powerd to use sysctl to import temps to drop freq to avoid heat crash

[Kevin Oberman]

On Thu, Jan 5, 2012 at 2:40 AM, Ian Smith <smithi at nimnet.asn.au> wrote:

> On Thu, 5 Jan 2012, Ian Smith wrote:
>  > =======
>  > #!/bin/sh
>  > # temp_t23 smithi v0 7/11/11, tidy 12/11/11, v2 fan read delay 22/11/11
>
>  + # Credit to Alexandre "Sunny" Kovalenko <gaijin.k at gmail.com> whose
>  + # earlier scripts for managing acpi_ibm resources inspired this one.
>
>  > # v3 18/12/11 suspend / resume resets dev.acpi_ibm.0.fan=1 (ie auto)
>  > none=0; slow=1; fast=3       # Thinkpad T23 fan levels (1-2, 3-7 same)
>
> And of course it was also Alexandre who (I think originally) proposed
> monitoring temperature to directly implement cooling via lower powerd
> freqs, according to old email, in Feb 2006.  I'd even forgotten having
> reviewed and added a line or two to that patch .. if I lost my archives
> I'd probably have no memory left at all :)
>
> This post:
>  http://lists.freebsd.org/pipermail/freebsd-acpi/2008-February/004521.html
> points to this PR:
>  http://www.freebsd.org/cgi/query-pr.cgi?pr=bin%2F120336&cat=
> which was closed with reference to this post:
>  http://docs.FreeBSD.org/cgi/mid.cgi?1203126071.833.19.camel
>
> Useless trying to apply anything like this to recent powerd sources,
> though.  Good luck with getting its fan to go, or a warranty claim!
>

First of all, I am highly suspicious of hardware issues. Like Ian says, the
temperature measured in the chip and quite a bit higher than those measured
on the motherboard. Beyond that, if the die temperature gets too high, all
modern CPUs kill  the power supply and the system dies almost instantly. I
suspect this may be what is happening to you due to poor heat transfer from
the die to the heatsink from poor attachment of the heatsink or a flaw in
the CPU thermal connection between the die and the thermal transfer plate
on the top of the case. (The former is FAR more likely.)

Beyond this, I don't think the OS should be trying to deal with this. All
"modern" CPUs, Intel or AMD, support some form of TCC and, if not
interfered with, it will slow the clock in increments of 12.5%  as needed
to keep the temperature below PSV. This is done in a combination of
hardware and BIOS and is supported by FreeBSD, but FreeBSD also tries to
use it to do power management and as test both by myself and, more recently
by mav@, this is a bad idea. Both throttling and TCC should be disabled and
I would love to see them completely removed from power management.

I have read papers which make it clear that only EST and sleep (Cx) states
are really useful for power management and that Cx is by far and away the
most significant, but enabling deep sleep states can cause the system to
lock up when combined with TCC or throttling.

If you want to keep a system cool, add:
performance_cx_lowest="LOW"
economy_cx_lowest="LOW"
to /etc/rc.conf and disable TCC and throttling in /boot/loader.conf.
-- 
R. Kevin Oberman, Network Engineer
E-mail: kob6558 at gmail.com