cvs commit: src/sys/i386/cpufreq est.c

John Baldwin jhb at
Mon Mar 17 13:36:15 PDT 2008

On Monday 17 March 2008 02:44:18 pm Maxim Sobolev wrote:
> Poul-Henning Kamp wrote:
> > In message <200803170933.48212.jhb at>, John Baldwin writes:
> >> On Monday 17 March 2008 05:01:43 am Poul-Henning Kamp wrote:
> >>> phk         2008-03-17 09:01:43 UTC
> >>>
> >>>   FreeBSD src repository
> >>>
> >>>   Modified files:
> >>>     sys/i386/cpufreq     est.c
> >>>   Log:
> >>>   Increase time we wait for things to settle to 1 millisecond,
> >>>   10 microseconds is too short.
> >>>
> >>>   Always set the cpu to the highest frequency so that we get through
> >>>   boot and don't handicap cpus where powerd(8) is not used.
> >> Hmm, I actually consider this a feature when I'm not running powerd to 
> >> less battery.  I think we should only bump up the CPU on battery power 
> >> using powerd so that it can be lowered again to save battery power when 
> >> CPU is idle.
> > 
> > We have cpufreq enabled by default now, badly configured machines run
> > at 50% of rated CPU power because people don't know that they need to
> > enable powerd(8) on servers.
> > 
> > This is only going to get worse when more EnergyStar compliant servers
> > hit the channel.
> > 
> > I think setting full speed is the correct choice, if people care about
> > powersaving, they need to configured it, if they don't they should get
> > their moneys worth out of their hardware.
> Perhaps make it a kernel option? But I agree that CPU should run at full 
> speed by default, otherwise it would break POLA for users upgrading from 
> previous releases.

Err, actually, it's the other way around.  On previous releases the BIOS is 
going to set your CPU to a lower speed on boot to save battery (on a laptop 
not connected to A/C during boot).  The CPU will stay in the lower speed 
unless you both enable cpufreq and powerd in 6.x and 7.x.  Now in HEAD just 
enabling the cpufreq driver causes the CPU to run at the full speed (and 
drain the battery faster) unless you also run powerd to slow it back down 
when it is idle.

John Baldwin

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