Re: acpicpu slowing down computer [was Re: firefox slowness -- X server problem?]

[Jukka Ruohonen <jruohonen%iki.fi@localhost>]

On Thu, Aug 19, 2010 at 11:04:30PM +0200, Jens Rehsack wrote:
> But how do you explain the test result? My firefox is really
> slow - it takes several seconds switching between windows.
> And if I understood Thomas correctly, on his system it's the
> same. After removing acpicpu(4) it's quick as it was before.
> Side effect?

If you want to help in testing, 'boot -x' with acpicpu(4) enabled but
options(4) ENHANCED_SPEEDSTEP disabled. And use the latest sources. Report
results to me preferably in private mail.

What CPU is this? One reason for this may be that on new Intel Nehalem CPUs
the highest frequency (P0-state) enables the so-called Turbo Boost. But the
P1-state is the "real" highest frequency.

You could see something like:

        acpicpu0: P0: FFH, lat  10 us, pow 35000 mW, 2534 MHz
        acpicpu0: P1: FFH, lat  10 us, pow 35000 mW, 2533 MHz

There is a 1 MHz difference between P0 and P1 with Turbo Boost, which, if
enabled, may either reduce or increase the frequencies behind our back based
on thermal conditions. It overclocks. (This could happen also with the
existing ENHANCED_SPEEDSTEP, but it would require a fair amount of good luck.)

- Jukka.

P.S. Needless to say, if you run a driver that is still actively being
developed, these things happen.