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Bug #367145 - Update powermanagement guide to reflect OpenRC changes

1 swift 1.1 <?xml version='1.0' encoding="UTF-8"?>
2     <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3 swift 1.47 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/power-management-guide.xml,v 1.46 2011/03/28 10:26:10 nightmorph Exp $ -->
4 nightmorph 1.42
5     <guide>
6 swift 1.1 <title>Power Management Guide</title>
7    
8 swift 1.4 <author title="Author">
9 nightmorph 1.17 <mail link="earthwings@gentoo.org">Dennis Nienhüser</mail>
10 swift 1.1 </author>
11 rane 1.19 <author title="Editor">
12     <mail link="chriswhite@gentoo.org">Chris White</mail>
13     </author>
14 nightmorph 1.26 <author title="Editor">
15 nightmorph 1.42 <mail link="nightmorph"/>
16 nightmorph 1.26 </author>
17 swift 1.1
18     <abstract>
19     Power Management is the key to extend battery run time on mobile systems like
20     laptops. This guide assists you setting it up on your laptop.
21     </abstract>
22    
23     <!-- The content of this document is licensed under the CC-BY-SA license -->
24 so 1.15 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
25 swift 1.1 <license/>
26    
27 swift 1.47 <version>3</version>
28     <date>2011-08-17</date>
29 swift 1.1
30     <chapter>
31     <title>Introduction</title>
32     <section>
33     <body>
34    
35     <p>
36 so 1.15 Capacity and lifetime of laptop batteries have improved much in the last years.
37 swift 1.1 Nevertheless modern processors consume much more energy than older ones and
38     each laptop generation introduces more devices hungry for energy. That's why
39     Power Management is more important than ever. Increasing battery run time
40     doesn't necessarily mean buying another battery. Much can be achieved applying
41     intelligent Power Management policies.
42     </p>
43    
44     </body>
45     </section>
46     <section>
47 rane 1.19 <title>A Quick Overview</title>
48 swift 1.1 <body>
49    
50     <p>
51     Please notice that this guide describes Power Management for <e>laptops</e>.
52     While some sections might also suite for <e>servers</e>, others do not and may
53     even cause harm. Please do not apply anything from this guide to a server
54     unless you really know what you are doing.
55     </p>
56    
57     <p>
58     As this guide has become rather long, here's a short overview helping you to
59     find your way through it.
60     </p>
61    
62     <p>
63 rane 1.19 The <uri link="#doc_chap2">Prerequisites</uri> chapter talks about some
64     requirements that should be met before any of the following device individual
65     sections will work. This includes BIOS settings, kernel configuration and some
66     simplifications in user land. The following three chapters focus on devices
67     that typically consume most energy - processor, display and hard drive. Each
68 nightmorph 1.46 can be configured separately. <uri link="#doc_chap3">CPU Power Management</uri>
69 rane 1.19 shows how to adjust the processor's frequency to save a maximum of energy
70 rane 1.21 without losing too much performance. A few different tricks prevent your hard
71 rane 1.19 drive from working unnecessarily often in <uri link="#doc_chap5">Disk Power
72     Management</uri> (decreasing noise level as a nice side effect). Some notes on
73 rane 1.20 graphics cards, Wireless LAN and USB finish the device section in <uri
74     link="#doc_chap6">Power Management For Other Devices</uri> while another
75 rane 1.19 chapter is dedicated to the (rather experimental) <uri link="#doc_chap7">sleep
76 rane 1.20 states</uri>. Last not least <uri link="#doc_chap8">Troubleshooting</uri> lists
77     common pitfalls.
78 swift 1.1 </p>
79    
80     </body>
81     </section>
82     <section>
83 rane 1.19 <title>Power Budget For Each Component</title>
84 swift 1.1 <body>
85    
86 swift 1.2 <figure link="/images/energy-budget.png" short="Which component consumes how
87 swift 1.1 much energy?" caption="Power budget for each component"/>
88    
89     <p>
90     Nearly every component can operate in different states - off, sleep, idle,
91     active to name a few - consuming a different amount of energy. Major parts are
92     consumed by the LCD display, CPU, chipset and hard drives. Often one is able to
93     activate OS-independent Power Management in the BIOS, but an intelligent setup
94     in the operating system adapting to different situations can achieve much more.
95     </p>
96    
97     </body>
98     </section>
99     </chapter>
100    
101     <chapter>
102     <title>Prerequisites</title>
103     <section>
104     <body>
105    
106     <p>
107 nightmorph 1.17 Before discussing the details of making individual devices Power Management
108 rane 1.20 aware, make sure certain requirements are met. After controlling BIOS settings,
109     some kernel options want to be enabled - these are in short ACPI, sleep states
110     and CPU frequency scaling. As power saving most of the time comes along with
111     performance loss or increased latency, it should only be enabled when running
112     on batteries. That's where a new runlevel <e>battery</e> comes in handy.
113 swift 1.1 </p>
114    
115     </body>
116     </section>
117     <section>
118 rane 1.19 <title>The BIOS Part</title>
119 swift 1.1 <body>
120    
121     <p>
122     First have a look into your BIOS Power Management settings. The best way is to
123     combine BIOS and operating system policies, but for the moment it's better to
124     disable most of the BIOS part. This makes sure it doesn't interfere with your
125     policies. Don't forget to re-check BIOS settings after you configured
126     everything else.
127     </p>
128    
129     </body>
130     </section>
131     <section>
132 rane 1.19 <title>Setting USE Flags</title>
133 nightmorph 1.17 <body>
134    
135     <p>
136     Please check that the <c>acpi</c> USE flag is set in
137     <path>/etc/make.conf</path>. Other USE flags that might be interesting for your
138     system are <c>apm</c>, <c>lm_sensors</c>, <c>nforce2</c>, <c>nvidia</c>,
139     <c>pmu</c>. See <path>/usr/portage/profiles/use*.desc</path> for details. If
140     you forgot to set one of these flags, you can recompile affected packages using
141 rane 1.19 the <c>--newuse</c> flag in <c>emerge</c>, see <c>man emerge</c>.
142 nightmorph 1.17 </p>
143    
144     </body>
145     </section>
146     <section>
147 rane 1.19 <title>Configuring The Kernel</title>
148 swift 1.1 <body>
149    
150     <p>
151     ACPI (Advanced Configuration and Power Interface) support in the kernel is
152     still work in progress. Using a recent kernel will make sure you'll get the
153     most out of it.
154     </p>
155    
156     <p>
157 rane 1.20 There are different kernel sources in Portage. I'd recommend using
158 jkt 1.33 <c>gentoo-sources</c> or <c>tuxonice-sources</c>. The latter contains patches
159 jkt 1.34 for TuxOnIce, see the chapter about <uri link="#doc_chap7">sleep states</uri>
160     for more details. When configuring the kernel, activate at least these options:
161 swift 1.1 </p>
162    
163     <pre caption="Minimum kernel setup for Power Management (Kernel 2.6)">
164 nightmorph 1.39 Power management and ACPI options ---&gt;
165 nightmorph 1.40 [*] Power Management support
166 swift 1.1 [ ] Software Suspend
167    
168     ACPI( Advanced Configuration and Power Interface ) Support ---&gt;
169 nightmorph 1.39 [ ] Deprecated /proc/acpi/ files
170 neysx 1.12 [*] AC Adapter
171     [*] Battery
172 swift 1.1 &lt;M&gt; Button
173 so 1.15 &lt;M&gt; Video
174     [ ] Generic Hotkey
175 swift 1.1 &lt;M&gt; Fan
176     &lt;M&gt; Processor
177     &lt;M&gt; Thermal Zone
178     &lt; &gt; ASUS/Medion Laptop Extras
179 so 1.15 &lt; &gt; IBM ThinkPad Laptop Extras
180 swift 1.1 &lt; &gt; Toshiba Laptop Extras
181 so 1.15 (0) Disable ACPI for systems before Jan 1st this year
182 swift 1.1 [ ] Debug Statements
183 so 1.15 [*] Power Management Timer Support
184     &lt; &gt; ACPI0004,PNP0A05 and PNP0A06 Container Driver (EXPERIMENTAL)
185 rane 1.20
186 swift 1.1 CPU Frequency Scaling ---&gt;
187     [*] CPU Frequency scaling
188 so 1.15 [ ] Enable CPUfreq debugging
189     &lt; &gt; CPU frequency translation statistics
190     [ ] CPU frequency translation statistics details
191 swift 1.1 Default CPUFreq governor (userspace)
192     &lt;*&gt; 'performance' governor
193     &lt;*&gt; 'powersave' governor
194 swift 1.8 &lt;*&gt; 'ondemand' cpufreq policy governor
195 so 1.15 &lt;*&gt; 'conservative' cpufreq governor
196 swift 1.1 &lt;*&gt; CPU frequency table helpers
197     &lt;M&gt; ACPI Processor P-States driver
198     &lt;*&gt; <i>CPUFreq driver for your processor</i>
199     </pre>
200    
201     <p>
202 so 1.15 Decide yourself whether you want to enable Software Suspend, and Sleep States
203     (see below). If you own an ASUS, Medion, IBM Thinkpad or Toshiba laptop, enable
204 neysx 1.12 the appropriate section.
205 swift 1.8 </p>
206    
207     <p>
208 rane 1.20 The kernel has to know how to enable CPU frequency scaling on your processor.
209     As each type of CPU has a different interface, you've got to choose the right
210 rane 1.19 driver for your processor. Be careful here - enabling <c>Intel Pentium 4 clock
211     modulation</c> on a Pentium M system will lead to strange results for example.
212 swift 1.8 Consult the kernel documentation if you're unsure which one to take.
213 swift 1.1 </p>
214    
215     <p>
216     Compile your kernel, make sure the right modules get loaded at startup and boot
217 rane 1.20 into your new ACPI-enabled kernel. Next run <c>emerge sys-power/acpid</c> to
218     get the acpi daemon. This one informs you about events like switching from AC
219     to battery or closing the lid. Make sure the modules are loaded if you didn't
220     compile them into the kernel and start acpid by executing <c>/etc/init.d/acpid
221     start</c>. Run <c>rc-update add acpid default</c> to load it on startup. You'll
222     soon see how to use it.
223 swift 1.1 </p>
224    
225     <pre caption="Installing acpid">
226 yoswink 1.10 # <i>emerge sys-power/acpid</i>
227 swift 1.1 # <i>/etc/init.d/acpid start</i>
228     # <i>rc-update add acpid default</i>
229     </pre>
230    
231     </body>
232     </section>
233     <section>
234 rane 1.19 <title>Creating A "battery" Runlevel</title>
235 swift 1.1 <body>
236    
237     <p>
238     The default policy will be to enable Power Management only when needed -
239     running on batteries. To make the switch between AC and battery convenient,
240 rane 1.19 create a runlevel <c>battery</c> that holds all the scripts starting and
241 swift 1.1 stopping Power Management.
242     </p>
243    
244     <note>
245     You can safely skip this section if you don't like the idea of having another
246     runlevel. However, skipping this step will make the rest a bit trickier to set
247 rane 1.19 up. The next sections assume a runlevel <c>battery</c> exists.
248 swift 1.1 </note>
249    
250     <pre caption="Creating a battery runlevel">
251     # <i>cd /etc/runlevels</i>
252     # <i>cp -a default battery</i>
253     </pre>
254    
255     <p>
256 rane 1.19 Finished. Your new runlevel <c>battery</c> contains everything like
257     <c>default</c>, but there is no automatic switch between both yet. Time to
258 swift 1.1 change it.
259     </p>
260    
261     </body>
262     </section>
263     <section>
264 rane 1.19 <title>Reacting On ACPI Events</title>
265 swift 1.1 <body>
266    
267     <p>
268     Typical ACPI events are closing the lid, changing the power source or pressing
269 swift 1.8 the sleep button. An important event is changing the power source, which should
270 so 1.15 cause a runlevel switch. A small script will take care of it.
271     </p>
272    
273     <p>
274     First you need a script which changes the runlevel to <c>default</c>
275     respectively <c>battery</c> depending on the power source. The script uses the
276 nightmorph 1.43 <c>on_ac_power</c> command from <c>sys-power/pm-utils</c> - make sure the
277 so 1.15 package is installed on your system.
278     </p>
279    
280 nightmorph 1.43 <pre caption="Installing pm-utils">
281     # <i>emerge pm-utils</i>
282 so 1.15 </pre>
283    
284     <p>
285 rane 1.20 You are now able to determine the power source by executing <c>on_ac_power
286     &amp;&amp; echo AC available || echo Running on batteries</c> in a shell. The
287     script below is responsible for changing runlevels. Save it as
288 so 1.15 <path>/etc/acpi/actions/pmg_switch_runlevel.sh</path>.
289 swift 1.8 </p>
290    
291 neysx 1.12 <pre caption="/etc/acpi/actions/pmg_switch_runlevel.sh">
292 swift 1.8 #!/bin/bash
293    
294 neysx 1.12 <comment># BEGIN configuration</comment>
295 swift 1.8 RUNLEVEL_AC="default"
296     RUNLEVEL_BATTERY="battery"
297 neysx 1.12 <comment># END configuration</comment>
298 swift 1.8
299 swift 1.1
300 neysx 1.12 if [ ! -d "/etc/runlevels/${RUNLEVEL_AC}" ]
301     then
302 nightmorph 1.17 logger "${0}: Runlevel ${RUNLEVEL_AC} does not exist. Aborting."
303     exit 1
304 neysx 1.12 fi
305 swift 1.8
306 neysx 1.12 if [ ! -d "/etc/runlevels/${RUNLEVEL_BATTERY}" ]
307     then
308 nightmorph 1.17 logger "${0}: Runlevel ${RUNLEVEL_BATTERY} does not exist. Aborting."
309     exit 1
310 neysx 1.12 fi
311 swift 1.1
312 neysx 1.12 if on_ac_power
313     then
314 rane 1.19 if [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_AC}" ]]
315 nightmorph 1.17 then
316     logger "Switching to ${RUNLEVEL_AC} runlevel"
317     /sbin/rc ${RUNLEVEL_AC}
318     fi
319 rane 1.19 elif [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_BATTERY}" ]]
320 neysx 1.12 then
321 nightmorph 1.17 logger "Switching to ${RUNLEVEL_BATTERY} runlevel"
322     /sbin/rc ${RUNLEVEL_BATTERY}
323 neysx 1.12 fi
324 swift 1.8 </pre>
325    
326 so 1.15 <p>
327     Dont forget to run <c>chmod +x /etc/acpi/actions/pmg_switch_runlevel.sh</c> to
328     make the script executable. The last thing that needs to be done is calling the
329     script whenever the power source changes. That's done by catching ACPI events
330     with the help of <c>acpid</c>. First you need to know which events are
331     generated when the power source changes. The events are called
332 rane 1.19 <c>ac_adapter</c> and <c>battery</c> on most laptops, but it might be different
333 so 1.15 on yours.
334     </p>
335    
336     <pre caption="Determining ACPI events for changing the power source">
337 nightmorph 1.42 # <i>tail -f /var/log/messages | grep "ACPI event"</i>
338 so 1.15 </pre>
339    
340     <p>
341 rane 1.20 Run the command above and pull the power cable. You should see something like
342     this:
343 so 1.15 </p>
344    
345     <pre caption="Sample output for power source changes">
346 nightmorph 1.42 [Tue Sep 20 17:39:06 2005] ACPI event "ac_adapter AC 00000080 00000000"
347     [Tue Sep 20 17:39:06 2005] ACPI event "battery BAT0 00000080 00000001"
348 so 1.15 </pre>
349    
350     <p>
351 jkt 1.44 The interesting part is the quoted string after <c>ACPI event</c>. It will
352 so 1.15 be matched by the event line in the files you are going to create below. Don't
353     worry if your system generates multiple events or always the same. As long as
354     any event is generated, runlevel changing will work.
355     </p>
356    
357 swift 1.8 <pre caption="/etc/acpi/events/pmg_ac_adapter">
358 neysx 1.12 <comment># replace "ac_adapter" below with the event generated on your laptop</comment>
359 so 1.15 <comment># For example, ac_adapter.* will match ac_adapter AC 00000080 00000000</comment>
360 swift 1.8 event=ac_adapter.*
361 neysx 1.12 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
362 swift 1.8 </pre>
363    
364     <pre caption="/etc/acpi/events/pmg_battery">
365 neysx 1.12 <comment># replace "battery" below with the event generated on your laptop</comment>
366 so 1.15 <comment># For example, battery.* will match battery BAT0 00000080 00000001</comment>
367 swift 1.8 event=battery.*
368 neysx 1.12 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
369 swift 1.8 </pre>
370 swift 1.1
371 swift 1.8 <p>
372 so 1.15 Finally acpid has to be restarted to recognize the changes.
373 swift 1.8 </p>
374 swift 1.1
375 swift 1.8 <pre caption="Finishing runlevel switching with acpid">
376 rane 1.19 # <i>/etc/init.d/acpid restart</i>
377 swift 1.1 </pre>
378    
379     <p>
380     Give it a try: Plug AC in and out and watch syslog for the "Switching to AC
381 rane 1.20 mode" or "Switching to battery mode" messages. See the <uri
382     link="#doc_chap8">Troubleshooting section</uri> if the script is not able to
383     detect the power source correctly.
384 swift 1.1 </p>
385    
386     <p>
387     Due to the nature of the event mechanism, your laptop will boot into runlevel
388 rane 1.19 <c>default</c> regardless of the AC/battery state. This is fine when running
389 rane 1.20 from AC, but we'd like to boot into the battery runlevel otherwise. One
390     solution would be to add another entry to the boot loader with the parameter
391 so 1.15 <c>softlevel=battery</c>, but it's likely to forget choosing it. A better way
392 rane 1.20 is faking an ACPI event in the end of the boot process and letting
393     <path>pmg_switch_runlevel.sh</path> script decide whether a runlevel change is
394 swift 1.47 necessary. Create a <path>/etc/local.d/battery.start</path> file with the
395     following contents:
396 swift 1.1 </p>
397    
398 swift 1.47 <pre caption="Runlevel adjustment at boot time through local.d/battery.start">
399     #!/bin/sh
400 swift 1.1 <comment># Fake acpi event to switch runlevel if running on batteries</comment>
401 neysx 1.12 /etc/acpi/actions/pmg_switch_runlevel.sh "battery/battery"
402 swift 1.1 </pre>
403    
404     <p>
405 swift 1.47 Don't forget to mark the file as executable (<c>chmod +x
406     /etc/local.d/battery.start</c>). Prepared like this you can activate Power
407     Management policies for individual devices.
408 swift 1.1 </p>
409    
410     </body>
411     </section>
412     </chapter>
413    
414     <chapter>
415     <title>CPU Power Management</title>
416     <section>
417 nightmorph 1.17 <body>
418    
419     <p>
420     Mobile processors can operate at different frequencies. Some allow changing
421     voltage as well. Most of the time your CPU doesn't need to run at full speed
422     and scaling it down will save much energy - often without any performance
423     decrease.
424     </p>
425    
426     </body>
427     </section>
428     <section>
429 rane 1.19 <title>Some Technical Terms</title>
430 swift 1.8 <body>
431    
432     <p>
433     CPU frequency scaling brings up some technical terms that might be unknown to
434     you. Here's a quick introduction.
435     </p>
436    
437     <p>
438 so 1.15 First of all, the kernel has to be able to change the processor's frequency.
439 rane 1.19 The <b>CPUfreq processor driver</b> knows the commands to do it on your CPU.
440 rane 1.20 Thus it's important to choose the right one in your kernel. You should already
441     have done it above. Once the kernel knows how to change frequencies, it has to
442     know which frequency it should set. This is done according to the <b>policy</b>
443     which consists of a <b>CPUfreq policy</b> and a <b>governor</b>. A CPUfreq
444     policy are just two numbers which define a range the frequency has to stay
445     between - minimal and maximal frequency. The governor now decides which of the
446     available frequencies in between minimal and maximal frequency to choose. For
447     example, the <b>powersave governor</b> always chooses the lowest frequency
448     available, the <b>performance governor</b> the highest one. The <b>userspace
449     governor</b> makes no decision but chooses whatever the user (or a program in
450     userspace) wants - which means it reads the frequency from
451 swift 1.8 <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed</path>.
452     </p>
453    
454     <p>
455     This doesn't sound like dynamic frequency changes yet and in fact it isn't.
456 rane 1.20 Dynamics however can be accomplished with various approaches. For example, the
457     <b>ondemand governor</b> makes its decisions depending on the current CPU load.
458     The same is done by various userland tools like <c>cpudyn</c>, <c>cpufreqd</c>,
459     <c>powernowd</c> and many more. ACPI events can be used to enable or disable
460     dynamic frequency changes depending on power source.
461 swift 1.8 </p>
462    
463     </body>
464     </section>
465     <section>
466 nightmorph 1.41 <title>Setting The Frequency</title>
467 swift 1.1 <body>
468    
469     <p>
470     Decreasing CPU speed and voltage has two advantages: On the one hand less
471     energy is consumed, on the other hand there is thermal improvement as your
472     system doesn't get as hot as running on full speed. The main disadvantage is
473     obviously the loss of performance. Decreasing processor speed is a trade off
474     between performance loss and energy saving.
475     </p>
476    
477     <note>
478     Not every laptop supports frequency scaling. If unsure, have a look at the list
479 rane 1.19 of supported processors in the <uri link="#doc_chap8">Troubleshooting</uri>
480     section to verify yours is supported.
481 swift 1.1 </note>
482    
483     <p>
484 neysx 1.12 It's time to test whether CPU frequency changing works. Let's install another
485 nightmorph 1.41 tool: <c>sys-power/cpufrequtils</c>.
486 swift 1.1 </p>
487    
488 neysx 1.12 <pre caption="Checking CPU frequency">
489     # <i>emerge cpufrequtils</i>
490     # <i>cpufreq-info</i>
491 swift 1.1 </pre>
492    
493     <p>
494 neysx 1.12 Here is an example output:
495 swift 1.1 </p>
496    
497 neysx 1.12 <pre caption="Sample output from cpufreq-info">
498 so 1.15 cpufrequtils 0.3: cpufreq-info (C) Dominik Brodowski 2004
499 neysx 1.12 Report errors and bugs to linux@brodo.de, please.
500     analyzing CPU 0:
501     driver: centrino
502     CPUs which need to switch frequency at the same time: 0
503     hardware limits: 600 MHz - 1.40 GHz
504     available frequency steps: 600 MHz, 800 MHz, 1000 MHz, 1.20 GHz, 1.40 GHz
505 so 1.15 available cpufreq governors: conservative, ondemand, powersave, userspace, performance
506 neysx 1.12 current policy: frequency should be within 924 MHz and 1.40 GHz.
507     The governor "performance" may decide which speed to use
508     within this range.
509 so 1.15 current CPU frequency is 1.40 GHz.
510 neysx 1.12 </pre>
511    
512 swift 1.1 <p>
513 neysx 1.12 Now play around with <c>cpufreq-set</c> to make sure frequency switching works.
514     Run <c>cpufreq-set -g ondemand</c> for example to activate the ondemand
515     governor and verify the change with <c>cpufreq-info</c>. If it doesn't work as
516 rane 1.20 expected, you might find help in the <uri link="#doc_chap8">Troubleshooting
517     section</uri> in the end of this guide.
518 swift 1.1 </p>
519    
520 nightmorph 1.41 <p>
521     <c>cpufrequtils</c> can operate in an automatic mode (when you use the
522     <b>ondemand</b> governor), you can also switch to the <b>userspace</b> governor
523     if you want to manually set a specific speed. You can also statically set your
524     CPU to its highest or lowest frequency by using the <b>performance</b>
525     and <b>powersave</b> governors, respectively.
526     </p>
527    
528     <pre caption="Changing CPU speeds">
529     <comment>(Set the highest available frequency)</comment>
530     # <i>cpufreq-set -g performance</i>
531     <comment>(Set the lowest available frequency)</comment>
532     # <i>cpufreq-set -g powersave</i>
533     <comment>(Set a specific frequency)</comment>
534     # <i>cpufreq-set -g userspace</i>
535     # <i>cpufreq-set -f 2.00ghz</i>
536     </pre>
537    
538 swift 1.1 </body>
539     </section>
540     <section>
541 nightmorph 1.41 <title>Other CPU Speed Utilities</title>
542 swift 1.1 <body>
543    
544     <p>
545 nightmorph 1.41 While <c>cpufrequtils</c> may be the best all-around program, there are some
546     other choices available in Portage. The following table gives a quick overview
547     of available CPU speed utilities. It's roughly separated in three categories
548     <b>kernel</b> for approaches that only need kernel support, <b>daemon</b> for
549     programs that run in the background and <b>graphical</b> for programs that
550     provide a GUI for easy configuration and changes.
551 swift 1.1 </p>
552    
553     <table>
554     <tr>
555     <th>Name</th>
556 swift 1.8 <th>Category</th>
557     <th>Switch decision</th>
558     <th>Kernel governors</th>
559     <th>Further governors</th>
560     <th>Comments</th>
561     </tr>
562     <tr>
563     <ti>'ondemand' governor</ti>
564     <ti>Kernel</ti>
565     <ti>CPU load</ti>
566     <ti>N.A.</ti>
567     <ti>N.A.</ti>
568     <ti>
569 so 1.15 Chooses maximal frequency on CPU load and slowly steps down when the CPU is
570     idle. Further tuning through files in
571 swift 1.8 <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
572     userland tools (programs, scripts) if governor switching or similar is
573     desired.
574     </ti>
575 swift 1.1 </tr>
576     <tr>
577 so 1.15 <ti>'conservative' governor</ti>
578     <ti>Kernel</ti>
579     <ti>CPU load</ti>
580     <ti>N.A.</ti>
581     <ti>N.A.</ti>
582     <ti>
583 neysx 1.16 Unlike the ondemand governor, conversative doesn't jump to maximum
584     frequency when CPU load is high, but increases the frequency step by step.
585     Further tuning through files in
586     <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
587     userland tools (programs, scripts) if governor switching or similar is
588     desired.
589 so 1.15 </ti>
590     </tr>
591     <tr>
592 swift 1.1 <ti><uri link="http://mnm.uib.es/~gallir/cpudyn/">cpudyn</uri></ti>
593 swift 1.8 <ti>Daemon</ti>
594     <ti>CPU load</ti>
595 neysx 1.12 <ti>Performance, powersave</ti>
596 swift 1.8 <ti>Dynamic</ti>
597     <ti>
598     Also supports disk standby - notice however that <e>laptop mode</e> in most
599     cases will do a better job.
600     </ti>
601 swift 1.1 </tr>
602     <tr>
603 swift 1.8 <ti><uri link="http://sourceforge.net/projects/cpufreqd/">cpufreqd</uri></ti>
604     <ti>Daemon</ti>
605 nightmorph 1.17 <ti>Battery state, CPU load, temperature, running programs and more</ti>
606 swift 1.8 <ti>All available</ti>
607     <ti>None</ti>
608     <ti>
609 nightmorph 1.17 Sophisticated (but somewhat complicated) setup. Extendible through plugins
610     like sensor monitoring (lm_sensors) or coordinating some NVidia based
611     graphics card memory and core. Cpufreqd is SMP aware and can optionally be
612     controlled manually at runtime.
613 swift 1.8 </ti>
614     </tr>
615     <tr>
616     <ti>
617     <uri link="http://www.deater.net/john/powernowd.html">powernowd</uri>
618     </ti>
619     <ti>Daemon</ti>
620     <ti>CPU load</ti>
621     <ti>None</ti>
622     <ti>Passive, sine, aggressive</ti>
623     <ti>
624     Supports SMP.
625     </ti>
626 swift 1.1 </tr>
627     <tr>
628 nightmorph 1.31 <ti>
629     <uri
630     link="http://projects.simpledesigns.com.pl/project/ncpufreqd/">ncpufreqd</uri>
631     </ti>
632 so 1.15 <ti>Daemon</ti>
633     <ti>Temperature</ti>
634     <ti>None</ti>
635     <ti>Powersave, performance</ti>
636     <ti>
637     Toggles the used governor between performance and powersave depending on
638     system temperature. Very useful on laptops with notorious heat problems.
639     </ti>
640     </tr>
641     <tr>
642 swift 1.1 <ti><uri link="http://www.goop.org/~jeremy/speedfreq/">speedfreq</uri></ti>
643 swift 1.8 <ti>Daemon</ti>
644     <ti>CPU load</ti>
645     <ti>None</ti>
646     <ti>Dynamic, powersave, performance, fixed speed</ti>
647     <ti>
648 so 1.15 Easy to configure with a nice client/server interface. Requires a 2.6
649     kernel. Unmaintained, broken and thus removed from Portage. Please switch
650     to cpufreqd if you're still using it.
651 swift 1.8 </ti>
652     </tr>
653     <tr>
654     <ti><uri link="http://cpuspeedy.sourceforge.net/">gtk-cpuspeedy</uri></ti>
655     <ti>Graphical</ti>
656     <ti>None</ti>
657     <ti>None</ti>
658     <ti>None</ti>
659 swift 1.1 <ti>
660 swift 1.8 Gnome application, a graphical tool to set CPU frequency manually. It does
661 neysx 1.12 not offer any automation.
662 swift 1.1 </ti>
663     </tr>
664     <tr>
665 swift 1.8 <ti>klaptopdaemon</ti>
666     <ti>Graphical</ti>
667     <ti>Battery state</ti>
668     <ti>All available</ti>
669     <ti>None</ti>
670     <ti>
671     KDE only, 'ondemand' governor required for dynamic frequency scaling.
672     </ti>
673 swift 1.1 </tr>
674     </table>
675    
676     <p>
677 so 1.15 While adjusting the frequency to the current load looks simple at a first
678     glance, it's not such a trivial task. A bad algorithm can cause switching
679     between two frequencies all the time or wasting energy when setting frequency
680 rane 1.20 to an unnecessary high level.
681 swift 1.1 </p>
682    
683     <p>
684 neysx 1.12 Which one to choose? If you have no idea about it, try <c>cpufreqd</c>:
685 swift 1.1 </p>
686    
687     <pre caption="Installing cpufreqd">
688     # <i>emerge cpufreqd</i>
689     </pre>
690    
691     <p>
692 neysx 1.12 <c>cpufreqd</c> can be configured by editing <path>/etc/cpufreqd.conf</path>.
693     The default one that ships with cpufreqd may look a bit confusing. I recommend
694 nightmorph 1.22 replacing it with the one from former Gentoo developer Henrik Brix Andersen
695     (see below). Please notice that you need cpufreqd-2.0.0 or later. Earlier
696     versions have a different syntax for the config file.
697 swift 1.1 </p>
698    
699 nightmorph 1.17 <pre caption="/etc/cpufreqd.conf (cpufreqd-2.0.0 and later)">
700 swift 1.1 [General]
701     pidfile=/var/run/cpufreqd.pid
702 nightmorph 1.17 poll_interval=3
703     enable_plugins=acpi_ac, acpi_battery
704 nightmorph 1.18 enable_remote=1
705     remote_group=wheel
706 neysx 1.12 verbosity=5
707 nightmorph 1.17 [/General]
708 swift 1.1
709     [Profile]
710 neysx 1.12 name=ondemand
711     minfreq=0%
712     maxfreq=100%
713     policy=ondemand
714 nightmorph 1.17 [/Profile]
715 swift 1.1
716     [Profile]
717 so 1.15 name=conservative
718     minfreq=0%
719     maxfreq=100%
720     policy=conservative
721 nightmorph 1.17 [/Profile]
722 so 1.15
723     [Profile]
724 neysx 1.12 name=powersave
725     minfreq=0%
726     maxfreq=100%
727 swift 1.1 policy=powersave
728 nightmorph 1.17 [/Profile]
729 swift 1.1
730     [Profile]
731 neysx 1.12 name=performance
732     minfreq=0%
733     maxfreq=100%
734     policy=performance
735 nightmorph 1.17 [/Profile]
736 swift 1.1
737     [Rule]
738 neysx 1.12 name=battery
739     ac=off
740 so 1.15 profile=conservative
741 nightmorph 1.17 [/Rule]
742 swift 1.1
743     [Rule]
744 neysx 1.12 name=battery_low
745 swift 1.1 ac=off
746 neysx 1.12 battery_interval=0-10
747     profile=powersave
748 nightmorph 1.17 [/Rule]
749 swift 1.1
750     [Rule]
751 neysx 1.12 name=ac
752     ac=on
753 so 1.15 profile=ondemand
754 nightmorph 1.17 [/Rule]
755 neysx 1.12 </pre>
756    
757     <p>
758 rane 1.19 Now you can start the cpufreqd daemon. Add it to the <c>default</c> and
759     <c>battery</c> runlevel as well.
760 swift 1.1 </p>
761    
762 neysx 1.12 <pre caption="Starting cpufreqd">
763     # <i>rc-update add cpufreqd default battery</i>
764 nightmorph 1.41 # <i>/etc/init.d/cpufreqd start</i>
765 neysx 1.12 </pre>
766    
767 nightmorph 1.17 <p>
768     Sometimes it can be desirable to select another policy than the daemon chooses,
769     for example when battery power is low, but you know that AC will be available
770 rane 1.20 soon. In that case you can turn on cpufreqd's manual mode with <c>cpufreqd-set
771     manual</c> and select one of your configured policies (as listed by
772     <c>cpufreqd-get</c>). You can leave manual mode by executing <c>cpufreqd-set
773     dynamic</c>.
774 nightmorph 1.17 </p>
775    
776 neysx 1.12 <warn>
777     Do not run more than one of the above programs at the same time. It may cause
778     confusion like switching between two frequencies all the time.
779     </warn>
780    
781 swift 1.8 </body>
782     </section>
783     <section>
784     <title>Verifying the result</title>
785     <body>
786    
787 swift 1.1 <p>
788     The last thing to check is that your new policies do a good job. An easy way to
789 swift 1.8 do so is monitoring CPU speed while working with your laptop:
790 swift 1.1 </p>
791    
792     <pre caption="Monitoring CPU speed">
793 yoswink 1.13 # <i>watch grep \"cpu MHz\" /proc/cpuinfo</i>
794 swift 1.1 </pre>
795    
796     <p>
797 rane 1.20 If <path>/proc/cpuinfo</path> doesn't get updated (see <uri
798 swift 1.32 link="#doc_chap8">Troubleshooting</uri>), monitor the CPU frequency with
799     <c>sys-apps/x86info</c>:
800 swift 1.1 </p>
801    
802     <pre caption="Alternative CPU speed monitoring">
803 neysx 1.12 # <i>watch x86info -mhz</i>
804 swift 1.1 </pre>
805    
806     <p>
807     Depending on your setup, CPU speed should increase on heavy load, decrease on
808 rane 1.19 no activity or just stay at the same level. When using <c>cpufreqd</c> and
809 rane 1.20 verbosity set to 5 or higher in <path>cpufreqd.conf</path> you'll get
810     additional information about what's happening reported to <c>syslog</c>.
811 swift 1.1 </p>
812    
813     </body>
814     </section>
815     </chapter>
816    
817     <chapter>
818     <title>LCD Power Management</title>
819     <section>
820     <body>
821    
822     <p>
823 rane 1.20 As you can see in <uri link="#doc_chap1_fig1">figure 1.1</uri>, the LCD
824     display consumes the biggest part of energy (might not be the case for
825     non-mobile CPU's). Thus it's quite important not only to shut the display off
826     when not needed, but also to reduce it's backlight if possible. Most laptops
827     offer the possibility to control the backlight dimming.
828 swift 1.1 </p>
829    
830 nightmorph 1.17 </body>
831     </section>
832     <section>
833     <title>Standby settings</title>
834     <body>
835    
836 swift 1.1 <p>
837 nightmorph 1.17 The first thing to check is the standby/suspend/off timings of the display. As
838     this depends heavily on your windowmanager, I'll let you figure it out
839 rane 1.20 yourself. Just two common places: Blanking the terminal can be done with
840 nightmorph 1.17 <c>setterm -blank &lt;number-of-minutesM&gt;</c>, <c>setterm -powersave on</c>
841     and <c>setterm -powerdown &lt;number-of-minutesM&gt;</c>. For X.org, modify
842     <path>/etc/X11/xorg.conf</path> similar to this:
843 swift 1.1 </p>
844    
845 nightmorph 1.35 <pre caption="LCD suspend settings in X.org">
846     Section "ServerFlags"
847     Option "blank time" "5" <comment># Blank the screen after 5 minutes (Fake)</comment>
848     Option "standby time" "10" <comment># Turn off screen after 10 minutes (DPMS)</comment>
849     Option "suspend time" "20" <comment># Full suspend after 20 minutes</comment>
850     Option "off time" "30" <comment># Turn off after half an hour</comment>
851 swift 1.1 [...]
852     EndSection
853    
854     [...]
855    
856     Section "Monitor"
857     Identifier [...]
858 nightmorph 1.35 Option "DPMS"
859 swift 1.1 [...]
860     EndSection
861     </pre>
862    
863 nightmorph 1.17 </body>
864     </section>
865     <section>
866     <title>Backlight dimming</title>
867     <body>
868    
869 swift 1.1 <p>
870     Probably more important is the backlight dimming. If you have access to the
871     dimming settings via a tool, write a small script that dims the backlight in
872 rane 1.19 battery mode and place it in your <c>battery</c> runlevel. The following script
873 nightmorph 1.17 should work on most IBM Thinkpads and Toshiba laptops. You've got to enable the
874 rane 1.20 appropriate option in your kernel (IBM Thinkpads only). For Toshiba laptops,
875 nightmorph 1.35 install <c>sys-power/acpitool</c> and skip configuration of <c>thinkpad_acpi</c>
876     (formerly called <c>ibm_acpi</c>) as described below.
877 neysx 1.12 </p>
878    
879     <warn>
880 swift 1.36 Support for setting brightness is marked experimental in thinkpad_acpi. It
881     accesses hardware directly and may cause severe harm to your system. Please
882     read the <uri link="http://ibm-acpi.sourceforge.net/">thinkpad_acpi
883     website</uri>
884 neysx 1.12 </warn>
885    
886     <p>
887 swift 1.36 To be able to set the brightness level, the thinkpad_acpi module has to be
888     loaded with the experimental parameter.
889 neysx 1.12 </p>
890    
891 swift 1.47 <pre caption="Automatically loading the thinkpad_acpi module">
892 neysx 1.12 <comment>(Please read the warnings above before doing this!)</comment>
893 swift 1.47
894 nightmorph 1.37 # <i>echo "options thinkpad_acpi experimental=1" >> /etc/modprobe.d/thinkpad_acpi</i>
895     # <i>update-modules</i>
896 swift 1.47 # <i>nano /etc/conf.d/modules</i>
897     <comment># Autoload the thinkpad_acpi module</comment>
898     modules_2_6="thinkpad_acpi"
899     <comment># Parameters for the thinkpad_acpi module</comment>
900     modules_thinkpad_acpi_args_2_6="experimental=1"
901    
902 nightmorph 1.35 # <i>modprobe thinkpad_acpi</i>
903 neysx 1.12 </pre>
904    
905     <p>
906     This should work without error messages and a file
907     <path>/proc/acpi/ibm/brightness</path> should be created after loading the
908 rane 1.20 module. An init script will take care of choosing the brightness according to
909     the power source.
910 neysx 1.12 </p>
911    
912     <pre caption="/etc/conf.d/lcd-brightness">
913     <comment># See /proc/acpi/ibm/brightness for available values</comment>
914 nightmorph 1.35 <comment># Please read /usr/src/linux/Documentation/thinkpad-acpi.txt</comment>
915 neysx 1.12
916 nightmorph 1.23 <comment># brightness level in ac mode. Default is 7.</comment>
917 neysx 1.12 BRIGHTNESS_AC=7
918    
919     <comment># brightness level in battery mode. Default is 4.</comment>
920     BRIGHTNESS_BATTERY=4
921     </pre>
922    
923     <pre caption="/etc/init.d/lcd-brightness">
924     #!/sbin/runscript
925    
926     set_brightness() {
927     if on_ac_power
928     then
929     LEVEL=${BRIGHTNESS_AC:-7}
930     else
931     LEVEL=${BRIGHTNESS_BATTERY:-4}
932     fi
933    
934     if [ -f /proc/acpi/ibm/brightness ]
935     then
936     ebegin "Setting LCD brightness"
937     echo "level ${LEVEL}" > /proc/acpi/ibm/brightness
938     eend $?
939 nightmorph 1.17 elif [[ -e /usr/bin/acpitool &amp;&amp; -n $(acpitool -T | grep "LCD brightness") ]]
940     then
941     ebegin "Setting LCD brightness"
942     acpitool -l $LEVEL >/dev/null || ewarn "Unable to set lcd brightness"
943     eend $?
944 neysx 1.12 else
945     ewarn "Setting LCD brightness is not supported."
946 nightmorph 1.35 ewarn "For IBM Thinkpads, check that thinkpad_acpi is loaded into the kernel"
947 nightmorph 1.23 ewarn "For Toshiba laptops, you've got to install sys-power/acpitool"
948 neysx 1.12 fi
949     }
950    
951     start() {
952     set_brightness
953     }
954    
955     stop () {
956     set_brightness
957     }
958     </pre>
959    
960     <p>
961     When done, make sure brightness is adjusted automatically by adding it to the
962     battery runlevel.
963 swift 1.1 </p>
964    
965 neysx 1.12 <pre caption="Enabling automatic brightness adjustment">
966 rane 1.19 # <i>chmod +x /etc/init.d/lcd-brightness</i>
967     # <i>rc-update add lcd-brightness battery</i>
968     # <i>rc</i>
969 neysx 1.12 </pre>
970    
971 swift 1.1 </body>
972     </section>
973     </chapter>
974    
975     <chapter>
976     <title>Disk Power Management</title>
977     <section>
978 nightmorph 1.17 <body>
979 rane 1.19
980 nightmorph 1.17 <p>
981     Hard disks consume less energy in sleep mode. Therefore it makes sense to
982     activate power saving features whenever the hard disk is not used for a certain
983     amount of time. I'll show you two alternative possibilities to do it. First,
984     laptop-mode will save most energy due to several measures which prevent or at
985     least delay write accesses. The drawback is that due to the delayed write
986     accesses a power outage or kernel crash will be more dangerous for data loss.
987     If you don't like this, you have to make sure that there are no processes which
988     write to your hard disk frequently. Afterwards you can enable power saving
989 rane 1.19 features of your hard disk with <c>hdparm</c> as the second alternative.
990 nightmorph 1.17 </p>
991    
992     </body>
993     </section>
994     <section>
995     <title>Increasing idle time - laptop-mode</title>
996 swift 1.1 <body>
997    
998     <p>
999 nightmorph 1.27 Recent 2.6 kernels include the so-called <c>laptop-mode</c>. When activated,
1000     dirty buffers are written to disk on read calls or after 10 minutes (instead of
1001     30 seconds). This minimizes the time the hard disk needs to be spun up.
1002 swift 1.1 </p>
1003    
1004 nightmorph 1.17 <pre caption="Automated start of laptop-mode">
1005     # <i>emerge laptop-mode-tools</i>
1006     </pre>
1007 swift 1.1
1008 nightmorph 1.17 <p>
1009     <c>laptop-mode-tools</c> has its configuration file in
1010     <path>/etc/laptop-mode/laptop-mode.conf</path>. Adjust it the way you like it,
1011     it's well commented. Run <c>rc-update add laptop_mode battery</c> to start it
1012     automatically.
1013     </p>
1014    
1015     <p>
1016     Recent versions (1.11 and later) of laptop-mode-tools include a new tool
1017     <c>lm-profiler</c>. It will monitor your system's disk usage and running
1018     network services and suggests to disable unneeded ones. You can either disable
1019     them through laptop-mode-tools builtin runlevel support (which will be reverted
1020 rane 1.19 by Gentoo's <c>/sbin/rc</c>) or use your <c>default</c>/<c>battery</c>
1021 nightmorph 1.17 runlevels (recommended).
1022     </p>
1023    
1024     <pre caption="Sample output from running lm-profiler">
1025 rane 1.19 # <i>lm-profiler</i>
1026 nightmorph 1.17 Profiling session started.
1027     Time remaining: 600 seconds
1028     [4296896.602000] amarokapp
1029     Time remaining: 599 seconds
1030     [4296897.714000] sort
1031     [4296897.970000] mv
1032     Time remaining: 598 seconds
1033     Time remaining: 597 seconds
1034     [4296900.482000] reiserfs/0
1035     </pre>
1036    
1037     <p>
1038     After profiling your system for ten minutes, lm-profiler will present a list of
1039     services which might have caused disk accesses during that time.
1040     </p>
1041    
1042     <pre caption="lm-profiler suggests to disable some services">
1043     Program: "atd"
1044     Reason: standard recommendation (program may not be running)
1045     Init script: /etc/init.d/atd (GUESSED)
1046    
1047 rane 1.19 Do you want to disable this service in battery mode? [y/N]: <i>n</i>
1048 swift 1.1 </pre>
1049    
1050     <p>
1051 nightmorph 1.17 To disable atd as suggested in the example above, you would run <c>rc-update
1052     del atd battery</c>. Be careful not to disable services that are needed for
1053 rane 1.20 your system to run properly - <c>lm-profiler</c> is likely to generate some
1054     false positives. Do not disable a service if you are unsure whether it's
1055     needed.
1056 nightmorph 1.17 </p>
1057    
1058     </body>
1059     </section>
1060     <section>
1061 rane 1.19 <title>Limiting Write Accesses</title>
1062 nightmorph 1.17 <body>
1063    
1064     <p>
1065     If you don't want to use laptop-mode, you must take special care to disable
1066     services that write to your disk frequently - <c>syslogd</c> is a good
1067     candidate, for example. You probably don't want to shut it down completely, but
1068     it's possible to modify the config file so that "unnecessary" things don't get
1069 rane 1.20 logged and thus don't create disk traffic. <c>Cups</c> writes to disk
1070     periodically, so consider shutting it down and only enable it manually when
1071     needed.
1072 nightmorph 1.17 </p>
1073    
1074     <pre caption="Disabling cups in battery mode">
1075     # <i>rc-update del cupsd battery</i>
1076     </pre>
1077    
1078     <p>
1079     You can also use <c>lm-profiler</c> from laptop-mode-tools (see above) to find
1080     services to disable. Once you eliminated all of them, go on with configuring
1081     hdparm.
1082     </p>
1083    
1084     </body>
1085     </section>
1086     <section>
1087     <title>hdparm</title>
1088     <body>
1089    
1090     <p>
1091 nightmorph 1.28 The second possibility is using <c>hdparm</c>. Skip this if
1092     you are using laptop-mode. Otherwise, edit <path>/etc/conf.d/hdparm</path> and
1093     add the following values to your drive entries. This example assumes your hard
1094     drive is called <b>hda</b>:
1095 swift 1.1 </p>
1096    
1097 nightmorph 1.28 <pre caption="Using /etc/conf.d/hdparm for disk standby">
1098     hda_args="-q -S12"
1099     </pre>
1100 neysx 1.12
1101 nightmorph 1.28 <p>
1102     This will activate power management for your hard drive. If you ever want to
1103     deactivate power management, you can edit <path>/etc/conf.d/hdparm</path> and
1104     change the values to <c>-q -S0</c>, or just run <c>hdparm -q -S0 /dev/hda</c>.
1105     </p>
1106 swift 1.1
1107     <p>
1108 nightmorph 1.28 See <c>man hdparm</c> for the options. Though you can always start <c>hdparm</c>
1109     manually when you are on battery power by running <c>/etc/init.d/hdparm
1110     start</c>, it's much easier to automate its startup and shutdown. To do so, add
1111     <c>hdparm</c> to the battery runlevel so that it will automatically enable power
1112     management.
1113 swift 1.1 </p>
1114    
1115     <pre caption="Automate disk standby settings">
1116 nightmorph 1.28 # <i>rc-update add hdparm battery</i>
1117 swift 1.1 </pre>
1118    
1119     <impo>
1120     Be careful with sleep/spin down settings of your hard drive. Setting it to
1121     small values might wear out your drive and lose warranty.
1122     </impo>
1123    
1124     </body>
1125     </section>
1126     <section>
1127     <title>Other tricks</title>
1128     <body>
1129    
1130     <p>
1131     Another possibility is to deactivate swap in battery mode. Before writing a
1132     swapon/swapoff switcher, make sure there is enough RAM and swap isn't used
1133     heavily, otherwise you'll be in big problems.
1134     </p>
1135    
1136     <p>
1137     If you don't want to use laptop-mode, it's still possible to minimize disk
1138 rane 1.19 access by mounting certain directories as <c>tmpfs</c> - write accesses are not
1139 swift 1.1 stored on a disk, but in main memory and get lost with unmounting. Often it's
1140     useful to mount <path>/tmp</path> like this - you don't have to pay special
1141     attention as it gets cleared on every reboot regardless whether it was mounted
1142     on disk or in RAM. Just make sure you have enough RAM and no program (like a
1143     download client or compress utility) needs extraordinary much space in
1144     <path>/tmp</path>. To activate this, enable tmpfs support in your kernel and
1145     add a line to <path>/etc/fstab</path> like this:
1146     </p>
1147    
1148     <pre caption="Editing /etc/fstab to make /tmp even more volatile">
1149     none /tmp tmpfs size=32m 0 0
1150     </pre>
1151    
1152     <warn>
1153     Pay attention to the size parameter and modify it for your system. If you're
1154 rane 1.21 unsure, don't try this at all, it can become a performance bottleneck easily. In
1155 swift 1.1 case you want to mount <path>/var/log</path> like this, make sure to merge the
1156     log files to disk before unmounting. They are essential. Don't attempt to mount
1157 rane 1.19 <path>/var/tmp</path> like this. Portage uses it for compiling...
1158 swift 1.1 </warn>
1159    
1160     </body>
1161     </section>
1162     </chapter>
1163    
1164     <chapter>
1165 rane 1.19 <title>Power Management For Other Devices</title>
1166 swift 1.1 <section>
1167 rane 1.19 <title>Graphics Cards</title>
1168 so 1.15 <body>
1169    
1170     <p>
1171     In case you own an ATI graphics card supporting PowerPlay (dynamic clock
1172 nightmorph 1.25 scaling for the graphics processing unit GPU), you can activate this
1173 rane 1.20 feature in X.org. Open <path>/etc/X11/xorg.conf</path> and add (or enable) the
1174     <c>DynamicClocks</c> option in the Device section. Please notice that this
1175     feature will lead to crashes on some systems.
1176 so 1.15 </p>
1177    
1178     <pre caption="Enabling ATI PowerPlay support in X.org">
1179     Section "Device"
1180     [...]
1181     Option "DynamicClocks" "on"
1182     EndSection
1183     </pre>
1184    
1185     </body>
1186     </section>
1187     <section>
1188 swift 1.1 <title>Wireless Power Management</title>
1189     <body>
1190    
1191     <p>
1192 nightmorph 1.17 Wireless LAN cards consume quite a bit of energy. Put them in Power Management
1193 nightmorph 1.28 mode just like your hard drives.
1194 swift 1.1 </p>
1195    
1196 nightmorph 1.17 <note>
1197     This script assumes your wireless interface is called <c>wlan0</c>; replace
1198     this with the actual name of your interface.
1199     </note>
1200    
1201 nightmorph 1.28 <p>
1202 nightmorph 1.29 Add the following option to <path>/etc/conf.d/net</path> to automatically enable
1203 nightmorph 1.28 power management for your wireless card:
1204     </p>
1205 swift 1.1
1206 nightmorph 1.28 <pre caption="Automated WLAN Power Management">
1207     iwconfig_wlan0="power on"
1208 swift 1.1 </pre>
1209    
1210     <p>
1211 nightmorph 1.28 See <c>man iwconfig</c> for details and more options like the period between
1212     wakeups or timeout settings. If your driver and access point support changing
1213     the beacon time, this is a good starting point to save even more energy.
1214 swift 1.1 </p>
1215    
1216     </body>
1217     </section>
1218     <section>
1219     <title>USB Power Management</title>
1220     <body>
1221    
1222     <p>
1223     There are two problems with USB devices regarding energy consumption: First,
1224     devices like USB mice, digital cameras or USB sticks consume energy while
1225     plugged in. You cannot avoid this (nevertheless remove them in case they're not
1226     needed). Second, when there are USB devices plugged in, the USB host controller
1227     periodically accesses the bus which in turn prevents the CPU from going into
1228 rane 1.20 sleep mode. The kernel offers an experimental option to enable suspension of
1229 so 1.15 USB devices through driver calls or one of the <path>power/state</path> files
1230     in <path>/sys</path>.
1231 swift 1.1 </p>
1232    
1233 so 1.15 <pre caption="Enabling USB suspend support in the kernel">
1234     Device Drivers
1235     USB support
1236     [*] Support for Host-side USB
1237     [*] USB suspend/resume (EXPERIMENTAL)
1238     </pre>
1239    
1240 swift 1.1 </body>
1241     </section>
1242     </chapter>
1243    
1244     <chapter>
1245 rane 1.19 <title>Sleep States: sleep, standby, and suspend to disk</title>
1246 swift 1.1 <section>
1247     <body>
1248    
1249     <p>
1250     ACPI defines different sleep states. The more important ones are
1251     </p>
1252    
1253 rane 1.20 <ul>
1254 swift 1.1 <li>S1 aka Standby</li>
1255     <li>S3 aka Suspend to RAM aka Sleep</li>
1256     <li>S4 aka Suspend to Disk aka Hibernate</li>
1257     </ul>
1258    
1259     <p>
1260     They can be called whenever the system is not in use, but a shutdown is not
1261     wanted due to the long boot time.
1262     </p>
1263    
1264     </body>
1265     </section>
1266     <section>
1267 so 1.15 <title>Sleep (S3)</title>
1268 swift 1.1 <body>
1269    
1270     <p>
1271 so 1.15 The ACPI support for these sleep states is marked experimental for good reason.
1272     APM sleep states seem to be more stable, however you can't use APM and ACPI
1273     together.
1274     </p>
1275    
1276     <pre caption="Kernel configuration for the various suspend types">
1277     Power Management Options ---&gt;
1278     [*] Power Management support
1279 nightmorph 1.40 [*] Suspend to RAM and standby
1280 so 1.15 </pre>
1281    
1282     <p>
1283 nightmorph 1.17 Once your kernel is properly configured, you can use the
1284 so 1.15 <c>hibernate-script</c> to activate suspend or sleep mode. Let's install that
1285     first.
1286     </p>
1287    
1288     <pre caption="Installing the hibernate-script">
1289 rane 1.19 # <i>emerge hibernate-script</i>
1290 so 1.15 </pre>
1291    
1292     <p>
1293 nightmorph 1.25 Some configuration has to be done in <path>/etc/hibernate</path>. The default
1294 nightmorph 1.24 package introduces a few configuration files for each sleep state. Options that
1295     are common to all suspend methods are placed in <path>common.conf</path>; make
1296     sure this file is properly set up for your system.
1297 so 1.15 </p>
1298    
1299     <p>
1300 nightmorph 1.24 To configure sleep, edit <path>sysfs-ram.conf</path> in
1301     <path>/etc/hibernate</path>. <c>UseSysfsPowerState mem</c> is already setup
1302 nightmorph 1.25 correctly, but if you need to make further changes to this particular sleep
1303     state (or any other sleep state) you should add them to
1304 nightmorph 1.24 <path>/etc/hibernate/hibernate.conf</path>. The comments and option names will
1305     guide you. If you use nfs or samba shares over the network, make sure to
1306     shutdown the appropriate init scripts to avoid timeouts.
1307 so 1.15 </p>
1308    
1309 nightmorph 1.24 <note>
1310     For more information on setting up sleep states, read <c>man
1311     hibernate.conf</c>.
1312     </note>
1313    
1314 so 1.15 <p>
1315     Ready? Now is the last chance to backup any data you want to keep after
1316     executing the next command. Notice that you probably have to hit a special key
1317 rane 1.19 like <c>Fn</c> to resume from sleep.
1318 so 1.15 </p>
1319    
1320     <pre caption="Calling sleep">
1321 rane 1.19 # <i>hibernate-ram</i>
1322 so 1.15 </pre>
1323    
1324     <p>
1325 rane 1.20 If you're still reading, it seems to work. You can also setup standby (S1) in a
1326 nightmorph 1.24 similar way by editing <path>sysfs-ram.conf</path> and changing
1327     "UseSysfsPowerState mem" to "UseSysfsPowerState standby". S3 and S4 are the more
1328     interesting sleep states due to greater energy savings however.
1329 so 1.15 </p>
1330    
1331     </body>
1332     </section>
1333     <section>
1334     <title>Hibernate (S4)</title>
1335     <body>
1336    
1337     <p>
1338     This section introduces hibernation, where a snapshot of the running system is
1339     written to disk before powering off. On resume, the snapshot is loaded and you
1340     can go on working at exactly the point you called hibernate before.
1341 swift 1.1 </p>
1342    
1343     <warn>
1344 so 1.15 Don't exchange non hot-pluggable hardware when suspended. Don't attempt to load
1345     a snapshot with a different kernel image than the one it was created with.
1346     Shutdown any NFS or samba server/client before hibernating.
1347 swift 1.1 </warn>
1348    
1349     <p>
1350 so 1.15 There are two different implementations for S4. The original one is swsusp,
1351 nightmorph 1.39 then there is the newer tuxonice (formerly suspend2) with a nicer interface
1352 swift 1.36 (including fbsplash support). A <uri
1353 nightmorph 1.39 link="http://tuxonice.net/features.html#compare">feature comparison</uri> is
1354     available at the <uri link="http://www.tuxonice.net">tuxonice homepage</uri>.
1355 swift 1.36 There used to be Suspend-to-Disk (pmdisk), a fork of swsusp, but it has been
1356     merged back.
1357 swift 1.1 </p>
1358    
1359     <p>
1360 jkt 1.33 TuxOnIce is not included in the mainline kernel yet, therefore you either have
1361 rane 1.20 to patch your kernel sources with the patches provided by <uri
1362 nightmorph 1.39 link="http://www.tuxonice.net">tuxonice.net</uri> or use
1363 jkt 1.33 <c>sys-kernel/tuxonice-sources</c>.
1364 swift 1.1 </p>
1365    
1366     <p>
1367 jkt 1.33 The kernel part for both swusp and TuxOnIce is as follows:
1368 swift 1.1 </p>
1369    
1370     <pre caption="Kernel configuration for the various suspend types">
1371 nightmorph 1.40 Power Management support ---&gt;
1372 swift 1.1 <comment>(hibernate with swsusp)</comment>
1373 nightmorph 1.39 [*] Hibernation (aka 'suspend to disk')
1374 so 1.15 <comment>(replace /dev/SWAP with your swap partition)</comment>
1375     (/dev/SWAP) Default resume partition
1376 rane 1.20
1377 jkt 1.33 <comment>(hibernate with TuxOnIce)</comment>
1378     Enhanced Hibernation (TuxOnIce)
1379 nightmorph 1.39 --- Image Storage (you need at least one allocator)
1380     [*] File Allocator
1381     [*] Swap Allocator
1382 so 1.15 --- General Options
1383 nightmorph 1.39 [*] Compression support
1384 so 1.15 [ ] Allow Keep Image Mode
1385 nightmorph 1.39 [*] Replace swsusp by default
1386 swift 1.1 </pre>
1387    
1388     <p>
1389 so 1.15 The configuration for swsusp is rather easy. If you didn't store the location
1390     of your swap partition in the kernel config, you can also pass it as a
1391     parameter with the <c>resume=/dev/SWAP</c> directive. If booting is not
1392     possible due to a broken image, use the <c>noresume</c> kernel parameter. The
1393 rane 1.20 <c>hibernate-cleanup</c> init script invalidates swsusp images during the boot
1394     process.
1395 swift 1.1 </p>
1396    
1397 so 1.15 <pre caption="Invalidating swsusp images during the boot process">
1398 rane 1.19 # <i>rc-update add hibernate-cleanup boot</i>
1399 so 1.15 </pre>
1400    
1401 swift 1.1 <p>
1402 so 1.15 To activate hibernate with swsusp, use the hibernate script and set
1403 nightmorph 1.24 <c>UseSysfsPowerState disk</c> in <path>/etc/hibernate/sysfs-disk</path>.
1404 swift 1.1 </p>
1405    
1406     <warn>
1407     Backup your data before doing this. Run <c>sync</c> before executing one of the
1408     commands to have cached data written to disk. First try it outside of X, then
1409     with X running, but not logged in.
1410     </warn>
1411 rane 1.20
1412 swift 1.1 <p>
1413     If you experience kernel panics due to uhci or similar, try to compile USB
1414     support as module and unload the modules before sending your laptop to sleep
1415 nightmorph 1.24 mode. There are configuration options for this in <path>common.conf</path>
1416 swift 1.1 </p>
1417    
1418 so 1.15 <pre caption="Hibernating with swsusp">
1419 nightmorph 1.24 # <i>nano -w /etc/hibernate/common.conf</i>
1420 so 1.15 <comment>(Make sure you have a backup of your data)</comment>
1421 rane 1.19 # <i>hibernate</i>
1422 so 1.15 </pre>
1423    
1424 swift 1.1 <p>
1425 jkt 1.34 The following section discusses the setup of TuxOnIce including fbsplash support
1426     for a nice graphical progress bar during suspend and resume.
1427 so 1.15 </p>
1428    
1429     <p>
1430 rane 1.20 The first part of the configuration is similar to the configuration of swsusp.
1431     In case you didn't store the location of your swap partition in the kernel
1432     config, you have to pass it as a kernel parameter with the
1433 jkt 1.33 <c>resume=swap:/dev/SWAP</c> directive. If booting is not possible due to a
1434     broken image, append the <c>noresume</c> parameter. Additionally, the
1435 jkt 1.34 <c>hibernate-cleanup</c> init script invalidates TuxOnIce images during the boot
1436     process.
1437 so 1.15 </p>
1438    
1439 jkt 1.33 <pre caption="Invalidating TuxOnIce images during the boot process">
1440 rane 1.19 # <i>rc-update add hibernate-cleanup boot</i>
1441 so 1.15 </pre>
1442    
1443 rane 1.20 <p>
1444 nightmorph 1.39 Now edit <path>/etc/hibernate/tuxonice.conf</path>, enable the <c>TuxOnIce</c>
1445 nightmorph 1.24 options you need. Do not enable the <c>fbsplash</c> options in
1446     <c>common.conf</c> just yet.
1447 swift 1.1 </p>
1448    
1449 jkt 1.33 <pre caption="Hibernating with TuxOnIce">
1450 nightmorph 1.39 # <i>nano -w /etc/hibernate/tuxonice.conf</i>
1451 so 1.15 <comment>(Make sure you have a backup of your data)</comment>
1452 rane 1.19 # <i>hibernate</i>
1453 swift 1.8 </pre>
1454    
1455 so 1.15 <p>
1456 rane 1.20 Please configure <c>fbsplash</c> now if you didn't do already. To enable
1457 jkt 1.34 fbsplash support during hibernation, the <c>sys-apps/tuxonice-userui</c> package
1458     is needed. Additionally, you've got to enable the <c>fbsplash</c> USE flag.
1459 so 1.15 </p>
1460    
1461 jkt 1.33 <pre caption="Installing tuxonice-userui">
1462     # <i>echo "sys-apps/tuxonice-userui fbsplash" >> /etc/portage/package.use</i>
1463     # <i>emerge tuxonice-userui</i>
1464 so 1.15 </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 nightmorph 1.39 # <i>ln -sfn /etc/splash/livecd-2005.1 /etc/splash/tuxonice</i>
1473 so 1.15 </pre>
1474    
1475     <p>
1476     If you don't want a black screen in the first part of the resume process, you
1477 jkt 1.33 have to add the <c>tuxoniceui_fbsplash</c> tool to your initrd image. Assuming
1478 so 1.15 you created the initrd image with <c>splash_geninitramfs</c> and saved it as
1479 rane 1.20 <path>/boot/fbsplash-emergence-1024x768</path>, here's how to do that.
1480 so 1.15 </p>
1481    
1482 jkt 1.33 <pre caption="Adding tuxoniceui_fbsplash to an initrd image">
1483 rane 1.19 # <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 jkt 1.33 # <i>cp /usr/sbin/tuxoniceui_fbsplash sbin/</i>
1490     # <i>find . | cpio --quiet --dereference -o -H newc | gzip -9 > /boot/fbsplash-tuxonice-emergence-1024x768</i>
1491 so 1.15 </pre>
1492    
1493     <p>
1494 nightmorph 1.24 Afterwards adjust <path>grub.conf</path> (or <path>lilo.conf</path>) so that
1495 jkt 1.33 your TuxOnIce kernel uses
1496     <path>/boot/fbsplash-tuxonice-emergence-1024x768</path> as initrd image. You can
1497 nightmorph 1.24 now test a dry run to see if everything is setup correctly.
1498 so 1.15 </p>
1499    
1500     <pre caption="Test run for fbsplash hibernation">
1501 jkt 1.33 # <i>tuxoniceui_fbsplash -t</i>
1502 so 1.15 </pre>
1503    
1504     <p>
1505 nightmorph 1.24 Afterwards open <path>/etc/hibernate/common.conf</path> and activate the
1506     fbsplash options. Execute <c>hibernate</c> and enjoy.
1507 so 1.15 </p>
1508    
1509 swift 1.1 </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 jkt 1.34 are supported by cpufreq (kernel 2.6.7): ARM Integrator, ARM-SA1100, ARM-SA1110,
1528     AMD Elan - SC400, SC410, AMD mobile K6-2+, AMD mobile K6-3+, AMD mobile Duron,
1529     AMD mobile Athlon, AMD Opteron, AMD Athlon 64, Cyrix Media GXm, Intel mobile
1530     PIII and Intel mobile PIII-M on certain chipsets, Intel Pentium 4, Intel Xeon,
1531     Intel Pentium M (Centrino), National Semiconductors Geode GX, Transmeta Crusoe,
1532     VIA Cyrix 3 / C3, UltraSPARC-III, SuperH SH-3, SH-4, several "PowerBook" and
1533     "iBook2" and various processors on some ACPI 2.0-compatible systems (only if
1534     "ACPI Processor Performance States" are available to the ACPI/BIOS interface).
1535 swift 1.1 </p>
1536    
1537     <p>
1538     <e>Q:</e> My laptop supports frequency scaling, but
1539     <path>/sys/devices/system/cpu/cpu0/cpufreq/</path> is empty.
1540     </p>
1541    
1542     <p>
1543     <e>A:</e> Look for ACPI related error messages with <c>dmesg | grep ACPI</c>.
1544     Try to update the BIOS, especially if a broken DSDT is reported. You can also
1545     try to fix it yourself (which is beyond the scope of this guide).
1546     </p>
1547    
1548     <p>
1549 rane 1.19 <e>Q:</e> My laptop supports frequency scaling, but according to
1550     <path>/proc/cpuinfo</path> the speed never changes.
1551 swift 1.1 </p>
1552    
1553     <p>
1554 swift 1.8 <e>A:</e> Probably you have activated symmetric multiprocessing support
1555     (CONFIG_SMP) in your kernel. Deactivate it and it should work. Some older
1556 rane 1.20 kernels had a bug causing this. In that case, run <c>emerge x86info</c>, update
1557 jkt 1.34 your kernel as asked and check the current frequency with <c>x86info -mhz</c>.
1558 swift 1.1 </p>
1559    
1560     <p>
1561     <e>Q:</e> I can change the CPU frequency, but the range is not as wide as in
1562     another OS.
1563     </p>
1564    
1565     <p>
1566     <e>A:</e> You can combine frequency scaling with ACPI throttling to get a lower
1567 jkt 1.34 minimum frequency. Notice that throttling doesn't save much energy and is mainly
1568     used for thermal management (keeping your laptop cool and quiet). You can read
1569     the current throttling state with <c>cat /proc/acpi/processor/CPU/throttling</c>
1570     and change it with <c>echo -n "0:x" > /proc/acpi/processor/CPU/limit</c>, where
1571     x is one of the Tx states listed in
1572 swift 1.1 <path>/proc/acpi/processor/CPU/throttling</path>.
1573     </p>
1574    
1575     <p>
1576 swift 1.8 <e>Q:</e> When configuring the kernel, powersave, performance and userspace
1577     governors show up, but that ondemand thing is missing. Where do I get it?
1578     </p>
1579    
1580     <p>
1581     <e>A:</e> The ondemand governor is only included in recent kernel sources. Try
1582     updating them.
1583     </p>
1584    
1585     <p>
1586 swift 1.1 <e>Q:</e> Battery life time seems to be worse than before.
1587     </p>
1588    
1589     <p>
1590     <e>A:</e> Check your BIOS settings. Maybe you forgot to re-enable some of the
1591     settings.
1592     </p>
1593    
1594     <p>
1595     <e>Q:</e> My battery is charged, but KDE reports there would be 0% left and
1596     immediately shuts down.
1597     </p>
1598    
1599     <p>
1600     <e>A:</e> Check that battery support is compiled into your kernel. If you use
1601     it as a module, make sure the module is loaded.
1602     </p>
1603    
1604     <p>
1605 rane 1.20 <e>Q:</e> My system logger reports things like "logger: ACPI group battery /
1606     action battery is not defined".
1607 nightmorph 1.17 </p>
1608    
1609     <p>
1610 rane 1.20 <e>A:</e> This message is generated by the <path>/etc/acpi/default.sh</path>
1611     script that is shipped with acpid. You can safely ignore it. If you like to get
1612     rid of it, you can comment the appropriate line in
1613     <path>/etc/acpi/default.sh</path> as shown below:
1614 nightmorph 1.17 </p>
1615    
1616     <pre caption="Disabling warnings about unknown acpi events">
1617     *) # logger "ACPI action $action is not defined"
1618     </pre>
1619    
1620     <p>
1621 swift 1.1 <e>Q:</e> I have a Dell Inspiron 51XX and I don't get any ACPI events.
1622     </p>
1623    
1624     <p>
1625     <e>A:</e> This seems to be a kernel bug. Read on <uri
1626     link="http://bugme.osdl.org/show_bug.cgi?id=1752">here</uri>.
1627     </p>
1628    
1629     <p>
1630 rane 1.20 <e>Q:</e> I activated the <c>DynamicClocks</c> option in <path>xorg.conf</path>
1631     and now X.org crashes / the screen stays black / my laptop doesn't shutdown
1632 so 1.15 properly.
1633     </p>
1634    
1635     <p>
1636 rane 1.20 <e>A:</e> This happens on some systems. You have to disable
1637     <c>DynamicClocks</c>.
1638 so 1.15 </p>
1639    
1640     <p>
1641 jkt 1.33 <e>Q:</e> I want to use TuxOnIce, but it tells me my swap partition is too
1642 so 1.15 small. Resizing is not an option.
1643     </p>
1644    
1645     <p>
1646 rane 1.20 <e>A:</e> If there is enough free space on your system, you can use the
1647 jkt 1.34 filewriter instead of the swapwriter. The <c>hibernate-script</c> supports it as
1648     well. More information can be found in
1649 jkt 1.33 <path>/usr/src/linux/Documentation/power/tuxonice.txt</path>.
1650 so 1.15 </p>
1651    
1652     <p>
1653 swift 1.1 <e>Q:</e> I just bought a brand new battery, but it only lasts for some
1654     minutes! What am I doing wrong?
1655     </p>
1656    
1657     <p>
1658     <e>A:</e> First follow your manufacturer's advice on how to charge the battery
1659 rane 1.20 correctly.
1660 swift 1.1 </p>
1661    
1662     <p>
1663     <e>Q:</e> The above didn't help. What should I do then?
1664     </p>
1665    
1666     <p>
1667     <e>A:</e> Some batteries sold as "new" are in fact old ones. Try the following:
1668     </p>
1669    
1670     <pre caption="Querying battery state">
1671     $ <i>grep capacity /proc/acpi/battery/BAT0/info</i>
1672     design capacity: 47520 mWh
1673     last full capacity: 41830 mWh
1674     </pre>
1675    
1676     <p>
1677     If the "last full capacity" differs significantly from the design capacity,
1678     your battery is probably broken. Try to claim your warranty.
1679     </p>
1680    
1681 swift 1.8 <p>
1682     <e>Q:</e> My problem is not listed above. Where should I go next?
1683     </p>
1684    
1685     <p>
1686 nightmorph 1.17 <e>A:</e> Don't fear to contact me, <mail link="earthwings@gentoo.org">Dennis
1687 rane 1.20 Nienhüser</mail>, directly. The <uri link="http://forums.gentoo.org">Gentoo
1688     Forums</uri> are a good place to get help as well. If you prefer IRC, try the
1689 nightmorph 1.38 <c>#gentoo-laptop</c> <uri link="irc://irc.gentoo.org">channel</uri>.
1690 swift 1.8 </p>
1691    
1692 swift 1.1 </body>
1693     </section>
1694     </chapter>
1695     </guide>

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