powerd / cpufreq question
mav at FreeBSD.org
Fri Apr 8 17:52:43 UTC 2011
On 08.04.2011 19:53, Daniel Gerzo wrote:
> On Fri, 08 Apr 2011 18:02:28 +0300, Alexander Motin wrote:
>>> OK, I understand what you are saying here. On the other side, I know
>>> pretty well how the load is distributed - in this particular case, the
>>> box is a web server, running ~30 php-cgi processes.
>>> This kind of operation doesn't require very high frequency and I suspect
>>> the cores are never waiting for each other. There could be an option
>>> which would allow an administrator to decide whether this is the case
>>> and allow him to set a higher -r and -i values, what do you think?
>> I think it should be possible with minimal changes.
> So, here is my attempt to implement it:
> Can you please review & comment? I should be able to commit it mysqlf if
> you consider it acceptable. It seems to work for me :)
Looks fine, except that -f option have to be the first, that is not
obvious. Another moment -- I've noticed some load constants hardcoded
there. They should also be handled to make higher values to work properly.
>>> Any idea what I should look for in the BIOS?
>> Something about C-states, or Cx-states on the CPU page. But first
>> look at dev.cpu.X.cx_supported to make sure it is not already present
>> and just unused.
> Seems like it was enabled by default. I have like these:
> dev.cpu.0.cx_supported: C1/3 C2/96 C3/128
> Does that mean I only need to set these in rc.conf?:
> Then run /etc/rc.d/power_profile 0x00?
It short - yes. In long - read the link I've given.
> May it cause any instability?
It you won't switch from LAPIC to other timer and it stop - your system
will freeze, or at least not work well. You should notice problems
immediately, if there are.
>>> This is 8-STABLE, any idea whether there's a MFC plan for the extra
>>> 9-CURRENT bonuses?
>> I suppose around May.
> Do you have some patches? If not you don't really need to make them just
> for me, I can wait a little.
Last ones I've generated are five months old:
They are large and I am not sure how good they apply now.
>>>> You may want to look here:
>>> From reading this, are you reffering above to the C2 states? (seems
>>> like C3 is not optimal for this kind of operation...)
>> The deeper state, the more power saved. To get most of it and to get
>> TurboBoost working you need at least C3 CPU state (ACPI may report it
>> with different number). Some latest Intel CPUs have no described
>> problems with C3 and LAPIC, for others described system tuning
> I believe this is pretty recent CPU (6 core Xeon X5650). Do you know
> about any problems?
I have no idea about these Xeons. I know just that LAPIC of the my Core
i5 works fine in C3, while one of the my Core i7 doesn't.
>> PS: Using powerd in best case wont hurt performance, while using
>> C-states may even increase it in some cases because of TurboBoost.
> If I want to use C-states, should I stop to use powerd, or is it
> possible to use them both together?
I am using both together on my laptop.
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