Improved Intel Turbo Boost status/control
mav at FreeBSD.org
Mon Mar 12 19:55:31 UTC 2012
On 03/12/12 21:33, Ivan Klymenko wrote:
> В Mon, 12 Mar 2012 21:15:35 +0200
> Alexander Motin<mav at FreeBSD.org> пишет:
>> I'd like to note that recent r232793 change to cpufreq(4) in HEAD
>> opened simple access to the Intel Turbo Boost status/control. I've
>> found that at least two of my desktop systems (based Nehalem and
>> SandyBridge Core i7s) with enabled Intel Turbo Boost in BIOS it is
>> not use it by default, unless powerd is enabled. And before this
>> change it was difficult to detect/fix.
>> ACPI reports extra performance level with frequency 1MHz above the
>> nominal to control Intel Turbo Boost operation. It is not a bug, but
>> dev.cpu.0.freq_levels: 2934/106000 2933/95000 2800/82000 ...
>> In this case value 2933 means 2.93GHz, but 2934 means 3.2-3.6GHz.
>> After boot with default settings I see:
>> dev.cpu.0.freq: 2933
>> , that means Turbo Boost is disabled.
>> Enabling powerd or just adding to rc.conf
>> enables Turbo Boost and adds extra 10-20% to the system performance.
>> Turbo Boost operation can be monitored in run-time via the PMC with
>> command that prints number or really executed cycles per CPU core:
>> pmcstat -s unhalted-core-cycles -w 1
> Thank you very much!
> and as this option must be combined with state of the processor C1 C2
The more CPU cores on package are sleeping and the deeper they are
sleeping, the bigger will be boost for remaining active cores. Without
using deeper C-states boost is usually quite small (about 100-200MHz for
desktop chips). Enabling C-states increases it in few times.
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