--- old/src/hotspot/share/runtime/serviceThread.cpp	2019-07-11 14:50:02.444950781 -0400
+++ new/src/hotspot/share/runtime/serviceThread.cpp	2019-07-11 14:50:01.960932893 -0400
@@ -108,6 +108,7 @@
     bool resolved_method_table_work = false;
     bool protection_domain_table_work = false;
     bool oopstorage_work = false;
+    bool deflate_idle_monitors = false;
     JvmtiDeferredEvent jvmti_event;
     {
       // Need state transition ThreadBlockInVM so that this thread
@@ -133,10 +134,14 @@
               (symboltable_work = SymbolTable::has_work()) |
               (resolved_method_table_work = ResolvedMethodTable::has_work()) |
               (protection_domain_table_work = SystemDictionary::pd_cache_table()->has_work()) |
-              (oopstorage_work = OopStorage::has_cleanup_work_and_reset()))
-             == 0) {
+              (oopstorage_work = OopStorage::has_cleanup_work_and_reset()) |
+              (deflate_idle_monitors = ObjectSynchronizer::is_async_deflation_needed())
+             ) == 0) {
         // Wait until notified that there is some work to do.
-        ml.wait();
+        // If AsyncDeflateIdleMonitors, then we wait for
+        // GuaranteedSafepointInterval so that is_async_deflation_needed()
+        // is checked at the same interval.
+        ml.wait(AsyncDeflateIdleMonitors ? GuaranteedSafepointInterval : 0);
       }
 
       if (has_jvmti_events) {
@@ -179,6 +184,31 @@
     if (oopstorage_work) {
       cleanup_oopstorages(oopstorages, oopstorage_count);
     }
+
+    if (deflate_idle_monitors) {
+      // Deflate any global idle monitors.
+      ObjectSynchronizer::deflate_global_idle_monitors_using_JT();
+
+      // deflate_per_thread_idle_monitors_using_JT() is called by
+      // each JavaThread from ObjectSynchronizer::omAlloc() as needed.
+      int count = 0;
+      for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
+        if (jt->omInUseCount > 0) {
+          // This JavaThread is using monitors so mark it.
+          jt->omShouldDeflateIdleMonitors = true;
+          count++;
+        }
+      }
+      if (count > 0) {
+        log_debug(monitorinflation)("requesting async deflation of idle monitors for %d thread(s).", count);
+      }
+      // The ServiceThread's async deflation request has been processed.
+      ObjectSynchronizer::set_is_async_deflation_requested(false);
+
+      // The global in-use list was handled above, but the request won't
+      // be complete until the JavaThreads have handled their in-use
+      // lists. This is the nature of an async deflation request.
+    }
   }
 }