powerd freeze with amd 5000 X2 but not with lower cpus

Stefan Eßer se at freebsd.org
Thu Aug 9 00:39:19 PDT 2007

Kris Kennaway schrieb:
> On Mon, Aug 06, 2007 at 10:54:08AM -0500, Scot Hetzel wrote:
>> On 8/6/07, JoaoBR <joao at matik.com.br> wrote:
>>> Only to remember the problem only ocurres when loading powerd and seems the
>>> freeze happens when cpu freq is upshifting not down.
>> Try setting:
>> hint.acpi_throttle.0.disabled="1"
>> in /boot/loader.conf, as acpi_throttle may be the cause of the freeze.
> FYI this worked for me.

Well, I never understood why we don't make this the default,.
Since throttling has a much higher impact on performance than
on power consumption, it always is lowering the throughput
per Watt value (or to use some other metric, it increases the
"Joule for completion of a task" value).

For systems that do not support EST or PowerNow! (or newer),
it may still be better to have the CPU work unthrottled and
then go into an extended halt instead of a simple halt (C0).

In case of systems with low voltage modes, throttling may
make the CPU draw significantly more power than in a higher
clocked, reduced voltage mode. (I.e. 2GHz->1.6GHz at lower
voltage draws less power than throttling 2GHz->1GHz at the
nominal operating voltage ...)

Throttling may be useful to prevent over-heating of certain
CPUs under extreme load, but AFAIK these implement it without
OS support (in on-chip hardware, since the days of the P4).

So, IMHO, we should normally have acpi_throttle disabled in
the default installation ...

Regards, STefan

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