/[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 1.41 - (show annotations) (download) (as text)
Wed Aug 12 02:24:57 2009 UTC (4 years, 11 months ago) by nightmorph
Branch: MAIN
Changes since 1.40: +31 -14 lines
File MIME type: application/xml
Rewrite some parts around the cpufreq comparison table. I missed these in the last commit when I switched stuff over to cpufrequtils as the default. Also added more examples on how to use cpufrequtils to show its flexibility. Other improvements elsewhere.

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 1.40 2009/08/05 14:51:17 nightmorph Exp $ -->
4 <guide link="/doc/en/power-management-guide.xml">
5 <title>Power Management Guide</title>
6
7 <author title="Author">
8 <mail link="earthwings@gentoo.org">Dennis Nienhüser</mail>
9 </author>
10 <author title="Editor">
11 <mail link="chriswhite@gentoo.org">Chris White</mail>
12 </author>
13 <author title="Editor">
14 <mail link="nightmorph@gentoo.org">Joshua Saddler</mail>
15 </author>
16
17 <abstract>
18 Power Management is the key to extend battery run time on mobile systems like
19 laptops. This guide assists you setting it up on your laptop.
20 </abstract>
21
22 <!-- The content of this document is licensed under the CC-BY-SA license -->
23 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
24 <license/>
25
26 <version>1.44</version>
27 <date>2009-08-11</date>
28
29 <chapter>
30 <title>Introduction</title>
31 <section>
32 <body>
33
34 <p>
35 Capacity and lifetime of laptop batteries have improved much in the last years.
36 Nevertheless modern processors consume much more energy than older ones and
37 each laptop generation introduces more devices hungry for energy. That's why
38 Power Management is more important than ever. Increasing battery run time
39 doesn't necessarily mean buying another battery. Much can be achieved applying
40 intelligent Power Management policies.
41 </p>
42
43 </body>
44 </section>
45 <section>
46 <title>A Quick Overview</title>
47 <body>
48
49 <p>
50 Please notice that this guide describes Power Management for <e>laptops</e>.
51 While some sections might also suite for <e>servers</e>, others do not and may
52 even cause harm. Please do not apply anything from this guide to a server
53 unless you really know what you are doing.
54 </p>
55
56 <p>
57 As this guide has become rather long, here's a short overview helping you to
58 find your way through it.
59 </p>
60
61 <p>
62 The <uri link="#doc_chap2">Prerequisites</uri> chapter talks about some
63 requirements that should be met before any of the following device individual
64 sections will work. This includes BIOS settings, kernel configuration and some
65 simplifications in user land. The following three chapters focus on devices
66 that typically consume most energy - processor, display and hard drive. Each
67 can be configured seperately. <uri link="#doc_chap3">CPU Power Management</uri>
68 shows how to adjust the processor's frequency to save a maximum of energy
69 without losing too much performance. A few different tricks prevent your hard
70 drive from working unnecessarily often in <uri link="#doc_chap5">Disk Power
71 Management</uri> (decreasing noise level as a nice side effect). Some notes on
72 graphics cards, Wireless LAN and USB finish the device section in <uri
73 link="#doc_chap6">Power Management For Other Devices</uri> while another
74 chapter is dedicated to the (rather experimental) <uri link="#doc_chap7">sleep
75 states</uri>. Last not least <uri link="#doc_chap8">Troubleshooting</uri> lists
76 common pitfalls.
77 </p>
78
79 </body>
80 </section>
81 <section>
82 <title>Power Budget For Each Component</title>
83 <body>
84
85 <figure link="/images/energy-budget.png" short="Which component consumes how
86 much energy?" caption="Power budget for each component"/>
87
88 <p>
89 Nearly every component can operate in different states - off, sleep, idle,
90 active to name a few - consuming a different amount of energy. Major parts are
91 consumed by the LCD display, CPU, chipset and hard drives. Often one is able to
92 activate OS-independent Power Management in the BIOS, but an intelligent setup
93 in the operating system adapting to different situations can achieve much more.
94 </p>
95
96 </body>
97 </section>
98 </chapter>
99
100 <chapter>
101 <title>Prerequisites</title>
102 <section>
103 <body>
104
105 <p>
106 Before discussing the details of making individual devices Power Management
107 aware, make sure certain requirements are met. After controlling BIOS settings,
108 some kernel options want to be enabled - these are in short ACPI, sleep states
109 and CPU frequency scaling. As power saving most of the time comes along with
110 performance loss or increased latency, it should only be enabled when running
111 on batteries. That's where a new runlevel <e>battery</e> comes in handy.
112 </p>
113
114 </body>
115 </section>
116 <section>
117 <title>The BIOS Part</title>
118 <body>
119
120 <p>
121 First have a look into your BIOS Power Management settings. The best way is to
122 combine BIOS and operating system policies, but for the moment it's better to
123 disable most of the BIOS part. This makes sure it doesn't interfere with your
124 policies. Don't forget to re-check BIOS settings after you configured
125 everything else.
126 </p>
127
128 </body>
129 </section>
130 <section>
131 <title>Setting USE Flags</title>
132 <body>
133
134 <p>
135 Please check that the <c>acpi</c> USE flag is set in
136 <path>/etc/make.conf</path>. Other USE flags that might be interesting for your
137 system are <c>apm</c>, <c>lm_sensors</c>, <c>nforce2</c>, <c>nvidia</c>,
138 <c>pmu</c>. See <path>/usr/portage/profiles/use*.desc</path> for details. If
139 you forgot to set one of these flags, you can recompile affected packages using
140 the <c>--newuse</c> flag in <c>emerge</c>, see <c>man emerge</c>.
141 </p>
142
143 </body>
144 </section>
145 <section>
146 <title>Configuring The Kernel</title>
147 <body>
148
149 <p>
150 ACPI (Advanced Configuration and Power Interface) support in the kernel is
151 still work in progress. Using a recent kernel will make sure you'll get the
152 most out of it.
153 </p>
154
155 <p>
156 There are different kernel sources in Portage. I'd recommend using
157 <c>gentoo-sources</c> or <c>tuxonice-sources</c>. The latter contains patches
158 for TuxOnIce, see the chapter about <uri link="#doc_chap7">sleep states</uri>
159 for more details. When configuring the kernel, activate at least these options:
160 </p>
161
162 <pre caption="Minimum kernel setup for Power Management (Kernel 2.6)">
163 Power management and ACPI options ---&gt;
164 [*] Power Management support
165 [ ] Software Suspend
166
167 ACPI( Advanced Configuration and Power Interface ) Support ---&gt;
168 [ ] Deprecated /proc/acpi/ files
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/messages | 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</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: <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 <p>
518 <c>cpufrequtils</c> can operate in an automatic mode (when you use the
519 <b>ondemand</b> governor), you can also switch to the <b>userspace</b> governor
520 if you want to manually set a specific speed. You can also statically set your
521 CPU to its highest or lowest frequency by using the <b>performance</b>
522 and <b>powersave</b> governors, respectively.
523 </p>
524
525 <pre caption="Changing CPU speeds">
526 <comment>(Set the highest available frequency)</comment>
527 # <i>cpufreq-set -g performance</i>
528 <comment>(Set the lowest available frequency)</comment>
529 # <i>cpufreq-set -g powersave</i>
530 <comment>(Set a specific frequency)</comment>
531 # <i>cpufreq-set -g userspace</i>
532 # <i>cpufreq-set -f 2.00ghz</i>
533 </pre>
534
535 </body>
536 </section>
537 <section>
538 <title>Other CPU Speed Utilities</title>
539 <body>
540
541 <p>
542 While <c>cpufrequtils</c> may be the best all-around program, there are some
543 other choices available in Portage. The following table gives a quick overview
544 of available CPU speed utilities. It's roughly separated in three categories
545 <b>kernel</b> for approaches that only need kernel support, <b>daemon</b> for
546 programs that run in the background and <b>graphical</b> for programs that
547 provide a GUI for easy configuration and changes.
548 </p>
549
550 <table>
551 <tr>
552 <th>Name</th>
553 <th>Category</th>
554 <th>Switch decision</th>
555 <th>Kernel governors</th>
556 <th>Further governors</th>
557 <th>Comments</th>
558 </tr>
559 <tr>
560 <ti>'ondemand' governor</ti>
561 <ti>Kernel</ti>
562 <ti>CPU load</ti>
563 <ti>N.A.</ti>
564 <ti>N.A.</ti>
565 <ti>
566 Chooses maximal frequency on CPU load and slowly steps down when the CPU is
567 idle. Further tuning through files in
568 <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
569 userland tools (programs, scripts) if governor switching or similar is
570 desired.
571 </ti>
572 </tr>
573 <tr>
574 <ti>'conservative' governor</ti>
575 <ti>Kernel</ti>
576 <ti>CPU load</ti>
577 <ti>N.A.</ti>
578 <ti>N.A.</ti>
579 <ti>
580 Unlike the ondemand governor, conversative doesn't jump to maximum
581 frequency when CPU load is high, but increases the frequency step by step.
582 Further tuning through files in
583 <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
584 userland tools (programs, scripts) if governor switching or similar is
585 desired.
586 </ti>
587 </tr>
588 <tr>
589 <ti><uri link="http://mnm.uib.es/~gallir/cpudyn/">cpudyn</uri></ti>
590 <ti>Daemon</ti>
591 <ti>CPU load</ti>
592 <ti>Performance, powersave</ti>
593 <ti>Dynamic</ti>
594 <ti>
595 Also supports disk standby - notice however that <e>laptop mode</e> in most
596 cases will do a better job.
597 </ti>
598 </tr>
599 <tr>
600 <ti><uri link="http://sourceforge.net/projects/cpufreqd/">cpufreqd</uri></ti>
601 <ti>Daemon</ti>
602 <ti>Battery state, CPU load, temperature, running programs and more</ti>
603 <ti>All available</ti>
604 <ti>None</ti>
605 <ti>
606 Sophisticated (but somewhat complicated) setup. Extendible through plugins
607 like sensor monitoring (lm_sensors) or coordinating some NVidia based
608 graphics card memory and core. Cpufreqd is SMP aware and can optionally be
609 controlled manually at runtime.
610 </ti>
611 </tr>
612 <tr>
613 <ti>
614 <uri link="http://www.deater.net/john/powernowd.html">powernowd</uri>
615 </ti>
616 <ti>Daemon</ti>
617 <ti>CPU load</ti>
618 <ti>None</ti>
619 <ti>Passive, sine, aggressive</ti>
620 <ti>
621 Supports SMP.
622 </ti>
623 </tr>
624 <tr>
625 <ti>
626 <uri
627 link="http://projects.simpledesigns.com.pl/project/ncpufreqd/">ncpufreqd</uri>
628 </ti>
629 <ti>Daemon</ti>
630 <ti>Temperature</ti>
631 <ti>None</ti>
632 <ti>Powersave, performance</ti>
633 <ti>
634 Toggles the used governor between performance and powersave depending on
635 system temperature. Very useful on laptops with notorious heat problems.
636 </ti>
637 </tr>
638 <tr>
639 <ti><uri link="http://www.goop.org/~jeremy/speedfreq/">speedfreq</uri></ti>
640 <ti>Daemon</ti>
641 <ti>CPU load</ti>
642 <ti>None</ti>
643 <ti>Dynamic, powersave, performance, fixed speed</ti>
644 <ti>
645 Easy to configure with a nice client/server interface. Requires a 2.6
646 kernel. Unmaintained, broken and thus removed from Portage. Please switch
647 to cpufreqd if you're still using it.
648 </ti>
649 </tr>
650 <tr>
651 <ti><uri link="http://cpuspeedy.sourceforge.net/">gtk-cpuspeedy</uri></ti>
652 <ti>Graphical</ti>
653 <ti>None</ti>
654 <ti>None</ti>
655 <ti>None</ti>
656 <ti>
657 Gnome application, a graphical tool to set CPU frequency manually. It does
658 not offer any automation.
659 </ti>
660 </tr>
661 <tr>
662 <ti>klaptopdaemon</ti>
663 <ti>Graphical</ti>
664 <ti>Battery state</ti>
665 <ti>All available</ti>
666 <ti>None</ti>
667 <ti>
668 KDE only, 'ondemand' governor required for dynamic frequency scaling.
669 </ti>
670 </tr>
671 </table>
672
673 <p>
674 While adjusting the frequency to the current load looks simple at a first
675 glance, it's not such a trivial task. A bad algorithm can cause switching
676 between two frequencies all the time or wasting energy when setting frequency
677 to an unnecessary high level.
678 </p>
679
680 <p>
681 Which one to choose? If you have no idea about it, try <c>cpufreqd</c>:
682 </p>
683
684 <pre caption="Installing cpufreqd">
685 # <i>emerge cpufreqd</i>
686 </pre>
687
688 <p>
689 <c>cpufreqd</c> can be configured by editing <path>/etc/cpufreqd.conf</path>.
690 The default one that ships with cpufreqd may look a bit confusing. I recommend
691 replacing it with the one from former Gentoo developer Henrik Brix Andersen
692 (see below). Please notice that you need cpufreqd-2.0.0 or later. Earlier
693 versions have a different syntax for the config file.
694 </p>
695
696 <pre caption="/etc/cpufreqd.conf (cpufreqd-2.0.0 and later)">
697 [General]
698 pidfile=/var/run/cpufreqd.pid
699 poll_interval=3
700 enable_plugins=acpi_ac, acpi_battery
701 enable_remote=1
702 remote_group=wheel
703 verbosity=5
704 [/General]
705
706 [Profile]
707 name=ondemand
708 minfreq=0%
709 maxfreq=100%
710 policy=ondemand
711 [/Profile]
712
713 [Profile]
714 name=conservative
715 minfreq=0%
716 maxfreq=100%
717 policy=conservative
718 [/Profile]
719
720 [Profile]
721 name=powersave
722 minfreq=0%
723 maxfreq=100%
724 policy=powersave
725 [/Profile]
726
727 [Profile]
728 name=performance
729 minfreq=0%
730 maxfreq=100%
731 policy=performance
732 [/Profile]
733
734 [Rule]
735 name=battery
736 ac=off
737 profile=conservative
738 [/Rule]
739
740 [Rule]
741 name=battery_low
742 ac=off
743 battery_interval=0-10
744 profile=powersave
745 [/Rule]
746
747 [Rule]
748 name=ac
749 ac=on
750 profile=ondemand
751 [/Rule]
752 </pre>
753
754 <p>
755 Now you can start the cpufreqd daemon. Add it to the <c>default</c> and
756 <c>battery</c> runlevel as well.
757 </p>
758
759 <pre caption="Starting cpufreqd">
760 # <i>rc-update add cpufreqd default battery</i>
761 # <i>/etc/init.d/cpufreqd start</i>
762 </pre>
763
764 <p>
765 Sometimes it can be desirable to select another policy than the daemon chooses,
766 for example when battery power is low, but you know that AC will be available
767 soon. In that case you can turn on cpufreqd's manual mode with <c>cpufreqd-set
768 manual</c> and select one of your configured policies (as listed by
769 <c>cpufreqd-get</c>). You can leave manual mode by executing <c>cpufreqd-set
770 dynamic</c>.
771 </p>
772
773 <warn>
774 Do not run more than one of the above programs at the same time. It may cause
775 confusion like switching between two frequencies all the time.
776 </warn>
777
778 </body>
779 </section>
780 <section>
781 <title>Verifying the result</title>
782 <body>
783
784 <p>
785 The last thing to check is that your new policies do a good job. An easy way to
786 do so is monitoring CPU speed while working with your laptop:
787 </p>
788
789 <pre caption="Monitoring CPU speed">
790 # <i>watch grep \"cpu MHz\" /proc/cpuinfo</i>
791 </pre>
792
793 <p>
794 If <path>/proc/cpuinfo</path> doesn't get updated (see <uri
795 link="#doc_chap8">Troubleshooting</uri>), monitor the CPU frequency with
796 <c>sys-apps/x86info</c>:
797 </p>
798
799 <pre caption="Alternative CPU speed monitoring">
800 # <i>watch x86info -mhz</i>
801 </pre>
802
803 <p>
804 Depending on your setup, CPU speed should increase on heavy load, decrease on
805 no activity or just stay at the same level. When using <c>cpufreqd</c> and
806 verbosity set to 5 or higher in <path>cpufreqd.conf</path> you'll get
807 additional information about what's happening reported to <c>syslog</c>.
808 </p>
809
810 </body>
811 </section>
812 </chapter>
813
814 <chapter>
815 <title>LCD Power Management</title>
816 <section>
817 <body>
818
819 <p>
820 As you can see in <uri link="#doc_chap1_fig1">figure 1.1</uri>, the LCD
821 display consumes the biggest part of energy (might not be the case for
822 non-mobile CPU's). Thus it's quite important not only to shut the display off
823 when not needed, but also to reduce it's backlight if possible. Most laptops
824 offer the possibility to control the backlight dimming.
825 </p>
826
827 </body>
828 </section>
829 <section>
830 <title>Standby settings</title>
831 <body>
832
833 <p>
834 The first thing to check is the standby/suspend/off timings of the display. As
835 this depends heavily on your windowmanager, I'll let you figure it out
836 yourself. Just two common places: Blanking the terminal can be done with
837 <c>setterm -blank &lt;number-of-minutesM&gt;</c>, <c>setterm -powersave on</c>
838 and <c>setterm -powerdown &lt;number-of-minutesM&gt;</c>. For X.org, modify
839 <path>/etc/X11/xorg.conf</path> similar to this:
840 </p>
841
842 <pre caption="LCD suspend settings in X.org">
843 Section "ServerFlags"
844 Option "blank time" "5" <comment># Blank the screen after 5 minutes (Fake)</comment>
845 Option "standby time" "10" <comment># Turn off screen after 10 minutes (DPMS)</comment>
846 Option "suspend time" "20" <comment># Full suspend after 20 minutes</comment>
847 Option "off time" "30" <comment># Turn off after half an hour</comment>
848 [...]
849 EndSection
850
851 [...]
852
853 Section "Monitor"
854 Identifier [...]
855 Option "DPMS"
856 [...]
857 EndSection
858 </pre>
859
860 </body>
861 </section>
862 <section>
863 <title>Backlight dimming</title>
864 <body>
865
866 <p>
867 Probably more important is the backlight dimming. If you have access to the
868 dimming settings via a tool, write a small script that dims the backlight in
869 battery mode and place it in your <c>battery</c> runlevel. The following script
870 should work on most IBM Thinkpads and Toshiba laptops. You've got to enable the
871 appropriate option in your kernel (IBM Thinkpads only). For Toshiba laptops,
872 install <c>sys-power/acpitool</c> and skip configuration of <c>thinkpad_acpi</c>
873 (formerly called <c>ibm_acpi</c>) as described below.
874 </p>
875
876 <warn>
877 Support for setting brightness is marked experimental in thinkpad_acpi. It
878 accesses hardware directly and may cause severe harm to your system. Please
879 read the <uri link="http://ibm-acpi.sourceforge.net/">thinkpad_acpi
880 website</uri>
881 </warn>
882
883 <p>
884 To be able to set the brightness level, the thinkpad_acpi module has to be
885 loaded with the experimental parameter.
886 </p>
887
888 <pre caption="automatically loading the thinkpad_acpi module">
889 <comment>(Please read the warnings above before doing this!)</comment>
890 # <i>echo "options thinkpad_acpi experimental=1" >> /etc/modprobe.d/thinkpad_acpi</i>
891 # <i>update-modules</i>
892 # <i>echo thinkpad_acpi >> /etc/modules.autoload.d/kernel-2.6</i>
893 # <i>modprobe thinkpad_acpi</i>
894 </pre>
895
896 <p>
897 This should work without error messages and a file
898 <path>/proc/acpi/ibm/brightness</path> should be created after loading the
899 module. An init script will take care of choosing the brightness according to
900 the power source.
901 </p>
902
903 <pre caption="/etc/conf.d/lcd-brightness">
904 <comment># See /proc/acpi/ibm/brightness for available values</comment>
905 <comment># Please read /usr/src/linux/Documentation/thinkpad-acpi.txt</comment>
906
907 <comment># brightness level in ac mode. Default is 7.</comment>
908 BRIGHTNESS_AC=7
909
910 <comment># brightness level in battery mode. Default is 4.</comment>
911 BRIGHTNESS_BATTERY=4
912 </pre>
913
914 <pre caption="/etc/init.d/lcd-brightness">
915 #!/sbin/runscript
916
917 set_brightness() {
918 if on_ac_power
919 then
920 LEVEL=${BRIGHTNESS_AC:-7}
921 else
922 LEVEL=${BRIGHTNESS_BATTERY:-4}
923 fi
924
925 if [ -f /proc/acpi/ibm/brightness ]
926 then
927 ebegin "Setting LCD brightness"
928 echo "level ${LEVEL}" > /proc/acpi/ibm/brightness
929 eend $?
930 elif [[ -e /usr/bin/acpitool &amp;&amp; -n $(acpitool -T | grep "LCD brightness") ]]
931 then
932 ebegin "Setting LCD brightness"
933 acpitool -l $LEVEL >/dev/null || ewarn "Unable to set lcd brightness"
934 eend $?
935 else
936 ewarn "Setting LCD brightness is not supported."
937 ewarn "For IBM Thinkpads, check that thinkpad_acpi is loaded into the kernel"
938 ewarn "For Toshiba laptops, you've got to install sys-power/acpitool"
939 fi
940 }
941
942 start() {
943 set_brightness
944 }
945
946 stop () {
947 set_brightness
948 }
949 </pre>
950
951 <p>
952 When done, make sure brightness is adjusted automatically by adding it to the
953 battery runlevel.
954 </p>
955
956 <pre caption="Enabling automatic brightness adjustment">
957 # <i>chmod +x /etc/init.d/lcd-brightness</i>
958 # <i>rc-update add lcd-brightness battery</i>
959 # <i>rc</i>
960 </pre>
961
962 </body>
963 </section>
964 </chapter>
965
966 <chapter>
967 <title>Disk Power Management</title>
968 <section>
969 <body>
970
971 <p>
972 Hard disks consume less energy in sleep mode. Therefore it makes sense to
973 activate power saving features whenever the hard disk is not used for a certain
974 amount of time. I'll show you two alternative possibilities to do it. First,
975 laptop-mode will save most energy due to several measures which prevent or at
976 least delay write accesses. The drawback is that due to the delayed write
977 accesses a power outage or kernel crash will be more dangerous for data loss.
978 If you don't like this, you have to make sure that there are no processes which
979 write to your hard disk frequently. Afterwards you can enable power saving
980 features of your hard disk with <c>hdparm</c> as the second alternative.
981 </p>
982
983 </body>
984 </section>
985 <section>
986 <title>Increasing idle time - laptop-mode</title>
987 <body>
988
989 <p>
990 Recent 2.6 kernels include the so-called <c>laptop-mode</c>. When activated,
991 dirty buffers are written to disk on read calls or after 10 minutes (instead of
992 30 seconds). This minimizes the time the hard disk needs to be spun up.
993 </p>
994
995 <pre caption="Automated start of laptop-mode">
996 # <i>emerge laptop-mode-tools</i>
997 </pre>
998
999 <p>
1000 <c>laptop-mode-tools</c> has its configuration file in
1001 <path>/etc/laptop-mode/laptop-mode.conf</path>. Adjust it the way you like it,
1002 it's well commented. Run <c>rc-update add laptop_mode battery</c> to start it
1003 automatically.
1004 </p>
1005
1006 <p>
1007 Recent versions (1.11 and later) of laptop-mode-tools include a new tool
1008 <c>lm-profiler</c>. It will monitor your system's disk usage and running
1009 network services and suggests to disable unneeded ones. You can either disable
1010 them through laptop-mode-tools builtin runlevel support (which will be reverted
1011 by Gentoo's <c>/sbin/rc</c>) or use your <c>default</c>/<c>battery</c>
1012 runlevels (recommended).
1013 </p>
1014
1015 <pre caption="Sample output from running lm-profiler">
1016 # <i>lm-profiler</i>
1017 Profiling session started.
1018 Time remaining: 600 seconds
1019 [4296896.602000] amarokapp
1020 Time remaining: 599 seconds
1021 [4296897.714000] sort
1022 [4296897.970000] mv
1023 Time remaining: 598 seconds
1024 Time remaining: 597 seconds
1025 [4296900.482000] reiserfs/0
1026 </pre>
1027
1028 <p>
1029 After profiling your system for ten minutes, lm-profiler will present a list of
1030 services which might have caused disk accesses during that time.
1031 </p>
1032
1033 <pre caption="lm-profiler suggests to disable some services">
1034 Program: "atd"
1035 Reason: standard recommendation (program may not be running)
1036 Init script: /etc/init.d/atd (GUESSED)
1037
1038 Do you want to disable this service in battery mode? [y/N]: <i>n</i>
1039 </pre>
1040
1041 <p>
1042 To disable atd as suggested in the example above, you would run <c>rc-update
1043 del atd battery</c>. Be careful not to disable services that are needed for
1044 your system to run properly - <c>lm-profiler</c> is likely to generate some
1045 false positives. Do not disable a service if you are unsure whether it's
1046 needed.
1047 </p>
1048
1049 </body>
1050 </section>
1051 <section>
1052 <title>Limiting Write Accesses</title>
1053 <body>
1054
1055 <p>
1056 If you don't want to use laptop-mode, you must take special care to disable
1057 services that write to your disk frequently - <c>syslogd</c> is a good
1058 candidate, for example. You probably don't want to shut it down completely, but
1059 it's possible to modify the config file so that "unnecessary" things don't get
1060 logged and thus don't create disk traffic. <c>Cups</c> writes to disk
1061 periodically, so consider shutting it down and only enable it manually when
1062 needed.
1063 </p>
1064
1065 <pre caption="Disabling cups in battery mode">
1066 # <i>rc-update del cupsd battery</i>
1067 </pre>
1068
1069 <p>
1070 You can also use <c>lm-profiler</c> from laptop-mode-tools (see above) to find
1071 services to disable. Once you eliminated all of them, go on with configuring
1072 hdparm.
1073 </p>
1074
1075 </body>
1076 </section>
1077 <section>
1078 <title>hdparm</title>
1079 <body>
1080
1081 <p>
1082 The second possibility is using <c>hdparm</c>. Skip this if
1083 you are using laptop-mode. Otherwise, edit <path>/etc/conf.d/hdparm</path> and
1084 add the following values to your drive entries. This example assumes your hard
1085 drive is called <b>hda</b>:
1086 </p>
1087
1088 <pre caption="Using /etc/conf.d/hdparm for disk standby">
1089 hda_args="-q -S12"
1090 </pre>
1091
1092 <p>
1093 This will activate power management for your hard drive. If you ever want to
1094 deactivate power management, you can edit <path>/etc/conf.d/hdparm</path> and
1095 change the values to <c>-q -S0</c>, or just run <c>hdparm -q -S0 /dev/hda</c>.
1096 </p>
1097
1098 <p>
1099 See <c>man hdparm</c> for the options. Though you can always start <c>hdparm</c>
1100 manually when you are on battery power by running <c>/etc/init.d/hdparm
1101 start</c>, it's much easier to automate its startup and shutdown. To do so, add
1102 <c>hdparm</c> to the battery runlevel so that it will automatically enable power
1103 management.
1104 </p>
1105
1106 <pre caption="Automate disk standby settings">
1107 # <i>rc-update add hdparm battery</i>
1108 </pre>
1109
1110 <impo>
1111 Be careful with sleep/spin down settings of your hard drive. Setting it to
1112 small values might wear out your drive and lose warranty.
1113 </impo>
1114
1115 </body>
1116 </section>
1117 <section>
1118 <title>Other tricks</title>
1119 <body>
1120
1121 <p>
1122 Another possibility is to deactivate swap in battery mode. Before writing a
1123 swapon/swapoff switcher, make sure there is enough RAM and swap isn't used
1124 heavily, otherwise you'll be in big problems.
1125 </p>
1126
1127 <p>
1128 If you don't want to use laptop-mode, it's still possible to minimize disk
1129 access by mounting certain directories as <c>tmpfs</c> - write accesses are not
1130 stored on a disk, but in main memory and get lost with unmounting. Often it's
1131 useful to mount <path>/tmp</path> like this - you don't have to pay special
1132 attention as it gets cleared on every reboot regardless whether it was mounted
1133 on disk or in RAM. Just make sure you have enough RAM and no program (like a
1134 download client or compress utility) needs extraordinary much space in
1135 <path>/tmp</path>. To activate this, enable tmpfs support in your kernel and
1136 add a line to <path>/etc/fstab</path> like this:
1137 </p>
1138
1139 <pre caption="Editing /etc/fstab to make /tmp even more volatile">
1140 none /tmp tmpfs size=32m 0 0
1141 </pre>
1142
1143 <warn>
1144 Pay attention to the size parameter and modify it for your system. If you're
1145 unsure, don't try this at all, it can become a performance bottleneck easily. In
1146 case you want to mount <path>/var/log</path> like this, make sure to merge the
1147 log files to disk before unmounting. They are essential. Don't attempt to mount
1148 <path>/var/tmp</path> like this. Portage uses it for compiling...
1149 </warn>
1150
1151 </body>
1152 </section>
1153 </chapter>
1154
1155 <chapter>
1156 <title>Power Management For Other Devices</title>
1157 <section>
1158 <title>Graphics Cards</title>
1159 <body>
1160
1161 <p>
1162 In case you own an ATI graphics card supporting PowerPlay (dynamic clock
1163 scaling for the graphics processing unit GPU), you can activate this
1164 feature in X.org. Open <path>/etc/X11/xorg.conf</path> and add (or enable) the
1165 <c>DynamicClocks</c> option in the Device section. Please notice that this
1166 feature will lead to crashes on some systems.
1167 </p>
1168
1169 <pre caption="Enabling ATI PowerPlay support in X.org">
1170 Section "Device"
1171 [...]
1172 Option "DynamicClocks" "on"
1173 EndSection
1174 </pre>
1175
1176 </body>
1177 </section>
1178 <section>
1179 <title>Wireless Power Management</title>
1180 <body>
1181
1182 <p>
1183 Wireless LAN cards consume quite a bit of energy. Put them in Power Management
1184 mode just like your hard drives.
1185 </p>
1186
1187 <note>
1188 This script assumes your wireless interface is called <c>wlan0</c>; replace
1189 this with the actual name of your interface.
1190 </note>
1191
1192 <p>
1193 Add the following option to <path>/etc/conf.d/net</path> to automatically enable
1194 power management for your wireless card:
1195 </p>
1196
1197 <pre caption="Automated WLAN Power Management">
1198 iwconfig_wlan0="power on"
1199 </pre>
1200
1201 <p>
1202 See <c>man iwconfig</c> for details and more options like the period between
1203 wakeups or timeout settings. If your driver and access point support changing
1204 the beacon time, this is a good starting point to save even more energy.
1205 </p>
1206
1207 </body>
1208 </section>
1209 <section>
1210 <title>USB Power Management</title>
1211 <body>
1212
1213 <p>
1214 There are two problems with USB devices regarding energy consumption: First,
1215 devices like USB mice, digital cameras or USB sticks consume energy while
1216 plugged in. You cannot avoid this (nevertheless remove them in case they're not
1217 needed). Second, when there are USB devices plugged in, the USB host controller
1218 periodically accesses the bus which in turn prevents the CPU from going into
1219 sleep mode. The kernel offers an experimental option to enable suspension of
1220 USB devices through driver calls or one of the <path>power/state</path> files
1221 in <path>/sys</path>.
1222 </p>
1223
1224 <pre caption="Enabling USB suspend support in the kernel">
1225 Device Drivers
1226 USB support
1227 [*] Support for Host-side USB
1228 [*] USB suspend/resume (EXPERIMENTAL)
1229 </pre>
1230
1231 </body>
1232 </section>
1233 </chapter>
1234
1235 <chapter>
1236 <title>Sleep States: sleep, standby, and suspend to disk</title>
1237 <section>
1238 <body>
1239
1240 <p>
1241 ACPI defines different sleep states. The more important ones are
1242 </p>
1243
1244 <ul>
1245 <li>S1 aka Standby</li>
1246 <li>S3 aka Suspend to RAM aka Sleep</li>
1247 <li>S4 aka Suspend to Disk aka Hibernate</li>
1248 </ul>
1249
1250 <p>
1251 They can be called whenever the system is not in use, but a shutdown is not
1252 wanted due to the long boot time.
1253 </p>
1254
1255 </body>
1256 </section>
1257 <section>
1258 <title>Sleep (S3)</title>
1259 <body>
1260
1261 <p>
1262 The ACPI support for these sleep states is marked experimental for good reason.
1263 APM sleep states seem to be more stable, however you can't use APM and ACPI
1264 together.
1265 </p>
1266
1267 <pre caption="Kernel configuration for the various suspend types">
1268 Power Management Options ---&gt;
1269 [*] Power Management support
1270 [*] Suspend to RAM and standby
1271 </pre>
1272
1273 <p>
1274 Once your kernel is properly configured, you can use the
1275 <c>hibernate-script</c> to activate suspend or sleep mode. Let's install that
1276 first.
1277 </p>
1278
1279 <pre caption="Installing the hibernate-script">
1280 # <i>emerge hibernate-script</i>
1281 </pre>
1282
1283 <p>
1284 Some configuration has to be done in <path>/etc/hibernate</path>. The default
1285 package introduces a few configuration files for each sleep state. Options that
1286 are common to all suspend methods are placed in <path>common.conf</path>; make
1287 sure this file is properly set up for your system.
1288 </p>
1289
1290 <p>
1291 To configure sleep, edit <path>sysfs-ram.conf</path> in
1292 <path>/etc/hibernate</path>. <c>UseSysfsPowerState mem</c> is already setup
1293 correctly, but if you need to make further changes to this particular sleep
1294 state (or any other sleep state) you should add them to
1295 <path>/etc/hibernate/hibernate.conf</path>. The comments and option names will
1296 guide you. If you use nfs or samba shares over the network, make sure to
1297 shutdown the appropriate init scripts to avoid timeouts.
1298 </p>
1299
1300 <note>
1301 For more information on setting up sleep states, read <c>man
1302 hibernate.conf</c>.
1303 </note>
1304
1305 <p>
1306 Ready? Now is the last chance to backup any data you want to keep after
1307 executing the next command. Notice that you probably have to hit a special key
1308 like <c>Fn</c> to resume from sleep.
1309 </p>
1310
1311 <pre caption="Calling sleep">
1312 # <i>hibernate-ram</i>
1313 </pre>
1314
1315 <p>
1316 If you're still reading, it seems to work. You can also setup standby (S1) in a
1317 similar way by editing <path>sysfs-ram.conf</path> and changing
1318 "UseSysfsPowerState mem" to "UseSysfsPowerState standby". S3 and S4 are the more
1319 interesting sleep states due to greater energy savings however.
1320 </p>
1321
1322 </body>
1323 </section>
1324 <section>
1325 <title>Hibernate (S4)</title>
1326 <body>
1327
1328 <p>
1329 This section introduces hibernation, where a snapshot of the running system is
1330 written to disk before powering off. On resume, the snapshot is loaded and you
1331 can go on working at exactly the point you called hibernate before.
1332 </p>
1333
1334 <warn>
1335 Don't exchange non hot-pluggable hardware when suspended. Don't attempt to load
1336 a snapshot with a different kernel image than the one it was created with.
1337 Shutdown any NFS or samba server/client before hibernating.
1338 </warn>
1339
1340 <p>
1341 There are two different implementations for S4. The original one is swsusp,
1342 then there is the newer tuxonice (formerly suspend2) with a nicer interface
1343 (including fbsplash support). A <uri
1344 link="http://tuxonice.net/features.html#compare">feature comparison</uri> is
1345 available at the <uri link="http://www.tuxonice.net">tuxonice homepage</uri>.
1346 There used to be Suspend-to-Disk (pmdisk), a fork of swsusp, but it has been
1347 merged back.
1348 </p>
1349
1350 <p>
1351 TuxOnIce is not included in the mainline kernel yet, therefore you either have
1352 to patch your kernel sources with the patches provided by <uri
1353 link="http://www.tuxonice.net">tuxonice.net</uri> or use
1354 <c>sys-kernel/tuxonice-sources</c>.
1355 </p>
1356
1357 <p>
1358 The kernel part for both swusp and TuxOnIce is as follows:
1359 </p>
1360
1361 <pre caption="Kernel configuration for the various suspend types">
1362 Power Management support ---&gt;
1363 <comment>(hibernate with swsusp)</comment>
1364 [*] Hibernation (aka 'suspend to disk')
1365 <comment>(replace /dev/SWAP with your swap partition)</comment>
1366 (/dev/SWAP) Default resume partition
1367
1368 <comment>(hibernate with TuxOnIce)</comment>
1369 Enhanced Hibernation (TuxOnIce)
1370 --- Image Storage (you need at least one allocator)
1371 [*] File Allocator
1372 [*] Swap Allocator
1373 --- General Options
1374 [*] Compression support
1375 [ ] Allow Keep Image Mode
1376 [*] Replace swsusp by default
1377 </pre>
1378
1379 <p>
1380 The configuration for swsusp is rather easy. If you didn't store the location
1381 of your swap partition in the kernel config, you can also pass it as a
1382 parameter with the <c>resume=/dev/SWAP</c> directive. If booting is not
1383 possible due to a broken image, use the <c>noresume</c> kernel parameter. The
1384 <c>hibernate-cleanup</c> init script invalidates swsusp images during the boot
1385 process.
1386 </p>
1387
1388 <pre caption="Invalidating swsusp images during the boot process">
1389 # <i>rc-update add hibernate-cleanup boot</i>
1390 </pre>
1391
1392 <p>
1393 To activate hibernate with swsusp, use the hibernate script and set
1394 <c>UseSysfsPowerState disk</c> in <path>/etc/hibernate/sysfs-disk</path>.
1395 </p>
1396
1397 <warn>
1398 Backup your data before doing this. Run <c>sync</c> before executing one of the
1399 commands to have cached data written to disk. First try it outside of X, then
1400 with X running, but not logged in.
1401 </warn>
1402
1403 <p>
1404 If you experience kernel panics due to uhci or similar, try to compile USB
1405 support as module and unload the modules before sending your laptop to sleep
1406 mode. There are configuration options for this in <path>common.conf</path>
1407 </p>
1408
1409 <pre caption="Hibernating with swsusp">
1410 # <i>nano -w /etc/hibernate/common.conf</i>
1411 <comment>(Make sure you have a backup of your data)</comment>
1412 # <i>hibernate</i>
1413 </pre>
1414
1415 <p>
1416 The following section discusses the setup of TuxOnIce including fbsplash support
1417 for a nice graphical progress bar during suspend and resume.
1418 </p>
1419
1420 <p>
1421 The first part of the configuration is similar to the configuration of swsusp.
1422 In case you didn't store the location of your swap partition in the kernel
1423 config, you have to pass it as a kernel parameter with the
1424 <c>resume=swap:/dev/SWAP</c> directive. If booting is not possible due to a
1425 broken image, append the <c>noresume</c> parameter. Additionally, the
1426 <c>hibernate-cleanup</c> init script invalidates TuxOnIce images during the boot
1427 process.
1428 </p>
1429
1430 <pre caption="Invalidating TuxOnIce images during the boot process">
1431 # <i>rc-update add hibernate-cleanup boot</i>
1432 </pre>
1433
1434 <p>
1435 Now edit <path>/etc/hibernate/tuxonice.conf</path>, enable the <c>TuxOnIce</c>
1436 options you need. Do not enable the <c>fbsplash</c> options in
1437 <c>common.conf</c> just yet.
1438 </p>
1439
1440 <pre caption="Hibernating with TuxOnIce">
1441 # <i>nano -w /etc/hibernate/tuxonice.conf</i>
1442 <comment>(Make sure you have a backup of your data)</comment>
1443 # <i>hibernate</i>
1444 </pre>
1445
1446 <p>
1447 Please configure <c>fbsplash</c> now if you didn't do already. To enable
1448 fbsplash support during hibernation, the <c>sys-apps/tuxonice-userui</c> package
1449 is needed. Additionally, you've got to enable the <c>fbsplash</c> USE flag.
1450 </p>
1451
1452 <pre caption="Installing tuxonice-userui">
1453 # <i>echo "sys-apps/tuxonice-userui fbsplash" >> /etc/portage/package.use</i>
1454 <comment>(It may be marked ~arch, so first it must be keyworded)</comment>
1455 # <i>echo "sys-apps/tuxonice-userui" >> /etc/portage/package.keywords</i>
1456 # <i>emerge tuxonice-userui</i>
1457 </pre>
1458
1459 <p>
1460 The ebuild tells you to make a symlink to the theme you want to use. For
1461 example, to use the <c>livecd-2005.1</c> theme, run the following command:
1462 </p>
1463
1464 <pre caption="Using the livecd-2005.1 theme during hibernation">
1465 # <i>ln -sfn /etc/splash/livecd-2005.1 /etc/splash/tuxonice</i>
1466 </pre>
1467
1468 <p>
1469 If you don't want a black screen in the first part of the resume process, you
1470 have to add the <c>tuxoniceui_fbsplash</c> tool to your initrd image. Assuming
1471 you created the initrd image with <c>splash_geninitramfs</c> and saved it as
1472 <path>/boot/fbsplash-emergence-1024x768</path>, here's how to do that.
1473 </p>
1474
1475 <pre caption="Adding tuxoniceui_fbsplash to an initrd image">
1476 # <i>mount /boot</i>
1477 # <i>mkdir ~/initrd.d</i>
1478 # <i>cp /boot/fbsplash-emergence-1024x768 ~/initrd.d/</i>
1479 # <i>cd ~/initrd.d</i>
1480 # <i>gunzip -c fbsplash-emergence-1024x768 | cpio -idm --quiet -H newc</i>
1481 # <i>rm fbsplash-emergence-1024x768</i>
1482 # <i>cp /usr/sbin/tuxoniceui_fbsplash sbin/</i>
1483 # <i>find . | cpio --quiet --dereference -o -H newc | gzip -9 > /boot/fbsplash-tuxonice-emergence-1024x768</i>
1484 </pre>
1485
1486 <p>
1487 Afterwards adjust <path>grub.conf</path> (or <path>lilo.conf</path>) so that
1488 your TuxOnIce kernel uses
1489 <path>/boot/fbsplash-tuxonice-emergence-1024x768</path> as initrd image. You can
1490 now test a dry run to see if everything is setup correctly.
1491 </p>
1492
1493 <pre caption="Test run for fbsplash hibernation">
1494 # <i>tuxoniceui_fbsplash -t</i>
1495 </pre>
1496
1497 <p>
1498 Afterwards open <path>/etc/hibernate/common.conf</path> and activate the
1499 fbsplash options. Execute <c>hibernate</c> and enjoy.
1500 </p>
1501
1502 </body>
1503 </section>
1504 </chapter>
1505
1506 <chapter>
1507 <title>Troubleshooting</title>
1508 <section>
1509 <body>
1510
1511 <p>
1512 <e>Q:</e> I'm trying to change the CPU frequency, but
1513 <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor</path> does not
1514 exist.
1515 </p>
1516
1517 <p>
1518 <e>A:</e> Make sure your processor supports CPU frequency scaling and you chose
1519 the right CPUFreq driver for your processor. Here is a list of processors that
1520 are supported by cpufreq (kernel 2.6.7): ARM Integrator, ARM-SA1100, ARM-SA1110,
1521 AMD Elan - SC400, SC410, AMD mobile K6-2+, AMD mobile K6-3+, AMD mobile Duron,
1522 AMD mobile Athlon, AMD Opteron, AMD Athlon 64, Cyrix Media GXm, Intel mobile
1523 PIII and Intel mobile PIII-M on certain chipsets, Intel Pentium 4, Intel Xeon,
1524 Intel Pentium M (Centrino), National Semiconductors Geode GX, Transmeta Crusoe,
1525 VIA Cyrix 3 / C3, UltraSPARC-III, SuperH SH-3, SH-4, several "PowerBook" and
1526 "iBook2" and various processors on some ACPI 2.0-compatible systems (only if
1527 "ACPI Processor Performance States" are available to the ACPI/BIOS interface).
1528 </p>
1529
1530 <p>
1531 <e>Q:</e> My laptop supports frequency scaling, but
1532 <path>/sys/devices/system/cpu/cpu0/cpufreq/</path> is empty.
1533 </p>
1534
1535 <p>
1536 <e>A:</e> Look for ACPI related error messages with <c>dmesg | grep ACPI</c>.
1537 Try to update the BIOS, especially if a broken DSDT is reported. You can also
1538 try to fix it yourself (which is beyond the scope of this guide).
1539 </p>
1540
1541 <p>
1542 <e>Q:</e> My laptop supports frequency scaling, but according to
1543 <path>/proc/cpuinfo</path> the speed never changes.
1544 </p>
1545
1546 <p>
1547 <e>A:</e> Probably you have activated symmetric multiprocessing support
1548 (CONFIG_SMP) in your kernel. Deactivate it and it should work. Some older
1549 kernels had a bug causing this. In that case, run <c>emerge x86info</c>, update
1550 your kernel as asked and check the current frequency with <c>x86info -mhz</c>.
1551 </p>
1552
1553 <p>
1554 <e>Q:</e> I can change the CPU frequency, but the range is not as wide as in
1555 another OS.
1556 </p>
1557
1558 <p>
1559 <e>A:</e> You can combine frequency scaling with ACPI throttling to get a lower
1560 minimum frequency. Notice that throttling doesn't save much energy and is mainly
1561 used for thermal management (keeping your laptop cool and quiet). You can read
1562 the current throttling state with <c>cat /proc/acpi/processor/CPU/throttling</c>
1563 and change it with <c>echo -n "0:x" > /proc/acpi/processor/CPU/limit</c>, where
1564 x is one of the Tx states listed in
1565 <path>/proc/acpi/processor/CPU/throttling</path>.
1566 </p>
1567
1568 <p>
1569 <e>Q:</e> When configuring the kernel, powersave, performance and userspace
1570 governors show up, but that ondemand thing is missing. Where do I get it?
1571 </p>
1572
1573 <p>
1574 <e>A:</e> The ondemand governor is only included in recent kernel sources. Try
1575 updating them.
1576 </p>
1577
1578 <p>
1579 <e>Q:</e> Battery life time seems to be worse than before.
1580 </p>
1581
1582 <p>
1583 <e>A:</e> Check your BIOS settings. Maybe you forgot to re-enable some of the
1584 settings.
1585 </p>
1586
1587 <p>
1588 <e>Q:</e> My battery is charged, but KDE reports there would be 0% left and
1589 immediately shuts down.
1590 </p>
1591
1592 <p>
1593 <e>A:</e> Check that battery support is compiled into your kernel. If you use
1594 it as a module, make sure the module is loaded.
1595 </p>
1596
1597 <p>
1598 <e>Q:</e> My system logger reports things like "logger: ACPI group battery /
1599 action battery is not defined".
1600 </p>
1601
1602 <p>
1603 <e>A:</e> This message is generated by the <path>/etc/acpi/default.sh</path>
1604 script that is shipped with acpid. You can safely ignore it. If you like to get
1605 rid of it, you can comment the appropriate line in
1606 <path>/etc/acpi/default.sh</path> as shown below:
1607 </p>
1608
1609 <pre caption="Disabling warnings about unknown acpi events">
1610 *) # logger "ACPI action $action is not defined"
1611 </pre>
1612
1613 <p>
1614 <e>Q:</e> I have a Dell Inspiron 51XX and I don't get any ACPI events.
1615 </p>
1616
1617 <p>
1618 <e>A:</e> This seems to be a kernel bug. Read on <uri
1619 link="http://bugme.osdl.org/show_bug.cgi?id=1752">here</uri>.
1620 </p>
1621
1622 <p>
1623 <e>Q:</e> I activated the <c>DynamicClocks</c> option in <path>xorg.conf</path>
1624 and now X.org crashes / the screen stays black / my laptop doesn't shutdown
1625 properly.
1626 </p>
1627
1628 <p>
1629 <e>A:</e> This happens on some systems. You have to disable
1630 <c>DynamicClocks</c>.
1631 </p>
1632
1633 <p>
1634 <e>Q:</e> I want to use TuxOnIce, but it tells me my swap partition is too
1635 small. Resizing is not an option.
1636 </p>
1637
1638 <p>
1639 <e>A:</e> If there is enough free space on your system, you can use the
1640 filewriter instead of the swapwriter. The <c>hibernate-script</c> supports it as
1641 well. More information can be found in
1642 <path>/usr/src/linux/Documentation/power/tuxonice.txt</path>.
1643 </p>
1644
1645 <p>
1646 <e>Q:</e> I just bought a brand new battery, but it only lasts for some
1647 minutes! What am I doing wrong?
1648 </p>
1649
1650 <p>
1651 <e>A:</e> First follow your manufacturer's advice on how to charge the battery
1652 correctly.
1653 </p>
1654
1655 <p>
1656 <e>Q:</e> The above didn't help. What should I do then?
1657 </p>
1658
1659 <p>
1660 <e>A:</e> Some batteries sold as "new" are in fact old ones. Try the following:
1661 </p>
1662
1663 <pre caption="Querying battery state">
1664 $ <i>grep capacity /proc/acpi/battery/BAT0/info</i>
1665 design capacity: 47520 mWh
1666 last full capacity: 41830 mWh
1667 </pre>
1668
1669 <p>
1670 If the "last full capacity" differs significantly from the design capacity,
1671 your battery is probably broken. Try to claim your warranty.
1672 </p>
1673
1674 <p>
1675 <e>Q:</e> My problem is not listed above. Where should I go next?
1676 </p>
1677
1678 <p>
1679 <e>A:</e> Don't fear to contact me, <mail link="earthwings@gentoo.org">Dennis
1680 Nienhüser</mail>, directly. The <uri link="http://forums.gentoo.org">Gentoo
1681 Forums</uri> are a good place to get help as well. If you prefer IRC, try the
1682 <c>#gentoo-laptop</c> <uri link="irc://irc.gentoo.org">channel</uri>.
1683 </p>
1684
1685 </body>
1686 </section>
1687 </chapter>
1688 </guide>

  ViewVC Help
Powered by ViewVC 1.1.20