Python resource.getrusage始终生成相同的结果

我正试图想出我自己的记忆测量装饰。就我而言，像内存分析器这样的libs不适合。 受此启发，我起草了以下代码

import time
from concurrent.futures import ThreadPoolExecutor
import resource
from time import sleep

def test():
    a = [1] * (10 ** 7)
    time.sleep(3)


class MemoryMonitor:

    def __init__(self):
        self.keep_measuring = True

    def measure_usage(self):
        max_usage = 0
        while self.keep_measuring:

            max_usage = max(
                max_usage,
                resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
            )
            sleep(0.1)
        return max_usage


if __name__ == '__main__':
    func = test
    with ThreadPoolExecutor() as executor:
        monitor = MemoryMonitor()
        mem_thread = executor.submit(monitor.measure_usage)
        try:
            fn_thread = executor.submit(func)
            result = fn_thread.result()
        finally:
            monitor.keep_measuring = False
            max_usage = mem_thread.result()
        print("Peak memory usage for {}: {}".format(func.__name__, max_usage))

对我来说，奇怪的是，出于某种原因，它总是产生相同的最大使用量结果，无论我放置

a=[1]*（10**7）

或

a=[1]*（10**6）

，或

a=[1]*（10**5）

。有什么我遗漏的吗