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

*** 275,285 ****
           * initialize t0
           */
          t0.t_stk = (caddr_t)rp - MINFRAME;
          t0.t_stkbase = t0stack;
          t0.t_pri = maxclsyspri - 3;
!         t0.t_schedflag = TS_LOAD | TS_DONT_SWAP;
          t0.t_procp = &p0;
          t0.t_plockp = &p0lock.pl_lock;
          t0.t_lwp = &lwp0;
          t0.t_forw = &t0;
          t0.t_back = &t0;
--- 275,285 ----
           * initialize t0
           */
          t0.t_stk = (caddr_t)rp - MINFRAME;
          t0.t_stkbase = t0stack;
          t0.t_pri = maxclsyspri - 3;
!         t0.t_schedflag = 0;
          t0.t_procp = &p0;
          t0.t_plockp = &p0lock.pl_lock;
          t0.t_lwp = &lwp0;
          t0.t_forw = &t0;
          t0.t_back = &t0;