tools: add memcg_shrinker.py

#!/usr/bin/env python3

#

# Copyright (C) 2022 Roman Gushchin <roman.gushchin@linux.dev>

# Copyright (C) 2022 Meta

import os

import argparse

import sys

def scan_cgroups(cgroup_root):

    cgroups = {}

    for root, subdirs, _ in os.walk(cgroup_root):

        for cgroup in subdirs:

            path = os.path.join(root, cgroup)

            ino = os.stat(path).st_ino

            cgroups[ino] = path

    # (memcg ino, path)

    return cgroups

def scan_shrinkers(shrinker_debugfs):

    shrinkers = []

    for root, subdirs, _ in os.walk(shrinker_debugfs):

        for shrinker in subdirs:

            count_path = os.path.join(root, shrinker, "count")

            with open(count_path) as f:

                for line in f.readlines():

                    items = line.split(' ')

                    ino = int(items[0])

                    # (count, shrinker, memcg ino)

                    shrinkers.append((int(items[1]), shrinker, ino))

    return shrinkers

def main():

    parser = argparse.ArgumentParser(description='Display biggest shrinkers')

    parser.add_argument('-n', '--lines', type=int, help='Number of lines to print')

    args = parser.parse_args()

    cgroups = scan_cgroups("/sys/fs/cgroup/")

    shrinkers = scan_shrinkers("/sys/kernel/debug/shrinker/")

    shrinkers = sorted(shrinkers, reverse = True, key = lambda x: x[0])

    n = 0

    for s in shrinkers:

        count, name, ino = (s[0], s[1], s[2])

        if count == 0:

            break

        if ino == 0 or ino == 1:

            cg = "/"

        else:

            try:

                cg = cgroups[ino]

            except KeyError:

                cg = "unknown (%d)" % ino

        print("%-8s %-20s %s" % (count, name, cg))

        n += 1

        if args.lines and n >= args.lines:

            break

if __name__ == '__main__':

    main()