Xeon E5 cpu work in low status

[Ian Smith]

On Mon, 4 Nov 2013, Adrian Chadd wrote:
 > On 4 November 2013 14:24, Konstantin Belousov <kostikbel at gmail.com> wrote:
 > 
 > > My Intel board DQ67OW starts with the fixed CPU speed, which is
 > > configurable in BIOS. Unless OS starts managing the frequency with the
 > > cpufreq and powerd, CPU is locked to the pre-configured speed. It was
 > > not easy to understand why my single-user memory b/w benchmarks show
 > > half of the expected throughput for the cache, until I found the setting
 > > and found that Intel defaults to 1/2 of the marketing frequency.
 > >
 > > For my board, it is Performance->Processor Overrides->Maximum Non-Turbo
 > > Ratio.  It was set to 17, normal CPU mode is 34, turbo is 38 max.
 > 
 > Does powerd throttle each individual core like this? I don't have
 > anything laptop-y that's recent enough for that to matter.

Unless something's changed recently I've missed, no.  My 9 box is still 
broken, so ref to 8.2 sources .. start with /sys/kern/kern_cpu.c, 
cpufreq(4) and results of find /sys/ -name "*freq*".  Nate Lawson 
commented way back:

        /*
         * Only initialize one set of sysctls for all CPUs.  In the future,
         * if multiple CPUs can have different settings, we can move these
         * sysctls to be under every CPU instead of just the first one.
         */
 
I recall that some CPUs had potential for individual settings (voltage, 
freq) but some only per-package rather than per-core, and then there's 
the thermal control settings as well.  I believe Kevin's right, p4tcc 
and acpi_throttle should be disabled by default, on most CPUs anyway, 
and that at least is just a simple change to hints, as a start.

It's quite a deep rabbit warren, and most docs are only in the code - eg 
still? no mans for most if not all of the absolute and relative cpufreq 
drivers mentioned in cpufreq(4), as I recall - and of course the moving 
targets with newer CPUs .. so have fun down there!

cheers, Ian