live_heap_tracker.py

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import sys
import time

import re
import subprocess

TOTAL_RE = re.compile(r'^Total +\d+ +(\d+)', re.MULTILINE)


def main():
    output_file = sys.argv[1]
    iterations = int(sys.argv[2])
    jmap_binary = sys.argv[3]
    benchmark = sys.argv[4:]
    with open(output_file, 'w') as f:
        for _ in range(iterations):
            proc = subprocess.Popen(benchmark)
            while proc.poll() is None:
                time.sleep(0.3)
                try:
                    jmap_output = subprocess.check_output(
                        [jmap_binary, '-histo:live', str(proc.pid)],
                        universal_newlines=True,
                        stderr=subprocess.DEVNULL,
                    )
                    if match := TOTAL_RE.search(jmap_output):
                        heap_bytes = int(match.group(1))
                        f.write(f'{heap_bytes}\n')
                except subprocess.CalledProcessError:
                    pass
            if proc.returncode != 0:
                sys.exit(proc.returncode)


if __name__ == '__main__':
    main()