On Sun, May 4, 2014 at 10:07 AM, Nathan Whitehorn <nwhiteh...@freebsd.org>wrote:

> On 05/04/14 10:05, Allan Jude wrote:
>> On 2014-05-04 11:47, Allan Jude wrote:
>>> On 2014-05-04 10:28, Matthias Apitz wrote:
>>>> El día Saturday, May 03, 2014 a las 04:59:48PM -0700, Kevin Oberman
>>>> escribió:
>>>>  On Sat, May 3, 2014 at 1:25 PM, Adrian Chadd <adr...@freebsd.org>
>>>>> wrote:
>>>>>  Set it to the lowest available Cx state that you see in dev.cpu.0 .
>>>>>>  Available is not required. Set it to C8. That guarantees that you
>>>>> will use
>>>>> the lowest available. The correct incantation in rc.conf is "Cmax".
>>>>> performance_cx_lowest="Cmax"
>>>>> economy_cx_lowest="Cmax"
>>>>> But, unless you want laggy performance, you will probably also want:
>>>>> hint.p4tcc.0.disabled=1
>>>>> hint.acpi_throttle.0.disabled=1
>>>>> in /boot/loader.conf. Low Cx states and TCC/throttling simply don't mix
>>>>> well and TCC is not effective, as mentioned earlier in this thread.
>>>> Re/ powerd I have in /etc/rc.conf:
>>>> # powerd
>>>> powerd_enable="YES"
>>>> powerd_flags="-a max -b adp"
>>>> #
>>>> performance_cx_lowest="Cmax"
>>>> economy_cx_lowest="Cmax"
>>>> (and the additional hint.* in /boot/loader.conf as well). Which process
>>>> 'performance_cx_lowest' and 'economy_cx_lowest' target exactly as config
>>>> values?
>>>> Thx
>>>>         matthias
>>>>  In a pretty unscientific test on my laptop (Lenovo T530 with Intel i5
>>> 3320M), setting hw.acpi.cpu.cx_lowest=C8 lowered power consumption at
>>> idle by about 3 watts, which adds about 30-45 minutes to my battery life
>>> during conservative usage.
>>> Using PCBSD 10, so hint.acpi_throttle.0.disabled=1 was already set
>>> (apparently solves some issue with powerd on some AMD systems)
>>> I have added hint.p4tcc.0.disabled=1 but not sure where to expect to see
>>> a difference.
>>>  I see the difference now, with the p4tcc stuff disabled, the lowest
>> cpufreq is now 1200mhz instead of 150mhz
> I just set the default for acpi_throttle and p4tcc in HEAD to disabled by
> adding these line to the default /boot/device.hints. If you want them back,
> editing your device.hints will restore them. This can be reverted if many
> people want throttling enabled by default, but all I have heard so far --
> and for the past many years -- is a unanimous chorus to turn it off.
> -Nathan

Anyone playing around with Thermal Management should read the article on
Tom's Hardware on the subject.  It explains things quite nicely. Even I
could understand it. :-)
The section on Thermal Monitor 2 was new to me as it has been added since I
last researched this several  years ago. Note the tie-in between TM2 and
EST rather than simple throttling (skipping N of every 8 clock cycles).
Section 2 of the article has thermal specs on a lot of processors, too..

Bottom line of the article is to make sure TM2 is enabled and just leave it
alone to do its thing. No throttling of any sort for power mis-management.

The one area that can stand a close look is the algorithm for adjusting
EST. It probably will make far less difference than C-states, but it is a
legitimate power management technique and it is under the control of
powerd. Several people have suggested modification for this and I think
it's at least worth a look.

Finally, if we don't default p4tcc and throttling to off and change the
default for C-states to Cmax, a lot of people will be very unhappy.
Disabling throttling really must come first.
R. Kevin Oberman, Network Engineer, Retired
E-mail: rkober...@gmail.co <rkober...@gmail.com>
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