commit 7be53f10f3df3c3183cc97d6bbadb78ebb61e8d2
Author: Campbell Barton <ideasman42@gmail.com>
Date:   Sun Oct 10 10:16:47 2021 +1100

    Support accessing the number of CPU's.

    Add (processor-count) for accessing the number of cores/CPU's.

diff --git a/src/emacs.c b/src/emacs.c
index 866e43fda9..26e2f6b1f2 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -3156,6 +3156,38 @@ DEFUN ("daemon-initialized", Fdaemon_initialized, Sdaemon_initialized, 0, 0, 0,
   return Qt;
 }

+DEFUN ("processor-count", Fprocessor_count, Sprocessor_count, 0, 0, 0,
+       doc: /* Return the number of CPUs in the system.
+
+The value will always be above zero, 1 for unsupported systems.  */)
+  (void)
+{
+  int nproc = -1;
+#ifdef WINDOWSNT
+  SYSTEM_INFO info;
+  GetSystemInfo(&info);
+  nproc = (int)info.dwNumberOfProcessors;
+#elif defined (__APPLE__) || \
+      defined (__OpenBSD__) || \
+      defined (__FreeBSD__) || \
+      defined (__NetBSD__) || \
+      defined (__DragonFly__)
+  int mib[2];
+  size_t len;
+
+  mib[0] = CTL_HW;
+  mib[1] = HW_NCPU;
+  len = sizeof(nproc);
+  sysctl(mib, 2, &nproc, &len, nullptr, 0);
+#elif defined (__hpux)
+  nproc = mpctl(MPC_GETNUMSPUS, NULL, NULL);
+#elif defined (_SC_NPROCESSORS_ONLN)
+  nproc = (int)sysconf(_SC_NPROCESSORS_ONLN);
+#endif
+
+  return make_fixnum (MAX(nproc, 1));
+}
+
 void
 syms_of_emacs (void)
 {
@@ -3176,6 +3208,7 @@ syms_of_emacs (void)
   defsubr (&Sinvocation_directory);
   defsubr (&Sdaemonp);
   defsubr (&Sdaemon_initialized);
+  defsubr (&Sprocessor_count);

   DEFVAR_LISP ("command-line-args", Vcommand_line_args,
 	       doc: /* Args passed by shell to Emacs, as a list of strings.