--- old/src/hotspot/share/gc/serial/serialHeap.hpp	2020-08-05 21:29:28.313604385 +0800
+++ new/src/hotspot/share/gc/serial/serialHeap.hpp	2020-08-05 21:29:28.009604374 +0800
@@ -77,6 +77,7 @@
                                     OopClosureType2* older);
 
   // Runs the given AbstractGangTask with the current active workers.
+  // No workGang for SerialHeap, work serially with thread 0.
   virtual void run_task(AbstractGangTask* task);
 };