code: def _configure_buffer_sizes():
      
      global PIPE_BUF_BYTES
      global OS_PIPE_SZ
  
      PIPE_BUF_BYTES = 65536
      OS_PIPE_SZ = None
  
      # Teach the 'fcntl' module about 'F_SETPIPE_SZ', which is a Linux-ism,
      # but a good one that can drastically reduce the number of syscalls
      # when dealing with high-throughput pipes.
      if not hasattr(fcntl, 'F_SETPIPE_SZ'):
          import platform
  
          if platform.system() == 'Linux':
              fcntl.F_SETPIPE_SZ = 1031
  
      # If Linux procfs (or something that looks like it) exposes its
      # maximum F_SETPIPE_SZ, adjust the default buffer sizes.
      try:
          with open('/proc/sys/fs/pipe-max-size', 'r') as f:
              # Figure out OS pipe size, but in case it is unusually large
              # or small restrain it to sensible values.
              OS_PIPE_SZ = min(int(f.read()), 1024 * 1024)
              PIPE_BUF_BYTES = max(OS_PIPE_SZ, PIPE_BUF_BYTES)
      except Exception:
          pass
docs: Set up module globals controlling buffer sizes