CVSROOT: /cvs
Module name: src
Changes by: sol...@cvs.openbsd.org 2020/05/30 08:42:59
Modified files:
sys/kern : sched_bsd.c
Log message:
In automatic performance mode on systems with offline CPUs because of SMT
mitigation the algorithm was still accounting the offline CPUs, leading to
a code path that would never be reached.
This should allow better frequency scaling on systems with many CPUs.
The frequency should scale up if one of two condition is true.
- if at least one CPU has less than 25% of idle cpu time
- if the average of all idle time is under 33%
The second condition was never met because offline CPU are always accounted as
100% idle.
A bit more explanations about the auto scaling in case someone want to improve
this later: When one condition is met, CPU frequency is set to maximum and a
counter set to 5, then the function will be run again 100ms later and decrement
the counter if both conditions are not met anymore. Once the counter reach 0
the frequency is set to minimum. This mean that it can take up to 100ms to
scale up and up to 500ms to scale down.
ok brynet@
looks good tedu@
