[macOS / M1] cpu_percent() gives incorrect information

[rmalouf]

Summary

• OS: macOS 11.4
• Architecture: ARM
• Psutil version: 5.8.0
• Python version: 3.9.4
• Type: core

Description

Process.cpu_percent() always reports very low cpu usage, in contradiction to top and Activity monitor. This test program:

from concurrent.futures import ThreadPoolExecutor
import psutil
import time
from math import log

def work(n):
    m = 0
    for i in range(1, n**2):
        m += log(i)
    return True
    
executor = ThreadPoolExecutor(max_workers=2)
task = executor.submit(work, 10000)

proc = psutil.Process()
while not task.done():
    print(proc.cpu_percent(interval=1))

consistently reports 2.4% usage on the Mac (vs. ~100% usage, as expected, on linux with the same version of psutil).

[rmalouf]

Some updates:

1. I've confirmed that this gives the correct result on an intel Mac, with the same versions of everything
2. The problem is really in cpu_times() -- cpu_percent() is just using the value it gets from there
3. The value returned by cpu_times() is consistently off by a factor of about 0.024. This makes me strongly suspect that the times reported by the kernel via proc_taskinfo aren't in the same units on an M1 vs. intel.

[giampaolo]

PR in #1958

[odormond]

Updated PR in #2011