bug#26397: 25.1; call-process slow on macOS and slower on larger frames

[Aaron Jensen]

On Sat, Apr 8, 2017 at 12:37 AM, YAMAMOTO Mitsuharu
<mituharu@math.s.chiba-u.ac.jp> wrote:
>
> Probably "fork" copies some GUI resources.  That would also explain
> why the performance is worse on the Mac port, where each frame
> allocates an extra NSWindow for overlaying.
>
> It becomes much faster and seemingly unaffected by the frame size if
> you comment out "#undef HAVE_WORKING_VFORK" and "#define vfork fork"
> in src/conf_post.h.  But I'm not sure if it is safe.

Wow, that does make a big difference. The comment says that Emacs
hangs when evaluating:

(make-comint "test0" "/nodir/nofile" nil "")

But I can not reproduce that currently with vfork. I do not understand
the second comment: "Also, setsid is not allowed in the vfork child's
context as of Darwin 9/Mac OS X 10.5."

How might I test that?

I'm happy to run with a build that has this change for a while and see
how it goes.

Perhaps this is no longer an issue in current macOS? Are there any
version specific pragmas for osx?