python - python 多处理的内存使用情况

Question

multiprocessing.Process 生成的进程所消耗的内存在进程加入后是否会被释放？

我想到的场景大致是这样的:

from multiprocessing import Process
from multiprocessing import Queue
import time
import os

def main():
  tasks = Queue()  
  for task in [1, 18, 1, 2, 5, 2]:
    tasks.put(task)

  num_proc = 3           # this many workers @ each point in time
  procs = []
  for j in range(num_proc):
     p = Process(target = run_q, args = (tasks,))  
     procs.append(p)
     p.start()

  # joines a worker once he's done
  while procs:
    for p in procs:
        if not p.is_alive():
            p.join()        # what happens to the memory allocated by run()?  
            procs.remove(p)
            print p, len(procs)
    time.sleep(1)  

def run_q(task_q):
    while not task_q.empty():  # while's stuff to do, keep working
        task = task_q.get()
        run(task)

def run(x):       # do real work, allocates memory
    print x, os.getpid()
    time.sleep(3*x)


if __name__ == "__main__":
  main()  

在实际代码中，任务的长度远大于CPU核心的数量，每个任务都是轻量级的，不同的任务占用的CPU时间差异很大(分钟到几天)以及截然不同的内存量(从花生米到几 GB)。所有这些内存都是 run 的本地内存，无需共享它 --- 所以问题是一旦 run 返回和/或一旦进程已加入。

Answer 1

进程消耗的内存在进程终止时被释放。在您的示例中，当 run_q() 返回时会发生这种情况。