diff a/src/hotspot/share/gc/shenandoah/shenandoahMark.hpp b/src/hotspot/share/gc/shenandoah/shenandoahMark.hpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahMark.hpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahMark.hpp
@@ -1,7 +1,8 @@
 /*
  * Copyright (c) 2021, 2022, Red Hat, Inc. All rights reserved.
+ * Copyright Amazon.com Inc. 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.
@@ -23,14 +24,16 @@
  */
 
 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHMARK_HPP
 #define SHARE_GC_SHENANDOAH_SHENANDOAHMARK_HPP
 
+#include "gc/shared/ageTable.hpp"
 #include "gc/shared/stringdedup/stringDedup.hpp"
 #include "gc/shared/taskTerminator.hpp"
 #include "gc/shenandoah/shenandoahGenerationType.hpp"
 #include "gc/shenandoah/shenandoahHeap.hpp"
+#include "gc/shenandoah/shenandoahGeneration.hpp"
 #include "gc/shenandoah/shenandoahTaskqueue.hpp"
 
 enum StringDedupMode {
   NO_DEDUP,      // Do not do anything for String deduplication
   ENQUEUE_DEDUP, // Enqueue candidate Strings for deduplication, if meet age threshold
@@ -43,55 +46,71 @@
 // Base class for mark
 // Mark class does not maintain states. Instead, mark states are
 // maintained by task queues, mark bitmap and SATB buffers (concurrent mark)
 class ShenandoahMark: public StackObj {
 protected:
+  ShenandoahGeneration* const _generation;
   ShenandoahObjToScanQueueSet* const _task_queues;
+  ShenandoahObjToScanQueueSet* const _old_gen_task_queues;
 
 protected:
-  ShenandoahMark();
+  ShenandoahMark(ShenandoahGeneration* generation);
 
 public:
   template<class T, ShenandoahGenerationType GENERATION>
-  static inline void mark_through_ref(T* p, ShenandoahObjToScanQueue* q, ShenandoahMarkingContext* const mark_context, bool weak);
-
-  static void clear();
+  static inline void mark_through_ref(T* p, ShenandoahObjToScanQueue* q, ShenandoahObjToScanQueue* old_q, ShenandoahMarkingContext* const mark_context, bool weak);
 
   // Loom support
   void start_mark();
   void end_mark();
 
   // Helpers
   inline ShenandoahObjToScanQueueSet* task_queues() const;
+  ShenandoahObjToScanQueueSet* old_task_queues() {
+    return _old_gen_task_queues;
+  }
+
   inline ShenandoahObjToScanQueue* get_queue(uint index) const;
+  inline ShenandoahObjToScanQueue* get_old_queue(uint index) const;
+
+  inline ShenandoahGeneration* generation() { return _generation; };
 
-// ---------- Marking loop and tasks
 private:
+// ---------- Marking loop and tasks
+
   template <class T, ShenandoahGenerationType GENERATION, StringDedupMode STRING_DEDUP>
-  inline void do_task(ShenandoahObjToScanQueue* q, T* cl, ShenandoahLiveData* live_data, StringDedup::Requests* const req, ShenandoahMarkTask* task);
+  inline void do_task(ShenandoahObjToScanQueue* q, T* cl, ShenandoahLiveData* live_data, StringDedup::Requests* const req, ShenandoahMarkTask* task, uint worker_id);
 
   template <class T>
   inline void do_chunked_array_start(ShenandoahObjToScanQueue* q, T* cl, oop array, bool weak);
 
   template <class T>
   inline void do_chunked_array(ShenandoahObjToScanQueue* q, T* cl, oop array, int chunk, int pow, bool weak);
 
   template <ShenandoahGenerationType GENERATION>
-  inline void count_liveness(ShenandoahLiveData* live_data, oop obj);
+  inline void count_liveness(ShenandoahLiveData* live_data, oop obj, uint worker_id);
 
   template <class T, ShenandoahGenerationType GENERATION, bool CANCELLABLE, StringDedupMode STRING_DEDUP>
   void mark_loop_work(T* cl, ShenandoahLiveData* live_data, uint worker_id, TaskTerminator *t, StringDedup::Requests* const req);
 
   template <ShenandoahGenerationType GENERATION, bool CANCELLABLE, StringDedupMode STRING_DEDUP>
-  void mark_loop_prework(uint worker_id, TaskTerminator *terminator, ShenandoahReferenceProcessor *rp, StringDedup::Requests* const req);
+  void mark_loop_prework(uint worker_id, TaskTerminator *terminator, ShenandoahReferenceProcessor *rp, StringDedup::Requests* const req, bool update_refs);
+
+  template <ShenandoahGenerationType GENERATION>
+  static bool in_generation(ShenandoahHeap* const heap, oop obj);
+
+  static void mark_ref(ShenandoahObjToScanQueue* q,
+                       ShenandoahMarkingContext* const mark_context,
+                       bool weak, oop obj);
 
   template <StringDedupMode STRING_DEDUP>
   inline void dedup_string(oop obj, StringDedup::Requests* const req);
 protected:
   template<bool CANCELLABLE, StringDedupMode STRING_DEDUP>
   void mark_loop(uint worker_id, TaskTerminator* terminator, ShenandoahReferenceProcessor *rp,
                  ShenandoahGenerationType generation, StringDedup::Requests* const req);
+
   void mark_loop(uint worker_id, TaskTerminator* terminator, ShenandoahReferenceProcessor *rp,
                  ShenandoahGenerationType generation, bool cancellable, StringDedupMode dedup_mode, StringDedup::Requests* const req);
 };
 
 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHMARK_HPP
