--- old/src/hotspot/share/runtime/objectMonitor.hpp	2019-08-28 15:03:30.106958426 -0400
+++ new/src/hotspot/share/runtime/objectMonitor.hpp	2019-08-28 15:03:29.914958433 -0400
@@ -126,6 +126,12 @@
 //     intptr_t. There's no reason to use a 64-bit type for this field
 //     in a 64-bit JVM.
 
+#ifndef OM_CACHE_LINE_SIZE
+// Use DEFAULT_CACHE_LINE_SIZE if not already specified for
+// the current build platform.
+#define OM_CACHE_LINE_SIZE DEFAULT_CACHE_LINE_SIZE
+#endif
+
 class ObjectMonitor {
  public:
   enum {
@@ -147,24 +153,39 @@
   // Enforced by the assert() in header_addr().
   volatile markWord _header;        // displaced object header word - mark
   void* volatile _object;           // backward object pointer - strong root
+  typedef enum {
+    Free = 0,  // Free must be 0 for monitor to be free after memset(..,0,..).
+    New,
+    Old
+  } AllocationState;
+  AllocationState _allocation_state;
  public:
   ObjectMonitor* _next_om;          // Next ObjectMonitor* linkage
  private:
   // Separate _header and _owner on different cache lines since both can
-  // have busy multi-threaded access. _header and _object are set at
-  // initial inflation and _object doesn't change until deflation so
-  // _object is a good choice to share the cache line with _header.
-  // _next_om shares _header's cache line for pre-monitor list historical
-  // reasons. _next_om only changes if the next ObjectMonitor is deflated.
-  DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE,
-                        sizeof(volatile markWord) + sizeof(void* volatile) +
-                        sizeof(ObjectMonitor *));
+  // have busy multi-threaded access. _header, _object and _allocation_state
+  // are set at initial inflation. _object and _allocation_state don't
+  // change until deflation so _object and _allocation_state are good
+  // choices to share the cache line with _header. _next_om shares _header's
+  // cache line for pre-monitor list historical reasons. _next_om only
+  // changes if the next ObjectMonitor is deflated.
+  DEFINE_PAD_MINUS_SIZE(0, OM_CACHE_LINE_SIZE, sizeof(volatile markWord) +
+                        sizeof(void* volatile) + sizeof(AllocationState) +
+                        sizeof(ObjectMonitor*));
   // Used by async deflation as a marker in the _owner field:
   #define DEFLATER_MARKER reinterpret_cast<void*>(-1)
  protected:                         // protected for JvmtiRawMonitor
   void* volatile _owner;            // pointer to owning thread OR BasicLock
  private:
   volatile jlong _previous_owner_tid;  // thread id of the previous owner of the monitor
+  // Separate _owner and _ref_count on different cache lines since both
+  // can have busy multi-threaded access. _previous_owner_tid is only
+  // changed by ObjectMonitor::exit() so it is a good choice to share the
+  // cache line with _owner.
+  DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(void* volatile) +
+                        sizeof(volatile jlong));
+  volatile jint _ref_count;         // ref count for ObjectMonitor* and used by the async deflation
+                                    // protocol. See ObjectSynchronizer::deflate_monitor_using_JT().
  protected:                         // protected for JvmtiRawMonitor
   volatile intptr_t _recursions;    // recursion count, 0 for first entry
   ObjectWaiter* volatile _EntryList;  // Threads blocked on entry or reentry.
@@ -187,14 +208,6 @@
   volatile jint  _waiters;          // number of waiting threads
  private:
   volatile int _WaitSetLock;        // protects Wait Queue - simple spinlock
-  volatile jint _ref_count;         // ref count for ObjectMonitor* and used by the async deflation
-                                    // protocol. See ObjectSynchronizer::deflate_monitor_using_JT().
-  typedef enum {
-    Free = 0,  // Free must be 0 for monitor to be free after memset(..,0,..).
-    New,
-    Old
-  } AllocationState;
-  AllocationState _allocation_state;
 
  public:
   static void Initialize();