Compiling 6.3->7: lapic frequency madness

[John Baldwin]

On Tuesday 18 March 2008 04:24:33 pm Sam Leffler wrote:
> Igor Mozolevsky wrote:
> > On 18/03/2008, John Baldwin <jhb at freebsd.org> wrote:
> >> On Tuesday 18 March 2008 11:49:29 am Igor Mozolevsky wrote:
> >>  > On 18/03/2008, John Baldwin <jhb at freebsd.org> wrote:
> >>  > > First, which one is broken?  Have you tried a RELENG_7_0 kernel and
> >>  > > does
> >>
> >>  it do
> >>
> >>  > >  the same as a release CD kernel?
> >>  >
> >>  > Tried both ISO image and RELENG_7_0, they both work ok, but RELENG_7
> >>
> >>  doesn't...
> >>
> >>
> >> Ok, and it is cpufreq related?  Which cpufreq drivers are attaching to
> >> your CPU?
> >
> > Well, I wouldn't say I'm sure it's 100% cpufreq related, but removing
> > it from the kernel fixes the problem... It's also possible that
> > cpufreq is interfering with something else... Anyhow, I've got both
> > est and p4tcc attaching.
>
> I'm having lots of problems with cpu freq throttling on t4x laptops.
> The system gets very sluggish and when I check the frequency it's been
> throttled down.  This happens even on ac (haven't checked what powerd is
> doing then).

My laptop actually wigs out if it throttles the CPU down too slow.  What 
happens to me is that an ACPI GPE triggers and it takes a long time to 
execute at 100Mhz and I actually end up with a sort of GPE storm where the 
CPU spends all its time handling the GPE interrupts. :-/  I worked around it 
by using the 'debug.cpufreq.lowest' (or whatever it's called, it's something 
like that) tunable to prevent the CPU from going slower than about 400 Mhz 
and since then CPU throttling has worked fine on my laptop w/o issues.

-- 
John Baldwin