The patch below is just for testing the impact of disabling
polling of job token pool.

A significant reduction in sys time (on freebsd hosts anyway)
is the main measurable result of disabling.


diff -r 31135c2cae3d bmake/job.c
--- a/bmake/job.c	Sun Apr 15 11:35:06 2018 -0700
+++ b/bmake/job.c	Thu May 03 17:30:43 2018 -0700
@@ -171,6 +171,15 @@
 # define STATIC static
 
 /*
+ * Use .MAKE.POLL_JOB_QUEUE=no to skip polling job queue
+ */
+#define MAKE_POLL_JOB_QUEUE ".MAKE.POLL_JOB_QUEUE"
+#ifndef MAKE_POLL_JOB_QUEUE_DEFAULT
+# define MAKE_POLL_JOB_QUEUE_DEFAULT TRUE
+#endif
+static int Poll_job_queue = MAKE_POLL_JOB_QUEUE_DEFAULT;
+
+/*
  * error handling variables
  */
 static int     	errors = 0;	    /* number of errors reported */
@@ -2409,6 +2418,8 @@
 
     lastNode =	  NULL;
 
+    Poll_job_queue = getBoolean(MAKE_POLL_JOB_QUEUE, Poll_job_queue);
+
     /*
      * There is a non-zero chance that we already have children.
      * eg after 'make -f- <<EOF'
@@ -3118,7 +3129,7 @@
 	}
 	if (DEBUG(JOB))
 	    fprintf(debug_file, "(%d) blocked for token\n", getpid());
-	wantToken = 1;
+	wantToken = Poll_job_queue;
 	return FALSE;
     }