I recently read that I can eke more performance out of my CPU by setting the governor to "performance" instead of "powersave". According to the Arch wiki, this will "run the CPU at the maximum frequency" instead of the "minimum frequency".
I found this wording confusing, so I also read the kernel documentation.
2.1 Performance
The CPUfreq governor "performance" sets the CPU statically to the highest frequency within the borders of scaling_min_freq and scaling_max_freq.
2.2 Powersave
The CPUfreq governor "powersave" sets the CPU statically to the lowest frequency within the borders of scaling_min_freq and scaling_max_freq.
What does "statically" mean? To me, it contrasts with "dynamic", and implies frequency would never change, i.e. with powersave the CPU frequency would always be a single value, equal to scaling_min_freq
. However, this is clearly not the case. I am currently running "powersave" by default. I can monitor the CPU frequencies with
$ watch grep \"cpu MHz\" /proc/cpuinfo
and see them changing dynamically.
What does the kernel documentation mean by "statically"? What factors affect the CPU frequency, and how do these change with "powersave" and "performance"? Hence, what are the implications of changing from the former to the latter? Would a higher frequency be used? During what circumstances? Specifically, will this affect power draw, heat and lifespan of my CPU?
hints
, and let it interpret that however it wants. However, in practice, I would have thought that the decision to increase the frequency (P-state) would occur only when load > cores. What else is there to base the decision on? Perhaps lag time before lowering P-state again? But I would have thought a processor would be capable of fairly rapid changes anyway. – Sparhawk Apr 25 '18 at 10:25performance
mode unless you need to do something as fast as possible. In everyday usage you will hardly notice any difference anyway. – don_crissti Apr 26 '18 at 10:03performance
mode. I'm on a desktop, so battery is irrelevant. The processor might run hotter, but for a shorter time, so it may well even out. Thanks for the link; that is very informative! – Sparhawk Apr 26 '18 at 12:47powersave
, a few cores run at 800 MHz, and most (~8 of 12) cores are < 3000 MHz. Withperformance
, the difference is drastic. All cores are > 3000 MHz, and most are > 4000 MHz. I'm not sure how to measure power draw, but there's no obvious change in temperature. – Sparhawk Apr 29 '18 at 02:03