Solved CPU consumes more energy after upgrade from 10.1. to 10.2

[zwieblum]

I have a slight problem with my X61 after upgrading from 10.1-RELEASE to 10.2-RELEASE:

Somehow the lowest cpu frequency was raised from 400 MHz to 800 MHz. This is most undesireable, as the system temperture is now 10°C higher than it used to be (56°C instead of 46°C).

Is there a way to get the old behaviour back?

 

[robroy]

ZWieblum, I'm seeing a similar symptom with my ThinkPad X230.

With 10.1-RELEASE, its fan stayed either off, or at level 1 (2,960 RPM) when idle; it was quiet.

With 10.2-RELEASE, it stays at level 2 or 3 (3,492 or 3,780 RPM, respectively).

10.2's powerd(8) reports that its CPU slows from 2600 MHz to a minimum of 1200 MHz. I didn't notice what 10.1's reported.

 

[zwieblum]

In the meantime I found that I had to add this line to /boot/loader.conf

hint.acpi_throttle.0.disabled=0

Now the cpufrequency drops to 100 MHz when idle

 

[robroy]

ZWieblum, thanks so much!

With your change, powerd(8) claims to take my X230 down to 150 MHz.

Weirdly, its fan's still at 3,780 RPM, yet maybe it still has to cool off from all that 1200 MHz idling business; it's at 66° C.

 

[zwieblum]

You'll definitely have to give it time to cool
BTW, what settings do you use for powerd(8)?

 

[robroy]

ZWieblum, thanks again.

I normally run powerd(8) with its default profile, which I guess is hiadaptive since it's on A/C.

 

[JanJurkus]

Uhh, isn't ACPI throttling something older? I would think it was disabled in 10.1-RELEASE by default too.

Anyway, read more on this subject here: https://wiki.freebsd.org/TuningPowerConsumption

It might also help to check for any bios updates, and check the settings, if all C-states have been enabled.

 

[zwieblum]

Ah, yes. I've added these to /etc/sysctl.conf:

dev.cpu.0.cx_lowest=C3
dev.cpu.1.cx_lowest=C3

Now power consumption went down about 10%.

 

[KevinOberman]

Ah, yes. I've added these to /etc/sysctl.conf:

dev.cpu.0.cx_lowest=C3
dev.cpu.1.cx_lowest=C3

Now power consumption went down about 10%.

A better choice is to set this in rc.conf:

performance_cx_lowest="Cmax"
economy_cx_lowest="Cmax"

Some systems may offer deeper sleep states than C3 and, worse, some have "missing states". E.g. "C1 C2 C4 C5" If you set Cmax to a value not available, it will not work well.

Also, if you set the cx values, be sure to disable both throttle or p4tcc (the default) as they interact very badly with elevated C-states on many systems and cause system freezes. Throttling and TCC were both created for thermal management, not power management.

 

[zwieblum]

The reason for C3 instead of Cmax is "C4-Fiepen" on older Thinkpads, i.e. a high-pitched buzzing sound when entering C4. ( http://thinkwiki.de/Geräuschentwicklung_reduzieren )