--- old/src/hotspot/share/runtime/synchronizer.hpp	2019-08-28 15:00:55.202963822 -0400
+++ new/src/hotspot/share/runtime/synchronizer.hpp	2019-08-28 15:00:55.042963828 -0400
@@ -32,6 +32,7 @@
 #include "runtime/perfData.hpp"
 
 class ObjectMonitor;
+class ObjectMonitorHandle;
 class ThreadsList;
 
 typedef PaddedEnd<ObjectMonitor, DEFAULT_CACHE_LINE_SIZE> PaddedObjectMonitor;
@@ -109,15 +110,16 @@
   static void reenter (Handle obj, intptr_t recursion, TRAPS);
 
   // thread-specific and global ObjectMonitor free list accessors
-  static ObjectMonitor* om_alloc(Thread* self);
+  static ObjectMonitor* om_alloc(Thread* self, const InflateCause cause);
   static void om_release(Thread* self, ObjectMonitor* m,
                          bool FromPerThreadAlloc);
   static void om_flush(Thread* self);
 
   // Inflate light weight monitor to heavy weight monitor
-  static ObjectMonitor* inflate(Thread* self, oop obj, const InflateCause cause);
+  static void inflate(ObjectMonitorHandle* omh_p, Thread* self, oop obj,
+                      const InflateCause cause);
   // This version is only for internal use
-  static void inflate_helper(oop obj);
+  static void inflate_helper(ObjectMonitorHandle* omh_p, oop obj);
   static const char* inflate_cause_name(const InflateCause cause);
 
   // Returns the identity hash value for an oop
@@ -139,6 +141,9 @@
   // Basically we deflate all monitors that are not busy.
   // An adaptive profile-based deflation policy could be used if needed
   static void deflate_idle_monitors(DeflateMonitorCounters* counters);
+  static void deflate_global_idle_monitors_using_JT();
+  static void deflate_per_thread_idle_monitors_using_JT();
+  static void deflate_common_idle_monitors_using_JT(bool is_global, JavaThread* self);
   static void deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters);
   static void prepare_deflate_idle_monitors(DeflateMonitorCounters* counters);
   static void finish_deflate_idle_monitors(DeflateMonitorCounters* counters);
@@ -147,10 +152,25 @@
   static int deflate_monitor_list(ObjectMonitor** list_p,
                                   ObjectMonitor** free_head_p,
                                   ObjectMonitor** free_tail_p);
+  // For a given in-use monitor list: global or per-thread, deflate idle
+  // monitors using a JavaThread.
+  static int deflate_monitor_list_using_JT(ObjectMonitor** list_p,
+                                           ObjectMonitor** free_head_p,
+                                           ObjectMonitor** free_tail_p,
+                                           ObjectMonitor** saved_mid_in_use_p);
   static bool deflate_monitor(ObjectMonitor* mid, oop obj,
                               ObjectMonitor** free_head_p,
                               ObjectMonitor** free_tail_p);
-  static bool is_cleanup_needed();
+  static bool deflate_monitor_using_JT(ObjectMonitor* mid,
+                                       ObjectMonitor** free_head_p,
+                                       ObjectMonitor** free_tail_p);
+  static bool is_async_deflation_needed();
+  static bool is_safepoint_deflation_needed();
+  static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
+  static bool is_special_deflation_requested() { return _is_special_deflation_requested; }
+  static void set_is_async_deflation_requested(bool new_value) { _is_async_deflation_requested = new_value; }
+  static void set_is_special_deflation_requested(bool new_value) { _is_special_deflation_requested = new_value; }
+  static jlong time_since_last_async_deflation_ms();
   static void oops_do(OopClosure* f);
   // Process oops in thread local used monitors
   static void thread_local_used_oops_do(Thread* thread, OopClosure* f);
@@ -175,6 +195,8 @@
   static int  log_monitor_list_counts(outputStream * out);
   static int  verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;
 
+  static void do_safepoint_work(DeflateMonitorCounters* _counters);
+
  private:
   friend class SynchronizerTest;
 
@@ -188,6 +210,9 @@
   static ObjectMonitor* volatile g_om_in_use_list;
   // count of entries in g_om_in_use_list
   static int g_om_in_use_count;
+  static volatile bool _is_async_deflation_requested;
+  static volatile bool _is_special_deflation_requested;
+  static jlong         _last_async_deflation_time_ns;
 
   // Process oops in all global used monitors (i.e. moribund thread's monitors)
   static void global_used_oops_do(OopClosure* f);