5 ms·

Didn't he just say that fork turns out to be comparatively faster to the non-fork samples we get? Ie Linux spawns processes faster than Microsoft's kernels?

• nvme0n1p1 3mo ago
  We don't have any broadly used non-fork samples. Windows, macOS, and Linux all have fork. So the presence of fork can't be the reason for the performance difference. (Windows's fork is called ZwCreateProcess)
  • dcrazy 3mo ago
    NtCreateProcess does not implement a forking model. It is analogous to posix_spawn.
    • nvme0n1p1 3mo ago
      If you pass null for the section handle, it shares pages with the calling process, thus implementing a forking model. Or at least the parts of a forking model that some people erroneously believe are responsible for performance differences.
  • Someone 3mo ago
    MacOS has posix_spawn. See https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/posix_spawn.2.html https://developer.apple.com/library/archive/documentation/Sy... (yes, that’s an iOS man page. MacOS has the call, too, but I couldn’t find the man page online and it looks identical to me) I don’t know how they implemented it, though. Under the hood, it could do the equivalent of a fork/exec pair.
    • plorkyeran 3mo ago
      XNU's posix_spawn implementation is not fork/exec-based. It does roughly what the API suggests it would do.
    • dcrazy 3mo ago
      XNU is open source; here’s a link into the middle of the implementation, after it’s copied all the necessary attributes of the parent into the new process structure: https://github.com/apple-oss-distributions/xnu/blob/f6217f891ac0bb64f3d375211650a4c1ff8ca1ea/bsd/kern/kern_exec.c#L4039 https://github.com/apple-oss-distributions/xnu/blob/f6217f89...
• mort96 3mo ago
  Didn't I just say that "the problem with fork isn't really that it's slow"? It's all the other OS design choices it forces on you if you want it to be fast.
  • theK 3mo ago
    Right, you did. I somehow misread your comment.