src/hotspot/share/runtime/objectMonitor.hpp

rev 57560 : imported patch 8235795.patch.cr0

*** 128,151 ****
  
    // The sync code expects the header field to be at offset zero (0).
    // Enforced by the assert() in header_addr().
    volatile markWord _header;        // displaced object header word - mark
    void* volatile _object;           // backward object pointer - strong root
-  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 *));
    void* volatile _owner;            // pointer to owning thread OR BasicLock
    volatile jlong _previous_owner_tid;  // thread id of the previous owner of the monitor
    volatile intx _recursions;        // recursion count, 0 for first entry
    ObjectWaiter* volatile _EntryList;  // Threads blocked on entry or reentry.
                                        // The list is actually composed of WaitNodes,
                                        // acting as proxies for Threads.
  
--- 128,155 ----
  
    // The sync code expects the header field to be at offset zero (0).
    // Enforced by the assert() in header_addr().
    volatile markWord _header;        // displaced object header word - mark
    void* volatile _object;           // backward object pointer - strong root
   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.
    DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE,
!                         sizeof(volatile markWord) + sizeof(void* volatile));
    void* volatile _owner;            // pointer to owning thread OR BasicLock
    volatile jlong _previous_owner_tid;  // thread id of the previous owner of the monitor
+   // Separate _owner and _next_om 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, DEFAULT_CACHE_LINE_SIZE, sizeof(void* volatile) +
+                         sizeof(volatile jlong));
+  public:
+   ObjectMonitor* _next_om;          // Next ObjectMonitor* linkage
+  private:
    volatile intx _recursions;        // recursion count, 0 for first entry
    ObjectWaiter* volatile _EntryList;  // Threads blocked on entry or reentry.
                                        // The list is actually composed of WaitNodes,
                                        // acting as proxies for Threads.