--- a/src/hotspot/share/gc/z/zDriver.cpp	Mon Oct 21 14:04:16 2019 +0800
+++ b/src/hotspot/share/gc/z/zDriver.cpp	Mon Oct 21 09:51:24 2019 +0200
@@ -250,11 +250,17 @@
   case GCCause::_z_allocation_stall:
   case GCCause::_z_proactive:
   case GCCause::_z_high_usage:
-  case GCCause::_metadata_GC_threshold:
     // Start asynchronous GC
     _gc_cycle_port.send_async(cause);
     break;
 
+  case GCCause::_metadata_GC_threshold:
+    // Start asynchronous GC, but only if the GC is warm
+    if (ZStatCycle::is_warm()) {
+      _gc_cycle_port.send_async(cause);
+    }
+    break;
+
   case GCCause::_gc_locker:
     // Restart VM operation previously blocked by the GC locker
     _gc_locker_port.signal();