re #13613 rb4516 Tunables needs volatile keyword

@@ -342,11 +342,11 @@
  * Automagic pageout.
  * When memory gets tight, start freeing pages popping out of the
  * write queue.
  */
 int     write_free = 1;
-pgcnt_t pages_before_pager = 200;       /* LMXXX */
+volatile pgcnt_t pages_before_pager = 200;      /* LMXXX */
 
 /*
  * Routine to be called when page-out's complete.
  * The caller, typically VOP_PUTPAGE, has to explicity call this routine
  * after waiting for i/o to complete (biowait) to free the list of