schedstat.py

#!/usr/bin/env python
from __future__ import print_function
import argparse
import math
import sys
import time

def schedstat_loop(interval):
    # scale time spent in the scheduler by this factor
    scale = 1024

    multiplier = scale / (1e9 * interval)
    prev_delays = []
    headings = ['Min', 'Max', 'MaxCPU', 'Mean', 'StdDev']
    loops = 0

    print(' '.join(map('{0: >16}'.format, headings)))
    while True:
        schedstat_lines = open('/proc/schedstat').readlines()
        delays = [
          int(i.split(' ')[8]) for i
          in schedstat_lines if i.startswith('cpu')
        ]
        # support CPU offlining
        if len(delays) != len(prev_delays):
            prev_delays = delays

        diffs = [int((a - b) * multiplier) for a, b in zip(delays, prev_delays)]
        count = len(diffs)
        mean = sum(diffs) / count
        (max_, argmax) = max((v, i) for (i, v) in enumerate(diffs))
        stddev = int((sum([(i - mean)**2 for i in diffs]) / count)**0.5)

        output = [min(diffs), max_, argmax, int(mean), stddev]

        print(' '.join(map('{0: 16b}'.format, output)))
        prev_delays = delays
        loops += 1
        time.sleep(interval)

def main():
    parser = argparse.ArgumentParser(description='Display measurements about scheduler latency')
    parser.add_argument('interval', type=float, default=0.05)
    args = parser.parse_args()
    schedstat_loop(args.interval)

if __name__ == '__main__':
    sys.exit(main())