多处理。水塘map不能并行工作

我想要达到的目标是:

并行化 一个函数,每次调用生成多个线程,如下所示:

 - PROCESS01 -> 16 Threads
 - PROCESS02 -> 16 Threads
 - ...
 - PROCESSn -> 16 Threads

代码:

with multiprocessing.Pool(4) as process_pool:
    results = process_pool.map(do_stuff, [drain_queue()])

哪里 drain_queue() 返回项目列表,并

do_stuff(item_list):
    print('> PID: ' + str(os.getpid()))
    with concurrent.futures.ThreadPoolExecutor(max_workers=16) as executor:
        result_dict = {executor.submit(thread_function, item): item for item in item_list}
        for future in concurrent.futures.as_completed(result_dict):
            pass

和 thread_function() 处理传递给它的每个项目。

但是,当执行时,代码输出如下:

> PID: 1000
(WAITS UNTIL THE PROCESS FINISHES, THEN START NEXT)
> PID: 2000
(WAITS UNTIL THE PROCESS FINISHES, THEN START NEXT)
> PID: 3000
(WAITS UNTIL THE PROCESS FINISHES, THEN START NEXT)
> PID: 3000
(WAITS UNTIL THE PROCESS FINISHES, THEN START NEXT)

Here is a screenshot of Task Manager

我错过了什么?我不明白为什么没有按预期工作。 谢谢