remove whole-process swapping
Long before Unix supported paging, it used process swapping to reclaim
memory.  The code is there and in theory it runs when we get *extremely* low
on memory.  In practice, it never runs since the definition of low-on-memory
is antiquated. (XXX: define what antiquated means)
You can check the number of swapout/swapin events with kstats:
$ kstat -p ::vm:swapin ::vm:swapout

*** 221,235 ****
           * Mark the time when thread is placed on wait queue. The microstate
           * accounting code uses this timestamp to determine wait times.
           */
          t->t_waitrq = gethrtime_unscaled();
  
-         /*
-          * Mark thread as not swappable.  If necessary, it will get
-          * swapped out when it returns to the userland.
-          */
-         t->t_schedflag |= TS_DONT_SWAP;
          DTRACE_SCHED1(cpucaps__sleep, kthread_t *, t);
          waitq_link(wq, t);
  
          THREAD_WAIT(t, &wq->wq_lock);
          return (1);
--- 221,230 ----