Does iowait time counted while psutil.cpu_percent are called?

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I want to know if iowait time are counted in psutil.cpu_percent(), so write a code as below to test

#cat test.py
import os
import psutil
import time


p = psutil.Process(os.getpid())


start = time.time()
times_before_workload = p.cpu_times()
# this function return cpu_percent between two call. so we have to call it once before workload
percent_before_workload = p.cpu_percent()  


# I call f open/close many times and read from the file 
# hoping cpu will spent time on both user system and iowait

c = 1000
while c:
    f = open('/tmp/big_text')
    content = f.read(10240)
    f.close()
    c -= 1

end = time.time()
percent_after_workload = p.cpu_percent()


times_after_workload = p.cpu_times()
user_seconds = times_after_workload.user - times_before_workload.user
system_seconds = times_after_workload.system - times_before_workload.system
iowait_seconds = times_after_workload.iowait - times_before_workload.iowait

# if cpu percent == user_percent + system_percent + iowait_percent then it means yes. iowait are counted

print 'user_percent %s' % round(user_seconds / (end - start) * 100, 2)
print 'system_percent %s' % round(system_seconds / (end - start) * 100, 2)
print 'iowait_percent %s' % round(iowait_seconds / (end - start) * 100, 2)
print 'percent %s' % percent_after_workload

here is this output

#python test.py
user_percent 67.06
system_percent 67.06
iowait_percent 0.0
percent 134.8

The iowait is 0 so still can not verify. So question are

  1. does iowait counted in cpu percent?
  2. how to make iowait happen?(no zero)
psutil cpu linux python
1 Answers
  1. No, iowait is not counted in cpu percent.
  2. Run vmtouch to evict pages from memory at the start of each iteration of the loop.

You may need to install vmtouch:

apt update
apt install vmtouch

Run vmtouch in Python:

import subprocess

subprocess.run(['vmtouch', '-e', '/tmp/big_text'], stdout=subprocess.DEVNULL)

Reference: Why iowait of reading file is zero?

user_86017600
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