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

*** 250,263 ****
          uint64_t pgfrec;                /* page reclaims from free list */
          uint64_t pgin;                  /* pageins */
          uint64_t pgpgin;                /* pages paged in */
          uint64_t pgout;                 /* pageouts */
          uint64_t pgpgout;               /* pages paged out */
-         uint64_t swapin;                /* swapins */
-         uint64_t pgswapin;              /* pages swapped in */
-         uint64_t swapout;               /* swapouts */
-         uint64_t pgswapout;             /* pages swapped out */
          uint64_t zfod;                  /* pages zero filled on demand */
          uint64_t dfree;                 /* pages freed by daemon or auto */
          uint64_t scan;                  /* pages examined by pageout daemon */
          uint64_t rev;                   /* revolutions of page daemon hand */
          uint64_t hat_fault;             /* minor page faults via hat_fault() */
--- 250,259 ----