cpufreq and changing driver

[Bruno Ducrot]

On Wed, Nov 30, 2005 at 12:23:52PM -0800, Nate Lawson wrote:
> Bruno Ducrot wrote:
> >On Wed, Nov 30, 2005 at 10:05:04AM -0800, Nate Lawson wrote:
> >
> >>Marco Calviani wrote:
> >>
> >>>Hi,
> >>>
> >>>2005/11/30, Bruno Ducrot <ducrot at poupinou.org>:
> >>>
> >>>
> >>>>You have to load the cpufreq.ko module at boot.
> >>>>Adding that line:
> >>>>cpufreq_load = "YES"
> >>>>to /boot/loader.conf
> >>>>should be OK.
> >>>
> >>>
> >>>I have that line in that position, and it seems working. The point is
> >>>that i would like to change the driver and use (AFAIU) a better driver
> >>>for my system (est).
> >>>In particular i have:
> >>>
> >>>dev.cpu.0.%desc: ACPI CPU
> >>>dev.cpu.0.%driver: cpu
> >>>dev.cpu.0.%location: handle=\_PR_.CPU0
> >>>dev.cpu.0.%pnpinfo: _HID=none _UID=0
> >>>dev.cpu.0.%parent: acpi0
> >>>
> >>>Maybe i didn't understood well: but what i have to do to use the Intel
> >>>Enhanced SpeedStep driver?
> >>
> >>You should send the full output of "sysctl dev.cpu".  There is no 
> >>cpufreq driver (est, acpi_perf, or other) driver running.  Perhaps look 
> >>at your dmesg to see if one is probing/attaching.
> >>
> >>If you are using acpi and load cpufreq.ko, you've got all the cpufreq 
> >>drivers in one package.  The right one for your platform will 
> >>automatically probe/attach.
> >>
> >>
> >>>>powerd need some rework in order to get it working properly.  There
> >>>>is one FreeBSD project on that subject if you are interrested.
> >>>
> >>>Well, thanks i'm very interested, although i'm not at all experienced
> >>>in kernel programming....
> >>>
> >>>I'm not inside this issue, but it would not be possible to "emulate"
> >>>the behaviour of the ondemand governor? (sorry if this question makes
> >>>no sense)
> >>
> >>I have no idea what you mean by "on-demand governor".  The only 
> >>automated control of cpu speed is either by the BIOS (which we can't 
> >>control) or the TM/TM2 (and that one is heat-based, not load-based).
> >>
> >
> >
> >The ondemand governor is basically an implemation of the following
> >algorithm:
> >
> >There is a counter, say count.
> >
> >at each given fixed intervall:
> >if (idle less than a watermark) {
> >    frequency full
> >    reinitialise count to 10
> >} else if (idle more than another watermark) {
> >    decrement count
> >    if count is 0 {
> >        down one step the frequency
> >    }
> >else reinitilize count to 10
> >
> >      
> >Note that in the latter case, the down step is performed only
> >after 10 such comparison.  In other word, intervall is ten times
> >larger for the down side than the full frequency one.
> >
> >This work well when you can perform, say, 20 to 50 transitions per
> >second.  Otherwise, it is pretty bad.
> >
> 
> Send me a URL to the datasheet that says Intel implemented this.

http://www.intel.com/cd/ids/developer/asmo-na/eng/195910.htm?prn=Y

> That algorithm is basically what powerd does.  So just run powerd.

Indeed.

-- 
Bruno Ducrot

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.