src/share/vm/runtime/arguments.cpp

@@ -2081,10 +2081,16 @@
   // biased locking on modern hardware are not covering the latency problems induced by
   // it. Therefore, unless user really wants it, disable biased locking.
   if (FLAG_IS_DEFAULT(UseBiasedLocking)) {
     FLAG_SET_DEFAULT(UseBiasedLocking, false);
   }
+
+  // In current Shenandoah, default System.gc() means full stop-the-world GC, which might
+  // surprise users. Replace it with full concurrent GC, unless user really wants otherwise.
+  if (FLAG_IS_DEFAULT(ExplicitGCInvokesConcurrent)) {
+    FLAG_SET_DEFAULT(ExplicitGCInvokesConcurrent, true);
+  }
 }
 
 void Arguments::set_gc_specific_flags() {
 #if INCLUDE_ALL_GCS
   // Set per-collector flags