Updated acpi_cpu patch

Nate Lawson nate at root.org
Fri Nov 21 13:59:51 PST 2003

> > On Tue, 18 Nov 2003, Lukas Ertl wrote:
> > > I'm gonna try some "buildkernelstones" with the different settings.  If
> > > you have some special benchmarks in mind I'd be happy to run them.
> >
> > That's probably ok.  It has a lot of IO.
> Now I've tried running make buildkernel and tarring /usr/src to a
> different location, with different setting for hw.acpi.cpu.cx_lowest.  I
> couldn't see any real difference - neither in performance nor in heat
> emission.

Well, heat emission will be high during benchmarks because the CPU is
rarely idle.  My fan always comes on my laptop during buildworld.  But the
difference is when it's mostly idle (checking email, web browsing).  With
machdep.cpu_idle_hlt=0, the fan is always on even when the box is sitting
there.  With cpu_idle_hlt=0 and cx_lowest=0 (C1), the fan goes off but the
box is still warm.  With cx_lowest=2 (C3, 120 us transition time), the box
is very cool but some IO gets a little slower (serial port).  But not

So there are actually two things to test for each setting:  temperature
when mostly idle/low use and performance loss for IO latency benchmarks.
Those are what is more interesting.  Also, can you send me your sysctl
hw.acpi.cpu.cx_history after you've used it for a while with the maximum
cx_lowest setting?


More information about the freebsd-current mailing list