Intel_P State

[heratic]

Hi i have been trying to change the intel setpoint for the P_state driver. Does anyone here know how i would do that on unraid. Cheers

 

Tuning Intel P-State driver

When HWP mode is not used, debugfs files have also been added to allow the
tuning of the internal governor algorithm. These files are located at
/sys/kernel/debug/pstate_snb/. The algorithm uses a PID (Proportional
Integral Derivative) controller. The PID tunable parameters are:

      deadband
      d_gain_pct
      i_gain_pct
      p_gain_pct
      sample_rate_ms
      setpoint

To adjust these parameters, some understanding of driver implementation is
necessary. There are some tweeks described here, but be very careful. Adjusting
them requires expert level understanding of power and performance relationship.
These limits are only useful when the "powersave" policy is active.

-To make the system more responsive to load changes, sample_rate_ms can
be adjusted  (current default is 10ms).
-To make the system use higher performance, even if the load is lower, setpoint
can be adjusted to a lower number. This will also lead to faster ramp up time
to reach the maximum P-State.
If there are no derivative and integral coefficients, The next P-State will be
equal to:
current P-State - ((setpoint - current cpu load) * p_gain_pct)

For example, if the current PID parameters are (Which are defaults for the core
processors like SandyBridge):
      deadband = 0
      d_gain_pct = 0
      i_gain_pct = 0
      p_gain_pct = 20
      sample_rate_ms = 10
      setpoint = 97

If the current P-State = 0x08 and current load = 100, this will result in the
next P-State = 0x08 - ((97 - 100) * 0.2) = 8.6 (rounded to 9). Here the P-State
goes up by only 1. If during next sample interval the current load doesn't
change and still 100, then P-State goes up by one again. This process will
continue as long as the load is more than the setpoint until the maximum P-State
is reached.

For the same load at setpoint = 60, this will result in the next P-State
= 0x08 - ((60 - 100) * 0.2) = 16
So by changing the setpoint from 97 to 60, there is an increase of the
next P-State from 9 to 16. So this will make processor execute at higher
P-State for the same CPU load. If the load continues to be more than the
setpoint during next sample intervals, then P-State will go up again till the
maximum P-State is reached. But the ramp up time to reach the maximum P-State
will be much faster when the setpoint is 60 compared to 97.