subprocess.Popen taking too long on WSL Linux

Question

I have this subprocess.Popen() context manager:

with Popen(
    args=command, shell=False, stdout=PIPE, bufsize=1, universal_newlines=True
) as process:

            


        

Answer 1

Windows Subsystem for Linux is a bit rubbish. It's got many, many bugs and it's significantly slower than it needs to be. This is just another bug manifesting itself. Here are some possible bottlenecks:

• Slow context switching in WSL.
• WSL not noticing that an entire process waiting for a pipe means that the other end of the pipe should be run now.
• The child process being executed lazily.
• Windows taking a while to figure out that it needs to use wsl.exe to launch the program (thanks RoadRunner!)
• The usual overhead of Windows, plus the usual (comparatively small) overhead of Linux.
• A poor choice of Ubuntu distro causing many unnecessary services to be running in systemd(?)
• Windows deciding to run other stuff before the child process for some unknown reason.
• Deliberate malice on the part of the Windows Subsystem for Linux developers, conspiring to "prove" that Windows is the superior operating system by setting up a strawman. Too silly.

There's nothing wrong with your Python code that would make this slow.