MADV_FREE vs MADV_DONTNEED benchmark

bench-madvise.py

#!/usr/bin/env python3

import mmap
import time

NUMBER_VMAS = 10000
VMA_SIZE = 1<<20
buffer = b'0' * VMA_SIZE

def make_vma():
    vma = mmap.mmap(-1, VMA_SIZE, mmap.MAP_PRIVATE, mmap.MADV_NOHUGEPAGE)
    vma.write(buffer)
    return vma

def elapsed_ns(func):
    start = time.time_ns()
    func()
    end = time.time_ns()
    return end - start


def main():
    vmas = [make_vma() for _ in range(NUMBER_VMAS)]
    def run_MADV_FREE():
        for vma in vmas:
            vma.madvise(mmap.MADV_FREE)
    e = elapsed_ns(run_MADV_FREE)
    print('MADV_FREE: {:.3f} us'.format(e / 1e3))
    del vmas

    vmas = [make_vma() for _ in range(NUMBER_VMAS)]
    def run_MADV_DONTNEED():
        for vma in vmas:
            vma.madvise(mmap.MADV_DONTNEED)
    e = elapsed_ns(run_MADV_DONTNEED)
    print('MADV_DONTNEED: {:.3f} us'.format(e / 1e3))
    del vmas

if __name__ == "__main__":
    main()

$ ./bench-madvise.py
MADV_FREE: 149425.587 us
MADV_DONTNEED: 204954.892 us