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1 swift 1.1 <?xml version='1.0' encoding="UTF-8"?>
2     <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3 nightmorph 1.40 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/power-management-guide.xml,v 1.39 2009/05/14 15:01:19 nightmorph Exp $ -->
4 so 1.15 <guide link="/doc/en/power-management-guide.xml">
5 swift 1.1 <title>Power Management Guide</title>
6    
7 swift 1.4 <author title="Author">
8 nightmorph 1.17 <mail link="earthwings@gentoo.org">Dennis Nienhüser</mail>
9 swift 1.1 </author>
10 rane 1.19 <author title="Editor">
11     <mail link="chriswhite@gentoo.org">Chris White</mail>
12     </author>
13 nightmorph 1.26 <author title="Editor">
14     <mail link="nightmorph@gentoo.org">Joshua Saddler</mail>
15     </author>
16 swift 1.1
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 so 1.15 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
24 swift 1.1 <license/>
25    
26 nightmorph 1.40 <version>1.43</version>
27     <date>2009-08-05</date>
28 swift 1.1
29     <chapter>
30     <title>Introduction</title>
31     <section>
32     <body>
33    
34     <p>
35 so 1.15 Capacity and lifetime of laptop batteries have improved much in the last years.
36 swift 1.1 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 rane 1.19 <title>A Quick Overview</title>
47 swift 1.1 <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 rane 1.19 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 rane 1.21 without losing too much performance. A few different tricks prevent your hard
70 rane 1.19 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 rane 1.20 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 rane 1.19 chapter is dedicated to the (rather experimental) <uri link="#doc_chap7">sleep
75 rane 1.20 states</uri>. Last not least <uri link="#doc_chap8">Troubleshooting</uri> lists
76     common pitfalls.
77 swift 1.1 </p>
78    
79     </body>
80     </section>
81     <section>
82 rane 1.19 <title>Power Budget For Each Component</title>
83 swift 1.1 <body>
84    
85 swift 1.2 <figure link="/images/energy-budget.png" short="Which component consumes how
86 swift 1.1 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 nightmorph 1.17 Before discussing the details of making individual devices Power Management
107 rane 1.20 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 swift 1.1 </p>
113    
114     </body>
115     </section>
116     <section>
117 rane 1.19 <title>The BIOS Part</title>
118 swift 1.1 <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 rane 1.19 <title>Setting USE Flags</title>
132 nightmorph 1.17 <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 rane 1.19 the <c>--newuse</c> flag in <c>emerge</c>, see <c>man emerge</c>.
141 nightmorph 1.17 </p>
142    
143     </body>
144     </section>
145     <section>
146 rane 1.19 <title>Configuring The Kernel</title>
147 swift 1.1 <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 rane 1.20 There are different kernel sources in Portage. I'd recommend using
157 jkt 1.33 <c>gentoo-sources</c> or <c>tuxonice-sources</c>. The latter contains patches
158 jkt 1.34 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 swift 1.1 </p>
161    
162     <pre caption="Minimum kernel setup for Power Management (Kernel 2.6)">
163 nightmorph 1.39 Power management and ACPI options ---&gt;
164 nightmorph 1.40 [*] Power Management support
165 swift 1.1 [ ] Software Suspend
166    
167     ACPI( Advanced Configuration and Power Interface ) Support ---&gt;
168 nightmorph 1.39 [ ] Deprecated /proc/acpi/ files
169 neysx 1.12 [*] AC Adapter
170     [*] Battery
171 swift 1.1 &lt;M&gt; Button
172 so 1.15 &lt;M&gt; Video
173     [ ] Generic Hotkey
174 swift 1.1 &lt;M&gt; Fan
175     &lt;M&gt; Processor
176     &lt;M&gt; Thermal Zone
177     &lt; &gt; ASUS/Medion Laptop Extras
178 so 1.15 &lt; &gt; IBM ThinkPad Laptop Extras
179 swift 1.1 &lt; &gt; Toshiba Laptop Extras
180 so 1.15 (0) Disable ACPI for systems before Jan 1st this year
181 swift 1.1 [ ] Debug Statements
182 so 1.15 [*] Power Management Timer Support
183     &lt; &gt; ACPI0004,PNP0A05 and PNP0A06 Container Driver (EXPERIMENTAL)
184 rane 1.20
185 swift 1.1 CPU Frequency Scaling ---&gt;
186     [*] CPU Frequency scaling
187 so 1.15 [ ] Enable CPUfreq debugging
188     &lt; &gt; CPU frequency translation statistics
189     [ ] CPU frequency translation statistics details
190 swift 1.1 Default CPUFreq governor (userspace)
191     &lt;*&gt; 'performance' governor
192     &lt;*&gt; 'powersave' governor
193 swift 1.8 &lt;*&gt; 'ondemand' cpufreq policy governor
194 so 1.15 &lt;*&gt; 'conservative' cpufreq governor
195 swift 1.1 &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 so 1.15 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 neysx 1.12 the appropriate section.
204 swift 1.8 </p>
205    
206     <p>
207 rane 1.20 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 rane 1.19 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 swift 1.8 Consult the kernel documentation if you're unsure which one to take.
212 swift 1.1 </p>
213    
214     <p>
215     Compile your kernel, make sure the right modules get loaded at startup and boot
216 rane 1.20 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 swift 1.1 </p>
223    
224     <pre caption="Installing acpid">
225 yoswink 1.10 # <i>emerge sys-power/acpid</i>
226 swift 1.1 # <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 rane 1.19 <title>Creating A "battery" Runlevel</title>
234 swift 1.1 <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 rane 1.19 create a runlevel <c>battery</c> that holds all the scripts starting and
240 swift 1.1 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 rane 1.19 up. The next sections assume a runlevel <c>battery</c> exists.
247 swift 1.1 </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 rane 1.19 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 swift 1.1 change it.
258     </p>
259    
260     </body>
261     </section>
262     <section>
263 rane 1.19 <title>Reacting On ACPI Events</title>
264 swift 1.1 <body>
265    
266     <p>
267     Typical ACPI events are closing the lid, changing the power source or pressing
268 swift 1.8 the sleep button. An important event is changing the power source, which should
269 so 1.15 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 rane 1.19 # <i>emerge powermgmt-base</i>
281 so 1.15 </pre>
282    
283     <p>
284 rane 1.20 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 so 1.15 <path>/etc/acpi/actions/pmg_switch_runlevel.sh</path>.
288 swift 1.8 </p>
289    
290 neysx 1.12 <pre caption="/etc/acpi/actions/pmg_switch_runlevel.sh">
291 swift 1.8 #!/bin/bash
292    
293 neysx 1.12 <comment># BEGIN configuration</comment>
294 swift 1.8 RUNLEVEL_AC="default"
295     RUNLEVEL_BATTERY="battery"
296 neysx 1.12 <comment># END configuration</comment>
297 swift 1.8
298 swift 1.1
299 neysx 1.12 if [ ! -d "/etc/runlevels/${RUNLEVEL_AC}" ]
300     then
301 nightmorph 1.17 logger "${0}: Runlevel ${RUNLEVEL_AC} does not exist. Aborting."
302     exit 1
303 neysx 1.12 fi
304 swift 1.8
305 neysx 1.12 if [ ! -d "/etc/runlevels/${RUNLEVEL_BATTERY}" ]
306     then
307 nightmorph 1.17 logger "${0}: Runlevel ${RUNLEVEL_BATTERY} does not exist. Aborting."
308     exit 1
309 neysx 1.12 fi
310 swift 1.1
311 neysx 1.12 if on_ac_power
312     then
313 rane 1.19 if [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_AC}" ]]
314 nightmorph 1.17 then
315     logger "Switching to ${RUNLEVEL_AC} runlevel"
316     /sbin/rc ${RUNLEVEL_AC}
317     fi
318 rane 1.19 elif [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_BATTERY}" ]]
319 neysx 1.12 then
320 nightmorph 1.17 logger "Switching to ${RUNLEVEL_BATTERY} runlevel"
321     /sbin/rc ${RUNLEVEL_BATTERY}
322 neysx 1.12 fi
323 swift 1.8 </pre>
324    
325 so 1.15 <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 rane 1.19 <c>ac_adapter</c> and <c>battery</c> on most laptops, but it might be different
332 so 1.15 on yours.
333     </p>
334    
335     <pre caption="Determining ACPI events for changing the power source">
336 swift 1.32 # <i>tail -f /var/log/messages | grep "received event"</i>
337 so 1.15 </pre>
338    
339     <p>
340 rane 1.20 Run the command above and pull the power cable. You should see something like
341     this:
342 so 1.15 </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 rane 1.19 The interesting part is the quoted string after <c>received event</c>. It will
351 so 1.15 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 swift 1.8 <pre caption="/etc/acpi/events/pmg_ac_adapter">
357 neysx 1.12 <comment># replace "ac_adapter" below with the event generated on your laptop</comment>
358 so 1.15 <comment># For example, ac_adapter.* will match ac_adapter AC 00000080 00000000</comment>
359 swift 1.8 event=ac_adapter.*
360 neysx 1.12 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
361 swift 1.8 </pre>
362    
363     <pre caption="/etc/acpi/events/pmg_battery">
364 neysx 1.12 <comment># replace "battery" below with the event generated on your laptop</comment>
365 so 1.15 <comment># For example, battery.* will match battery BAT0 00000080 00000001</comment>
366 swift 1.8 event=battery.*
367 neysx 1.12 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
368 swift 1.8 </pre>
369 swift 1.1
370 swift 1.8 <p>
371 so 1.15 Finally acpid has to be restarted to recognize the changes.
372 swift 1.8 </p>
373 swift 1.1
374 swift 1.8 <pre caption="Finishing runlevel switching with acpid">
375 rane 1.19 # <i>/etc/init.d/acpid restart</i>
376 swift 1.1 </pre>
377    
378     <p>
379     Give it a try: Plug AC in and out and watch syslog for the "Switching to AC
380 rane 1.20 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 swift 1.1 </p>
384    
385     <p>
386     Due to the nature of the event mechanism, your laptop will boot into runlevel
387 rane 1.19 <c>default</c> regardless of the AC/battery state. This is fine when running
388 rane 1.20 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 so 1.15 <c>softlevel=battery</c>, but it's likely to forget choosing it. A better way
391 rane 1.20 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 swift 1.1 </p>
396    
397 so 1.15 <pre caption="Runlevel adjustment at boot time by editing local.start">
398 swift 1.1 <comment># Fake acpi event to switch runlevel if running on batteries</comment>
399 neysx 1.12 /etc/acpi/actions/pmg_switch_runlevel.sh "battery/battery"
400 swift 1.1 </pre>
401    
402     <p>
403 rane 1.20 Prepared like this you can activate Power Management policies for individual
404 swift 1.1 devices.
405     </p>
406    
407     </body>
408     </section>
409     </chapter>
410    
411     <chapter>
412     <title>CPU Power Management</title>
413     <section>
414 nightmorph 1.17 <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 rane 1.19 <title>Some Technical Terms</title>
427 swift 1.8 <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 so 1.15 First of all, the kernel has to be able to change the processor's frequency.
436 rane 1.19 The <b>CPUfreq processor driver</b> knows the commands to do it on your CPU.
437 rane 1.20 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 swift 1.8 <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 rane 1.20 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 swift 1.8 </p>
459    
460     </body>
461     </section>
462     <section>
463 rane 1.19 <title>Setting The Frequency Manually</title>
464 swift 1.1 <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 rane 1.19 of supported processors in the <uri link="#doc_chap8">Troubleshooting</uri>
477     section to verify yours is supported.
478 swift 1.1 </note>
479    
480     <p>
481 neysx 1.12 It's time to test whether CPU frequency changing works. Let's install another
482     tool which is very handy for debugging purposes: <c>sys-power/cpufrequtils</c>
483 swift 1.1 </p>
484    
485 neysx 1.12 <pre caption="Checking CPU frequency">
486     # <i>emerge cpufrequtils</i>
487     # <i>cpufreq-info</i>
488 swift 1.1 </pre>
489    
490     <p>
491 neysx 1.12 Here is an example output:
492 swift 1.1 </p>
493    
494 neysx 1.12 <pre caption="Sample output from cpufreq-info">
495 so 1.15 cpufrequtils 0.3: cpufreq-info (C) Dominik Brodowski 2004
496 neysx 1.12 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 so 1.15 available cpufreq governors: conservative, ondemand, powersave, userspace, performance
503 neysx 1.12 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 so 1.15 current CPU frequency is 1.40 GHz.
507 neysx 1.12 </pre>
508    
509 swift 1.1 <p>
510 neysx 1.12 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 rane 1.20 expected, you might find help in the <uri link="#doc_chap8">Troubleshooting
514     section</uri> in the end of this guide.
515 swift 1.1 </p>
516    
517     </body>
518     </section>
519     <section>
520     <title>Automated frequency adaption</title>
521     <body>
522    
523     <p>
524     The above is quite nice, but not doable in daily life. Better let your system
525 so 1.15 set the appropriate frequency automatically. There are many different
526     approaches to do this. The following table gives a quick overview to help you
527 rane 1.21 decide on one of them. It's roughly separated in three categories <b>kernel</b>
528 rane 1.20 for approaches that only need kernel support, <b>daemon</b> for programs that
529     run in the background and <b>graphical</b> for programs that provide a GUI for
530     easy configuration and changes.
531 swift 1.1 </p>
532    
533     <table>
534     <tr>
535     <th>Name</th>
536 swift 1.8 <th>Category</th>
537     <th>Switch decision</th>
538     <th>Kernel governors</th>
539     <th>Further governors</th>
540     <th>Comments</th>
541     </tr>
542     <tr>
543     <ti>'ondemand' governor</ti>
544     <ti>Kernel</ti>
545     <ti>CPU load</ti>
546     <ti>N.A.</ti>
547     <ti>N.A.</ti>
548     <ti>
549 so 1.15 Chooses maximal frequency on CPU load and slowly steps down when the CPU is
550     idle. Further tuning through files in
551 swift 1.8 <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
552     userland tools (programs, scripts) if governor switching or similar is
553     desired.
554     </ti>
555 swift 1.1 </tr>
556     <tr>
557 so 1.15 <ti>'conservative' governor</ti>
558     <ti>Kernel</ti>
559     <ti>CPU load</ti>
560     <ti>N.A.</ti>
561     <ti>N.A.</ti>
562     <ti>
563 neysx 1.16 Unlike the ondemand governor, conversative doesn't jump to maximum
564     frequency when CPU load is high, but increases the frequency step by step.
565     Further tuning through files in
566     <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
567     userland tools (programs, scripts) if governor switching or similar is
568     desired.
569 so 1.15 </ti>
570     </tr>
571     <tr>
572 swift 1.1 <ti><uri link="http://mnm.uib.es/~gallir/cpudyn/">cpudyn</uri></ti>
573 swift 1.8 <ti>Daemon</ti>
574     <ti>CPU load</ti>
575 neysx 1.12 <ti>Performance, powersave</ti>
576 swift 1.8 <ti>Dynamic</ti>
577     <ti>
578     Also supports disk standby - notice however that <e>laptop mode</e> in most
579     cases will do a better job.
580     </ti>
581 swift 1.1 </tr>
582     <tr>
583 swift 1.8 <ti><uri link="http://sourceforge.net/projects/cpufreqd/">cpufreqd</uri></ti>
584     <ti>Daemon</ti>
585 nightmorph 1.17 <ti>Battery state, CPU load, temperature, running programs and more</ti>
586 swift 1.8 <ti>All available</ti>
587     <ti>None</ti>
588     <ti>
589 nightmorph 1.17 Sophisticated (but somewhat complicated) setup. Extendible through plugins
590     like sensor monitoring (lm_sensors) or coordinating some NVidia based
591     graphics card memory and core. Cpufreqd is SMP aware and can optionally be
592     controlled manually at runtime.
593 swift 1.8 </ti>
594     </tr>
595     <tr>
596     <ti>
597     <uri link="http://www.deater.net/john/powernowd.html">powernowd</uri>
598     </ti>
599     <ti>Daemon</ti>
600     <ti>CPU load</ti>
601     <ti>None</ti>
602     <ti>Passive, sine, aggressive</ti>
603     <ti>
604     Supports SMP.
605     </ti>
606 swift 1.1 </tr>
607     <tr>
608 nightmorph 1.31 <ti>
609     <uri
610     link="http://projects.simpledesigns.com.pl/project/ncpufreqd/">ncpufreqd</uri>
611     </ti>
612 so 1.15 <ti>Daemon</ti>
613     <ti>Temperature</ti>
614     <ti>None</ti>
615     <ti>Powersave, performance</ti>
616     <ti>
617     Toggles the used governor between performance and powersave depending on
618     system temperature. Very useful on laptops with notorious heat problems.
619     </ti>
620     </tr>
621     <tr>
622 swift 1.1 <ti><uri link="http://www.goop.org/~jeremy/speedfreq/">speedfreq</uri></ti>
623 swift 1.8 <ti>Daemon</ti>
624     <ti>CPU load</ti>
625     <ti>None</ti>
626     <ti>Dynamic, powersave, performance, fixed speed</ti>
627     <ti>
628 so 1.15 Easy to configure with a nice client/server interface. Requires a 2.6
629     kernel. Unmaintained, broken and thus removed from Portage. Please switch
630     to cpufreqd if you're still using it.
631 swift 1.8 </ti>
632     </tr>
633     <tr>
634     <ti><uri link="http://cpuspeedy.sourceforge.net/">gtk-cpuspeedy</uri></ti>
635     <ti>Graphical</ti>
636     <ti>None</ti>
637     <ti>None</ti>
638     <ti>None</ti>
639 swift 1.1 <ti>
640 swift 1.8 Gnome application, a graphical tool to set CPU frequency manually. It does
641 neysx 1.12 not offer any automation.
642 swift 1.1 </ti>
643     </tr>
644     <tr>
645 swift 1.8 <ti>klaptopdaemon</ti>
646     <ti>Graphical</ti>
647     <ti>Battery state</ti>
648     <ti>All available</ti>
649     <ti>None</ti>
650     <ti>
651     KDE only, 'ondemand' governor required for dynamic frequency scaling.
652     </ti>
653 swift 1.1 </tr>
654     </table>
655    
656     <p>
657 so 1.15 While adjusting the frequency to the current load looks simple at a first
658     glance, it's not such a trivial task. A bad algorithm can cause switching
659     between two frequencies all the time or wasting energy when setting frequency
660 rane 1.20 to an unnecessary high level.
661 swift 1.1 </p>
662    
663     <p>
664 neysx 1.12 Which one to choose? If you have no idea about it, try <c>cpufreqd</c>:
665 swift 1.1 </p>
666    
667     <pre caption="Installing cpufreqd">
668     # <i>emerge cpufreqd</i>
669     </pre>
670    
671     <p>
672 neysx 1.12 <c>cpufreqd</c> can be configured by editing <path>/etc/cpufreqd.conf</path>.
673     The default one that ships with cpufreqd may look a bit confusing. I recommend
674 nightmorph 1.22 replacing it with the one from former Gentoo developer Henrik Brix Andersen
675     (see below). Please notice that you need cpufreqd-2.0.0 or later. Earlier
676     versions have a different syntax for the config file.
677 swift 1.1 </p>
678    
679 nightmorph 1.17 <pre caption="/etc/cpufreqd.conf (cpufreqd-2.0.0 and later)">
680 swift 1.1 [General]
681     pidfile=/var/run/cpufreqd.pid
682 nightmorph 1.17 poll_interval=3
683     enable_plugins=acpi_ac, acpi_battery
684 nightmorph 1.18 enable_remote=1
685     remote_group=wheel
686 neysx 1.12 verbosity=5
687 nightmorph 1.17 [/General]
688 swift 1.1
689     [Profile]
690 neysx 1.12 name=ondemand
691     minfreq=0%
692     maxfreq=100%
693     policy=ondemand
694 nightmorph 1.17 [/Profile]
695 swift 1.1
696     [Profile]
697 so 1.15 name=conservative
698     minfreq=0%
699     maxfreq=100%
700     policy=conservative
701 nightmorph 1.17 [/Profile]
702 so 1.15
703     [Profile]
704 neysx 1.12 name=powersave
705     minfreq=0%
706     maxfreq=100%
707 swift 1.1 policy=powersave
708 nightmorph 1.17 [/Profile]
709 swift 1.1
710     [Profile]
711 neysx 1.12 name=performance
712     minfreq=0%
713     maxfreq=100%
714     policy=performance
715 nightmorph 1.17 [/Profile]
716 swift 1.1
717     [Rule]
718 neysx 1.12 name=battery
719     ac=off
720 so 1.15 profile=conservative
721 nightmorph 1.17 [/Rule]
722 swift 1.1
723     [Rule]
724 neysx 1.12 name=battery_low
725 swift 1.1 ac=off
726 neysx 1.12 battery_interval=0-10
727     profile=powersave
728 nightmorph 1.17 [/Rule]
729 swift 1.1
730     [Rule]
731 neysx 1.12 name=ac
732     ac=on
733 so 1.15 profile=ondemand
734 nightmorph 1.17 [/Rule]
735 neysx 1.12 </pre>
736    
737     <p>
738 rane 1.19 Now you can start the cpufreqd daemon. Add it to the <c>default</c> and
739     <c>battery</c> runlevel as well.
740 swift 1.1 </p>
741    
742 neysx 1.12 <pre caption="Starting cpufreqd">
743     # <i>rc-update add cpufreqd default battery</i>
744     # <i>rc</i>
745     </pre>
746    
747 nightmorph 1.17 <p>
748     Sometimes it can be desirable to select another policy than the daemon chooses,
749     for example when battery power is low, but you know that AC will be available
750 rane 1.20 soon. In that case you can turn on cpufreqd's manual mode with <c>cpufreqd-set
751     manual</c> and select one of your configured policies (as listed by
752     <c>cpufreqd-get</c>). You can leave manual mode by executing <c>cpufreqd-set
753     dynamic</c>.
754 nightmorph 1.17 </p>
755    
756 neysx 1.12 <warn>
757     Do not run more than one of the above programs at the same time. It may cause
758     confusion like switching between two frequencies all the time.
759     </warn>
760    
761 swift 1.8 </body>
762     </section>
763     <section>
764     <title>Verifying the result</title>
765     <body>
766    
767 swift 1.1 <p>
768     The last thing to check is that your new policies do a good job. An easy way to
769 swift 1.8 do so is monitoring CPU speed while working with your laptop:
770 swift 1.1 </p>
771    
772     <pre caption="Monitoring CPU speed">
773 yoswink 1.13 # <i>watch grep \"cpu MHz\" /proc/cpuinfo</i>
774 swift 1.1 </pre>
775    
776     <p>
777 rane 1.20 If <path>/proc/cpuinfo</path> doesn't get updated (see <uri
778 swift 1.32 link="#doc_chap8">Troubleshooting</uri>), monitor the CPU frequency with
779     <c>sys-apps/x86info</c>:
780 swift 1.1 </p>
781    
782     <pre caption="Alternative CPU speed monitoring">
783 neysx 1.12 # <i>watch x86info -mhz</i>
784 swift 1.1 </pre>
785    
786     <p>
787     Depending on your setup, CPU speed should increase on heavy load, decrease on
788 rane 1.19 no activity or just stay at the same level. When using <c>cpufreqd</c> and
789 rane 1.20 verbosity set to 5 or higher in <path>cpufreqd.conf</path> you'll get
790     additional information about what's happening reported to <c>syslog</c>.
791 swift 1.1 </p>
792    
793     </body>
794     </section>
795     </chapter>
796    
797     <chapter>
798     <title>LCD Power Management</title>
799     <section>
800     <body>
801    
802     <p>
803 rane 1.20 As you can see in <uri link="#doc_chap1_fig1">figure 1.1</uri>, the LCD
804     display consumes the biggest part of energy (might not be the case for
805     non-mobile CPU's). Thus it's quite important not only to shut the display off
806     when not needed, but also to reduce it's backlight if possible. Most laptops
807     offer the possibility to control the backlight dimming.
808 swift 1.1 </p>
809    
810 nightmorph 1.17 </body>
811     </section>
812     <section>
813     <title>Standby settings</title>
814     <body>
815    
816 swift 1.1 <p>
817 nightmorph 1.17 The first thing to check is the standby/suspend/off timings of the display. As
818     this depends heavily on your windowmanager, I'll let you figure it out
819 rane 1.20 yourself. Just two common places: Blanking the terminal can be done with
820 nightmorph 1.17 <c>setterm -blank &lt;number-of-minutesM&gt;</c>, <c>setterm -powersave on</c>
821     and <c>setterm -powerdown &lt;number-of-minutesM&gt;</c>. For X.org, modify
822     <path>/etc/X11/xorg.conf</path> similar to this:
823 swift 1.1 </p>
824    
825 nightmorph 1.35 <pre caption="LCD suspend settings in X.org">
826     Section "ServerFlags"
827     Option "blank time" "5" <comment># Blank the screen after 5 minutes (Fake)</comment>
828     Option "standby time" "10" <comment># Turn off screen after 10 minutes (DPMS)</comment>
829     Option "suspend time" "20" <comment># Full suspend after 20 minutes</comment>
830     Option "off time" "30" <comment># Turn off after half an hour</comment>
831 swift 1.1 [...]
832     EndSection
833    
834     [...]
835    
836     Section "Monitor"
837     Identifier [...]
838 nightmorph 1.35 Option "DPMS"
839 swift 1.1 [...]
840     EndSection
841     </pre>
842    
843 nightmorph 1.17 </body>
844     </section>
845     <section>
846     <title>Backlight dimming</title>
847     <body>
848    
849 swift 1.1 <p>
850     Probably more important is the backlight dimming. If you have access to the
851     dimming settings via a tool, write a small script that dims the backlight in
852 rane 1.19 battery mode and place it in your <c>battery</c> runlevel. The following script
853 nightmorph 1.17 should work on most IBM Thinkpads and Toshiba laptops. You've got to enable the
854 rane 1.20 appropriate option in your kernel (IBM Thinkpads only). For Toshiba laptops,
855 nightmorph 1.35 install <c>sys-power/acpitool</c> and skip configuration of <c>thinkpad_acpi</c>
856     (formerly called <c>ibm_acpi</c>) as described below.
857 neysx 1.12 </p>
858    
859     <warn>
860 swift 1.36 Support for setting brightness is marked experimental in thinkpad_acpi. It
861     accesses hardware directly and may cause severe harm to your system. Please
862     read the <uri link="http://ibm-acpi.sourceforge.net/">thinkpad_acpi
863     website</uri>
864 neysx 1.12 </warn>
865    
866     <p>
867 swift 1.36 To be able to set the brightness level, the thinkpad_acpi module has to be
868     loaded with the experimental parameter.
869 neysx 1.12 </p>
870    
871 nightmorph 1.35 <pre caption="automatically loading the thinkpad_acpi module">
872 neysx 1.12 <comment>(Please read the warnings above before doing this!)</comment>
873 nightmorph 1.37 # <i>echo "options thinkpad_acpi experimental=1" >> /etc/modprobe.d/thinkpad_acpi</i>
874     # <i>update-modules</i>
875 nightmorph 1.35 # <i>echo thinkpad_acpi >> /etc/modules.autoload.d/kernel-2.6</i>
876     # <i>modprobe thinkpad_acpi</i>
877 neysx 1.12 </pre>
878    
879     <p>
880     This should work without error messages and a file
881     <path>/proc/acpi/ibm/brightness</path> should be created after loading the
882 rane 1.20 module. An init script will take care of choosing the brightness according to
883     the power source.
884 neysx 1.12 </p>
885    
886     <pre caption="/etc/conf.d/lcd-brightness">
887     <comment># See /proc/acpi/ibm/brightness for available values</comment>
888 nightmorph 1.35 <comment># Please read /usr/src/linux/Documentation/thinkpad-acpi.txt</comment>
889 neysx 1.12
890 nightmorph 1.23 <comment># brightness level in ac mode. Default is 7.</comment>
891 neysx 1.12 BRIGHTNESS_AC=7
892    
893     <comment># brightness level in battery mode. Default is 4.</comment>
894     BRIGHTNESS_BATTERY=4
895     </pre>
896    
897     <pre caption="/etc/init.d/lcd-brightness">
898     #!/sbin/runscript
899    
900     set_brightness() {
901     if on_ac_power
902     then
903     LEVEL=${BRIGHTNESS_AC:-7}
904     else
905     LEVEL=${BRIGHTNESS_BATTERY:-4}
906     fi
907    
908     if [ -f /proc/acpi/ibm/brightness ]
909     then
910     ebegin "Setting LCD brightness"
911     echo "level ${LEVEL}" > /proc/acpi/ibm/brightness
912     eend $?
913 nightmorph 1.17 elif [[ -e /usr/bin/acpitool &amp;&amp; -n $(acpitool -T | grep "LCD brightness") ]]
914     then
915     ebegin "Setting LCD brightness"
916     acpitool -l $LEVEL >/dev/null || ewarn "Unable to set lcd brightness"
917     eend $?
918 neysx 1.12 else
919     ewarn "Setting LCD brightness is not supported."
920 nightmorph 1.35 ewarn "For IBM Thinkpads, check that thinkpad_acpi is loaded into the kernel"
921 nightmorph 1.23 ewarn "For Toshiba laptops, you've got to install sys-power/acpitool"
922 neysx 1.12 fi
923     }
924    
925     start() {
926     set_brightness
927     }
928    
929     stop () {
930     set_brightness
931     }
932     </pre>
933    
934     <p>
935     When done, make sure brightness is adjusted automatically by adding it to the
936     battery runlevel.
937 swift 1.1 </p>
938    
939 neysx 1.12 <pre caption="Enabling automatic brightness adjustment">
940 rane 1.19 # <i>chmod +x /etc/init.d/lcd-brightness</i>
941     # <i>rc-update add lcd-brightness battery</i>
942     # <i>rc</i>
943 neysx 1.12 </pre>
944    
945 swift 1.1 </body>
946     </section>
947     </chapter>
948    
949     <chapter>
950     <title>Disk Power Management</title>
951     <section>
952 nightmorph 1.17 <body>
953 rane 1.19
954 nightmorph 1.17 <p>
955     Hard disks consume less energy in sleep mode. Therefore it makes sense to
956     activate power saving features whenever the hard disk is not used for a certain
957     amount of time. I'll show you two alternative possibilities to do it. First,
958     laptop-mode will save most energy due to several measures which prevent or at
959     least delay write accesses. The drawback is that due to the delayed write
960     accesses a power outage or kernel crash will be more dangerous for data loss.
961     If you don't like this, you have to make sure that there are no processes which
962     write to your hard disk frequently. Afterwards you can enable power saving
963 rane 1.19 features of your hard disk with <c>hdparm</c> as the second alternative.
964 nightmorph 1.17 </p>
965    
966     </body>
967     </section>
968     <section>
969     <title>Increasing idle time - laptop-mode</title>
970 swift 1.1 <body>
971    
972     <p>
973 nightmorph 1.27 Recent 2.6 kernels include the so-called <c>laptop-mode</c>. When activated,
974     dirty buffers are written to disk on read calls or after 10 minutes (instead of
975     30 seconds). This minimizes the time the hard disk needs to be spun up.
976 swift 1.1 </p>
977    
978 nightmorph 1.17 <pre caption="Automated start of laptop-mode">
979     # <i>emerge laptop-mode-tools</i>
980     </pre>
981 swift 1.1
982 nightmorph 1.17 <p>
983     <c>laptop-mode-tools</c> has its configuration file in
984     <path>/etc/laptop-mode/laptop-mode.conf</path>. Adjust it the way you like it,
985     it's well commented. Run <c>rc-update add laptop_mode battery</c> to start it
986     automatically.
987     </p>
988    
989     <p>
990     Recent versions (1.11 and later) of laptop-mode-tools include a new tool
991     <c>lm-profiler</c>. It will monitor your system's disk usage and running
992     network services and suggests to disable unneeded ones. You can either disable
993     them through laptop-mode-tools builtin runlevel support (which will be reverted
994 rane 1.19 by Gentoo's <c>/sbin/rc</c>) or use your <c>default</c>/<c>battery</c>
995 nightmorph 1.17 runlevels (recommended).
996     </p>
997    
998     <pre caption="Sample output from running lm-profiler">
999 rane 1.19 # <i>lm-profiler</i>
1000 nightmorph 1.17 Profiling session started.
1001     Time remaining: 600 seconds
1002     [4296896.602000] amarokapp
1003     Time remaining: 599 seconds
1004     [4296897.714000] sort
1005     [4296897.970000] mv
1006     Time remaining: 598 seconds
1007     Time remaining: 597 seconds
1008     [4296900.482000] reiserfs/0
1009     </pre>
1010    
1011     <p>
1012     After profiling your system for ten minutes, lm-profiler will present a list of
1013     services which might have caused disk accesses during that time.
1014     </p>
1015    
1016     <pre caption="lm-profiler suggests to disable some services">
1017     Program: "atd"
1018     Reason: standard recommendation (program may not be running)
1019     Init script: /etc/init.d/atd (GUESSED)
1020    
1021 rane 1.19 Do you want to disable this service in battery mode? [y/N]: <i>n</i>
1022 swift 1.1 </pre>
1023    
1024     <p>
1025 nightmorph 1.17 To disable atd as suggested in the example above, you would run <c>rc-update
1026     del atd battery</c>. Be careful not to disable services that are needed for
1027 rane 1.20 your system to run properly - <c>lm-profiler</c> is likely to generate some
1028     false positives. Do not disable a service if you are unsure whether it's
1029     needed.
1030 nightmorph 1.17 </p>
1031    
1032     </body>
1033     </section>
1034     <section>
1035 rane 1.19 <title>Limiting Write Accesses</title>
1036 nightmorph 1.17 <body>
1037    
1038     <p>
1039     If you don't want to use laptop-mode, you must take special care to disable
1040     services that write to your disk frequently - <c>syslogd</c> is a good
1041     candidate, for example. You probably don't want to shut it down completely, but
1042     it's possible to modify the config file so that "unnecessary" things don't get
1043 rane 1.20 logged and thus don't create disk traffic. <c>Cups</c> writes to disk
1044     periodically, so consider shutting it down and only enable it manually when
1045     needed.
1046 nightmorph 1.17 </p>
1047    
1048     <pre caption="Disabling cups in battery mode">
1049     # <i>rc-update del cupsd battery</i>
1050     </pre>
1051    
1052     <p>
1053     You can also use <c>lm-profiler</c> from laptop-mode-tools (see above) to find
1054     services to disable. Once you eliminated all of them, go on with configuring
1055     hdparm.
1056     </p>
1057    
1058     </body>
1059     </section>
1060     <section>
1061     <title>hdparm</title>
1062     <body>
1063    
1064     <p>
1065 nightmorph 1.28 The second possibility is using <c>hdparm</c>. Skip this if
1066     you are using laptop-mode. Otherwise, edit <path>/etc/conf.d/hdparm</path> and
1067     add the following values to your drive entries. This example assumes your hard
1068     drive is called <b>hda</b>:
1069 swift 1.1 </p>
1070    
1071 nightmorph 1.28 <pre caption="Using /etc/conf.d/hdparm for disk standby">
1072     hda_args="-q -S12"
1073     </pre>
1074 neysx 1.12
1075 nightmorph 1.28 <p>
1076     This will activate power management for your hard drive. If you ever want to
1077     deactivate power management, you can edit <path>/etc/conf.d/hdparm</path> and
1078     change the values to <c>-q -S0</c>, or just run <c>hdparm -q -S0 /dev/hda</c>.
1079     </p>
1080 swift 1.1
1081     <p>
1082 nightmorph 1.28 See <c>man hdparm</c> for the options. Though you can always start <c>hdparm</c>
1083     manually when you are on battery power by running <c>/etc/init.d/hdparm
1084     start</c>, it's much easier to automate its startup and shutdown. To do so, add
1085     <c>hdparm</c> to the battery runlevel so that it will automatically enable power
1086     management.
1087 swift 1.1 </p>
1088    
1089     <pre caption="Automate disk standby settings">
1090 nightmorph 1.28 # <i>rc-update add hdparm battery</i>
1091 swift 1.1 </pre>
1092    
1093     <impo>
1094     Be careful with sleep/spin down settings of your hard drive. Setting it to
1095     small values might wear out your drive and lose warranty.
1096     </impo>
1097    
1098     </body>
1099     </section>
1100     <section>
1101     <title>Other tricks</title>
1102     <body>
1103    
1104     <p>
1105     Another possibility is to deactivate swap in battery mode. Before writing a
1106     swapon/swapoff switcher, make sure there is enough RAM and swap isn't used
1107     heavily, otherwise you'll be in big problems.
1108     </p>
1109    
1110     <p>
1111     If you don't want to use laptop-mode, it's still possible to minimize disk
1112 rane 1.19 access by mounting certain directories as <c>tmpfs</c> - write accesses are not
1113 swift 1.1 stored on a disk, but in main memory and get lost with unmounting. Often it's
1114     useful to mount <path>/tmp</path> like this - you don't have to pay special
1115     attention as it gets cleared on every reboot regardless whether it was mounted
1116     on disk or in RAM. Just make sure you have enough RAM and no program (like a
1117     download client or compress utility) needs extraordinary much space in
1118     <path>/tmp</path>. To activate this, enable tmpfs support in your kernel and
1119     add a line to <path>/etc/fstab</path> like this:
1120     </p>
1121    
1122     <pre caption="Editing /etc/fstab to make /tmp even more volatile">
1123     none /tmp tmpfs size=32m 0 0
1124     </pre>
1125    
1126     <warn>
1127     Pay attention to the size parameter and modify it for your system. If you're
1128 rane 1.21 unsure, don't try this at all, it can become a performance bottleneck easily. In
1129 swift 1.1 case you want to mount <path>/var/log</path> like this, make sure to merge the
1130     log files to disk before unmounting. They are essential. Don't attempt to mount
1131 rane 1.19 <path>/var/tmp</path> like this. Portage uses it for compiling...
1132 swift 1.1 </warn>
1133    
1134     </body>
1135     </section>
1136     </chapter>
1137    
1138     <chapter>
1139 rane 1.19 <title>Power Management For Other Devices</title>
1140 swift 1.1 <section>
1141 rane 1.19 <title>Graphics Cards</title>
1142 so 1.15 <body>
1143    
1144     <p>
1145     In case you own an ATI graphics card supporting PowerPlay (dynamic clock
1146 nightmorph 1.25 scaling for the graphics processing unit GPU), you can activate this
1147 rane 1.20 feature in X.org. Open <path>/etc/X11/xorg.conf</path> and add (or enable) the
1148     <c>DynamicClocks</c> option in the Device section. Please notice that this
1149     feature will lead to crashes on some systems.
1150 so 1.15 </p>
1151    
1152     <pre caption="Enabling ATI PowerPlay support in X.org">
1153     Section "Device"
1154     [...]
1155     Option "DynamicClocks" "on"
1156     EndSection
1157     </pre>
1158    
1159     </body>
1160     </section>
1161     <section>
1162 swift 1.1 <title>Wireless Power Management</title>
1163     <body>
1164    
1165     <p>
1166 nightmorph 1.17 Wireless LAN cards consume quite a bit of energy. Put them in Power Management
1167 nightmorph 1.28 mode just like your hard drives.
1168 swift 1.1 </p>
1169    
1170 nightmorph 1.17 <note>
1171     This script assumes your wireless interface is called <c>wlan0</c>; replace
1172     this with the actual name of your interface.
1173     </note>
1174    
1175 nightmorph 1.28 <p>
1176 nightmorph 1.29 Add the following option to <path>/etc/conf.d/net</path> to automatically enable
1177 nightmorph 1.28 power management for your wireless card:
1178     </p>
1179 swift 1.1
1180 nightmorph 1.28 <pre caption="Automated WLAN Power Management">
1181     iwconfig_wlan0="power on"
1182 swift 1.1 </pre>
1183    
1184     <p>
1185 nightmorph 1.28 See <c>man iwconfig</c> for details and more options like the period between
1186     wakeups or timeout settings. If your driver and access point support changing
1187     the beacon time, this is a good starting point to save even more energy.
1188 swift 1.1 </p>
1189    
1190     </body>
1191     </section>
1192     <section>
1193     <title>USB Power Management</title>
1194     <body>
1195    
1196     <p>
1197     There are two problems with USB devices regarding energy consumption: First,
1198     devices like USB mice, digital cameras or USB sticks consume energy while
1199     plugged in. You cannot avoid this (nevertheless remove them in case they're not
1200     needed). Second, when there are USB devices plugged in, the USB host controller
1201     periodically accesses the bus which in turn prevents the CPU from going into
1202 rane 1.20 sleep mode. The kernel offers an experimental option to enable suspension of
1203 so 1.15 USB devices through driver calls or one of the <path>power/state</path> files
1204     in <path>/sys</path>.
1205 swift 1.1 </p>
1206    
1207 so 1.15 <pre caption="Enabling USB suspend support in the kernel">
1208     Device Drivers
1209     USB support
1210     [*] Support for Host-side USB
1211     [*] USB suspend/resume (EXPERIMENTAL)
1212     </pre>
1213    
1214 swift 1.1 </body>
1215     </section>
1216     </chapter>
1217    
1218     <chapter>
1219 rane 1.19 <title>Sleep States: sleep, standby, and suspend to disk</title>
1220 swift 1.1 <section>
1221     <body>
1222    
1223     <p>
1224     ACPI defines different sleep states. The more important ones are
1225     </p>
1226    
1227 rane 1.20 <ul>
1228 swift 1.1 <li>S1 aka Standby</li>
1229     <li>S3 aka Suspend to RAM aka Sleep</li>
1230     <li>S4 aka Suspend to Disk aka Hibernate</li>
1231     </ul>
1232    
1233     <p>
1234     They can be called whenever the system is not in use, but a shutdown is not
1235     wanted due to the long boot time.
1236     </p>
1237    
1238     </body>
1239     </section>
1240     <section>
1241 so 1.15 <title>Sleep (S3)</title>
1242 swift 1.1 <body>
1243    
1244     <p>
1245 so 1.15 The ACPI support for these sleep states is marked experimental for good reason.
1246     APM sleep states seem to be more stable, however you can't use APM and ACPI
1247     together.
1248     </p>
1249    
1250     <pre caption="Kernel configuration for the various suspend types">
1251     Power Management Options ---&gt;
1252     [*] Power Management support
1253 nightmorph 1.40 [*] Suspend to RAM and standby
1254 so 1.15 </pre>
1255    
1256     <p>
1257 nightmorph 1.17 Once your kernel is properly configured, you can use the
1258 so 1.15 <c>hibernate-script</c> to activate suspend or sleep mode. Let's install that
1259     first.
1260     </p>
1261    
1262     <pre caption="Installing the hibernate-script">
1263 rane 1.19 # <i>emerge hibernate-script</i>
1264 so 1.15 </pre>
1265    
1266     <p>
1267 nightmorph 1.25 Some configuration has to be done in <path>/etc/hibernate</path>. The default
1268 nightmorph 1.24 package introduces a few configuration files for each sleep state. Options that
1269     are common to all suspend methods are placed in <path>common.conf</path>; make
1270     sure this file is properly set up for your system.
1271 so 1.15 </p>
1272    
1273     <p>
1274 nightmorph 1.24 To configure sleep, edit <path>sysfs-ram.conf</path> in
1275     <path>/etc/hibernate</path>. <c>UseSysfsPowerState mem</c> is already setup
1276 nightmorph 1.25 correctly, but if you need to make further changes to this particular sleep
1277     state (or any other sleep state) you should add them to
1278 nightmorph 1.24 <path>/etc/hibernate/hibernate.conf</path>. The comments and option names will
1279     guide you. If you use nfs or samba shares over the network, make sure to
1280     shutdown the appropriate init scripts to avoid timeouts.
1281 so 1.15 </p>
1282    
1283 nightmorph 1.24 <note>
1284     For more information on setting up sleep states, read <c>man
1285     hibernate.conf</c>.
1286     </note>
1287    
1288 so 1.15 <p>
1289     Ready? Now is the last chance to backup any data you want to keep after
1290     executing the next command. Notice that you probably have to hit a special key
1291 rane 1.19 like <c>Fn</c> to resume from sleep.
1292 so 1.15 </p>
1293    
1294     <pre caption="Calling sleep">
1295 rane 1.19 # <i>hibernate-ram</i>
1296 so 1.15 </pre>
1297    
1298     <p>
1299 rane 1.20 If you're still reading, it seems to work. You can also setup standby (S1) in a
1300 nightmorph 1.24 similar way by editing <path>sysfs-ram.conf</path> and changing
1301     "UseSysfsPowerState mem" to "UseSysfsPowerState standby". S3 and S4 are the more
1302     interesting sleep states due to greater energy savings however.
1303 so 1.15 </p>
1304    
1305     </body>
1306     </section>
1307     <section>
1308     <title>Hibernate (S4)</title>
1309     <body>
1310    
1311     <p>
1312     This section introduces hibernation, where a snapshot of the running system is
1313     written to disk before powering off. On resume, the snapshot is loaded and you
1314     can go on working at exactly the point you called hibernate before.
1315 swift 1.1 </p>
1316    
1317     <warn>
1318 so 1.15 Don't exchange non hot-pluggable hardware when suspended. Don't attempt to load
1319     a snapshot with a different kernel image than the one it was created with.
1320     Shutdown any NFS or samba server/client before hibernating.
1321 swift 1.1 </warn>
1322    
1323     <p>
1324 so 1.15 There are two different implementations for S4. The original one is swsusp,
1325 nightmorph 1.39 then there is the newer tuxonice (formerly suspend2) with a nicer interface
1326 swift 1.36 (including fbsplash support). A <uri
1327 nightmorph 1.39 link="http://tuxonice.net/features.html#compare">feature comparison</uri> is
1328     available at the <uri link="http://www.tuxonice.net">tuxonice homepage</uri>.
1329 swift 1.36 There used to be Suspend-to-Disk (pmdisk), a fork of swsusp, but it has been
1330     merged back.
1331 swift 1.1 </p>
1332    
1333     <p>
1334 jkt 1.33 TuxOnIce is not included in the mainline kernel yet, therefore you either have
1335 rane 1.20 to patch your kernel sources with the patches provided by <uri
1336 nightmorph 1.39 link="http://www.tuxonice.net">tuxonice.net</uri> or use
1337 jkt 1.33 <c>sys-kernel/tuxonice-sources</c>.
1338 swift 1.1 </p>
1339    
1340     <p>
1341 jkt 1.33 The kernel part for both swusp and TuxOnIce is as follows:
1342 swift 1.1 </p>
1343    
1344     <pre caption="Kernel configuration for the various suspend types">
1345 nightmorph 1.40 Power Management support ---&gt;
1346 swift 1.1 <comment>(hibernate with swsusp)</comment>
1347 nightmorph 1.39 [*] Hibernation (aka 'suspend to disk')
1348 so 1.15 <comment>(replace /dev/SWAP with your swap partition)</comment>
1349     (/dev/SWAP) Default resume partition
1350 rane 1.20
1351 jkt 1.33 <comment>(hibernate with TuxOnIce)</comment>
1352     Enhanced Hibernation (TuxOnIce)
1353 nightmorph 1.39 --- Image Storage (you need at least one allocator)
1354     [*] File Allocator
1355     [*] Swap Allocator
1356 so 1.15 --- General Options
1357 nightmorph 1.39 [*] Compression support
1358 so 1.15 [ ] Allow Keep Image Mode
1359 nightmorph 1.39 [*] Replace swsusp by default
1360 swift 1.1 </pre>
1361    
1362     <p>
1363 so 1.15 The configuration for swsusp is rather easy. If you didn't store the location
1364     of your swap partition in the kernel config, you can also pass it as a
1365     parameter with the <c>resume=/dev/SWAP</c> directive. If booting is not
1366     possible due to a broken image, use the <c>noresume</c> kernel parameter. The
1367 rane 1.20 <c>hibernate-cleanup</c> init script invalidates swsusp images during the boot
1368     process.
1369 swift 1.1 </p>
1370    
1371 so 1.15 <pre caption="Invalidating swsusp images during the boot process">
1372 rane 1.19 # <i>rc-update add hibernate-cleanup boot</i>
1373 so 1.15 </pre>
1374    
1375 swift 1.1 <p>
1376 so 1.15 To activate hibernate with swsusp, use the hibernate script and set
1377 nightmorph 1.24 <c>UseSysfsPowerState disk</c> in <path>/etc/hibernate/sysfs-disk</path>.
1378 swift 1.1 </p>
1379    
1380     <warn>
1381     Backup your data before doing this. Run <c>sync</c> before executing one of the
1382     commands to have cached data written to disk. First try it outside of X, then
1383     with X running, but not logged in.
1384     </warn>
1385 rane 1.20
1386 swift 1.1 <p>
1387     If you experience kernel panics due to uhci or similar, try to compile USB
1388     support as module and unload the modules before sending your laptop to sleep
1389 nightmorph 1.24 mode. There are configuration options for this in <path>common.conf</path>
1390 swift 1.1 </p>
1391    
1392 so 1.15 <pre caption="Hibernating with swsusp">
1393 nightmorph 1.24 # <i>nano -w /etc/hibernate/common.conf</i>
1394 so 1.15 <comment>(Make sure you have a backup of your data)</comment>
1395 rane 1.19 # <i>hibernate</i>
1396 so 1.15 </pre>
1397    
1398 swift 1.1 <p>
1399 jkt 1.34 The following section discusses the setup of TuxOnIce including fbsplash support
1400     for a nice graphical progress bar during suspend and resume.
1401 so 1.15 </p>
1402    
1403     <p>
1404 rane 1.20 The first part of the configuration is similar to the configuration of swsusp.
1405     In case you didn't store the location of your swap partition in the kernel
1406     config, you have to pass it as a kernel parameter with the
1407 jkt 1.33 <c>resume=swap:/dev/SWAP</c> directive. If booting is not possible due to a
1408     broken image, append the <c>noresume</c> parameter. Additionally, the
1409 jkt 1.34 <c>hibernate-cleanup</c> init script invalidates TuxOnIce images during the boot
1410     process.
1411 so 1.15 </p>
1412    
1413 jkt 1.33 <pre caption="Invalidating TuxOnIce images during the boot process">
1414 rane 1.19 # <i>rc-update add hibernate-cleanup boot</i>
1415 so 1.15 </pre>
1416    
1417 rane 1.20 <p>
1418 nightmorph 1.39 Now edit <path>/etc/hibernate/tuxonice.conf</path>, enable the <c>TuxOnIce</c>
1419 nightmorph 1.24 options you need. Do not enable the <c>fbsplash</c> options in
1420     <c>common.conf</c> just yet.
1421 swift 1.1 </p>
1422    
1423 jkt 1.33 <pre caption="Hibernating with TuxOnIce">
1424 nightmorph 1.39 # <i>nano -w /etc/hibernate/tuxonice.conf</i>
1425 so 1.15 <comment>(Make sure you have a backup of your data)</comment>
1426 rane 1.19 # <i>hibernate</i>
1427 swift 1.8 </pre>
1428    
1429 so 1.15 <p>
1430 rane 1.20 Please configure <c>fbsplash</c> now if you didn't do already. To enable
1431 jkt 1.34 fbsplash support during hibernation, the <c>sys-apps/tuxonice-userui</c> package
1432     is needed. Additionally, you've got to enable the <c>fbsplash</c> USE flag.
1433 so 1.15 </p>
1434    
1435 jkt 1.33 <pre caption="Installing tuxonice-userui">
1436     # <i>echo "sys-apps/tuxonice-userui fbsplash" >> /etc/portage/package.use</i>
1437 nightmorph 1.24 <comment>(It may be marked ~arch, so first it must be keyworded)</comment>
1438 jkt 1.33 # <i>echo "sys-apps/tuxonice-userui" >> /etc/portage/package.keywords</i>
1439     # <i>emerge tuxonice-userui</i>
1440 so 1.15 </pre>
1441    
1442     <p>
1443     The ebuild tells you to make a symlink to the theme you want to use. For
1444     example, to use the <c>livecd-2005.1</c> theme, run the following command:
1445     </p>
1446    
1447     <pre caption="Using the livecd-2005.1 theme during hibernation">
1448 nightmorph 1.39 # <i>ln -sfn /etc/splash/livecd-2005.1 /etc/splash/tuxonice</i>
1449 so 1.15 </pre>
1450    
1451     <p>
1452     If you don't want a black screen in the first part of the resume process, you
1453 jkt 1.33 have to add the <c>tuxoniceui_fbsplash</c> tool to your initrd image. Assuming
1454 so 1.15 you created the initrd image with <c>splash_geninitramfs</c> and saved it as
1455 rane 1.20 <path>/boot/fbsplash-emergence-1024x768</path>, here's how to do that.
1456 so 1.15 </p>
1457    
1458 jkt 1.33 <pre caption="Adding tuxoniceui_fbsplash to an initrd image">
1459 rane 1.19 # <i>mount /boot</i>
1460     # <i>mkdir ~/initrd.d</i>
1461     # <i>cp /boot/fbsplash-emergence-1024x768 ~/initrd.d/</i>
1462     # <i>cd ~/initrd.d</i>
1463     # <i>gunzip -c fbsplash-emergence-1024x768 | cpio -idm --quiet -H newc</i>
1464     # <i>rm fbsplash-emergence-1024x768</i>
1465 jkt 1.33 # <i>cp /usr/sbin/tuxoniceui_fbsplash sbin/</i>
1466     # <i>find . | cpio --quiet --dereference -o -H newc | gzip -9 > /boot/fbsplash-tuxonice-emergence-1024x768</i>
1467 so 1.15 </pre>
1468    
1469     <p>
1470 nightmorph 1.24 Afterwards adjust <path>grub.conf</path> (or <path>lilo.conf</path>) so that
1471 jkt 1.33 your TuxOnIce kernel uses
1472     <path>/boot/fbsplash-tuxonice-emergence-1024x768</path> as initrd image. You can
1473 nightmorph 1.24 now test a dry run to see if everything is setup correctly.
1474 so 1.15 </p>
1475    
1476     <pre caption="Test run for fbsplash hibernation">
1477 jkt 1.33 # <i>tuxoniceui_fbsplash -t</i>
1478 so 1.15 </pre>
1479    
1480     <p>
1481 nightmorph 1.24 Afterwards open <path>/etc/hibernate/common.conf</path> and activate the
1482     fbsplash options. Execute <c>hibernate</c> and enjoy.
1483 so 1.15 </p>
1484    
1485 swift 1.1 </body>
1486     </section>
1487     </chapter>
1488    
1489     <chapter>
1490     <title>Troubleshooting</title>
1491     <section>
1492     <body>
1493    
1494     <p>
1495     <e>Q:</e> I'm trying to change the CPU frequency, but
1496     <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor</path> does not
1497     exist.
1498     </p>
1499    
1500     <p>
1501     <e>A:</e> Make sure your processor supports CPU frequency scaling and you chose
1502     the right CPUFreq driver for your processor. Here is a list of processors that
1503 jkt 1.34 are supported by cpufreq (kernel 2.6.7): ARM Integrator, ARM-SA1100, ARM-SA1110,
1504     AMD Elan - SC400, SC410, AMD mobile K6-2+, AMD mobile K6-3+, AMD mobile Duron,
1505     AMD mobile Athlon, AMD Opteron, AMD Athlon 64, Cyrix Media GXm, Intel mobile
1506     PIII and Intel mobile PIII-M on certain chipsets, Intel Pentium 4, Intel Xeon,
1507     Intel Pentium M (Centrino), National Semiconductors Geode GX, Transmeta Crusoe,
1508     VIA Cyrix 3 / C3, UltraSPARC-III, SuperH SH-3, SH-4, several "PowerBook" and
1509     "iBook2" and various processors on some ACPI 2.0-compatible systems (only if
1510     "ACPI Processor Performance States" are available to the ACPI/BIOS interface).
1511 swift 1.1 </p>
1512    
1513     <p>
1514     <e>Q:</e> My laptop supports frequency scaling, but
1515     <path>/sys/devices/system/cpu/cpu0/cpufreq/</path> is empty.
1516     </p>
1517    
1518     <p>
1519     <e>A:</e> Look for ACPI related error messages with <c>dmesg | grep ACPI</c>.
1520     Try to update the BIOS, especially if a broken DSDT is reported. You can also
1521     try to fix it yourself (which is beyond the scope of this guide).
1522     </p>
1523    
1524     <p>
1525 rane 1.19 <e>Q:</e> My laptop supports frequency scaling, but according to
1526     <path>/proc/cpuinfo</path> the speed never changes.
1527 swift 1.1 </p>
1528    
1529     <p>
1530 swift 1.8 <e>A:</e> Probably you have activated symmetric multiprocessing support
1531     (CONFIG_SMP) in your kernel. Deactivate it and it should work. Some older
1532 rane 1.20 kernels had a bug causing this. In that case, run <c>emerge x86info</c>, update
1533 jkt 1.34 your kernel as asked and check the current frequency with <c>x86info -mhz</c>.
1534 swift 1.1 </p>
1535    
1536     <p>
1537     <e>Q:</e> I can change the CPU frequency, but the range is not as wide as in
1538     another OS.
1539     </p>
1540    
1541     <p>
1542     <e>A:</e> You can combine frequency scaling with ACPI throttling to get a lower
1543 jkt 1.34 minimum frequency. Notice that throttling doesn't save much energy and is mainly
1544     used for thermal management (keeping your laptop cool and quiet). You can read
1545     the current throttling state with <c>cat /proc/acpi/processor/CPU/throttling</c>
1546     and change it with <c>echo -n "0:x" > /proc/acpi/processor/CPU/limit</c>, where
1547     x is one of the Tx states listed in
1548 swift 1.1 <path>/proc/acpi/processor/CPU/throttling</path>.
1549     </p>
1550    
1551     <p>
1552 swift 1.8 <e>Q:</e> When configuring the kernel, powersave, performance and userspace
1553     governors show up, but that ondemand thing is missing. Where do I get it?
1554     </p>
1555    
1556     <p>
1557     <e>A:</e> The ondemand governor is only included in recent kernel sources. Try
1558     updating them.
1559     </p>
1560    
1561     <p>
1562 swift 1.1 <e>Q:</e> Battery life time seems to be worse than before.
1563     </p>
1564    
1565     <p>
1566     <e>A:</e> Check your BIOS settings. Maybe you forgot to re-enable some of the
1567     settings.
1568     </p>
1569    
1570     <p>
1571     <e>Q:</e> My battery is charged, but KDE reports there would be 0% left and
1572     immediately shuts down.
1573     </p>
1574    
1575     <p>
1576     <e>A:</e> Check that battery support is compiled into your kernel. If you use
1577     it as a module, make sure the module is loaded.
1578     </p>
1579    
1580     <p>
1581 rane 1.20 <e>Q:</e> My system logger reports things like "logger: ACPI group battery /
1582     action battery is not defined".
1583 nightmorph 1.17 </p>
1584    
1585     <p>
1586 rane 1.20 <e>A:</e> This message is generated by the <path>/etc/acpi/default.sh</path>
1587     script that is shipped with acpid. You can safely ignore it. If you like to get
1588     rid of it, you can comment the appropriate line in
1589     <path>/etc/acpi/default.sh</path> as shown below:
1590 nightmorph 1.17 </p>
1591    
1592     <pre caption="Disabling warnings about unknown acpi events">
1593     *) # logger "ACPI action $action is not defined"
1594     </pre>
1595    
1596     <p>
1597 swift 1.1 <e>Q:</e> I have a Dell Inspiron 51XX and I don't get any ACPI events.
1598     </p>
1599    
1600     <p>
1601     <e>A:</e> This seems to be a kernel bug. Read on <uri
1602     link="http://bugme.osdl.org/show_bug.cgi?id=1752">here</uri>.
1603     </p>
1604    
1605     <p>
1606 rane 1.20 <e>Q:</e> I activated the <c>DynamicClocks</c> option in <path>xorg.conf</path>
1607     and now X.org crashes / the screen stays black / my laptop doesn't shutdown
1608 so 1.15 properly.
1609     </p>
1610    
1611     <p>
1612 rane 1.20 <e>A:</e> This happens on some systems. You have to disable
1613     <c>DynamicClocks</c>.
1614 so 1.15 </p>
1615    
1616     <p>
1617 jkt 1.33 <e>Q:</e> I want to use TuxOnIce, but it tells me my swap partition is too
1618 so 1.15 small. Resizing is not an option.
1619     </p>
1620    
1621     <p>
1622 rane 1.20 <e>A:</e> If there is enough free space on your system, you can use the
1623 jkt 1.34 filewriter instead of the swapwriter. The <c>hibernate-script</c> supports it as
1624     well. More information can be found in
1625 jkt 1.33 <path>/usr/src/linux/Documentation/power/tuxonice.txt</path>.
1626 so 1.15 </p>
1627    
1628     <p>
1629 swift 1.1 <e>Q:</e> I just bought a brand new battery, but it only lasts for some
1630     minutes! What am I doing wrong?
1631     </p>
1632    
1633     <p>
1634     <e>A:</e> First follow your manufacturer's advice on how to charge the battery
1635 rane 1.20 correctly.
1636 swift 1.1 </p>
1637    
1638     <p>
1639     <e>Q:</e> The above didn't help. What should I do then?
1640     </p>
1641    
1642     <p>
1643     <e>A:</e> Some batteries sold as "new" are in fact old ones. Try the following:
1644     </p>
1645    
1646     <pre caption="Querying battery state">
1647     $ <i>grep capacity /proc/acpi/battery/BAT0/info</i>
1648     design capacity: 47520 mWh
1649     last full capacity: 41830 mWh
1650     </pre>
1651    
1652     <p>
1653     If the "last full capacity" differs significantly from the design capacity,
1654     your battery is probably broken. Try to claim your warranty.
1655     </p>
1656    
1657 swift 1.8 <p>
1658     <e>Q:</e> My problem is not listed above. Where should I go next?
1659     </p>
1660    
1661     <p>
1662 nightmorph 1.17 <e>A:</e> Don't fear to contact me, <mail link="earthwings@gentoo.org">Dennis
1663 rane 1.20 Nienhüser</mail>, directly. The <uri link="http://forums.gentoo.org">Gentoo
1664     Forums</uri> are a good place to get help as well. If you prefer IRC, try the
1665 nightmorph 1.38 <c>#gentoo-laptop</c> <uri link="irc://irc.gentoo.org">channel</uri>.
1666 swift 1.8 </p>
1667    
1668 swift 1.1 </body>
1669     </section>
1670     </chapter>
1671     </guide>

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