On Wed, Mar 6, 2024 at 1:08 AM Mark Geisert via Cygwin <cygwin@cygwin.com> wrote: > On 3/5/2024 2:42 PM, Dan Shelton via Cygwin wrote: > > On Mon, 4 Mar 2024 at 07:45, Mark Geisert via Cygwin <cygwin@cygwin.com> > > wrote: > >> On 3/3/2024 7:27 PM, Dan Shelton via Cygwin wrote: > [...] > >>> strace does not help, as I need the Win32 calls BELOW posix_spawn(), > >>> to see the implementation details. > >> > >> Check the source code, then. It's at: > >> https://cygwin.com/cgit/newlib-cygwin/tree/winsup/cygwin/fork.cc > >> > >> Look at line 587; there's the static function dofork(). Look at the > >> thirty or so lines above that; there's both fork() and > >> __posix_spawn_fork() calling dofork(). So both those user-level > >> functions call into the exact same internals. (BTW __posix_spawn_fork() > >> is called from posix_spawn(); the latter is in newlib and not Cygwin.) > >> > >> You can even see the reason it's done this way by reading the comment. > > > > Yes, but it is as I feared, Cygwin posix_spawn() does not use Win32 > > spawn() at all, and instead uses a rather inefficient vfork() > > solution. > > Cygwin's vfork() is just a wrapper around fork(), so yes. But anyway... > > > posix_spawn() was added to POSIX so a Win32 implementation can use Win32 > > spawn() > > ...now I see what you're getting at: > > If posix_spawn() is intended to launch truly unrelated processes, with > minimal or no coordination with the launching process, why can't it just > use Windows' CreateProcess? I assume here that's what Win32 spawn() does. > > That's an interesting research question for somebody. If somebody steps > up for that, great, otherwise as usual PTC. > Regards,
Just one note (which applies to UNIX/Linux): When I was at SUN we had severe performance problems with large JAVA&&database processes launching little helper apps. It turned out to be a |fork()|+|exec()| problem - the |fork()| was basically harmless, but the |exec()| syscall required to tear down all address space, which involved cross-calls to all other CPUs. The performance penalty on a 64 CPU Enterprise 10000 or 72 CPU (up to 144 threads) SF25k was *DEVASTATING* ( <--- understatement). This was fixed for Solaris 11 in several ways: 1. Solaris 11 got a native |posix_spawn()| syscall, and which avoids both |fork()| and the (in this context) dreaded |exec()|, and just sets up a new process with copying only the bare minimum of data from the parent process. 2. Solaris's ksh93 (which is used as /sbin/sh+/bin/sh) got support for |posix_spawn()| (thanks for David Korn and Glenn Fowler for doing that) 3. JAVA was modified to use |posix_spawn()| 4. Oracle was asked to use |posix_spawn()| too For Cygwin I think it would be good to implement a |posix_spawn()| using the native Win32 API too... ---- Bye, Roland -- __ . . __ (o.\ \/ /.o) roland.ma...@nrubsig.org \__\/\/__/ MPEG specialist, C&&JAVA&&Sun&&Unix programmer /O /==\ O\ TEL +49 641 3992797 (;O/ \/ \O;) -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple