timings of the display. As
817 this depends heavily on your windowmanager, I'll let you figure it out
818 yourself. Just two common places: Blanking the terminal can be done with
819 <c>setterm -blank &lt;number-of-minutesM&gt;</c>, <c>setterm -powersave on</c>
820 and <c>setterm -powerdown &lt;number-of-minutesM&gt;</c>. For X.org, modify
821 <path>/etc/X11/xorg.conf</path> similar to this:
822 </p>
823
824 <pre caption="LCD suspend settings in X.org and XFree86">
825 Section "ServerLayout"
826 Identifier [...]
827 [...]
828 Option "BlankTime" "5" <comment># Blank the screen after 5 minutes (Fake)</comment>
829 Option "StandbyTime" "10" <comment># Turn off screen after 10 minutes (DPMS)</comment>
830 Option "SuspendTime" "20" <comment># Full suspend after 20 minutes</comment>
831 Option "OffTime" "30" <comment># Turn off after half an hour</comment>
832 [...]
833 EndSection
834
835 [...]
836
837 Section "Monitor"
838 Identifier [...]
839 Option "DPMS" "true"
840 [...]
841 EndSection
842 </pre>
843
844 <p>
845 This is the same for XFree86 and <path>/etc/X11/XF86Config</path>.
846 </p>
847
848 </body>
849 </section>
850 <section>
851 <title>Backlight dimming</title>
852 <body>
853
854 <p>
855 Probably more important is the backlight dimming. If you have access to the
856 dimming settings via a tool, write a small script that dims the backlight in
857 battery mode and place it in your <c>battery</c> runlevel. The following script
858 should work on most IBM Thinkpads and Toshiba laptops. You've got to enable the
859 appropriate option in your kernel (IBM Thinkpads only). For Toshiba laptops,
860 install <c>app-laptop/acpitool</c> and skip configuration of <c>ibm_acpi</c> as
861 described below.
862 </p>
863
864 <warn>
865 Support for setting brightness is marked experimental in ibm-acpi. It accesses
866 hardware directly and may cause severe harm to your system. Please read the
867 <uri link="http://ibm-acpi.sourceforge.net/">ibm-acpi website</uri>
868 </warn>
869
870 <p>
871 To be able to set the brightness level, the ibm_acpi module has to be loaded
872 with the experimental parameter.
873 </p>
874
875 <pre caption="automatically loading the ibm_acpi module">
876 <comment>(Please read the warnings above before doing this!)</comment>
877 # <i>echo "options ibm_acpi experimental=1" >> /etc/modules.d/ibm_acpi</i>
878 # <i>/sbin/modules-update</i>
879 # <i>echo ibm_acpi >> /etc/modules.autoload.d/kernel-2.6</i>
880 # <i>modprobe ibm_acpi</i>
881 </pre>
882
883 <p>
884 This should work without error messages and a file
885 <path>/proc/acpi/ibm/brightness</path> should be created after loading the
886 module. An init script will take care of choosing the brightness according to
887 the power source.
888 </p>
889
890 <pre caption="/etc/conf.d/lcd-brightness">
891 <comment># See /proc/acpi/ibm/brightness for available values</comment>
892 <comment># Please read /usr/src/linux/Documentation/ibm-acpi.txt</comment>
893
894 <comment># brigthness level in ac mode. Default is 7.</comment>
895 BRIGHTNESS_AC=7
896
897 <comment># brightness level in battery mode. Default is 4.</comment>
898 BRIGHTNESS_BATTERY=4
899 </pre>
900
901 <pre caption="/etc/init.d/lcd-brightness">
902 #!/sbin/runscript
903
904 set_brightness() {
905 if on_ac_power
906 then
907 LEVEL=${BRIGHTNESS_AC:-7}
908 else
909 LEVEL=${BRIGHTNESS_BATTERY:-4}
910 fi
911
912 if [ -f /proc/acpi/ibm/brightness ]
913 then
914 ebegin "Setting LCD brightness"
915 echo "level ${LEVEL}" > /proc/acpi/ibm/brightness
916 eend $?
917 elif [[ -e /usr/bin/acpitool &amp;&amp; -n $(acpitool -T | grep "LCD brightness") ]]
918 then
919 ebegin "Setting LCD brightness"
920 acpitool -l $LEVEL >/dev/null || ewarn "Unable to set lcd brightness"
921 eend $?
922 else
923 ewarn "Setting LCD brightness is not supported."
924 ewarn "For IBM Thinkpads, check that ibm_acpi is loaded into the kernel"
925 ewarn "For Toshiba laptops, you've got to install app-laptop/acpitool"
926 fi
927 }
928
929 start() {
930 set_brightness
931 }
932
933 stop () {
934 set_brightness
935 }
936 </pre>
937
938 <p>
939 When done, make sure brightness is adjusted automatically by adding it to the
940 battery runlevel.
941 </p>
942
943 <pre caption="Enabling automatic brightness adjustment">
944 # <i>chmod +x /etc/init.d/lcd-brightness</i>
945 # <i>rc-update add lcd-brightness battery</i>
946 # <i>rc</i>
947 </pre>
948
949 </body>
950 </section>
951 </chapter>
952
953 <chapter>
954 <title>Disk Power Management</title>
955 <section>
956 <body>
957
958 <p>
959 Hard disks consume less energy in sleep mode. Therefore it makes sense to
960 activate power saving features whenever the hard disk is not used for a certain
961 amount of time. I'll show you two alternative possibilities to do it. First,
962 laptop-mode will save most energy due to several measures which prevent or at
963 least delay write accesses. The drawback is that due to the delayed write
964 accesses a power outage or kernel crash will be more dangerous for data loss.
965 If you don't like this, you have to make sure that there are no processes which
966 write to your hard disk frequently. Afterwards you can enable power saving
967 features of your hard disk with <c>hdparm</c> as the second alternative.
968 </p>
969
970 </body>
971 </section>
972 <section>
973 <title>Increasing idle time - laptop-mode</title>
974 <body>
975
976 <p>
977 Recent kernels (2.6.6 and greater, recent 2.4 ones and others with patches)
978 include the so-called <c>laptop-mode</c>. When activated, dirty buffers are
979 written to disk on read calls or after 10 minutes (instead of 30 seconds). This
980 minimizes the time the hard disk needs to be spun up.
981 </p>
982
983 <pre caption="Automated start of laptop-mode">
984 # <i>emerge laptop-mode-tools</i>
985 </pre>
986
987 <p>
988 <c>laptop-mode-tools</c> has its configuration file in
989 <path>/etc/laptop-mode/laptop-mode.conf</path>. Adjust it the way you like it,
990 it's well commented. Run <c>rc-update add laptop_mode battery</c> to start it
991 automatically.
992 </p>
993
994 <p>
995 Recent versions (1.11 and later) of laptop-mode-tools include a new tool
996 <c>lm-profiler</c>. It will monitor your system's disk usage and running
997 network services and suggests to disable unneeded ones. You can either disable
998 them through laptop-mode-tools builtin runlevel support (which will be reverted
999 by Gentoo's <c>/sbin/rc</c>) or use your <c>default</c>/<c>battery</c>
1000 runlevels (recommended).
1001 </p>
1002
1003 <pre caption="Sample output from running lm-profiler">
1004 # <i>lm-profiler</i>
1005 Profiling session started.
1006 Time remaining: 600 seconds
1007 [4296896.602000] amarokapp
1008 Time remaining: 599 seconds
1009 [4296897.714000] sort
1010 [4296897.970000] mv
1011 Time remaining: 598 seconds
1012 Time remaining: 597 seconds
1013 [4296900.482000] reiserfs/0
1014 </pre>
1015
1016 <p>
1017 After profiling your system for ten minutes, lm-profiler will present a list of
1018 services which might have caused disk accesses during that time.
1019 </p>
1020
1021 <pre caption="lm-profiler suggests to disable some services">
1022 Program: "atd"
1023 Reason: standard recommendation (program may not be running)
1024 Init script: /etc/init.d/atd (GUESSED)
1025
1026 Do you want to disable this service in battery mode? [y/N]: <i>n</i>
1027 </pre>
1028
1029 <p>
1030 To disable atd as suggested in the example above, you would run <c>rc-update
1031 del atd battery</c>. Be careful not to disable services that are needed for
1032 your system to run properly - <c>lm-profiler</c> is likely to generate some
1033 false positives. Do not disable a service if you are unsure whether it's
1034 needed.
1035 </p>
1036
1037 </body>
1038 </section>
1039 <section>
1040 <title>Limiting Write Accesses</title>
1041 <body>
1042
1043 <p>
1044 If you don't want to use laptop-mode, you must take special care to disable
1045 services that write to your disk frequently - <c>syslogd</c> is a good
1046 candidate, for example. You probably don't want to shut it down completely, but
1047 it's possible to modify the config file so that "unnecessary" things don't get
1048 logged and thus don't create disk traffic. <c>Cups</c> writes to disk
1049 periodically, so consider shutting it down and only enable it manually when
1050 needed.
1051 </p>
1052
1053 <pre caption="Disabling cups in battery mode">
1054 # <i>rc-update del cupsd battery</i>
1055 </pre>
1056
1057 <p>
1058 You can also use <c>lm-profiler</c> from laptop-mode-tools (see above) to find
1059 services to disable. Once you eliminated all of them, go on with configuring
1060 hdparm.
1061 </p>
1062
1063 </body>
1064 </section>
1065 <section>
1066 <title>hdparm</title>
1067 <body>
1068
1069 <p>
1070 The second possibility is using a small script and <c>hdparm</c>. Skip this if
1071 you are using laptop-mode. Otherwise, create <path>/etc/init.d/pmg_hda</path>:
1072 </p>
1073
1074 <pre caption="Using hdparm for disk standby">
1075 #!/sbin/runscript
1076
1077 depend() {
1078 after hdparm
1079 }
1080
1081 start() {
1082 ebegin "Activating Power Management for Hard Drives"
1083 hdparm -q -S12 /dev/hda
1084 eend $?
1085 }
1086
1087 stop () {
1088 ebegin "Deactivating Power Management for Hard Drives"
1089 hdparm -q -S253 /dev/hda
1090 eend $?
1091 }
1092 </pre>
1093
1094 <p>
1095 See <c>man hdparm</c> for the options. If your script is ready, add it to the
1096 battery runlevel.
1097 </p>
1098
1099 <pre caption="Automate disk standby settings">
1100 # <i>chmod +x /etc/init.d/pmg_hda</i>
1101 # <i>/sbin/depscan.sh</i>
1102 # <i>rc-update add pmg_hda battery</i>
1103 </pre>
1104
1105 <impo>
1106 Be careful with sleep/spin down settings of your hard drive. Setting it to
1107 small values might wear out your drive and lose warranty.
1108 </impo>
1109
1110 </body>
1111 </section>
1112 <section>
1113 <title>Other tricks</title>
1114 <body>
1115
1116 <p>
1117 Another possibility is to deactivate swap in battery mode. Before writing a
1118 swapon/swapoff switcher, make sure there is enough RAM and swap isn't used
1119 heavily, otherwise you'll be in big problems.
1120 </p>
1121
1122 <p>
1123 If you don't want to use laptop-mode, it's still possible to minimize disk
1124 access by mounting certain directories as <c>tmpfs</c> - write accesses are not
1125 stored on a disk, but in main memory and get lost with unmounting. Often it's
1126 useful to mount <path>/tmp</path> like this - you don't have to pay special
1127 attention as it gets cleared on every reboot regardless whether it was mounted
1128 on disk or in RAM. Just make sure you have enough RAM and no program (like a
1129 download client or compress utility) needs extraordinary much space in
1130 <path>/tmp</path>. To activate this, enable tmpfs support in your kernel and
1131 add a line to <path>/etc/fstab</path> like this:
1132 </p>
1133
1134 <pre caption="Editing /etc/fstab to make /tmp even more volatile">
1135 none /tmp tmpfs size=32m 0 0
1136 </pre>
1137
1138 <warn>
1139 Pay attention to the size parameter and modify it for your system. If you're
1140 unsure, don't try this at all, it can become a performance bottleneck easily. In
1141 case you want to mount <path>/var/log</path> like this, make sure to merge the
1142 log files to disk before unmounting. They are essential. Don't attempt to mount
1143 <path>/var/tmp</path> like this. Portage uses it for compiling...
1144 </warn>
1145
1146 </body>
1147 </section>
1148 </chapter>
1149
1150 <chapter>
1151 <title>Power Management For Other Devices</title>
1152 <section>
1153 <title>Graphics Cards</title>
1154 <body>
1155
1156 <p>
1157 In case you own an ATI graphics card supporting PowerPlay (dynamic clock
1158 scaling for the the graphics processing unit GPU), you can activate this
1159 feature in X.org. Open <path>/etc/X11/xorg.conf</path> and add (or enable) the
1160 <c>DynamicClocks</c> option in the Device section. Please notice that this
1161 feature will lead to crashes on some systems.
1162 </p>
1163
1164 <pre caption="Enabling ATI PowerPlay support in X.org">
1165 Section "Device"
1166 [...]
1167 Option "DynamicClocks" "on"
1168 EndSection
1169 </pre>
1170
1171 </body>
1172 </section>
1173 <section>
1174 <title>Wireless Power Management</title>
1175 <body>
1176
1177 <p>
1178 Wireless LAN cards consume quite a bit of energy. Put them in Power Management
1179 mode in analogy to the <c>pmg_hda</c> script.
1180 </p>
1181
1182 <note>
1183 This script assumes your wireless interface is called <c>wlan0</c>; replace
1184 this with the actual name of your interface.
1185 </note>
1186
1187 <pre caption="WLAN Power Management automated">
1188 #!/sbin/runscript
1189 start() {
1190 ebegin "Activating Power Management for Wireless LAN"
1191 iwconfig wlan0 power on
1192 eend $?
1193 }
1194
1195 stop () {
1196 ebegin "Deactivating Power Management for Wireless LAN"
1197 iwconfig wlan0 power off
1198 eend $?
1199 }
1200 </pre>
1201
1202 <p>
1203 Starting this script will activate power saving features for wlan0. Save it as
1204 <path>/etc/init.d/pmg_wlan0</path> and add it to the battery runlevel like the
1205 disk script above. See <c>man iwconfig</c> for details and more options like
1206 the period between wakeups or timeout settings. If your driver and access point
1207 support changing the beacon time, this is a good starting point to save even
1208 more energy.
1209 </p>
1210
1211 <pre caption="Power Management for WLAN">
1212 # <i>chmod +x /etc/init.d/pmg_wlan0</i>
1213 # <i>/sbin/depscan.sh</i>
1214 # <i>rc-update add pmg_wlan0 battery</i>
1215 </pre>
1216
1217 </body>
1218 </section>
1219 <section>
1220 <title>USB Power Management</title>
1221 <body>
1222
1223 <p>
1224 There are two problems with USB devices regarding energy consumption: First,
1225 devices like USB mice, digital cameras or USB sticks consume energy while
1226 plugged in. You cannot avoid this (nevertheless remove them in case they're not
1227 needed). Second, when there are USB devices plugged in, the USB host controller
1228 periodically accesses the bus which in turn prevents the CPU from going into
1229 sleep mode. The kernel offers an experimental option to enable suspension of
1230 USB devices through driver calls or one of the <path>power/state</path> files
1231 in <path>/sys</path>.
1232 </p>
1233
1234 <pre caption="Enabling USB suspend support in the kernel">
1235 Device Drivers
1236 USB support
1237 [*] Support for Host-side USB
1238 [*] USB suspend/resume (EXPERIMENTAL)
1239 </pre>
1240
1241 </body>
1242 </section>
1243 </chapter>
1244
1245 <chapter>
1246 <title>Sleep States: sleep, standby, and suspend to disk</title>
1247 <section>
1248 <body>
1249
1250 <p>
1251 ACPI defines different sleep states. The more important ones are
1252 </p>
1253
1254 <ul>
1255 <li>S1 aka Standby</li>
1256 <li>S3 aka Suspend to RAM aka Sleep</li>
1257 <li>S4 aka Suspend to Disk aka Hibernate</li>
1258 </ul>
1259
1260 <p>
1261 They can be called whenever the system is not in use, but a shutdown is not
1262 wanted due to the long boot time.
1263 </p>
1264
1265 </body>
1266 </section>
1267 <section>
1268 <title>Sleep (S3)</title>
1269 <body>
1270
1271 <p>
1272 The ACPI support for these sleep states is marked experimental for good reason.
1273 APM sleep states seem to be more stable, however you can't use APM and ACPI
1274 together.
1275 </p>
1276
1277 <pre caption="Kernel configuration for the various suspend types">
1278 Power Management Options ---&gt;
1279 [*] Power Management support
1280 ACPI (Advanced Configuration and Power Interface) Support ---&gt;
1281 [*] ACPI Support
1282 [*] Sleep States
1283 </pre>
1284
1285 <p>
1286 Once your kernel is properly configured, you can use the
1287 <c>hibernate-script</c> to activate suspend or sleep mode. Let's install that
1288 first.
1289 </p>
1290
1291 <pre caption="Installing the hibernate-script">
1292 # <i>emerge hibernate-script</i>
1293 </pre>
1294
1295 <p>
1296 Some configuration has to be done in <path>/etc/hibernate</path> The default
1297 package introduces two configuration files <path>hibernate.conf</path> and
1298 <path>ram.conf</path>.
1299 </p>
1300
1301 <p>
1302 To configure sleep, edit <path>ram.conf</path> in <path>/etc/hibernate</path>.
1303 <c>UseSysfsPowerState mem</c> is already setup correctly, but you have to go
1304 through the rest of the configuration file and set it up for your system. The
1305 comments and option names will guide you. If you use nfs or samba shares over
1306 the network, make sure to shutdown the appropriate init scripts to avoid
1307 timeouts.
1308 </p>
1309
1310 <p>
1311 Ready? Now is the last chance to backup any data you want to keep after
1312 executing the next command. Notice that you probably have to hit a special key
1313 like <c>Fn</c> to resume from sleep.
1314 </p>
1315
1316 <pre caption="Calling sleep">
1317 # <i>hibernate-ram</i>
1318 </pre>
1319
1320 <p>
1321 If you're still reading, it seems to work. You can also setup standby (S1) in a
1322 similar way by copying <path>ram.conf</path> to <path>standby.conf</path> and
1323 creating a symlink <path>/usr/sbin/hibernate-standby</path> pointing to
1324 <path>/usr/sbin/hibernate</path>. S3 and S4 are the more interesting sleep
1325 states due to greater energy savings however.
1326 </p>
1327
1328 </body>
1329 </section>
1330 <section>
1331 <title>Hibernate (S4)</title>
1332 <body>
1333
1334 <p>
1335 This section introduces hibernation, where a snapshot of the running system is
1336 written to disk before powering off. On resume, the snapshot is loaded and you
1337 can go on working at exactly the point you called hibernate before.
1338 </p>
1339
1340 <warn>
1341 Don't exchange non hot-pluggable hardware when suspended. Don't attempt to load
1342 a snapshot with a different kernel image than the one it was created with.
1343 Shutdown any NFS or samba server/client before hibernating.
1344 </warn>
1345
1346 <p>
1347 There are two different implementations for S4. The original one is swsusp,
1348 then there is the newer suspend2 with a nicer interface (including fbsplash
1349 support). A <uri link="http://suspend2.net/features.html#compare"> feature
1350 comparison</uri> is available at the <uri link="http://suspend2.net"> suspend2
1351 Homepage</uri>. There used to be Suspend-to-Disk (pmdisk), a fork of swsusp,
1352 but it has been merged back.
1353 </p>
1354
1355 <p>
1356 Suspend2 is not included in the mainline kernel yet, therefore you either have
1357 to patch your kernel sources with the patches provided by <uri
1358 link="http://suspend2.net">suspend2.net</uri> or use
1359 <c>sys-kernel/suspend2-sources</c>.
1360 </p>
1361
1362 <p>
1363 The kernel part for both swusp and suspend2 is as follows:
1364 </p>
1365
1366 <pre caption="Kernel configuration for the various suspend types">
1367 Power Management Options ---&gt;
1368 <comment>(hibernate with swsusp)</comment>
1369 [*] Software Suspend
1370 <comment>(replace /dev/SWAP with your swap partition)</comment>
1371 (/dev/SWAP) Default resume partition
1372
1373 <comment>(hibernate with suspend2)</comment>
1374 Software Suspend 2
1375 --- Image Storage (you need at least one writer)
1376 [*] File Writer
1377 [*] Swap Writer
1378 --- General Options
1379 [*] LZF image compression
1380 <comment>(replace /dev/SWAP with your swap partition)</comment>
1381 (swap:/dev/SWAP) Default resume device name
1382 [ ] Allow Keep Image Mode
1383 </pre>
1384
1385 <p>
1386 The configuration for swsusp is rather easy. If you didn't store the location
1387 of your swap partition in the kernel config, you can also pass it as a
1388 parameter with the <c>resume=/dev/SWAP</c> directive. If booting is not
1389 possible due to a broken image, use the <c>noresume</c> kernel parameter. The
1390 <c>hibernate-cleanup</c> init script invalidates swsusp images during the boot
1391 process.
1392 </p>
1393
1394 <pre caption="Invalidating swsusp images during the boot process">
1395 # <i>rc-update add hibernate-cleanup boot</i>
1396 </pre>
1397
1398 <p>
1399 To activate hibernate with swsusp, use the hibernate script and set
1400 <c>UseSysfsPowerState disk</c> in <path>/etc/hibernate/hibernate.conf</path>.
1401 </p>
1402
1403 <warn>
1404 Backup your data before doing this. Run <c>sync</c> before executing one of the
1405 commands to have cached data written to disk. First try it outside of X, then
1406 with X running, but not logged in.
1407 </warn>
1408
1409 <p>
1410 If you experience kernel panics due to uhci or similar, try to compile USB
1411 support as module and unload the modules before sending your laptop to sleep
1412 mode. There are configuration options for this in <path>hibernate.conf</path>
1413 </p>
1414
1415 <pre caption="Hibernating with swsusp">
1416 # <i>nano -w /etc/hibernate.conf</i>
1417 <comment>(Make sure you have a backup of your data)</comment>
1418 # <i>hibernate</i>
1419 </pre>
1420
1421 <p>
1422 The following section discusses the setup of suspend2 including fbsplash
1423 support for a nice graphical progress bar during suspend and resume.
1424 </p>
1425
1426 <p>
1427 The first part of the configuration is similar to the configuration of swsusp.
1428 In case you didn't store the location of your swap partition in the kernel
1429 config, you have to pass it as a kernel parameter with the
1430 <c>resume2=swap:/dev/SWAP</c> directive. If booting is not possible due to a
1431 broken image, append the <c>noresume2</c> parameter. Additionally, the
1432 <c>hibernate-cleanup</c> init script invalidates suspend2 images during the
1433 boot process.
1434 </p>
1435
1436 <pre caption="Invalidating suspend2 images during the boot process">
1437 # <i>rc-update add hibernate-cleanup boot</i>
1438 </pre>
1439
1440 <p>
1441 Now edit <path>/etc/hibernate/hibernate.conf</path>, enable the <c>suspend2</c>
1442 section and comment everything in the <c>sysfs_power_state</c> and
1443 <c>acpi_sleep</c> sections. Do not enable the <c>fbsplash</c> part in global
1444 options yet.
1445 </p>
1446
1447 <pre caption="Hibernating with suspend2">
1448 # <i>nano -w /etc/hibernate.conf</i>
1449 <comment>(Make sure you have a backup of your data)</comment>
1450 # <i>hibernate</i>
1451 </pre>
1452
1453 <p>
1454 Please configure <c>fbsplash</c> now if you didn't do already. To enable
1455 fbsplash support during hibernation, the <c>sys-apps/suspend2-userui</c>
1456 package is needed. Additionally, you've got to enable the <c>fbsplash</c> USE
1457 flag.
1458 </p>
1459
1460 <pre caption="Installing suspend2-userui">
1461 # <i>mkdir -p /etc/portage</i>
1462 # <i>echo "sys-apps/suspend2-userui fbsplash" >> /etc/portage/package.use</i>
1463 # <i>emerge suspend2-userui</i>
1464 </pre>
1465
1466 <p>
1467 The ebuild tells you to make a symlink to the theme you want to use. For
1468 example, to use the <c>livecd-2005.1</c> theme, run the following command:
1469 </p>
1470
1471 <pre caption="Using the livecd-2005.1 theme during hibernation">
1472 # <i>ln -sfn /etc/splash/livecd-2005.1 /etc/splash/suspend2</i>
1473 </pre>
1474
1475 <p>
1476 If you don't want a black screen in the first part of the resume process, you
1477 have to add the <c>suspend2ui_fbsplash</c> tool to your initrd image. Assuming
1478 you created the initrd image with <c>splash_geninitramfs</c> and saved it as
1479 <path>/boot/fbsplash-emergence-1024x768</path>, here's how to do that.
1480 </p>
1481
1482 <pre caption="Adding suspend2ui_fbsplash to an initrd image">
1483 # <i>mount /boot</i>
1484 # <i>mkdir ~/initrd.d</i>
1485 # <i>cp /boot/fbsplash-emergence-1024x768 ~/initrd.d/</i>
1486 # <i>cd ~/initrd.d</i>
1487 # <i>gunzip -c fbsplash-emergence-1024x768 | cpio -idm --quiet -H newc</i>
1488 # <i>rm fbsplash-emergence-1024x768</i>
1489 # <i>cp /usr/sbin/suspend2ui_fbsplash sbin/</i>
1490 # <i>find . | cpio --quiet --dereference -o -H newc | gzip -9 > /boot/fbsplash-suspend2-emergence-1024x768</i>
1491 </pre>
1492
1493 <p>
1494 Afterwards adjust <path>grub.conf</path> respectively <path>lilo.conf</path> so
1495 that your suspend2 kernel uses
1496 <path>/boot/fbsplash-suspend2-emergence-1024x768</path> as initrd image. You
1497 can now test a dry run to see if everything is setup correctly.
1498 </p>
1499
1500 <pre caption="Test run for fbsplash hibernation">
1501 # <i>suspend2ui_fbsplash -t</i>
1502 </pre>
1503
1504 <p>
1505 Afterwards open <path>/etc/hibernate/hibernate.conf</path> again and activate
1506 the fbsplash options. Execute <c>hibernate</c> and enjoy.
1507 </p>
1508
1509 </body>
1510 </section>
1511 </chapter>
1512
1513 <chapter>
1514 <title>Troubleshooting</title>
1515 <section>
1516 <body>
1517
1518 <p>
1519 <e>Q:</e> I'm trying to change the CPU frequency, but
1520 <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor</path> does not
1521 exist.
1522 </p>
1523
1524 <p>
1525 <e>A:</e> Make sure your processor supports CPU frequency scaling and you chose
1526 the right CPUFreq driver for your processor. Here is a list of processors that
1527 are supported by cpufreq (kernel 2.6.7): ARM Integrator, ARM-SA1100,
1528 ARM-SA1110, AMD Elan - SC400, SC410, AMD mobile K6-2+, AMD mobile K6-3+, AMD
1529 mobile Duron, AMD mobile Athlon, AMD Opteron, AMD Athlon 64, Cyrix Media GXm,
1530 Intel mobile PIII and Intel mobile PIII-M on certain chipsets, Intel Pentium 4,
1531 Intel Xeon, Intel Pentium M (Centrino), National Semiconductors Geode GX,
1532 Transmeta Crusoe, VIA Cyrix 3 / C3, UltraSPARC-III, SuperH SH-3, SH-4, several
1533 "PowerBook" and "iBook2" and various processors on some ACPI 2.0-compatible
1534 systems (only if "ACPI Processor Performance States" are available to the
1535 ACPI/BIOS interface).
1536 </p>
1537
1538 <p>
1539 <e>Q:</e> My laptop supports frequency scaling, but
1540 <path>/sys/devices/system/cpu/cpu0/cpufreq/</path> is empty.
1541 </p>
1542
1543 <p>
1544 <e>A:</e> Look for ACPI related error messages with <c>dmesg | grep ACPI</c>.
1545 Try to update the BIOS, especially if a broken DSDT is reported. You can also
1546 try to fix it yourself (which is beyond the scope of this guide).
1547 </p>
1548
1549 <p>
1550 <e>Q:</e> My laptop supports frequency scaling, but according to
1551 <path>/proc/cpuinfo</path> the speed never changes.
1552 </p>
1553
1554 <p>
1555 <e>A:</e> Probably you have activated symmetric multiprocessing support
1556 (CONFIG_SMP) in your kernel. Deactivate it and it should work. Some older
1557 kernels had a bug causing this. In that case, run <c>emerge x86info</c>, update
1558 your kernel as asked and check the current frequency with
1559 <c>x86info -mhz</c>.
1560 </p>
1561
1562 <p>
1563 <e>Q:</e> I can change the CPU frequency, but the range is not as wide as in
1564 another OS.
1565 </p>
1566
1567 <p>
1568 <e>A:</e> You can combine frequency scaling with ACPI throttling to get a lower
1569 minimum frequency. Notice that throttling doesn't save much energy and is
1570 mainly used for thermal management (keeping your laptop cool and quiet). You
1571 can read the current throttling state with <c>cat
1572 /proc/acpi/processor/CPU/throttling</c> and change it with <c>echo -n "0:x" >
1573 /proc/acpi/processor/CPU/limit</c>, where x is one of the Tx states listed in
1574 <path>/proc/acpi/processor/CPU/throttling</path>.
1575 </p>
1576
1577 <p>
1578 <e>Q:</e> When configuring the kernel, powersave, performance and userspace
1579 governors show up, but that ondemand thing is missing. Where do I get it?
1580 </p>
1581
1582 <p>
1583 <e>A:</e> The ondemand governor is only included in recent kernel sources. Try
1584 updating them.
1585 </p>
1586
1587 <p>
1588 <e>Q:</e> Battery life time seems to be worse than before.
1589 </p>
1590
1591 <p>
1592 <e>A:</e> Check your BIOS settings. Maybe you forgot to re-enable some of the
1593 settings.
1594 </p>
1595
1596 <p>
1597 <e>Q:</e> My battery is charged, but KDE reports there would be 0% left and
1598 immediately shuts down.
1599 </p>
1600
1601 <p>
1602 <e>A:</e> Check that battery support is compiled into your kernel. If you use
1603 it as a module, make sure the module is loaded.
1604 </p>
1605
1606 <p>
1607 <e>Q:</e> My system logger reports things like "logger: ACPI group battery /
1608 action battery is not defined".
1609 </p>
1610
1611 <p>
1612 <e>A:</e> This message is generated by the <path>/etc/acpi/default.sh</path>
1613 script that is shipped with acpid. You can safely ignore it. If you like to get
1614 rid of it, you can comment the appropriate line in
1615 <path>/etc/acpi/default.sh</path> as shown below:
1616 </p>
1617
1618 <pre caption="Disabling warnings about unknown acpi events">
1619 *) # logger "ACPI action $action is not defined"
1620 </pre>
1621
1622 <p>
1623 <e>Q:</e> I have a Dell Inspiron 51XX and I don't get any ACPI events.
1624 </p>
1625
1626 <p>
1627 <e>A:</e> This seems to be a kernel bug. Read on <uri
1628 link="http://bugme.osdl.org/show_bug.cgi?id=1752">here</uri>.
1629 </p>
1630
1631 <p>
1632 <e>Q:</e> I activated the <c>DynamicClocks</c> option in <path>xorg.conf</path>
1633 and now X.org crashes / the screen stays black / my laptop doesn't shutdown
1634 properly.
1635 </p>
1636
1637 <p>
1638 <e>A:</e> This happens on some systems. You have to disable
1639 <c>DynamicClocks</c>.
1640 </p>
1641
1642 <p>
1643 <e>Q:</e> I want to use suspend2, but it tells me my swap partition is too
1644 small. Resizing is not an option.
1645 </p>
1646
1647 <p>
1648 <e>A:</e> If there is enough free space on your system, you can use the
1649 filewriter instead of the swapwriter. The <c>hibernate-script</c> supports it
1650 as well. More information can be found in
1651 <path>/usr/src/linux/Documentation/power/suspend2.txt</path>.
1652 </p>
1653
1654 <p>
1655 <e>Q:</e> I just bought a brand new battery, but it only lasts for some
1656 minutes! What am I doing wrong?
1657 </p>
1658
1659 <p>
1660 <e>A:</e> First follow your manufacturer's advice on how to charge the battery
1661 correctly.
1662 </p>
1663
1664 <p>
1665 <e>Q:</e> The above didn't help. What should I do then?
1666 </p>
1667
1668 <p>
1669 <e>A:</e> Some batteries sold as "new" are in fact old ones. Try the following:
1670 </p>
1671
1672 <pre caption="Querying battery state">
1673 $ <i>grep capacity /proc/acpi/battery/BAT0/info</i>
1674 design capacity: 47520 mWh
1675 last full capacity: 41830 mWh
1676 </pre>
1677
1678 <p>
1679 If the "last full capacity" differs significantly from the design capacity,
1680 your battery is probably broken. Try to claim your warranty.
1681 </p>
1682
1683 <p>
1684 <e>Q:</e> My problem is not listed above. Where should I go next?
1685 </p>
1686
1687 <p>
1688 <e>A:</e> Don't fear to contact me, <mail link="earthwings@gentoo.org">Dennis
1689 Nienhüser</mail>, directly. The <uri link="http://forums.gentoo.org">Gentoo
1690 Forums</uri> are a good place to get help as well. If you prefer IRC, try the
1691 <c>#gentoo-laptop</c> channel at <uri
1692 link="irc://irc.freenode.net">irc.freenode.net</uri>.
1693 </p>
1694
1695 </body>
1696 </section>
1697 </chapter>
1698 </guide>

  ViewVC Help
Powered by ViewVC 1.1.20