- Taking non-idle time into account when calculating core busy
time was a mistake and led to a performance regression. Since
the problem it was supposed to address is now taken care of in
a different way, we don't need to do it any more, so drop the
non-idle time tracking from intel_pstate. Dirk Brandewie.
- Changing to fixed point math throughout the busy calculation
introduced rounding errors that adversely affect the accuracy
of intel_pstate's computations. Fix from Dirk Brandewie.
- The PID controller algorithm used by intel_pstate assumes that
the time interval between two adjacent samples will always be the
same which is not the case for deferable timers (used by
intel_pstate) when the system is idle. This leads to inaccurate
predictions and artificially increases convergence times for
the minimum P-state. Fix from Dirk Brandewie.
- intel_pstate carries out computations using 32-bit variables
that may overflow for large enough values of APERF/MPERF. Switch
to using 64-bit variables for computations, from Doug Smythies.
/
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Merge tag 'pm-3.15-final' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull intel pstate fixes from Rafael Wysocki:
"Final power management fixes for 3.15
- Taking non-idle time into account when calculating core busy time
was a mistake and led to a performance regression. Since the
problem it was supposed to address is now taken care of in a
different way, we don't need to do it any more, so drop the
non-idle time tracking from intel_pstate. Dirk Brandewie.
- Changing to fixed point math throughout the busy calculation
introduced rounding errors that adversely affect the accuracy of
intel_pstate's computations. Fix from Dirk Brandewie.
- The PID controller algorithm used by intel_pstate assumes that the
time interval between two adjacent samples will always be the same
which is not the case for deferable timers (used by intel_pstate)
when the system is idle. This leads to inaccurate predictions and
artificially increases convergence times for the minimum P-state.
Fix from Dirk Brandewie.
- intel_pstate carries out computations using 32-bit variables that
may overflow for large enough values of APERF/MPERF. Switch to
using 64-bit variables for computations, from Doug Smythies"
* tag 'pm-3.15-final' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
intel_pstate: Improve initial busy calculation
intel_pstate: add sample time scaling
intel_pstate: Correct rounding in busy calculation
intel_pstate: Remove C0 tracking
c717d15614