diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/gc/g1/collectionSetChooser.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/collectionSetChooser.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,198 @@
+/*
+ * Copyright (c) 2001, 2016, 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.
+ *
+ * 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.
+ *
+ */
+
+#ifndef SHARE_VM_GC_G1_COLLECTIONSETCHOOSER_HPP
+#define SHARE_VM_GC_G1_COLLECTIONSETCHOOSER_HPP
+
+#include "gc/g1/heapRegion.hpp"
+#include "utilities/growableArray.hpp"
+
+class CollectionSetChooser: public CHeapObj<mtGC> {
+
+  GrowableArray<HeapRegion*> _regions;
+
+  // Unfortunately, GrowableArray uses ints for length and indexes. To
+  // avoid excessive casting in the rest of the class the following
+  // wrapper methods are provided that use uints.
+
+  uint regions_length()          { return (uint) _regions.length(); }
+  HeapRegion* regions_at(uint i) { return _regions.at((int) i);     }
+  void regions_at_put(uint i, HeapRegion* hr) {
+    _regions.at_put((int) i, hr);
+  }
+  void regions_at_put_grow(uint i, HeapRegion* hr) {
+    _regions.at_put_grow((int) i, hr);
+  }
+  void regions_trunc_to(uint i)  { _regions.trunc_to((uint) i); }
+
+  // The index of the next candidate old region to be considered for
+  // addition to the CSet.
+  uint _front;
+
+  // The index of the last candidate old region
+  uint _end;
+
+  // Keeps track of the start of the next array chunk to be claimed by
+  // parallel GC workers.
+  uint _first_par_unreserved_idx;
+
+  // If a region has more live bytes than this threshold, it will not
+  // be added to the CSet chooser and will not be a candidate for
+  // collection.
+  size_t _region_live_threshold_bytes;
+
+  // The sum of reclaimable bytes over all the regions in the CSet chooser.
+  size_t _remaining_reclaimable_bytes;
+
+  // Calculate and return chunk size (in number of regions) for parallel
+  // addition of regions
+  uint calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const;
+public:
+
+  // Return the current candidate region to be considered for
+  // collection without removing it from the CSet chooser.
+  HeapRegion* peek() {
+    HeapRegion* res = NULL;
+    if (_front < _end) {
+      res = regions_at(_front);
+      assert(res != NULL, "Unexpected NULL hr in _regions at index %u", _front);
+    }
+    return res;
+  }
+
+  // Remove the given region from the CSet chooser and move to the
+  // next one.
+  HeapRegion* pop() {
+    HeapRegion* hr = regions_at(_front);
+    assert(hr != NULL, "pre-condition");
+    assert(_front < _end, "pre-condition");
+    regions_at_put(_front, NULL);
+    assert(hr->reclaimable_bytes() <= _remaining_reclaimable_bytes,
+           "remaining reclaimable bytes inconsistent "
+           "from region: " SIZE_FORMAT " remaining: " SIZE_FORMAT,
+           hr->reclaimable_bytes(), _remaining_reclaimable_bytes);
+    _remaining_reclaimable_bytes -= hr->reclaimable_bytes();
+    _front += 1;
+    return hr;
+  }
+
+  void push(HeapRegion* hr);
+
+  CollectionSetChooser();
+
+  void sort_regions();
+
+  // Determine whether to add the given region to the CSet chooser or
+  // not. Currently, we skip pinned regions and regions whose live
+  // bytes are over the threshold. Humongous regions may be reclaimed during cleanup.
+  bool should_add(HeapRegion* hr) {
+    assert(hr->is_marked(), "pre-condition");
+    assert(!hr->is_young(), "should never consider young regions");
+    return !hr->is_pinned() &&
+            hr->live_bytes() < _region_live_threshold_bytes;
+  }
+
+  // Returns the number candidate old regions added
+  uint length() { return _end; }
+
+  // Serial version.
+  void add_region(HeapRegion *hr);
+
+  // Must be called before calls to claim_array_chunk().
+  // n_regions is the number of regions, chunk_size the chunk size.
+  void prepare_for_par_region_addition(uint n_threads, uint n_regions, uint chunk_size);
+  // Returns the first index in a contiguous chunk of chunk_size indexes
+  // that the calling thread has reserved.  These must be set by the
+  // calling thread using set_region() (to NULL if necessary).
+  uint claim_array_chunk(uint chunk_size);
+  // Set the marked array entry at index to hr.  Careful to claim the index
+  // first if in parallel.
+  void set_region(uint index, HeapRegion* hr);
+  // Atomically increment the number of added regions by region_num
+  // and the amount of reclaimable bytes by reclaimable_bytes.
+  void update_totals(uint region_num, size_t reclaimable_bytes);
+
+  void clear();
+
+  void rebuild(WorkGang* workers, uint n_regions);
+
+  // Return the number of candidate regions that remain to be collected.
+  uint remaining_regions() { return _end - _front; }
+
+  // Determine whether the CSet chooser has more candidate regions or not.
+  bool is_empty() { return remaining_regions() == 0; }
+
+  // Return the reclaimable bytes that remain to be collected on
+  // all the candidate regions in the CSet chooser.
+  size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; }
+
+  // Returns true if the used portion of "_regions" is properly
+  // sorted, otherwise asserts false.
+  void verify() PRODUCT_RETURN;
+};
+
+class CSetChooserParUpdater : public StackObj {
+private:
+  CollectionSetChooser* _chooser;
+  bool _parallel;
+  uint _chunk_size;
+  uint _cur_chunk_idx;
+  uint _cur_chunk_end;
+  uint _regions_added;
+  size_t _reclaimable_bytes_added;
+
+public:
+  CSetChooserParUpdater(CollectionSetChooser* chooser,
+                        bool parallel, uint chunk_size) :
+    _chooser(chooser), _parallel(parallel), _chunk_size(chunk_size),
+    _cur_chunk_idx(0), _cur_chunk_end(0),
+    _regions_added(0), _reclaimable_bytes_added(0) { }
+
+  ~CSetChooserParUpdater() {
+    if (_parallel && _regions_added > 0) {
+      _chooser->update_totals(_regions_added, _reclaimable_bytes_added);
+    }
+  }
+
+  void add_region(HeapRegion* hr) {
+    if (_parallel) {
+      if (_cur_chunk_idx == _cur_chunk_end) {
+        _cur_chunk_idx = _chooser->claim_array_chunk(_chunk_size);
+        _cur_chunk_end = _cur_chunk_idx + _chunk_size;
+      }
+      assert(_cur_chunk_idx < _cur_chunk_end, "invariant");
+      _chooser->set_region(_cur_chunk_idx, hr);
+      _cur_chunk_idx += 1;
+    } else {
+      _chooser->add_region(hr);
+    }
+    _regions_added += 1;
+    _reclaimable_bytes_added += hr->reclaimable_bytes();
+  }
+
+  bool should_add(HeapRegion* hr) { return _chooser->should_add(hr); }
+};
+
+#endif // SHARE_VM_GC_G1_COLLECTIONSETCHOOSER_HPP
+