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Old 9th November 2008
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Post HOWTO: FreeBSD CPU Scaling with cpufreq.ko

For those who do not know FreeBSD is able to scale CPU speed (both desktop and mobile onesm thy just nned to support it and have enabled it in BIOS).

To enable that feature you need to add this line to /etc/rc.conf:
Code:
powerd_enable="YES"
You can also tweak how much you CPU will scale depends on the load, for example:
Code:
powerd_flags="-i 85 -r 60 -p 100"
powerd by default use adaptive mode (thanks to BSDKaffee)

You can also tweak lowest CPU frequency used by CPU by setting this in /etc/sysctl.conf or /boot/loader.conf:
Code:
debug.cpufreq.lowest=600
You can also set it by hand in terminal using sysctl:
Code:
sysctl debug.cpufreq.lowest=600
Up to yesterday there was no option to set highest value to limit max CPU speed to save power or limit overheat, but Boris Kochergin wrote a patch to support also the highest limit with debug.cpufreq.highest oid:
Code:
sysctl debug.cpufreq.highest=1200
These patches are for 7.0-RELEASE and 7-STABLE (I did not checked 8-CURRENT but propably also works):

/usr/src/sys/kern/kern_cpu.c (driver):
Code:
--- kern_cpu.c.orig	2008-11-08 13:12:24.000000000 -0500
+++ kern_cpu.c	2008-11-08 10:33:18.000000000 -0500
@@ -131,12 +131,16 @@
 DRIVER_MODULE(cpufreq, cpu, cpufreq_driver, cpufreq_dc, 0, 0);
 
 static int		cf_lowest_freq;
+static int		cf_highest_freq;
 static int		cf_verbose;
 TUNABLE_INT("debug.cpufreq.lowest", &cf_lowest_freq);
+TUNABLE_INT("debug.cpufreq.highest", &cf_highest_freq);
 TUNABLE_INT("debug.cpufreq.verbose", &cf_verbose);
 SYSCTL_NODE(_debug, OID_AUTO, cpufreq, CTLFLAG_RD, NULL, "cpufreq debugging");
 SYSCTL_INT(_debug_cpufreq, OID_AUTO, lowest, CTLFLAG_RW, &cf_lowest_freq, 1,
     "Don't provide levels below this frequency.");
+SYSCTL_INT(_debug_cpufreq, OID_AUTO, highest, CTLFLAG_RW, &cf_highest_freq, 1,
+    "Don't provide levels above this frequency.");
 SYSCTL_INT(_debug_cpufreq, OID_AUTO, verbose, CTLFLAG_RW, &cf_verbose, 1,
     "Print verbose debugging messages");
 
@@ -295,6 +299,14 @@
 		goto out;
 	}
 
+	/* Reject levels that are above our specified threshold. */
+	if (cf_highest_freq > 0 && level->total_set.freq > cf_highest_freq) {
+		CF_DEBUG("rejecting freq %d, greater than %d limit\n",
+		    level->total_set.freq, cf_highest_freq);
+		error = EINVAL;
+		goto out;
+	}
+
 	/* If already at this level, just return. */
 	if (CPUFREQ_CMP(sc->curr_level.total_set.freq, level->total_set.freq)) {
 		CF_DEBUG("skipping freq %d, same as current level %d\n",
@@ -617,8 +629,13 @@
 			continue;
 		}
 
-		/* Skip levels that have a frequency that is too low. */
-		if (lev->total_set.freq < cf_lowest_freq) {
+		/*
+		 * Skip levels that have a frequency that is too low or too
+		 * high.
+		 */
+		if (lev->total_set.freq < cf_lowest_freq ||
+		    (cf_highest_freq > 0 &&
+		     lev->total_set.freq > cf_highest_freq)) {
 			sc->all_count--;
 			continue;
 		}
/usr/src/share/man/man4/cpufreq.4 (man page):
Code:
--- cpufreq.4.orig	2008-11-08 13:08:19.000000000 -0500
+++ cpufreq.4	2008-11-08 13:08:51.000000000 -0500
@@ -98,6 +98,11 @@
 This setting is also accessible via a tunable with the same name.
 This can be used to disable very low levels that may be unusable on
 some systems.
+.It Va debug.cpufreq.highest
+Highest CPU frequency in MHz to offer to users.
+This setting is also accessible via a tunable with the same name.
+This can be used to disable very high levels that may be unusable on
+some systems.
 .It Va debug.cpufreq.verbose
 Print verbose messages.
 This setting is also accessible via a tunable with the same name.
Apply them like that:
Code:
# cd /usr/src/share/man/man4
# patch < /path/to/cpufreq.4.patch
# 
# cd /usr/src/sys/kern
# patch < /path/to/kern_cpu.c
Then rebuild kernel and reboot to use it.

This /usr/src/share/man/man4/cpufreq.4 is just a manpage so its not mandatory to apply/rebuid it.

Abialable CPU frequencies are aviable via dev.cpu.0.freq_levels oid, example:
Code:
# sysctl dev.cpu.0.freq_levels 
dev.cpu.0.freq_levels: 1200/13000 1050/11375 900/9750 750/8125 600/6500
You can also set Cx sleep state for your CPUs with dev.cpu.1.cx_lowest and dev.cpu.0.cx_lowest and so per CPU.

You can change them that:
Code:
# sysctl dev.cpu.0.cx_lowest=C3
dev.cpu.1.cx_lowest: C1 -> C3
WARN: Dunno for other laptops but when I use lowest C3 step for all cores, then I have little lag when I use my touchpad, this can be easily eliminated when you set one of the CPUs to C2 and all other to C3 to save power, no lag with that settings.

List of supported states are avialable via these oids:
Code:
dev.cpu.0.cx_supported: C1/1 C2/1 C3/57
dev.cpu.1.cx_supported: C1/1 C2/1 C3/57
You can read more about Intel C power states here:
http://software.intel.com/en-us/blog...more-c-states/
http://www.techarp.com/showarticle.a...tno=420&pgno=6

I measured power consumption of my CPU which is Intel T7300 (in my Dell D630) under full load*[1], by a small device called wattmeter, it is connected like that:

Code:
power (in the wall) <--> wattmeter <--> laptop (without batteries)
Here are the results:
Code:
 MHz    system power consumption (whole laptop)
 150    22W
 300    22W
 450    23W
 600    23W
 750    24W
 900    25W
1050    26W
1200    27W
1400    33W
1750    42W
2000    47W
1200MHz seems to have best power/performance ratio and that is what I personally use.

[1] 999999999999999999999999999 ** 999999999999999999999999999; launched 4 times (to full load two cores) in python.

... and by the way, setting kern.hz=100 in /boot/loader.conf will also make your battery life little longer.

WARN: If these options differ for AMD CPUs, then let me know, or just pot them in this thread.

If you have any questions or I forgot about something then let me know
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Old 9th November 2008
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>Up to yesterday there was no option to set highest value to limit max CPU speed to save power or limit overheat, but Boris Kochergin

Yeah I've seen your request on the ml =)
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Old 9th November 2008
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Quote:
Originally Posted by cabal View Post
Yeah I've seen your request on the ml =)
Heh I wonder if it will make it into RELEASE
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Old 9th November 2008
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I hope so it's a useful addon.
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Old 10th November 2008
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I don't mean to sound too critical, but I think the multiple spelling errors detract from this otherwise interesting guide. I know other guides have the same problem, so I'm not just picking on vermaden here. In my opinion guides should be given special care from ordinary posts and be written with a minimally educated user in mind as they may take an error at face value.

A few things besides spelling (that are somewhat important):
Quote:
Originally Posted by vermaden View Post
Code:
power_enable="YES"
Should be:
Code:
powerd_enable="YES"
Quote:
Originally Posted by vermaden View Post
Code:
powerd_flags="-a adaptive -b adaptive -n adaptive -i 85 -r 60 -p 100"
powerd defaults to use adaptive mode, so the following line would be sufficient:
Code:
powerd_flags="-i 85 -r 60 -p 100"
Just out of curiosity, could you also explain why you think these are better values than the defaults? Especially the polling interval.
Quote:
Originally Posted by vermaden View Post
Code:
# sudo sysctl dev.cpu.0.cx_lowest=C3
dev.cpu.1.cx_lowest: C1 -> C3
Not everyone uses sudo, and since the prompt is already '#', I think that would be sufficient enough to explain that the command needs to be run as root.

Thanks...just trying to be constructive.
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Old 10th November 2008
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Quote:
Originally Posted by BSDKaffee View Post
I don't mean to sound too critical, but I think the multiple spelling errors detract from this otherwise interesting guide.
Thanks mate, I think I corrected them.

Quote:
Originally Posted by BSDKaffee View Post
Just out of curiosity, could you also explain why you think these are better values than the defaults? Especially the polling interval.
Uses lower frequencies, these values (as from manual) specifya at what load level to change current speed to lower or higher value, default values higher the clock at lower load and the same for lower clock. The interval specifies how often the clock speed will change, many processes lower down their CPU usage for short period of time, with 500ms (0.5 second) you will not be able to "catch" these chances to save power, with 100 (or even 50 but you use more CPU power for polling) you are able to higher frequency much faster, in both sides.

Quote:
Originally Posted by BSDKaffee View Post
Not everyone uses sudo, and since the prompt is already '#', I think that would be sufficient enough to explain that the command needs to be run as root.
And that was the purpose of #, I just forgot to remove sudo.

Quote:
Originally Posted by BSDKaffee View Post
Thanks...just trying to be constructive.
Thanks for corrections mate

I added power consumption of my CPU depends on MHz used.
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Old 5th January 2009
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Check this of you want to get your AMD Phenom/Barcelona/K10 CPU scaling:
https://forums.freebsd.org/showpost....9&postcount=12
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Old 20th March 2009
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Quote:
Originally Posted by vermaden
Up to yesterday there was no option to set highest value to limit max CPU speed to save power or limit overheat, but Boris Kochergin wrote a patch to support also the highest limit with debug.cpufreq.highest oid:
Code:
sysctl debug.cpufreq.highest=1200
I've been thinking, and I wonder just how useful this is.

A 2GHz CPU running at 1GHz will not consume anywhere near half the power, while a CPU running at 2GHz will complete a task close to twice as fast.
The result is that the CPU will take more time to complete a task, and it will require more power in the end.

I haven't done any test, but I suspect that setting this value lower than the maximum will actually cause the battery to last shorter.
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Old 24th September 2009
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CPU scaling is something I would love to take advantage of, especially as my battery gets older and older... but running powerd has a tendency to cause my laptop to hang!
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Old 27th October 2010
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Default powerd(8) support for CPU scaling minimum and maximum

A breadcrumb for others finding this thread:

While Boris' original patch to add debug.cpufreq.highest sysctl support to kern_cpu.c was gently rejected (PR 144232, I'm too new to port URLs yet), he then filed a patch to add -M and -m to powerd(8) (PR 145063), which allows the user to set minimum and maximum clock speeds.

The patch was committed to 7-STABLE and 8-STABLE in September 2010, and should be part of 7.4 and 8.2.
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Old 27th October 2010
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@royce

Yes, I have heard about these great news, but not about MFC into 8.x

Currently I always add these patches into GENERIC config and rebuild kernel with:
Code:
# make NO_MODULES=1 buildkernel
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