--- old/src/hotspot/share/runtime/serviceThread.cpp	2019-05-25 10:46:33.902883664 -0400
+++ new/src/hotspot/share/runtime/serviceThread.cpp	2019-05-25 10:46:33.186883626 -0400
@@ -127,6 +127,7 @@
     bool protection_domain_table_work = false;
     bool oopstorage_work = false;
     bool oopstorages_cleanup[oopstorage_count] = {}; // Zero (false) initialize.
+    bool deflate_idle_monitors = false;
     JvmtiDeferredEvent jvmti_event;
     {
       // Need state transition ThreadBlockInVM so that this thread
@@ -154,11 +155,14 @@
               (protection_domain_table_work = SystemDictionary::pd_cache_table()->has_work()) |
               (oopstorage_work = needs_oopstorage_cleanup(oopstorages,
                                                           oopstorages_cleanup,
-                                                          oopstorage_count)))
-
-             == 0) {
+                                                          oopstorage_count)) |
+              (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) {
@@ -201,6 +205,26 @@
     if (oopstorage_work) {
       cleanup_oopstorages(oopstorages, oopstorages_cleanup, 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);
+      }
+      ObjectSynchronizer::set_is_async_deflation_requested(false);  // async deflation has been requested
+    }
   }
 }