Python:subprocess.Popen()的第一个实例非常慢 [英] Python: first instance of subprocess.Popen() is very slow

问题描述

我确定我缺少一些简单的东西，但是在使用子流程模块时，要启动第一个子流程要花很长时间(> 10秒).第二个开始在第一个之后不久.有没有什么办法解决这一问题?下面的代码:

I'm sure I'm missing something simple, but when using the subprocess module, there is a very significant wait (> 10 seconds) to starting the first subprocess. The second one starts shortly after the first. Is there any way to fix this? Code below:

要添加，HWAccess(在proc.py中)链接一个dll.这可能与它有关吗? 我将测试归结为开始一个SINGLE子进程，与直接从cmd提示符下直接运行proc.py相比，导入HWAccess所花费的时间要长得多.我看不出这与dll有什么关系，特别是如果它从cmd快速加载，但不是通过test.py作为子进程的话.

To add, HWAccess (in proc.py) links a dll. Could this have anything to do with it? I've boiled the test down to starting a SINGLE subprocess and it takes significantly longer to import HWAccess than if I just run proc.py directly from cmd prompt. I don't see how this has anything to do with the dll specifically if it loads fast from cmd, but not as a sub-process through test.py

test.py:

import subprocess
import os
import time

print 'STARTING'
proc0 = subprocess.Popen(['python','proc.py','0'])
proc1 = subprocess.Popen(['python','proc.py','1'])

while True: 
    try: pass
    except KeyboardInterrupt: 
    os._exit(0)
except ValueError: 
    pass

proc.py:

print 'Process starting...'
import HWAccess
print 'HWAccess imported...'
import sys
print 'sys imported...'
import time
print 'time imported...'

print 'hi from ',sys.argv[1]

放入打印件之后，大约需要5秒钟才能到达第一个处理开始..."，第二个处理之后立即打印处理开始...".然后会有大约30秒的暂停来导入HWAccess(在单个进程上运行仅需几秒钟)，然后第二个进程立即打印出它也已经导入了HWAccess ...从那时起执行速度很快. HWAccess链接了一个.dll，所以我想知道两个试图导入HWAccess的进程是否会导致某种竞争状态，而这需要花费一些时间进行协商.

After putting the prints in, there is around 5s to reach the first 'Process starting...', the second process prints 'Process starting...' immediately afterwards. Then there is a ~30 second pause to import HWAccess (takes a matter of seconds running on an individual process), the second process then immediately prints that it too has imported HWAccess... from then on execution is fast. HWAccess links a .dll so I'm wondering if two processes trying to import HWAccess result in some sort of race condition that takes a while to negotiate.

推荐答案

我不确定这是否是正确的方法，但是我记得在启动一个进程时会看到这样的延迟(而且一点也不与Python相关)，并且原来，它们与我计算机上某些配置错误的网络设置有关.在子进程启动时，它必须建立进程间通信，并且这些设置可能会干扰.

I am not sure if this is the right track, but I remember seeing such delays when starting a process wayyy back (and not at all Python related), and it turned out they were related to some badly configured network settings on my computer. Upon subprocess start-up, it has to set up interprocess communication, and those settings might interfere.

我记得我的问题与在计算机上使用错误的主机名有关，该主机名在网络上配置不正确-您可以检查是否属于您的情况吗?如果不是生产计算机，请尝试完全不设置主机名，而将其保留为"localhost".

I remember my problems were related to using a false hostname for the machine, which was not properly configured on the network - can you check to see if it is your case? If it is not a production machine, try not setting a hostname at all, leaving it as "localhost".

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