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Adjustments for Large Number of Concurrent Processes on macOS

Make the following adjustments if you are running a system that requires a large number of processes or telnet logins:

  1. Remote connections — The number of pty (pseudo terminal) connections is limited to 128 system-wide. If your applications count on telnet or other pty-using connections for users to access, keep this in mind.

  2. Number of processes — If the pty limit is not a problem, but you need to run a larger number of processes, there are limits to that as well.

    • System-wide process limits — The kern.maxproc, kern.maxprocperuid parameters are set to 532 and 100 by default. You can change them using the following commands:

      administrator$ sudo sysctl -w kern.maxproc=2500
      kern.maxproc: 2065 -> 2500
      administrator$ sudo sysctl -w kern.maxprocperuid=2500
      kern.maxprocperuid: 2000 -> 2500
      administrator$ sysctl -a | grep maxproc
      kern.maxproc = 2500
      kern.maxprocperuid = 2500

      Note, however, that 2500 is the absolute unchangeable upper limit.

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