diff a/src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp b/src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp
@@ -1,7 +1,8 @@
 /*
  * Copyright (c) 2015, 2020, 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.
@@ -38,18 +39,20 @@
 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
 #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
-#include "gc/shenandoah/shenandoahControlThread.hpp"
+#include "gc/shenandoah/shenandoahGeneration.hpp"
 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
+#include "gc/shenandoah/mode/shenandoahMode.hpp"
 #include "oops/compressedOops.inline.hpp"
 #include "oops/oop.inline.hpp"
 #include "runtime/atomic.hpp"
 #include "runtime/javaThread.hpp"
 #include "runtime/prefetch.inline.hpp"
+#include "runtime/objectMonitor.inline.hpp"
 #include "utilities/copy.hpp"
 #include "utilities/globalDefinitions.hpp"
 
 inline ShenandoahHeap* ShenandoahHeap::heap() {
   return named_heap<ShenandoahHeap>(CollectedHeap::Shenandoah);
@@ -71,18 +74,30 @@
 
 inline WorkerThreads* ShenandoahHeap::safepoint_workers() {
   return _safepoint_workers;
 }
 
+inline void ShenandoahHeap::notify_gc_progress() {
+  Atomic::store(&_gc_no_progress_count, (size_t) 0);
+
+}
+inline void ShenandoahHeap::notify_gc_no_progress() {
+  Atomic::inc(&_gc_no_progress_count);
+}
+
+inline size_t ShenandoahHeap::get_gc_no_progress_count() const {
+  return Atomic::load(&_gc_no_progress_count);
+}
+
 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
   uintptr_t region_start = ((uintptr_t) addr);
   uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
   assert(index < num_regions(), "Region index is in bounds: " PTR_FORMAT, p2i(addr));
   return index;
 }
 
-inline ShenandoahHeapRegion* const ShenandoahHeap::heap_region_containing(const void* addr) const {
+inline ShenandoahHeapRegion* ShenandoahHeap::heap_region_containing(const void* addr) const {
   size_t index = heap_region_index_containing(addr);
   ShenandoahHeapRegion* const result = get_region(index);
   assert(addr >= result->bottom() && addr < result->end(), "Heap region contains the address: " PTR_FORMAT, p2i(addr));
   return result;
 }
@@ -250,13 +265,20 @@
     }
   }
   return cancelled_gc();
 }
 
-inline void ShenandoahHeap::clear_cancelled_gc() {
+inline void ShenandoahHeap::clear_cancelled_gc(bool clear_oom_handler) {
   _cancelled_gc.set(CANCELLABLE);
-  _oom_evac_handler.clear();
+  if (_cancel_requested_time > 0) {
+    log_debug(gc)("GC cancellation took %.3fs", (os::elapsedTime() - _cancel_requested_time));
+    _cancel_requested_time = 0;
+  }
+
+  if (clear_oom_handler) {
+    _oom_evac_handler.clear();
+  }
 }
 
 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
   assert(UseTLAB, "TLABs should be enabled");
 
@@ -269,91 +291,153 @@
   }
   HeapWord* obj = gclab->allocate(size);
   if (obj != nullptr) {
     return obj;
   }
-  // Otherwise...
   return allocate_from_gclab_slow(thread, size);
 }
 
-inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
-  if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
-    // This thread went through the OOM during evac protocol and it is safe to return
-    // the forward pointer. It must not attempt to evacuate any more.
-    return ShenandoahBarrierSet::resolve_forwarded(p);
+void ShenandoahHeap::increase_object_age(oop obj, uint additional_age) {
+  // This operates on new copy of an object. This means that the object's mark-word
+  // is thread-local and therefore safe to access. However, when the mark is
+  // displaced (i.e. stack-locked or monitor-locked), then it must be considered
+  // a shared memory location. It can be accessed by other threads.
+  // In particular, a competing evacuating thread can succeed to install its copy
+  // as the forwardee and continue to unlock the object, at which point 'our'
+  // write to the foreign stack-location would potentially over-write random
+  // information on that stack. Writing to a monitor is less problematic,
+  // but still not safe: while the ObjectMonitor would not randomly disappear,
+  // the other thread would also write to the same displaced header location,
+  // possibly leading to increase the age twice.
+  // For all these reasons, we take the conservative approach and not attempt
+  // to increase the age when the header is displaced.
+  markWord w = obj->mark();
+  // The mark-word has been copied from the original object. It can not be
+  // inflating, because inflation can not be interrupted by a safepoint,
+  // and after a safepoint, a Java thread would first have to successfully
+  // evacuate the object before it could inflate the monitor.
+  assert(!w.is_being_inflated() || LockingMode == LM_LIGHTWEIGHT, "must not inflate monitor before evacuation of object succeeds");
+  // It is possible that we have copied the object after another thread has
+  // already successfully completed evacuation. While harmless (we would never
+  // publish our copy), don't even attempt to modify the age when that
+  // happens.
+  if (!w.has_displaced_mark_helper() && !w.is_marked()) {
+    w = w.set_age(MIN2(markWord::max_age, w.age() + additional_age));
+    obj->set_mark(w);
   }
+}
 
-  assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
+// Return the object's age, or a sentinel value when the age can't
+// necessarily be determined because of concurrent locking by the
+// mutator
+uint ShenandoahHeap::get_object_age(oop obj) {
+  markWord w = obj->mark();
+  assert(!w.is_marked(), "must not be forwarded");
+  if (w.has_monitor()) {
+    w = w.monitor()->header();
+  } else if (w.is_being_inflated() || w.has_displaced_mark_helper()) {
+    // Informs caller that we aren't able to determine the age
+    return markWord::max_age + 1; // sentinel
+  }
+  assert(w.age() <= markWord::max_age, "Impossible!");
+  return w.age();
+}
 
-  size_t size = p->size();
+bool ShenandoahHeap::is_in(const void* p) const {
+  HeapWord* heap_base = (HeapWord*) base();
+  HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
+  return p >= heap_base && p < last_region_end;
+}
 
-  assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
+inline bool ShenandoahHeap::is_in_active_generation(oop obj) const {
+  if (!mode()->is_generational()) {
+    // everything is the same single generation
+    assert(is_in(obj), "Otherwise shouldn't return true below");
+    return true;
+  }
 
-  bool alloc_from_gclab = true;
-  HeapWord* copy = nullptr;
+  ShenandoahGeneration* const gen = active_generation();
 
-#ifdef ASSERT
-  if (ShenandoahOOMDuringEvacALot &&
-      (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
-        copy = nullptr;
-  } else {
-#endif
-    if (UseTLAB) {
-      copy = allocate_from_gclab(thread, size);
-    }
-    if (copy == nullptr) {
-      ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
-      copy = allocate_memory(req);
-      alloc_from_gclab = false;
-    }
-#ifdef ASSERT
+  if (gen == nullptr) {
+    // no collection is happening: only expect this to be called
+    // when concurrent processing is active, but that could change
+    return false;
   }
-#endif
 
-  if (copy == nullptr) {
-    control_thread()->handle_alloc_failure_evac(size);
+  assert(is_in(obj), "only check if is in active generation for objects (" PTR_FORMAT ") in heap", p2i(obj));
+  assert(gen->is_old() || gen->is_young() || gen->is_global(),
+         "Active generation must be old, young, or global");
+
+  size_t index = heap_region_containing(obj)->index();
+
+  // No flickering!
+  assert(gen == active_generation(), "Race?");
+
+  switch (_affiliations[index]) {
+  case ShenandoahAffiliation::FREE:
+    // Free regions are in old, young, and global collections
+    return true;
+  case ShenandoahAffiliation::YOUNG_GENERATION:
+    // Young regions are in young and global collections, not in old collections
+    return !gen->is_old();
+  case ShenandoahAffiliation::OLD_GENERATION:
+    // Old regions are in old and global collections, not in young collections
+    return !gen->is_young();
+  default:
+    assert(false, "Bad affiliation (%d) for region " SIZE_FORMAT, _affiliations[index], index);
+    return false;
+  }
+}
+
+inline bool ShenandoahHeap::is_in_young(const void* p) const {
+  return is_in(p) && (_affiliations[heap_region_index_containing(p)] == ShenandoahAffiliation::YOUNG_GENERATION);
+}
 
-    _oom_evac_handler.handle_out_of_memory_during_evacuation();
+inline bool ShenandoahHeap::is_in_old(const void* p) const {
+  return is_in(p) && (_affiliations[heap_region_index_containing(p)] == ShenandoahAffiliation::OLD_GENERATION);
+}
 
-    return ShenandoahBarrierSet::resolve_forwarded(p);
-  }
+inline bool ShenandoahHeap::is_in_old_during_young_collection(oop obj) const {
+  return active_generation()->is_young() && is_in_old(obj);
+}
 
-  // Copy the object:
-  Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
-
-  // Try to install the new forwarding pointer.
-  oop copy_val = cast_to_oop(copy);
-  ContinuationGCSupport::relativize_stack_chunk(copy_val);
-
-  oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
-  if (result == copy_val) {
-    // Successfully evacuated. Our copy is now the public one!
-    shenandoah_assert_correct(nullptr, copy_val);
-    return copy_val;
-  }  else {
-    // Failed to evacuate. We need to deal with the object that is left behind. Since this
-    // new allocation is certainly after TAMS, it will be considered live in the next cycle.
-    // But if it happens to contain references to evacuated regions, those references would
-    // not get updated for this stale copy during this cycle, and we will crash while scanning
-    // it the next cycle.
-    //
-    // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
-    // object will overwrite this stale copy, or the filler object on LAB retirement will
-    // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
-    // have to explicitly overwrite the copy with the filler object. With that overwrite,
-    // we have to keep the fwdptr initialized and pointing to our (stale) copy.
-    if (alloc_from_gclab) {
-      ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
-    } else {
-      fill_with_object(copy, size);
-      shenandoah_assert_correct(nullptr, copy_val);
-    }
-    shenandoah_assert_correct(nullptr, result);
-    return result;
+inline ShenandoahAffiliation ShenandoahHeap::region_affiliation(const ShenandoahHeapRegion *r) {
+  return (ShenandoahAffiliation) _affiliations[r->index()];
+}
+
+inline void ShenandoahHeap::assert_lock_for_affiliation(ShenandoahAffiliation orig_affiliation,
+                                                        ShenandoahAffiliation new_affiliation) {
+  // A lock is required when changing from FREE to NON-FREE.  Though it may be possible to elide the lock when
+  // transitioning from in-use to FREE, the current implementation uses a lock for this transition.  A lock is
+  // not required to change from YOUNG to OLD (i.e. when promoting humongous region).
+  //
+  //         new_affiliation is:     FREE   YOUNG   OLD
+  //  orig_affiliation is:  FREE      X       L      L
+  //                       YOUNG      L       X
+  //                         OLD      L       X      X
+  //  X means state transition won't happen (so don't care)
+  //  L means lock should be held
+  //  Blank means no lock required because affiliation visibility will not be required until subsequent safepoint
+  //
+  // Note: during full GC, all transitions between states are possible.  During Full GC, we should be in a safepoint.
+
+  if ((orig_affiliation == ShenandoahAffiliation::FREE) || (new_affiliation == ShenandoahAffiliation::FREE)) {
+    shenandoah_assert_heaplocked_or_safepoint();
   }
 }
 
+inline void ShenandoahHeap::set_affiliation(ShenandoahHeapRegion* r, ShenandoahAffiliation new_affiliation) {
+#ifdef ASSERT
+  assert_lock_for_affiliation(region_affiliation(r), new_affiliation);
+#endif
+  _affiliations[r->index()] = (uint8_t) new_affiliation;
+}
+
+inline ShenandoahAffiliation ShenandoahHeap::region_affiliation(size_t index) {
+  return (ShenandoahAffiliation) _affiliations[index];
+}
+
 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
   oop obj = cast_to_oop(entry);
   return !_marking_context->is_marked_strong(obj);
 }
 
@@ -377,10 +461,18 @@
 
 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
   return _gc_state.is_set(MARKING);
 }
 
+inline bool ShenandoahHeap::is_concurrent_young_mark_in_progress() const {
+  return _gc_state.is_set(YOUNG_MARKING);
+}
+
+inline bool ShenandoahHeap::is_concurrent_old_mark_in_progress() const {
+  return _gc_state.is_set(OLD_MARKING);
+}
+
 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
   return _gc_state.is_set(EVACUATION);
 }
 
 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
@@ -418,12 +510,11 @@
 
 template<class T>
 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
   assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
 
-  ShenandoahMarkingContext* const ctx = complete_marking_context();
-  assert(ctx->is_complete(), "sanity");
+  ShenandoahMarkingContext* const ctx = marking_context();
 
   HeapWord* tams = ctx->top_at_mark_start(region);
 
   size_t skip_bitmap_delta = 1;
   HeapWord* start = region->bottom();
@@ -542,26 +633,18 @@
     ShenandoahObjectToOopClosure<T> objs(cl);
     marked_object_iterate(region, &objs, top);
   }
 }
 
-inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
+inline ShenandoahHeapRegion* ShenandoahHeap::get_region(size_t region_idx) const {
   if (region_idx < _num_regions) {
     return _regions[region_idx];
   } else {
     return nullptr;
   }
 }
 
-inline void ShenandoahHeap::mark_complete_marking_context() {
-  _marking_context->mark_complete();
-}
-
-inline void ShenandoahHeap::mark_incomplete_marking_context() {
-  _marking_context->mark_incomplete();
-}
-
 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
   assert (_marking_context->is_complete()," sanity");
   return _marking_context;
 }
 
