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Revision 1.35 - (hide annotations) (download) (as text)
Thu Jan 31 23:38:05 2008 UTC (7 years, 1 month ago) by nightmorph
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Changes since 1.34: +21 -27 lines
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bring it a little more up to date. punt outdated Xfree86 references. ibm_acpi is now known as thinkpad_acpi. for xorg.conf, DPMS is no longer a boolean variable, and screen blank settings have been moved to a different section.

1 swift 1.1 <?xml version='1.0' encoding="UTF-8"?>
2     <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3 nightmorph 1.35 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/power-management-guide.xml,v 1.34 2008/01/21 12:15:56 jkt 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 1.35 <version>1.39</version>
27     <date>2008-01-31</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     Power Management Options ---&gt;
164     [*] Power Management Support
165     [ ] Software Suspend
166    
167     ACPI( Advanced Configuration and Power Interface ) Support ---&gt;
168     [*] ACPI Support
169     [ ] Sleep States
170 so 1.15 [ ] /proc/acpi/sleep (deprecated)
171 neysx 1.12 [*] AC Adapter
172     [*] Battery
173 swift 1.1 &lt;M&gt; Button
174 so 1.15 &lt;M&gt; Video
175     [ ] Generic Hotkey
176 swift 1.1 &lt;M&gt; Fan
177     &lt;M&gt; Processor
178     &lt;M&gt; Thermal Zone
179     &lt; &gt; ASUS/Medion Laptop Extras
180 so 1.15 &lt; &gt; IBM ThinkPad Laptop Extras
181 swift 1.1 &lt; &gt; Toshiba Laptop Extras
182 so 1.15 (0) Disable ACPI for systems before Jan 1st this year
183 swift 1.1 [ ] Debug Statements
184 so 1.15 [*] Power Management Timer Support
185     &lt; &gt; ACPI0004,PNP0A05 and PNP0A06 Container Driver (EXPERIMENTAL)
186 rane 1.20
187 swift 1.1 CPU Frequency Scaling ---&gt;
188     [*] CPU Frequency scaling
189 so 1.15 [ ] Enable CPUfreq debugging
190     &lt; &gt; CPU frequency translation statistics
191     [ ] CPU frequency translation statistics details
192 swift 1.1 Default CPUFreq governor (userspace)
193     &lt;*&gt; 'performance' governor
194     &lt;*&gt; 'powersave' governor
195 swift 1.8 &lt;*&gt; 'ondemand' cpufreq policy governor
196 so 1.15 &lt;*&gt; 'conservative' cpufreq governor
197 swift 1.1 &lt;*&gt; CPU frequency table helpers
198     &lt;M&gt; ACPI Processor P-States driver
199     &lt;*&gt; <i>CPUFreq driver for your processor</i>
200     </pre>
201    
202     <p>
203 so 1.15 Decide yourself whether you want to enable Software Suspend, and Sleep States
204     (see below). If you own an ASUS, Medion, IBM Thinkpad or Toshiba laptop, enable
205 neysx 1.12 the appropriate section.
206 swift 1.8 </p>
207    
208     <p>
209 rane 1.20 The kernel has to know how to enable CPU frequency scaling on your processor.
210     As each type of CPU has a different interface, you've got to choose the right
211 rane 1.19 driver for your processor. Be careful here - enabling <c>Intel Pentium 4 clock
212     modulation</c> on a Pentium M system will lead to strange results for example.
213 swift 1.8 Consult the kernel documentation if you're unsure which one to take.
214 swift 1.1 </p>
215    
216     <p>
217     Compile your kernel, make sure the right modules get loaded at startup and boot
218 rane 1.20 into your new ACPI-enabled kernel. Next run <c>emerge sys-power/acpid</c> to
219     get the acpi daemon. This one informs you about events like switching from AC
220     to battery or closing the lid. Make sure the modules are loaded if you didn't
221     compile them into the kernel and start acpid by executing <c>/etc/init.d/acpid
222     start</c>. Run <c>rc-update add acpid default</c> to load it on startup. You'll
223     soon see how to use it.
224 swift 1.1 </p>
225    
226     <pre caption="Installing acpid">
227 yoswink 1.10 # <i>emerge sys-power/acpid</i>
228 swift 1.1 # <i>/etc/init.d/acpid start</i>
229     # <i>rc-update add acpid default</i>
230     </pre>
231    
232     </body>
233     </section>
234     <section>
235 rane 1.19 <title>Creating A "battery" Runlevel</title>
236 swift 1.1 <body>
237    
238     <p>
239     The default policy will be to enable Power Management only when needed -
240     running on batteries. To make the switch between AC and battery convenient,
241 rane 1.19 create a runlevel <c>battery</c> that holds all the scripts starting and
242 swift 1.1 stopping Power Management.
243     </p>
244    
245     <note>
246     You can safely skip this section if you don't like the idea of having another
247     runlevel. However, skipping this step will make the rest a bit trickier to set
248 rane 1.19 up. The next sections assume a runlevel <c>battery</c> exists.
249 swift 1.1 </note>
250    
251     <pre caption="Creating a battery runlevel">
252     # <i>cd /etc/runlevels</i>
253     # <i>cp -a default battery</i>
254     </pre>
255    
256     <p>
257 rane 1.19 Finished. Your new runlevel <c>battery</c> contains everything like
258     <c>default</c>, but there is no automatic switch between both yet. Time to
259 swift 1.1 change it.
260     </p>
261    
262     </body>
263     </section>
264     <section>
265 rane 1.19 <title>Reacting On ACPI Events</title>
266 swift 1.1 <body>
267    
268     <p>
269     Typical ACPI events are closing the lid, changing the power source or pressing
270 swift 1.8 the sleep button. An important event is changing the power source, which should
271 so 1.15 cause a runlevel switch. A small script will take care of it.
272     </p>
273    
274     <p>
275     First you need a script which changes the runlevel to <c>default</c>
276     respectively <c>battery</c> depending on the power source. The script uses the
277     <c>on_ac_power</c> command from <c>sys-power/powermgmt-base</c> - make sure the
278     package is installed on your system.
279     </p>
280    
281     <pre caption="Installing powermgt-base">
282 rane 1.19 # <i>emerge powermgmt-base</i>
283 so 1.15 </pre>
284    
285     <p>
286 rane 1.20 You are now able to determine the power source by executing <c>on_ac_power
287     &amp;&amp; echo AC available || echo Running on batteries</c> in a shell. The
288     script below is responsible for changing runlevels. Save it as
289 so 1.15 <path>/etc/acpi/actions/pmg_switch_runlevel.sh</path>.
290 swift 1.8 </p>
291    
292 neysx 1.12 <pre caption="/etc/acpi/actions/pmg_switch_runlevel.sh">
293 swift 1.8 #!/bin/bash
294    
295 neysx 1.12 <comment># BEGIN configuration</comment>
296 swift 1.8 RUNLEVEL_AC="default"
297     RUNLEVEL_BATTERY="battery"
298 neysx 1.12 <comment># END configuration</comment>
299 swift 1.8
300 swift 1.1
301 neysx 1.12 if [ ! -d "/etc/runlevels/${RUNLEVEL_AC}" ]
302     then
303 nightmorph 1.17 logger "${0}: Runlevel ${RUNLEVEL_AC} does not exist. Aborting."
304     exit 1
305 neysx 1.12 fi
306 swift 1.8
307 neysx 1.12 if [ ! -d "/etc/runlevels/${RUNLEVEL_BATTERY}" ]
308     then
309 nightmorph 1.17 logger "${0}: Runlevel ${RUNLEVEL_BATTERY} does not exist. Aborting."
310     exit 1
311 neysx 1.12 fi
312 swift 1.1
313 neysx 1.12 if on_ac_power
314     then
315 rane 1.19 if [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_AC}" ]]
316 nightmorph 1.17 then
317     logger "Switching to ${RUNLEVEL_AC} runlevel"
318     /sbin/rc ${RUNLEVEL_AC}
319     fi
320 rane 1.19 elif [[ "$(&lt;/var/lib/init.d/softlevel)" != "${RUNLEVEL_BATTERY}" ]]
321 neysx 1.12 then
322 nightmorph 1.17 logger "Switching to ${RUNLEVEL_BATTERY} runlevel"
323     /sbin/rc ${RUNLEVEL_BATTERY}
324 neysx 1.12 fi
325 swift 1.8 </pre>
326    
327 so 1.15 <p>
328     Dont forget to run <c>chmod +x /etc/acpi/actions/pmg_switch_runlevel.sh</c> to
329     make the script executable. The last thing that needs to be done is calling the
330     script whenever the power source changes. That's done by catching ACPI events
331     with the help of <c>acpid</c>. First you need to know which events are
332     generated when the power source changes. The events are called
333 rane 1.19 <c>ac_adapter</c> and <c>battery</c> on most laptops, but it might be different
334 so 1.15 on yours.
335     </p>
336    
337     <pre caption="Determining ACPI events for changing the power source">
338 swift 1.32 # <i>tail -f /var/log/messages | grep "received event"</i>
339 so 1.15 </pre>
340    
341     <p>
342 rane 1.20 Run the command above and pull the power cable. You should see something like
343     this:
344 so 1.15 </p>
345    
346     <pre caption="Sample output for power source changes">
347     [Tue Sep 20 17:39:06 2005] received event "ac_adapter AC 00000080 00000000"
348     [Tue Sep 20 17:39:06 2005] received event "battery BAT0 00000080 00000001"
349     </pre>
350    
351     <p>
352 rane 1.19 The interesting part is the quoted string after <c>received event</c>. It will
353 so 1.15 be matched by the event line in the files you are going to create below. Don't
354     worry if your system generates multiple events or always the same. As long as
355     any event is generated, runlevel changing will work.
356     </p>
357    
358 swift 1.8 <pre caption="/etc/acpi/events/pmg_ac_adapter">
359 neysx 1.12 <comment># replace "ac_adapter" below with the event generated on your laptop</comment>
360 so 1.15 <comment># For example, ac_adapter.* will match ac_adapter AC 00000080 00000000</comment>
361 swift 1.8 event=ac_adapter.*
362 neysx 1.12 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
363 swift 1.8 </pre>
364    
365     <pre caption="/etc/acpi/events/pmg_battery">
366 neysx 1.12 <comment># replace "battery" below with the event generated on your laptop</comment>
367 so 1.15 <comment># For example, battery.* will match battery BAT0 00000080 00000001</comment>
368 swift 1.8 event=battery.*
369 neysx 1.12 action=/etc/acpi/actions/pmg_switch_runlevel.sh %e
370 swift 1.8 </pre>
371 swift 1.1
372 swift 1.8 <p>
373 so 1.15 Finally acpid has to be restarted to recognize the changes.
374 swift 1.8 </p>
375 swift 1.1
376 swift 1.8 <pre caption="Finishing runlevel switching with acpid">
377 rane 1.19 # <i>/etc/init.d/acpid restart</i>
378 swift 1.1 </pre>
379    
380     <p>
381     Give it a try: Plug AC in and out and watch syslog for the "Switching to AC
382 rane 1.20 mode" or "Switching to battery mode" messages. See the <uri
383     link="#doc_chap8">Troubleshooting section</uri> if the script is not able to
384     detect the power source correctly.
385 swift 1.1 </p>
386    
387     <p>
388     Due to the nature of the event mechanism, your laptop will boot into runlevel
389 rane 1.19 <c>default</c> regardless of the AC/battery state. This is fine when running
390 rane 1.20 from AC, but we'd like to boot into the battery runlevel otherwise. One
391     solution would be to add another entry to the boot loader with the parameter
392 so 1.15 <c>softlevel=battery</c>, but it's likely to forget choosing it. A better way
393 rane 1.20 is faking an ACPI event in the end of the boot process and letting
394     <path>pmg_switch_runlevel.sh</path> script decide whether a runlevel change is
395     necessary. Open <path>/etc/conf.d/local.start</path> in your favourite editor
396     and add these lines:
397 swift 1.1 </p>
398    
399 so 1.15 <pre caption="Runlevel adjustment at boot time by editing local.start">
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 rane 1.20 Prepared like this you can activate Power Management policies for individual
406 swift 1.1 devices.
407     </p>
408    
409     </body>
410     </section>
411     </chapter>
412    
413     <chapter>
414     <title>CPU Power Management</title>
415     <section>
416 nightmorph 1.17 <body>
417    
418     <p>
419     Mobile processors can operate at different frequencies. Some allow changing
420     voltage as well. Most of the time your CPU doesn't need to run at full speed
421     and scaling it down will save much energy - often without any performance
422     decrease.
423     </p>
424    
425     </body>
426     </section>
427     <section>
428 rane 1.19 <title>Some Technical Terms</title>
429 swift 1.8 <body>
430    
431     <p>
432     CPU frequency scaling brings up some technical terms that might be unknown to
433     you. Here's a quick introduction.
434     </p>
435    
436     <p>
437 so 1.15 First of all, the kernel has to be able to change the processor's frequency.
438 rane 1.19 The <b>CPUfreq processor driver</b> knows the commands to do it on your CPU.
439 rane 1.20 Thus it's important to choose the right one in your kernel. You should already
440     have done it above. Once the kernel knows how to change frequencies, it has to
441     know which frequency it should set. This is done according to the <b>policy</b>
442     which consists of a <b>CPUfreq policy</b> and a <b>governor</b>. A CPUfreq
443     policy are just two numbers which define a range the frequency has to stay
444     between - minimal and maximal frequency. The governor now decides which of the
445     available frequencies in between minimal and maximal frequency to choose. For
446     example, the <b>powersave governor</b> always chooses the lowest frequency
447     available, the <b>performance governor</b> the highest one. The <b>userspace
448     governor</b> makes no decision but chooses whatever the user (or a program in
449     userspace) wants - which means it reads the frequency from
450 swift 1.8 <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed</path>.
451     </p>
452    
453     <p>
454     This doesn't sound like dynamic frequency changes yet and in fact it isn't.
455 rane 1.20 Dynamics however can be accomplished with various approaches. For example, the
456     <b>ondemand governor</b> makes its decisions depending on the current CPU load.
457     The same is done by various userland tools like <c>cpudyn</c>, <c>cpufreqd</c>,
458     <c>powernowd</c> and many more. ACPI events can be used to enable or disable
459     dynamic frequency changes depending on power source.
460 swift 1.8 </p>
461    
462     </body>
463     </section>
464     <section>
465 rane 1.19 <title>Setting The Frequency Manually</title>
466 swift 1.1 <body>
467    
468     <p>
469     Decreasing CPU speed and voltage has two advantages: On the one hand less
470     energy is consumed, on the other hand there is thermal improvement as your
471     system doesn't get as hot as running on full speed. The main disadvantage is
472     obviously the loss of performance. Decreasing processor speed is a trade off
473     between performance loss and energy saving.
474     </p>
475    
476     <note>
477     Not every laptop supports frequency scaling. If unsure, have a look at the list
478 rane 1.19 of supported processors in the <uri link="#doc_chap8">Troubleshooting</uri>
479     section to verify yours is supported.
480 swift 1.1 </note>
481    
482     <p>
483 neysx 1.12 It's time to test whether CPU frequency changing works. Let's install another
484     tool which is very handy for debugging purposes: <c>sys-power/cpufrequtils</c>
485 swift 1.1 </p>
486    
487 neysx 1.12 <pre caption="Checking CPU frequency">
488     # <i>emerge cpufrequtils</i>
489     # <i>cpufreq-info</i>
490 swift 1.1 </pre>
491    
492     <p>
493 neysx 1.12 Here is an example output:
494 swift 1.1 </p>
495    
496 neysx 1.12 <pre caption="Sample output from cpufreq-info">
497 so 1.15 cpufrequtils 0.3: cpufreq-info (C) Dominik Brodowski 2004
498 neysx 1.12 Report errors and bugs to linux@brodo.de, please.
499     analyzing CPU 0:
500     driver: centrino
501     CPUs which need to switch frequency at the same time: 0
502     hardware limits: 600 MHz - 1.40 GHz
503     available frequency steps: 600 MHz, 800 MHz, 1000 MHz, 1.20 GHz, 1.40 GHz
504 so 1.15 available cpufreq governors: conservative, ondemand, powersave, userspace, performance
505 neysx 1.12 current policy: frequency should be within 924 MHz and 1.40 GHz.
506     The governor "performance" may decide which speed to use
507     within this range.
508 so 1.15 current CPU frequency is 1.40 GHz.
509 neysx 1.12 </pre>
510    
511 swift 1.1 <p>
512 neysx 1.12 Now play around with <c>cpufreq-set</c> to make sure frequency switching works.
513     Run <c>cpufreq-set -g ondemand</c> for example to activate the ondemand
514     governor and verify the change with <c>cpufreq-info</c>. If it doesn't work as
515 rane 1.20 expected, you might find help in the <uri link="#doc_chap8">Troubleshooting
516     section</uri> in the end of this guide.
517 swift 1.1 </p>
518    
519     </body>
520     </section>
521     <section>
522     <title>Automated frequency adaption</title>
523     <body>
524    
525     <p>
526     The above is quite nice, but not doable in daily life. Better let your system
527 so 1.15 set the appropriate frequency automatically. There are many different
528     approaches to do this. The following table gives a quick overview to help you
529 rane 1.21 decide on one of them. It's roughly separated in three categories <b>kernel</b>
530 rane 1.20 for approaches that only need kernel support, <b>daemon</b> for programs that
531     run in the background and <b>graphical</b> for programs that provide a GUI for
532     easy configuration and changes.
533 swift 1.1 </p>
534    
535     <table>
536     <tr>
537     <th>Name</th>
538 swift 1.8 <th>Category</th>
539     <th>Switch decision</th>
540     <th>Kernel governors</th>
541     <th>Further governors</th>
542     <th>Comments</th>
543     </tr>
544     <tr>
545     <ti>'ondemand' governor</ti>
546     <ti>Kernel</ti>
547     <ti>CPU load</ti>
548     <ti>N.A.</ti>
549     <ti>N.A.</ti>
550     <ti>
551 so 1.15 Chooses maximal frequency on CPU load and slowly steps down when the CPU is
552     idle. Further tuning through files in
553 swift 1.8 <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
554     userland tools (programs, scripts) if governor switching or similar is
555     desired.
556     </ti>
557 swift 1.1 </tr>
558     <tr>
559 so 1.15 <ti>'conservative' governor</ti>
560     <ti>Kernel</ti>
561     <ti>CPU load</ti>
562     <ti>N.A.</ti>
563     <ti>N.A.</ti>
564     <ti>
565 neysx 1.16 Unlike the ondemand governor, conversative doesn't jump to maximum
566     frequency when CPU load is high, but increases the frequency step by step.
567     Further tuning through files in
568     <path>/sys/devices/system/cpu/cpu0/cpufreq/ondemand/</path>. Still requires
569     userland tools (programs, scripts) if governor switching or similar is
570     desired.
571 so 1.15 </ti>
572     </tr>
573     <tr>
574 swift 1.1 <ti><uri link="http://mnm.uib.es/~gallir/cpudyn/">cpudyn</uri></ti>
575 swift 1.8 <ti>Daemon</ti>
576     <ti>CPU load</ti>
577 neysx 1.12 <ti>Performance, powersave</ti>
578 swift 1.8 <ti>Dynamic</ti>
579     <ti>
580     Also supports disk standby - notice however that <e>laptop mode</e> in most
581     cases will do a better job.
582     </ti>
583 swift 1.1 </tr>
584     <tr>
585 swift 1.8 <ti><uri link="http://sourceforge.net/projects/cpufreqd/">cpufreqd</uri></ti>
586     <ti>Daemon</ti>
587 nightmorph 1.17 <ti>Battery state, CPU load, temperature, running programs and more</ti>
588 swift 1.8 <ti>All available</ti>
589     <ti>None</ti>
590     <ti>
591 nightmorph 1.17 Sophisticated (but somewhat complicated) setup. Extendible through plugins
592     like sensor monitoring (lm_sensors) or coordinating some NVidia based
593     graphics card memory and core. Cpufreqd is SMP aware and can optionally be
594     controlled manually at runtime.
595 swift 1.8 </ti>
596     </tr>
597     <tr>
598     <ti>
599     <uri link="http://www.deater.net/john/powernowd.html">powernowd</uri>
600     </ti>
601     <ti>Daemon</ti>
602     <ti>CPU load</ti>
603     <ti>None</ti>
604     <ti>Passive, sine, aggressive</ti>
605     <ti>
606     Supports SMP.
607     </ti>
608 swift 1.1 </tr>
609     <tr>
610 nightmorph 1.31 <ti>
611     <uri
612     link="http://projects.simpledesigns.com.pl/project/ncpufreqd/">ncpufreqd</uri>
613     </ti>
614 so 1.15 <ti>Daemon</ti>
615     <ti>Temperature</ti>
616     <ti>None</ti>
617     <ti>Powersave, performance</ti>
618     <ti>
619     Toggles the used governor between performance and powersave depending on
620     system temperature. Very useful on laptops with notorious heat problems.
621     </ti>
622     </tr>
623     <tr>
624 swift 1.1 <ti><uri link="http://www.goop.org/~jeremy/speedfreq/">speedfreq</uri></ti>
625 swift 1.8 <ti>Daemon</ti>
626     <ti>CPU load</ti>
627     <ti>None</ti>
628     <ti>Dynamic, powersave, performance, fixed speed</ti>
629     <ti>
630 so 1.15 Easy to configure with a nice client/server interface. Requires a 2.6
631     kernel. Unmaintained, broken and thus removed from Portage. Please switch
632     to cpufreqd if you're still using it.
633 swift 1.8 </ti>
634     </tr>
635     <tr>
636     <ti><uri link="http://cpuspeedy.sourceforge.net/">gtk-cpuspeedy</uri></ti>
637     <ti>Graphical</ti>
638     <ti>None</ti>
639     <ti>None</ti>
640     <ti>None</ti>
641 swift 1.1 <ti>
642 swift 1.8 Gnome application, a graphical tool to set CPU frequency manually. It does
643 neysx 1.12 not offer any automation.
644 swift 1.1 </ti>
645     </tr>
646     <tr>
647 swift 1.8 <ti>klaptopdaemon</ti>
648     <ti>Graphical</ti>
649     <ti>Battery state</ti>
650     <ti>All available</ti>
651     <ti>None</ti>
652     <ti>
653     KDE only, 'ondemand' governor required for dynamic frequency scaling.
654     </ti>
655 swift 1.1 </tr>
656     </table>
657    
658     <p>
659 so 1.15 While adjusting the frequency to the current load looks simple at a first
660     glance, it's not such a trivial task. A bad algorithm can cause switching
661     between two frequencies all the time or wasting energy when setting frequency
662 rane 1.20 to an unnecessary high level.
663 swift 1.1 </p>
664    
665     <p>
666 neysx 1.12 Which one to choose? If you have no idea about it, try <c>cpufreqd</c>:
667 swift 1.1 </p>
668    
669     <pre caption="Installing cpufreqd">
670     # <i>emerge cpufreqd</i>
671     </pre>
672    
673     <p>
674 neysx 1.12 <c>cpufreqd</c> can be configured by editing <path>/etc/cpufreqd.conf</path>.
675     The default one that ships with cpufreqd may look a bit confusing. I recommend
676 nightmorph 1.22 replacing it with the one from former Gentoo developer Henrik Brix Andersen
677     (see below). Please notice that you need cpufreqd-2.0.0 or later. Earlier
678     versions have a different syntax for the config file.
679 swift 1.1 </p>
680    
681 nightmorph 1.17 <pre caption="/etc/cpufreqd.conf (cpufreqd-2.0.0 and later)">
682 swift 1.1 [General]
683     pidfile=/var/run/cpufreqd.pid
684 nightmorph 1.17 poll_interval=3
685     enable_plugins=acpi_ac, acpi_battery
686 nightmorph 1.18 enable_remote=1
687     remote_group=wheel
688 neysx 1.12 verbosity=5
689 nightmorph 1.17 [/General]
690 swift 1.1
691     [Profile]
692 neysx 1.12 name=ondemand
693     minfreq=0%
694     maxfreq=100%
695     policy=ondemand
696 nightmorph 1.17 [/Profile]
697 swift 1.1
698     [Profile]
699 so 1.15 name=conservative
700     minfreq=0%
701     maxfreq=100%
702     policy=conservative
703 nightmorph 1.17 [/Profile]
704 so 1.15
705     [Profile]
706 neysx 1.12 name=powersave
707     minfreq=0%
708     maxfreq=100%
709 swift 1.1 policy=powersave
710 nightmorph 1.17 [/Profile]
711 swift 1.1
712     [Profile]
713 neysx 1.12 name=performance
714     minfreq=0%
715     maxfreq=100%
716     policy=performance
717 nightmorph 1.17 [/Profile]
718 swift 1.1
719     [Rule]
720 neysx 1.12 name=battery
721     ac=off
722 so 1.15 profile=conservative
723 nightmorph 1.17 [/Rule]
724 swift 1.1
725     [Rule]
726 neysx 1.12 name=battery_low
727 swift 1.1 ac=off
728 neysx 1.12 battery_interval=0-10
729     profile=powersave
730 nightmorph 1.17 [/Rule]
731 swift 1.1
732     [Rule]
733 neysx 1.12 name=ac
734     ac=on
735 so 1.15 profile=ondemand
736 nightmorph 1.17 [/Rule]
737 neysx 1.12 </pre>
738    
739     <p>
740 rane 1.19 Now you can start the cpufreqd daemon. Add it to the <c>default</c> and
741     <c>battery</c> runlevel as well.
742 swift 1.1 </p>
743    
744 neysx 1.12 <pre caption="Starting cpufreqd">
745     # <i>rc-update add cpufreqd default battery</i>
746     # <i>rc</i>
747     </pre>
748    
749 nightmorph 1.17 <p>
750     Sometimes it can be desirable to select another policy than the daemon chooses,
751     for example when battery power is low, but you know that AC will be available
752 rane 1.20 soon. In that case you can turn on cpufreqd's manual mode with <c>cpufreqd-set
753     manual</c> and select one of your configured policies (as listed by
754     <c>cpufreqd-get</c>). You can leave manual mode by executing <c>cpufreqd-set
755     dynamic</c>.
756 nightmorph 1.17 </p>
757    
758 neysx 1.12 <warn>
759     Do not run more than one of the above programs at the same time. It may cause
760     confusion like switching between two frequencies all the time.
761     </warn>
762    
763 swift 1.8 </body>
764     </section>
765     <section>
766     <title>Verifying the result</title>
767     <body>
768    
769 swift 1.1 <p>
770     The last thing to check is that your new policies do a good job. An easy way to
771 swift 1.8 do so is monitoring CPU speed while working with your laptop:
772 swift 1.1 </p>
773    
774     <pre caption="Monitoring CPU speed">
775 yoswink 1.13 # <i>watch grep \"cpu MHz\" /proc/cpuinfo</i>
776 swift 1.1 </pre>
777    
778     <p>
779 rane 1.20 If <path>/proc/cpuinfo</path> doesn't get updated (see <uri
780 swift 1.32 link="#doc_chap8">Troubleshooting</uri>), monitor the CPU frequency with
781     <c>sys-apps/x86info</c>:
782 swift 1.1 </p>
783    
784     <pre caption="Alternative CPU speed monitoring">
785 neysx 1.12 # <i>watch x86info -mhz</i>
786 swift 1.1 </pre>
787    
788     <p>
789     Depending on your setup, CPU speed should increase on heavy load, decrease on
790 rane 1.19 no activity or just stay at the same level. When using <c>cpufreqd</c> and
791 rane 1.20 verbosity set to 5 or higher in <path>cpufreqd.conf</path> you'll get
792     additional information about what's happening reported to <c>syslog</c>.
793 swift 1.1 </p>
794    
795     </body>
796     </section>
797     </chapter>
798    
799     <chapter>
800     <title>LCD Power Management</title>
801     <section>
802     <body>
803    
804     <p>
805 rane 1.20 As you can see in <uri link="#doc_chap1_fig1">figure 1.1</uri>, the LCD
806     display consumes the biggest part of energy (might not be the case for
807     non-mobile CPU's). Thus it's quite important not only to shut the display off
808     when not needed, but also to reduce it's backlight if possible. Most laptops
809     offer the possibility to control the backlight dimming.
810 swift 1.1 </p>
811    
812 nightmorph 1.17 </body>
813     </section>
814     <section>
815     <title>Standby settings</title>
816     <body>
817    
818 swift 1.1 <p>
819 nightmorph 1.17 The first thing to check is the standby/suspend/off timings of the display. As
820     this depends heavily on your windowmanager, I'll let you figure it out
821 rane 1.20 yourself. Just two common places: Blanking the terminal can be done with
822 nightmorph 1.17 <c>setterm -blank &lt;number-of-minutesM&gt;</c>, <c>setterm -powersave on</c>
823     and <c>setterm -powerdown &lt;number-of-minutesM&gt;</c>. For X.org, modify
824     <path>/etc/X11/xorg.conf</path> similar to this:
825 swift 1.1 </p>
826    
827 nightmorph 1.35 <pre caption="LCD suspend settings in X.org">
828     Section "ServerFlags"
829     Option "blank time" "5" <comment># Blank the screen after 5 minutes (Fake)</comment>
830     Option "standby time" "10" <comment># Turn off screen after 10 minutes (DPMS)</comment>
831     Option "suspend time" "20" <comment># Full suspend after 20 minutes</comment>
832     Option "off time" "30" <comment># Turn off after half an hour</comment>
833 swift 1.1 [...]
834     EndSection
835    
836     [...]
837    
838     Section "Monitor"
839     Identifier [...]
840 nightmorph 1.35 Option "DPMS"
841 swift 1.1 [...]
842     EndSection
843     </pre>
844    
845 nightmorph 1.17 </body>
846     </section>
847     <section>
848     <title>Backlight dimming</title>
849     <body>
850    
851 swift 1.1 <p>
852     Probably more important is the backlight dimming. If you have access to the
853     dimming settings via a tool, write a small script that dims the backlight in
854 rane 1.19 battery mode and place it in your <c>battery</c> runlevel. The following script
855 nightmorph 1.17 should work on most IBM Thinkpads and Toshiba laptops. You've got to enable the
856 rane 1.20 appropriate option in your kernel (IBM Thinkpads only). For Toshiba laptops,
857 nightmorph 1.35 install <c>sys-power/acpitool</c> and skip configuration of <c>thinkpad_acpi</c>
858     (formerly called <c>ibm_acpi</c>) as described below.
859 neysx 1.12 </p>
860    
861     <warn>
862 nightmorph 1.35 Support for setting brightness is marked experimental in thinkpad_acpi. It accesses
863 neysx 1.12 hardware directly and may cause severe harm to your system. Please read the
864 nightmorph 1.35 <uri link="http://ibm-acpi.sourceforge.net/">thinkpad_acpi website</uri>
865 neysx 1.12 </warn>
866    
867     <p>
868 nightmorph 1.35 To be able to set the brightness level, the thinkpad_acpi module has to be loaded
869 neysx 1.12 with the experimental parameter.
870     </p>
871    
872 nightmorph 1.35 <pre caption="automatically loading the thinkpad_acpi module">
873 neysx 1.12 <comment>(Please read the warnings above before doing this!)</comment>
874 nightmorph 1.35 # <i>echo "options thinkpad_acpi experimental=1" >> /etc/modules.d/thinkpad_acpi</i>
875 nightmorph 1.26 # <i>/sbin/update-modules</i>
876 nightmorph 1.35 # <i>echo thinkpad_acpi >> /etc/modules.autoload.d/kernel-2.6</i>
877     # <i>modprobe thinkpad_acpi</i>
878 neysx 1.12 </pre>
879    
880     <p>
881     This should work without error messages and a file
882     <path>/proc/acpi/ibm/brightness</path> should be created after loading the
883 rane 1.20 module. An init script will take care of choosing the brightness according to
884     the power source.
885 neysx 1.12 </p>
886    
887     <pre caption="/etc/conf.d/lcd-brightness">
888     <comment># See /proc/acpi/ibm/brightness for available values</comment>
889 nightmorph 1.35 <comment># Please read /usr/src/linux/Documentation/thinkpad-acpi.txt</comment>
890 neysx 1.12
891 nightmorph 1.23 <comment># brightness level in ac mode. Default is 7.</comment>
892 neysx 1.12 BRIGHTNESS_AC=7
893    
894     <comment># brightness level in battery mode. Default is 4.</comment>
895     BRIGHTNESS_BATTERY=4
896     </pre>
897    
898     <pre caption="/etc/init.d/lcd-brightness">
899     #!/sbin/runscript
900    
901     set_brightness() {
902     if on_ac_power
903     then
904     LEVEL=${BRIGHTNESS_AC:-7}
905     else
906     LEVEL=${BRIGHTNESS_BATTERY:-4}
907     fi
908    
909     if [ -f /proc/acpi/ibm/brightness ]
910     then
911     ebegin "Setting LCD brightness"
912     echo "level ${LEVEL}" > /proc/acpi/ibm/brightness
913     eend $?
914 nightmorph 1.17 elif [[ -e /usr/bin/acpitool &amp;&amp; -n $(acpitool -T | grep "LCD brightness") ]]
915     then
916     ebegin "Setting LCD brightness"
917     acpitool -l $LEVEL >/dev/null || ewarn "Unable to set lcd brightness"
918     eend $?
919 neysx 1.12 else
920     ewarn "Setting LCD brightness is not supported."
921 nightmorph 1.35 ewarn "For IBM Thinkpads, check that thinkpad_acpi is loaded into the kernel"
922 nightmorph 1.23 ewarn "For Toshiba laptops, you've got to install sys-power/acpitool"
923 neysx 1.12 fi
924     }
925    
926     start() {
927     set_brightness
928     }
929    
930     stop () {
931     set_brightness
932     }
933     </pre>
934    
935     <p>
936     When done, make sure brightness is adjusted automatically by adding it to the
937     battery runlevel.
938 swift 1.1 </p>
939    
940 neysx 1.12 <pre caption="Enabling automatic brightness adjustment">
941 rane 1.19 # <i>chmod +x /etc/init.d/lcd-brightness</i>
942     # <i>rc-update add lcd-brightness battery</i>
943     # <i>rc</i>
944 neysx 1.12 </pre>
945    
946 swift 1.1 </body>
947     </section>
948     </chapter>
949    
950     <chapter>
951     <title>Disk Power Management</title>
952     <section>
953 nightmorph 1.17 <body>
954 rane 1.19
955 nightmorph 1.17 <p>
956     Hard disks consume less energy in sleep mode. Therefore it makes sense to
957     activate power saving features whenever the hard disk is not used for a certain
958     amount of time. I'll show you two alternative possibilities to do it. First,
959     laptop-mode will save most energy due to several measures which prevent or at
960     least delay write accesses. The drawback is that due to the delayed write
961     accesses a power outage or kernel crash will be more dangerous for data loss.
962     If you don't like this, you have to make sure that there are no processes which
963     write to your hard disk frequently. Afterwards you can enable power saving
964 rane 1.19 features of your hard disk with <c>hdparm</c> as the second alternative.
965 nightmorph 1.17 </p>
966    
967     </body>
968     </section>
969     <section>
970     <title>Increasing idle time - laptop-mode</title>
971 swift 1.1 <body>
972    
973     <p>
974 nightmorph 1.27 Recent 2.6 kernels include the so-called <c>laptop-mode</c>. When activated,
975     dirty buffers are written to disk on read calls or after 10 minutes (instead of
976     30 seconds). This minimizes the time the hard disk needs to be spun up.
977 swift 1.1 </p>
978    
979 nightmorph 1.17 <pre caption="Automated start of laptop-mode">
980     # <i>emerge laptop-mode-tools</i>
981     </pre>
982 swift 1.1
983 nightmorph 1.17 <p>
984     <c>laptop-mode-tools</c> has its configuration file in
985     <path>/etc/laptop-mode/laptop-mode.conf</path>. Adjust it the way you like it,
986     it's well commented. Run <c>rc-update add laptop_mode battery</c> to start it
987     automatically.
988     </p>
989    
990     <p>
991     Recent versions (1.11 and later) of laptop-mode-tools include a new tool
992     <c>lm-profiler</c>. It will monitor your system's disk usage and running
993     network services and suggests to disable unneeded ones. You can either disable
994     them through laptop-mode-tools builtin runlevel support (which will be reverted
995 rane 1.19 by Gentoo's <c>/sbin/rc</c>) or use your <c>default</c>/<c>battery</c>
996 nightmorph 1.17 runlevels (recommended).
997     </p>
998    
999     <pre caption="Sample output from running lm-profiler">
1000 rane 1.19 # <i>lm-profiler</i>
1001 nightmorph 1.17 Profiling session started.
1002     Time remaining: 600 seconds
1003     [4296896.602000] amarokapp
1004     Time remaining: 599 seconds
1005     [4296897.714000] sort
1006     [4296897.970000] mv
1007     Time remaining: 598 seconds
1008     Time remaining: 597 seconds
1009     [4296900.482000] reiserfs/0
1010     </pre>
1011    
1012     <p>
1013     After profiling your system for ten minutes, lm-profiler will present a list of
1014     services which might have caused disk accesses during that time.
1015     </p>
1016    
1017     <pre caption="lm-profiler suggests to disable some services">
1018     Program: "atd"
1019     Reason: standard recommendation (program may not be running)
1020     Init script: /etc/init.d/atd (GUESSED)
1021    
1022 rane 1.19 Do you want to disable this service in battery mode? [y/N]: <i>n</i>
1023 swift 1.1 </pre>
1024    
1025     <p>
1026 nightmorph 1.17 To disable atd as suggested in the example above, you would run <c>rc-update
1027     del atd battery</c>. Be careful not to disable services that are needed for
1028 rane 1.20 your system to run properly - <c>lm-profiler</c> is likely to generate some
1029     false positives. Do not disable a service if you are unsure whether it's
1030     needed.
1031 nightmorph 1.17 </p>
1032    
1033     </body>
1034     </section>
1035     <section>
1036 rane 1.19 <title>Limiting Write Accesses</title>
1037 nightmorph 1.17 <body>
1038    
1039     <p>
1040     If you don't want to use laptop-mode, you must take special care to disable
1041     services that write to your disk frequently - <c>syslogd</c> is a good
1042     candidate, for example. You probably don't want to shut it down completely, but
1043     it's possible to modify the config file so that "unnecessary" things don't get
1044 rane 1.20 logged and thus don't create disk traffic. <c>Cups</c> writes to disk
1045     periodically, so consider shutting it down and only enable it manually when
1046     needed.
1047 nightmorph 1.17 </p>
1048    
1049     <pre caption="Disabling cups in battery mode">
1050     # <i>rc-update del cupsd battery</i>
1051     </pre>
1052    
1053     <p>
1054     You can also use <c>lm-profiler</c> from laptop-mode-tools (see above) to find
1055     services to disable. Once you eliminated all of them, go on with configuring
1056     hdparm.
1057     </p>
1058    
1059     </body>
1060     </section>
1061     <section>
1062     <title>hdparm</title>
1063     <body>
1064    
1065     <p>
1066 nightmorph 1.28 The second possibility is using <c>hdparm</c>. Skip this if
1067     you are using laptop-mode. Otherwise, edit <path>/etc/conf.d/hdparm</path> and
1068     add the following values to your drive entries. This example assumes your hard
1069     drive is called <b>hda</b>:
1070 swift 1.1 </p>
1071    
1072 nightmorph 1.28 <pre caption="Using /etc/conf.d/hdparm for disk standby">
1073     hda_args="-q -S12"
1074     </pre>
1075 neysx 1.12
1076 nightmorph 1.28 <p>
1077     This will activate power management for your hard drive. If you ever want to
1078     deactivate power management, you can edit <path>/etc/conf.d/hdparm</path> and
1079     change the values to <c>-q -S0</c>, or just run <c>hdparm -q -S0 /dev/hda</c>.
1080     </p>
1081 swift 1.1
1082     <p>
1083 nightmorph 1.28 See <c>man hdparm</c> for the options. Though you can always start <c>hdparm</c>
1084     manually when you are on battery power by running <c>/etc/init.d/hdparm
1085     start</c>, it's much easier to automate its startup and shutdown. To do so, add
1086     <c>hdparm</c> to the battery runlevel so that it will automatically enable power
1087     management.
1088 swift 1.1 </p>
1089    
1090     <pre caption="Automate disk standby settings">
1091 nightmorph 1.28 # <i>rc-update add hdparm battery</i>
1092 swift 1.1 </pre>
1093    
1094     <impo>
1095     Be careful with sleep/spin down settings of your hard drive. Setting it to
1096     small values might wear out your drive and lose warranty.
1097     </impo>
1098    
1099     </body>
1100     </section>
1101     <section>
1102     <title>Other tricks</title>
1103     <body>
1104    
1105     <p>
1106     Another possibility is to deactivate swap in battery mode. Before writing a
1107     swapon/swapoff switcher, make sure there is enough RAM and swap isn't used
1108     heavily, otherwise you'll be in big problems.
1109     </p>
1110    
1111     <p>
1112     If you don't want to use laptop-mode, it's still possible to minimize disk
1113 rane 1.19 access by mounting certain directories as <c>tmpfs</c> - write accesses are not
1114 swift 1.1 stored on a disk, but in main memory and get lost with unmounting. Often it's
1115     useful to mount <path>/tmp</path> like this - you don't have to pay special
1116     attention as it gets cleared on every reboot regardless whether it was mounted
1117     on disk or in RAM. Just make sure you have enough RAM and no program (like a
1118     download client or compress utility) needs extraordinary much space in
1119     <path>/tmp</path>. To activate this, enable tmpfs support in your kernel and
1120     add a line to <path>/etc/fstab</path> like this:
1121     </p>
1122    
1123     <pre caption="Editing /etc/fstab to make /tmp even more volatile">
1124     none /tmp tmpfs size=32m 0 0
1125     </pre>
1126    
1127     <warn>
1128     Pay attention to the size parameter and modify it for your system. If you're
1129 rane 1.21 unsure, don't try this at all, it can become a performance bottleneck easily. In
1130 swift 1.1 case you want to mount <path>/var/log</path> like this, make sure to merge the
1131     log files to disk before unmounting. They are essential. Don't attempt to mount
1132 rane 1.19 <path>/var/tmp</path> like this. Portage uses it for compiling...
1133 swift 1.1 </warn>
1134    
1135     </body>
1136     </section>
1137     </chapter>
1138    
1139     <chapter>
1140 rane 1.19 <title>Power Management For Other Devices</title>
1141 swift 1.1 <section>
1142 rane 1.19 <title>Graphics Cards</title>
1143 so 1.15 <body>
1144    
1145     <p>
1146     In case you own an ATI graphics card supporting PowerPlay (dynamic clock
1147 nightmorph 1.25 scaling for the graphics processing unit GPU), you can activate this
1148 rane 1.20 feature in X.org. Open <path>/etc/X11/xorg.conf</path> and add (or enable) the
1149     <c>DynamicClocks</c> option in the Device section. Please notice that this
1150     feature will lead to crashes on some systems.
1151 so 1.15 </p>
1152    
1153     <pre caption="Enabling ATI PowerPlay support in X.org">
1154     Section "Device"
1155     [...]
1156     Option "DynamicClocks" "on"
1157     EndSection
1158     </pre>
1159    
1160     </body>
1161     </section>
1162     <section>
1163 swift 1.1 <title>Wireless Power Management</title>
1164     <body>
1165    
1166     <p>
1167 nightmorph 1.17 Wireless LAN cards consume quite a bit of energy. Put them in Power Management
1168 nightmorph 1.28 mode just like your hard drives.
1169 swift 1.1 </p>
1170    
1171 nightmorph 1.17 <note>
1172     This script assumes your wireless interface is called <c>wlan0</c>; replace
1173     this with the actual name of your interface.
1174     </note>
1175    
1176 nightmorph 1.28 <p>
1177 nightmorph 1.29 Add the following option to <path>/etc/conf.d/net</path> to automatically enable
1178 nightmorph 1.28 power management for your wireless card:
1179     </p>
1180 swift 1.1
1181 nightmorph 1.28 <pre caption="Automated WLAN Power Management">
1182     iwconfig_wlan0="power on"
1183 swift 1.1 </pre>
1184    
1185     <p>
1186 nightmorph 1.28 See <c>man iwconfig</c> for details and more options like the period between
1187     wakeups or timeout settings. If your driver and access point support changing
1188     the beacon time, this is a good starting point to save even more energy.
1189 swift 1.1 </p>
1190    
1191     </body>
1192     </section>
1193     <section>
1194     <title>USB Power Management</title>
1195     <body>
1196    
1197     <p>
1198     There are two problems with USB devices regarding energy consumption: First,
1199     devices like USB mice, digital cameras or USB sticks consume energy while
1200     plugged in. You cannot avoid this (nevertheless remove them in case they're not
1201     needed). Second, when there are USB devices plugged in, the USB host controller
1202     periodically accesses the bus which in turn prevents the CPU from going into
1203 rane 1.20 sleep mode. The kernel offers an experimental option to enable suspension of
1204 so 1.15 USB devices through driver calls or one of the <path>power/state</path> files
1205     in <path>/sys</path>.
1206 swift 1.1 </p>
1207    
1208 so 1.15 <pre caption="Enabling USB suspend support in the kernel">
1209     Device Drivers
1210     USB support
1211     [*] Support for Host-side USB
1212     [*] USB suspend/resume (EXPERIMENTAL)
1213     </pre>
1214    
1215 swift 1.1 </body>
1216     </section>
1217     </chapter>
1218    
1219     <chapter>
1220 rane 1.19 <title>Sleep States: sleep, standby, and suspend to disk</title>
1221 swift 1.1 <section>
1222     <body>
1223    
1224     <p>
1225     ACPI defines different sleep states. The more important ones are
1226     </p>
1227    
1228 rane 1.20 <ul>
1229 swift 1.1 <li>S1 aka Standby</li>
1230     <li>S3 aka Suspend to RAM aka Sleep</li>
1231     <li>S4 aka Suspend to Disk aka Hibernate</li>
1232     </ul>
1233    
1234     <p>
1235     They can be called whenever the system is not in use, but a shutdown is not
1236     wanted due to the long boot time.
1237     </p>
1238    
1239     </body>
1240     </section>
1241     <section>
1242 so 1.15 <title>Sleep (S3)</title>
1243 swift 1.1 <body>
1244    
1245     <p>
1246 so 1.15 The ACPI support for these sleep states is marked experimental for good reason.
1247     APM sleep states seem to be more stable, however you can't use APM and ACPI
1248     together.
1249     </p>
1250    
1251     <pre caption="Kernel configuration for the various suspend types">
1252     Power Management Options ---&gt;
1253     [*] Power Management support
1254     ACPI (Advanced Configuration and Power Interface) Support ---&gt;
1255     [*] ACPI Support
1256     [*] Sleep States
1257     </pre>
1258    
1259     <p>
1260 nightmorph 1.17 Once your kernel is properly configured, you can use the
1261 so 1.15 <c>hibernate-script</c> to activate suspend or sleep mode. Let's install that
1262     first.
1263     </p>
1264    
1265     <pre caption="Installing the hibernate-script">
1266 rane 1.19 # <i>emerge hibernate-script</i>
1267 so 1.15 </pre>
1268    
1269     <p>
1270 nightmorph 1.25 Some configuration has to be done in <path>/etc/hibernate</path>. The default
1271 nightmorph 1.24 package introduces a few configuration files for each sleep state. Options that
1272     are common to all suspend methods are placed in <path>common.conf</path>; make
1273     sure this file is properly set up for your system.
1274 so 1.15 </p>
1275    
1276     <p>
1277 nightmorph 1.24 To configure sleep, edit <path>sysfs-ram.conf</path> in
1278     <path>/etc/hibernate</path>. <c>UseSysfsPowerState mem</c> is already setup
1279 nightmorph 1.25 correctly, but if you need to make further changes to this particular sleep
1280     state (or any other sleep state) you should add them to
1281 nightmorph 1.24 <path>/etc/hibernate/hibernate.conf</path>. The comments and option names will
1282     guide you. If you use nfs or samba shares over the network, make sure to
1283     shutdown the appropriate init scripts to avoid timeouts.
1284 so 1.15 </p>
1285    
1286 nightmorph 1.24 <note>
1287     For more information on setting up sleep states, read <c>man
1288     hibernate.conf</c>.
1289     </note>
1290    
1291 so 1.15 <p>
1292     Ready? Now is the last chance to backup any data you want to keep after
1293     executing the next command. Notice that you probably have to hit a special key
1294 rane 1.19 like <c>Fn</c> to resume from sleep.
1295 so 1.15 </p>
1296    
1297     <pre caption="Calling sleep">
1298 rane 1.19 # <i>hibernate-ram</i>
1299 so 1.15 </pre>
1300    
1301     <p>
1302 rane 1.20 If you're still reading, it seems to work. You can also setup standby (S1) in a
1303 nightmorph 1.24 similar way by editing <path>sysfs-ram.conf</path> and changing
1304     "UseSysfsPowerState mem" to "UseSysfsPowerState standby". S3 and S4 are the more
1305     interesting sleep states due to greater energy savings however.
1306 so 1.15 </p>
1307    
1308     </body>
1309     </section>
1310     <section>
1311     <title>Hibernate (S4)</title>
1312     <body>
1313    
1314     <p>
1315     This section introduces hibernation, where a snapshot of the running system is
1316     written to disk before powering off. On resume, the snapshot is loaded and you
1317     can go on working at exactly the point you called hibernate before.
1318 swift 1.1 </p>
1319    
1320     <warn>
1321 so 1.15 Don't exchange non hot-pluggable hardware when suspended. Don't attempt to load
1322     a snapshot with a different kernel image than the one it was created with.
1323     Shutdown any NFS or samba server/client before hibernating.
1324 swift 1.1 </warn>
1325    
1326     <p>
1327 so 1.15 There are two different implementations for S4. The original one is swsusp,
1328 jkt 1.33 then there is the newer tuxonice (former suspend2) with a nicer interface (including fbsplash
1329     support). A <uri link="http://tuxonice.net/features.html#compare"> feature
1330     comparison</uri> is available at the <uri link="http://www.tuxonice.net">tuxonice
1331 rane 1.20 Homepage</uri>. There used to be Suspend-to-Disk (pmdisk), a fork of swsusp,
1332     but it has been merged back.
1333 swift 1.1 </p>
1334    
1335     <p>
1336 jkt 1.33 TuxOnIce is not included in the mainline kernel yet, therefore you either have
1337 rane 1.20 to patch your kernel sources with the patches provided by <uri
1338 jkt 1.33 link="http://tuxonice.net">tuxonice.net</uri> or use
1339     <c>sys-kernel/tuxonice-sources</c>.
1340 swift 1.1 </p>
1341    
1342     <p>
1343 jkt 1.33 The kernel part for both swusp and TuxOnIce is as follows:
1344 swift 1.1 </p>
1345    
1346     <pre caption="Kernel configuration for the various suspend types">
1347     Power Management Options ---&gt;
1348     <comment>(hibernate with swsusp)</comment>
1349 so 1.15 [*] Software Suspend
1350     <comment>(replace /dev/SWAP with your swap partition)</comment>
1351     (/dev/SWAP) Default resume partition
1352 rane 1.20
1353 jkt 1.33 <comment>(hibernate with TuxOnIce)</comment>
1354     Enhanced Hibernation (TuxOnIce)
1355 swift 1.1 --- Image Storage (you need at least one writer)
1356 so 1.15 [*] File Writer
1357 swift 1.1 [*] Swap Writer
1358 so 1.15 --- General Options
1359 swift 1.1 [*] LZF image compression
1360 so 1.15 <comment>(replace /dev/SWAP with your swap partition)</comment>
1361     (swap:/dev/SWAP) Default resume device name
1362     [ ] Allow Keep Image Mode
1363 swift 1.1 </pre>
1364    
1365     <p>
1366 so 1.15 The configuration for swsusp is rather easy. If you didn't store the location
1367     of your swap partition in the kernel config, you can also pass it as a
1368     parameter with the <c>resume=/dev/SWAP</c> directive. If booting is not
1369     possible due to a broken image, use the <c>noresume</c> kernel parameter. The
1370 rane 1.20 <c>hibernate-cleanup</c> init script invalidates swsusp images during the boot
1371     process.
1372 swift 1.1 </p>
1373    
1374 so 1.15 <pre caption="Invalidating swsusp images during the boot process">
1375 rane 1.19 # <i>rc-update add hibernate-cleanup boot</i>
1376 so 1.15 </pre>
1377    
1378 swift 1.1 <p>
1379 so 1.15 To activate hibernate with swsusp, use the hibernate script and set
1380 nightmorph 1.24 <c>UseSysfsPowerState disk</c> in <path>/etc/hibernate/sysfs-disk</path>.
1381 swift 1.1 </p>
1382    
1383     <warn>
1384     Backup your data before doing this. Run <c>sync</c> before executing one of the
1385     commands to have cached data written to disk. First try it outside of X, then
1386     with X running, but not logged in.
1387     </warn>
1388 rane 1.20
1389 swift 1.1 <p>
1390     If you experience kernel panics due to uhci or similar, try to compile USB
1391     support as module and unload the modules before sending your laptop to sleep
1392 nightmorph 1.24 mode. There are configuration options for this in <path>common.conf</path>
1393 swift 1.1 </p>
1394    
1395 so 1.15 <pre caption="Hibernating with swsusp">
1396 nightmorph 1.24 # <i>nano -w /etc/hibernate/common.conf</i>
1397 so 1.15 <comment>(Make sure you have a backup of your data)</comment>
1398 rane 1.19 # <i>hibernate</i>
1399 so 1.15 </pre>
1400    
1401 swift 1.1 <p>
1402 jkt 1.34 The following section discusses the setup of TuxOnIce including fbsplash support
1403     for a nice graphical progress bar during suspend and resume.
1404 so 1.15 </p>
1405    
1406     <p>
1407 rane 1.20 The first part of the configuration is similar to the configuration of swsusp.
1408     In case you didn't store the location of your swap partition in the kernel
1409     config, you have to pass it as a kernel parameter with the
1410 jkt 1.33 <c>resume=swap:/dev/SWAP</c> directive. If booting is not possible due to a
1411     broken image, append the <c>noresume</c> parameter. Additionally, the
1412 jkt 1.34 <c>hibernate-cleanup</c> init script invalidates TuxOnIce images during the boot
1413     process.
1414 so 1.15 </p>
1415    
1416 jkt 1.33 <pre caption="Invalidating TuxOnIce images during the boot process">
1417 rane 1.19 # <i>rc-update add hibernate-cleanup boot</i>
1418 so 1.15 </pre>
1419    
1420 rane 1.20 <p>
1421 jkt 1.33 Now edit <path>/etc/hibernate/suspend2.conf</path>, enable the <c>TuxOnIce</c>
1422 nightmorph 1.24 options you need. Do not enable the <c>fbsplash</c> options in
1423     <c>common.conf</c> just yet.
1424 swift 1.1 </p>
1425    
1426 jkt 1.33 <pre caption="Hibernating with TuxOnIce">
1427 nightmorph 1.24 # <i>nano -w /etc/hibernate/suspend2.conf</i>
1428 so 1.15 <comment>(Make sure you have a backup of your data)</comment>
1429 rane 1.19 # <i>hibernate</i>
1430 swift 1.8 </pre>
1431    
1432 so 1.15 <p>
1433 rane 1.20 Please configure <c>fbsplash</c> now if you didn't do already. To enable
1434 jkt 1.34 fbsplash support during hibernation, the <c>sys-apps/tuxonice-userui</c> package
1435     is needed. Additionally, you've got to enable the <c>fbsplash</c> USE flag.
1436 so 1.15 </p>
1437    
1438 jkt 1.33 <pre caption="Installing tuxonice-userui">
1439     # <i>echo "sys-apps/tuxonice-userui fbsplash" >> /etc/portage/package.use</i>
1440 nightmorph 1.24 <comment>(It may be marked ~arch, so first it must be keyworded)</comment>
1441 jkt 1.33 # <i>echo "sys-apps/tuxonice-userui" >> /etc/portage/package.keywords</i>
1442     # <i>emerge tuxonice-userui</i>
1443 so 1.15 </pre>
1444    
1445     <p>
1446     The ebuild tells you to make a symlink to the theme you want to use. For
1447     example, to use the <c>livecd-2005.1</c> theme, run the following command:
1448     </p>
1449    
1450     <pre caption="Using the livecd-2005.1 theme during hibernation">
1451 rane 1.19 # <i>ln -sfn /etc/splash/livecd-2005.1 /etc/splash/suspend2</i>
1452 so 1.15 </pre>
1453    
1454     <p>
1455     If you don't want a black screen in the first part of the resume process, you
1456 jkt 1.33 have to add the <c>tuxoniceui_fbsplash</c> tool to your initrd image. Assuming
1457 so 1.15 you created the initrd image with <c>splash_geninitramfs</c> and saved it as
1458 rane 1.20 <path>/boot/fbsplash-emergence-1024x768</path>, here's how to do that.
1459 so 1.15 </p>
1460    
1461 jkt 1.33 <pre caption="Adding tuxoniceui_fbsplash to an initrd image">
1462 rane 1.19 # <i>mount /boot</i>
1463     # <i>mkdir ~/initrd.d</i>
1464     # <i>cp /boot/fbsplash-emergence-1024x768 ~/initrd.d/</i>
1465     # <i>cd ~/initrd.d</i>
1466     # <i>gunzip -c fbsplash-emergence-1024x768 | cpio -idm --quiet -H newc</i>
1467     # <i>rm fbsplash-emergence-1024x768</i>
1468 jkt 1.33 # <i>cp /usr/sbin/tuxoniceui_fbsplash sbin/</i>
1469     # <i>find . | cpio --quiet --dereference -o -H newc | gzip -9 > /boot/fbsplash-tuxonice-emergence-1024x768</i>
1470 so 1.15 </pre>
1471    
1472     <p>
1473 nightmorph 1.24 Afterwards adjust <path>grub.conf</path> (or <path>lilo.conf</path>) so that
1474 jkt 1.33 your TuxOnIce kernel uses
1475     <path>/boot/fbsplash-tuxonice-emergence-1024x768</path> as initrd image. You can
1476 nightmorph 1.24 now test a dry run to see if everything is setup correctly.
1477 so 1.15 </p>
1478    
1479     <pre caption="Test run for fbsplash hibernation">
1480 jkt 1.33 # <i>tuxoniceui_fbsplash -t</i>
1481 so 1.15 </pre>
1482    
1483     <p>
1484 nightmorph 1.24 Afterwards open <path>/etc/hibernate/common.conf</path> and activate the
1485     fbsplash options. Execute <c>hibernate</c> and enjoy.
1486 so 1.15 </p>
1487    
1488 swift 1.1 </body>
1489     </section>
1490     </chapter>
1491    
1492     <chapter>
1493     <title>Troubleshooting</title>
1494     <section>
1495     <body>
1496    
1497     <p>
1498     <e>Q:</e> I'm trying to change the CPU frequency, but
1499     <path>/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor</path> does not
1500     exist.
1501     </p>
1502    
1503     <p>
1504     <e>A:</e> Make sure your processor supports CPU frequency scaling and you chose
1505     the right CPUFreq driver for your processor. Here is a list of processors that
1506 jkt 1.34 are supported by cpufreq (kernel 2.6.7): ARM Integrator, ARM-SA1100, ARM-SA1110,
1507     AMD Elan - SC400, SC410, AMD mobile K6-2+, AMD mobile K6-3+, AMD mobile Duron,
1508     AMD mobile Athlon, AMD Opteron, AMD Athlon 64, Cyrix Media GXm, Intel mobile
1509     PIII and Intel mobile PIII-M on certain chipsets, Intel Pentium 4, Intel Xeon,
1510     Intel Pentium M (Centrino), National Semiconductors Geode GX, Transmeta Crusoe,
1511     VIA Cyrix 3 / C3, UltraSPARC-III, SuperH SH-3, SH-4, several "PowerBook" and
1512     "iBook2" and various processors on some ACPI 2.0-compatible systems (only if
1513     "ACPI Processor Performance States" are available to the ACPI/BIOS interface).
1514 swift 1.1 </p>
1515    
1516     <p>
1517     <e>Q:</e> My laptop supports frequency scaling, but
1518     <path>/sys/devices/system/cpu/cpu0/cpufreq/</path> is empty.
1519     </p>
1520    
1521     <p>
1522     <e>A:</e> Look for ACPI related error messages with <c>dmesg | grep ACPI</c>.
1523     Try to update the BIOS, especially if a broken DSDT is reported. You can also
1524     try to fix it yourself (which is beyond the scope of this guide).
1525     </p>
1526    
1527     <p>
1528 rane 1.19 <e>Q:</e> My laptop supports frequency scaling, but according to
1529     <path>/proc/cpuinfo</path> the speed never changes.
1530 swift 1.1 </p>
1531    
1532     <p>
1533 swift 1.8 <e>A:</e> Probably you have activated symmetric multiprocessing support
1534     (CONFIG_SMP) in your kernel. Deactivate it and it should work. Some older
1535 rane 1.20 kernels had a bug causing this. In that case, run <c>emerge x86info</c>, update
1536 jkt 1.34 your kernel as asked and check the current frequency with <c>x86info -mhz</c>.
1537 swift 1.1 </p>
1538    
1539     <p>
1540     <e>Q:</e> I can change the CPU frequency, but the range is not as wide as in
1541     another OS.
1542     </p>
1543    
1544     <p>
1545     <e>A:</e> You can combine frequency scaling with ACPI throttling to get a lower
1546 jkt 1.34 minimum frequency. Notice that throttling doesn't save much energy and is mainly
1547     used for thermal management (keeping your laptop cool and quiet). You can read
1548     the current throttling state with <c>cat /proc/acpi/processor/CPU/throttling</c>
1549     and change it with <c>echo -n "0:x" > /proc/acpi/processor/CPU/limit</c>, where
1550     x is one of the Tx states listed in
1551 swift 1.1 <path>/proc/acpi/processor/CPU/throttling</path>.
1552     </p>
1553    
1554     <p>
1555 swift 1.8 <e>Q:</e> When configuring the kernel, powersave, performance and userspace
1556     governors show up, but that ondemand thing is missing. Where do I get it?
1557     </p>
1558    
1559     <p>
1560     <e>A:</e> The ondemand governor is only included in recent kernel sources. Try
1561     updating them.
1562     </p>
1563    
1564     <p>
1565 swift 1.1 <e>Q:</e> Battery life time seems to be worse than before.
1566     </p>
1567    
1568     <p>
1569     <e>A:</e> Check your BIOS settings. Maybe you forgot to re-enable some of the
1570     settings.
1571     </p>
1572    
1573     <p>
1574     <e>Q:</e> My battery is charged, but KDE reports there would be 0% left and
1575     immediately shuts down.
1576     </p>
1577    
1578     <p>
1579     <e>A:</e> Check that battery support is compiled into your kernel. If you use
1580     it as a module, make sure the module is loaded.
1581     </p>
1582    
1583     <p>
1584 rane 1.20 <e>Q:</e> My system logger reports things like "logger: ACPI group battery /
1585     action battery is not defined".
1586 nightmorph 1.17 </p>
1587    
1588     <p>
1589 rane 1.20 <e>A:</e> This message is generated by the <path>/etc/acpi/default.sh</path>
1590     script that is shipped with acpid. You can safely ignore it. If you like to get
1591     rid of it, you can comment the appropriate line in
1592     <path>/etc/acpi/default.sh</path> as shown below:
1593 nightmorph 1.17 </p>
1594    
1595     <pre caption="Disabling warnings about unknown acpi events">
1596     *) # logger "ACPI action $action is not defined"
1597     </pre>
1598    
1599     <p>
1600 swift 1.1 <e>Q:</e> I have a Dell Inspiron 51XX and I don't get any ACPI events.
1601     </p>
1602    
1603     <p>
1604     <e>A:</e> This seems to be a kernel bug. Read on <uri
1605     link="http://bugme.osdl.org/show_bug.cgi?id=1752">here</uri>.
1606     </p>
1607    
1608     <p>
1609 rane 1.20 <e>Q:</e> I activated the <c>DynamicClocks</c> option in <path>xorg.conf</path>
1610     and now X.org crashes / the screen stays black / my laptop doesn't shutdown
1611 so 1.15 properly.
1612     </p>
1613    
1614     <p>
1615 rane 1.20 <e>A:</e> This happens on some systems. You have to disable
1616     <c>DynamicClocks</c>.
1617 so 1.15 </p>
1618    
1619     <p>
1620 jkt 1.33 <e>Q:</e> I want to use TuxOnIce, but it tells me my swap partition is too
1621 so 1.15 small. Resizing is not an option.
1622     </p>
1623    
1624     <p>
1625 rane 1.20 <e>A:</e> If there is enough free space on your system, you can use the
1626 jkt 1.34 filewriter instead of the swapwriter. The <c>hibernate-script</c> supports it as
1627     well. More information can be found in
1628 jkt 1.33 <path>/usr/src/linux/Documentation/power/tuxonice.txt</path>.
1629 so 1.15 </p>
1630    
1631     <p>
1632 swift 1.1 <e>Q:</e> I just bought a brand new battery, but it only lasts for some
1633     minutes! What am I doing wrong?
1634     </p>
1635    
1636     <p>
1637     <e>A:</e> First follow your manufacturer's advice on how to charge the battery
1638 rane 1.20 correctly.
1639 swift 1.1 </p>
1640    
1641     <p>
1642     <e>Q:</e> The above didn't help. What should I do then?
1643     </p>
1644    
1645     <p>
1646     <e>A:</e> Some batteries sold as "new" are in fact old ones. Try the following:
1647     </p>
1648    
1649     <pre caption="Querying battery state">
1650     $ <i>grep capacity /proc/acpi/battery/BAT0/info</i>
1651     design capacity: 47520 mWh
1652     last full capacity: 41830 mWh
1653     </pre>
1654    
1655     <p>
1656     If the "last full capacity" differs significantly from the design capacity,
1657     your battery is probably broken. Try to claim your warranty.
1658     </p>
1659    
1660 swift 1.8 <p>
1661     <e>Q:</e> My problem is not listed above. Where should I go next?
1662     </p>
1663    
1664     <p>
1665 nightmorph 1.17 <e>A:</e> Don't fear to contact me, <mail link="earthwings@gentoo.org">Dennis
1666 rane 1.20 Nienhüser</mail>, directly. The <uri link="http://forums.gentoo.org">Gentoo
1667     Forums</uri> are a good place to get help as well. If you prefer IRC, try the
1668     <c>#gentoo-laptop</c> channel at <uri
1669     link="irc://irc.freenode.net">irc.freenode.net</uri>.
1670 swift 1.8 </p>
1671    
1672 swift 1.1 </body>
1673     </section>
1674     </chapter>
1675     </guide>

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