diff -r 420ff459906f -r 9c18c9d839d3 src/hotspot/share/gc/shenandoah/shenandoahCollectionSet.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shenandoah/shenandoahCollectionSet.cpp	Mon Dec 10 15:47:44 2018 +0100
@@ -0,0 +1,160 @@
+/*
+ * Copyright (c) 2016, 2018, Red Hat, Inc. All rights reserved.
+ *
+ * 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.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+
+#include "gc/shenandoah/shenandoahCollectionSet.hpp"
+#include "gc/shenandoah/shenandoahHeap.inline.hpp"
+#include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
+#include "gc/shenandoah/shenandoahUtils.hpp"
+#include "runtime/atomic.hpp"
+#include "utilities/copy.hpp"
+
+ShenandoahCollectionSet::ShenandoahCollectionSet(ShenandoahHeap* heap, HeapWord* heap_base) :
+  _map_size(heap->num_regions()),
+  _region_size_bytes_shift(ShenandoahHeapRegion::region_size_bytes_shift()),
+  _cset_map(NEW_C_HEAP_ARRAY(jbyte, _map_size, mtGC)),
+  _biased_cset_map(_cset_map - ((uintx)heap_base >> _region_size_bytes_shift)),
+  _heap(heap),
+  _garbage(0),
+  _live_data(0),
+  _used(0),
+  _region_count(0),
+  _current_index(0) {
+  // Use 1-byte data type
+  STATIC_ASSERT(sizeof(jbyte) == 1);
+
+  // Initialize cset map
+  Copy::zero_to_bytes(_cset_map, _map_size);
+}
+
+void ShenandoahCollectionSet::add_region(ShenandoahHeapRegion* r) {
+  assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
+  assert(Thread::current()->is_VM_thread(), "Must be VMThread");
+  assert(!is_in(r), "Already in collection set");
+  _cset_map[r->region_number()] = 1;
+  _region_count ++;
+  _garbage += r->garbage();
+  _live_data += r->get_live_data_bytes();
+  _used += r->used();
+}
+
+bool ShenandoahCollectionSet::add_region_check_for_duplicates(ShenandoahHeapRegion* r) {
+  if (!is_in(r)) {
+    add_region(r);
+    return true;
+  } else {
+    return false;
+  }
+}
+
+void ShenandoahCollectionSet::remove_region(ShenandoahHeapRegion* r) {
+  assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
+  assert(Thread::current()->is_VM_thread(), "Must be VMThread");
+  assert(is_in(r), "Not in collection set");
+  _cset_map[r->region_number()] = 0;
+  _region_count --;
+}
+
+void ShenandoahCollectionSet::update_region_status() {
+  for (size_t index = 0; index < _heap->num_regions(); index ++) {
+    ShenandoahHeapRegion* r = _heap->get_region(index);
+    if (is_in(r)) {
+      r->make_cset();
+    } else {
+      assert (!r->is_cset(), "should not be cset");
+    }
+  }
+}
+
+void ShenandoahCollectionSet::clear() {
+  assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
+  Copy::zero_to_bytes(_cset_map, _map_size);
+
+#ifdef ASSERT
+  for (size_t index = 0; index < _heap->num_regions(); index ++) {
+    assert (!_heap->get_region(index)->is_cset(), "should have been cleared before");
+  }
+#endif
+
+  _garbage = 0;
+  _live_data = 0;
+  _used = 0;
+
+  _region_count = 0;
+  _current_index = 0;
+}
+
+ShenandoahHeapRegion* ShenandoahCollectionSet::claim_next() {
+  size_t num_regions = _heap->num_regions();
+  if (_current_index >= (jint)num_regions) {
+    return NULL;
+  }
+
+  jint saved_current = _current_index;
+  size_t index = (size_t)saved_current;
+
+  while(index < num_regions) {
+    if (is_in(index)) {
+      jint cur = Atomic::cmpxchg((jint)(index + 1), &_current_index, saved_current);
+      assert(cur >= (jint)saved_current, "Must move forward");
+      if (cur == saved_current) {
+        assert(is_in(index), "Invariant");
+        return _heap->get_region(index);
+      } else {
+        index = (size_t)cur;
+        saved_current = cur;
+      }
+    } else {
+      index ++;
+    }
+  }
+  return NULL;
+}
+
+ShenandoahHeapRegion* ShenandoahCollectionSet::next() {
+  assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
+  assert(Thread::current()->is_VM_thread(), "Must be VMThread");
+  size_t num_regions = _heap->num_regions();
+  for (size_t index = (size_t)_current_index; index < num_regions; index ++) {
+    if (is_in(index)) {
+      _current_index = (jint)(index + 1);
+      return _heap->get_region(index);
+    }
+  }
+
+  return NULL;
+}
+
+void ShenandoahCollectionSet::print_on(outputStream* out) const {
+  out->print_cr("Collection Set : " SIZE_FORMAT "", count());
+
+  debug_only(size_t regions = 0;)
+  for (size_t index = 0; index < _heap->num_regions(); index ++) {
+    if (is_in(index)) {
+      _heap->get_region(index)->print_on(out);
+      debug_only(regions ++;)
+    }
+  }
+  assert(regions == count(), "Must match");
+}