0

How is idle percentage calculated in Activity Monitor with Asymmetrical Multiprocessing (Mx series of chips)?

Anton Tropashko
  • 455
  • 1
    You're talking about Efficiency Cores and Performance cores? Either way, the amount of each CPU core used is calculable, regardless of which cores are being used. What problem are you trying to solve? – benwiggy Jun 27 '23 at 21:08
  • I'm satisfying my curiousity how these EC and PC core utilizations are weighed given their different nature and a single percentage figure given by the monitor. – Anton Tropashko Jun 28 '23 at 08:42
  • 2
    I'm not convinced that there is any weighting. If you've got 10 cores, and only one of them is being used to 100%, then you'll have 90% idle, whichever type of core it is. – benwiggy Jun 28 '23 at 08:50
  • thanks. So idle percentage is newly a random number in the brave new ASMP world. – Anton Tropashko Jun 29 '23 at 11:46
  • 1
    No, not random: it gives you some indication of how much of how much CPU capacity you have left. It's a rough guide. You can't micro-manage the CPU usage yourself. Which cores get used is going to depend on a whole bunch of factors; and the extent to which a given process can use multiple cores without serial limitations will vary wildly. Apple could give you a matrix of data for CPU and process usage, but you'd probably need another computer to calculate anything meaningful from it. – benwiggy Jun 29 '23 at 14:36
  • well two idle figures for EC and PC would have sufficed. Remember how windows used to show perf in a separate graph per core? not sure how it's done on a modern version of windows but XP/2000/7 were sane in that regard even without having much of an ASMP on the PCs of the day – Anton Tropashko Jun 29 '23 at 16:11
  • In any event this could have been an accepted answer if you would've written it as such Ben – Anton Tropashko Jun 29 '23 at 16:12

1 Answers1

1

Activity Monitor will show you each core's usage, which will graphically give you an indication of how idle each core is. That may be as good as way as any to gauge total core usage/idleness.

enter image description here

The first cores on the left are the efficiency ones; in this case I have 4 in my M2 Pro.

There are 20 bars for each core, so 5% each. The 44 bars here correspond to a CPU usage of 22%, thus 88% idle. This figure is in line with the numerical data at the bottom of the Activity Monitor window.

So it seems as though the different core types count equally towards the total.

Conceivably, the 12 bars of Performance cores could be 'worth' a bigger fraction than the 32 bars of Efficiency cores: further sampling of different values would be required to confirm.
(This is left as an exercise for the reader...)

Given the complex nature of core management that the SoC performs (better than any human could); and the complex interaction of threads in a process, and the extent to which they can be independently divided across cores, any single value measure would be a rough guide at best.

benwiggy
  • 35,635