bin/120490: powerd should let me specify desired frequencies

[Kris Kennaway]

The following reply was made to PR bin/120490; it has been noted by GNATS.

From: Kris Kennaway <kris at FreeBSD.org>
To: Nate Eldredge <neldredge at ucsd.edu>
Cc: freebsd-gnats-submit at FreeBSD.org
Subject: Re: bin/120490: powerd should let me specify desired frequencies
Date: Sun, 17 Feb 2008 13:02:21 +0100

 Nate Eldredge wrote:
 
 > powerd(8) in adaptive mode adjusts the CPU frequency based on the list from dev.cpu.0.freq_levels, it gradually moves through all available frequencies.  However, in my case this is not desirable; only two of the available frequencies are actually useful.  The CPU's full speed is 1800 MHz; powernow also has a 1000 MHz setting that saves about 20W.  But there are a bunch of other frequencies that apparently come from ACPI.  They do slow down the CPU, but based on my tests the machine's power consumption d oes not actually change, so there is not much point in using them.  Furthermore, the ACPI frequencies include some really low ones (250MHz or so) which crash the machine if selected.  So I really just want powerd to switch between 1800 and 1000.
 > 
 > It would be useful for powerd to have an option to manually specify a list of desired frequencies.
 
 Just disable the services that are providing the alternate frequencies. 
   Probably acpi_throttle.
 
 Kris