--- old/src/hotspot/share/runtime/os.hpp	2017-11-20 13:39:28.780831439 -0500
+++ new/src/hotspot/share/runtime/os.hpp	2017-11-20 13:39:28.643831670 -0500
@@ -135,6 +135,8 @@
   static void   pd_free_memory(char *addr, size_t bytes, size_t alignment_hint);
   static void   pd_realign_memory(char *addr, size_t bytes, size_t alignment_hint);
 
+  static size_t pd_committed_stack_size(address bottom, size_t size);
+
   static size_t page_size_for_region(size_t region_size, size_t min_pages, bool must_be_aligned);
 
   // Get summary strings for system information in buffer provided
@@ -268,6 +270,10 @@
   static void map_stack_shadow_pages(address sp);
   static bool stack_shadow_pages_available(Thread *thread, const methodHandle& method, address sp);
 
+  // Return size of stack that is actually committed. For Java thread, the bottom should be above
+  // guard pages (stack grows downward)
+  static size_t committed_stack_size(address bottom, size_t size);
+
   // OS interface to Virtual Memory
 
   // Return the default page size.