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

*** 166,182 ****
          extern boolean_t tick_stick_emulation_active;
  #endif  /* sun4v */
  
          CPU_STATS_ADDQ(CPU, sys, trap, 1);
  
- #ifdef SF_ERRATA_23 /* call causes illegal-insn */
-         ASSERT((curthread->t_schedflag & TS_DONT_SWAP) ||
-             (type == T_UNIMP_INSTR));
- #else
-         ASSERT(curthread->t_schedflag & TS_DONT_SWAP);
- #endif /* SF_ERRATA_23 */
- 
          if (USERMODE(rp->r_tstate) || (type & T_USER)) {
                  /*
                   * Set lwp_state before trying to acquire any
                   * adaptive lock
                   */
--- 166,175 ----
*** 1370,1381 ****
          uint32_t inst;
          utrap_handler_t *utrapp;
  
          CPU_STATS_ADDQ(CPU, sys, trap, 1);
  
-         ASSERT(curthread->t_schedflag & TS_DONT_SWAP);
- 
          if (USERMODE(rp->r_tstate)) {
                  /*
                   * Set lwp_state before trying to acquire any
                   * adaptive lock
                   */
--- 1363,1372 ----