diff a/src/hotspot/share/gc/shared/space.hpp b/src/hotspot/share/gc/shared/space.hpp
--- a/src/hotspot/share/gc/shared/space.hpp
+++ b/src/hotspot/share/gc/shared/space.hpp
@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
@@ -67,15 +67,10 @@
   HeapWord* _end;
 
   // Used in support of save_marks()
   HeapWord* _saved_mark_word;
 
-  // A sequential tasks done structure. This supports
-  // parallel GC, where we have threads dynamically
-  // claiming sub-tasks from a larger parallel task.
-  SequentialSubTasksDone _par_seq_tasks;
-
   Space():
     _bottom(NULL), _end(NULL) { }
 
  public:
   // Accessors
@@ -223,13 +218,10 @@
   virtual void print_on(outputStream* st) const;
   virtual void print_short() const;
   virtual void print_short_on(outputStream* st) const;
 
 
-  // Accessor for parallel sequential tasks.
-  SequentialSubTasksDone* par_seq_tasks() { return &_par_seq_tasks; }
-
   // IF "this" is a ContiguousSpace, return it, else return NULL.
   virtual ContiguousSpace* toContiguousSpace() {
     return NULL;
   }