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

*** 45,57 ****
          uchar_t         fsi_panic;      /* thread called panic() */
          uchar_t         fsi_max_depth;  /* stack frames available */
  } findstack_info_t;
  
  #define FSI_FAIL_BADTHREAD      1
! #define FSI_FAIL_NOTINMEMORY    2
! #define FSI_FAIL_THREADCORRUPT  3
! #define FSI_FAIL_STACKNOTFOUND  4
  
  typedef struct stacks_module {
          char            sm_name[MAXPATHLEN]; /* name of module */
          uintptr_t       sm_text;        /* base address of text in module */
          size_t          sm_size;        /* size of text in module */
--- 45,56 ----
          uchar_t         fsi_panic;      /* thread called panic() */
          uchar_t         fsi_max_depth;  /* stack frames available */
  } findstack_info_t;
  
  #define FSI_FAIL_BADTHREAD      1
! #define FSI_FAIL_THREADCORRUPT  2
! #define FSI_FAIL_STACKNOTFOUND  3
  
  typedef struct stacks_module {
          char            sm_name[MAXPATHLEN]; /* name of module */
          uintptr_t       sm_text;        /* base address of text in module */
          size_t          sm_size;        /* size of text in module */