src/hotspot/share/gc/parallel/psParallelCompact.cpp
changeset 47216 71c04702a3d5
parent 47106 bed18a111b90
child 47546 64ba55ba8516
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/parallel/psParallelCompact.cpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,3184 @@
+/*
+ * Copyright (c) 2005, 2017, 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.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "aot/aotLoader.hpp"
+#include "classfile/stringTable.hpp"
+#include "classfile/symbolTable.hpp"
+#include "classfile/systemDictionary.hpp"
+#include "code/codeCache.hpp"
+#include "gc/parallel/gcTaskManager.hpp"
+#include "gc/parallel/parallelScavengeHeap.inline.hpp"
+#include "gc/parallel/parMarkBitMap.inline.hpp"
+#include "gc/parallel/pcTasks.hpp"
+#include "gc/parallel/psAdaptiveSizePolicy.hpp"
+#include "gc/parallel/psCompactionManager.inline.hpp"
+#include "gc/parallel/psMarkSweep.hpp"
+#include "gc/parallel/psMarkSweepDecorator.hpp"
+#include "gc/parallel/psOldGen.hpp"
+#include "gc/parallel/psParallelCompact.inline.hpp"
+#include "gc/parallel/psPromotionManager.inline.hpp"
+#include "gc/parallel/psScavenge.hpp"
+#include "gc/parallel/psYoungGen.hpp"
+#include "gc/shared/gcCause.hpp"
+#include "gc/shared/gcHeapSummary.hpp"
+#include "gc/shared/gcId.hpp"
+#include "gc/shared/gcLocker.inline.hpp"
+#include "gc/shared/gcTimer.hpp"
+#include "gc/shared/gcTrace.hpp"
+#include "gc/shared/gcTraceTime.inline.hpp"
+#include "gc/shared/isGCActiveMark.hpp"
+#include "gc/shared/referencePolicy.hpp"
+#include "gc/shared/referenceProcessor.hpp"
+#include "gc/shared/spaceDecorator.hpp"
+#include "logging/log.hpp"
+#include "memory/resourceArea.hpp"
+#include "oops/instanceKlass.inline.hpp"
+#include "oops/instanceMirrorKlass.inline.hpp"
+#include "oops/methodData.hpp"
+#include "oops/objArrayKlass.inline.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/atomic.hpp"
+#include "runtime/safepoint.hpp"
+#include "runtime/vmThread.hpp"
+#include "services/management.hpp"
+#include "services/memTracker.hpp"
+#include "services/memoryService.hpp"
+#include "utilities/align.hpp"
+#include "utilities/debug.hpp"
+#include "utilities/events.hpp"
+#include "utilities/formatBuffer.hpp"
+#include "utilities/stack.inline.hpp"
+
+#include <math.h>
+
+// All sizes are in HeapWords.
+const size_t ParallelCompactData::Log2RegionSize  = 16; // 64K words
+const size_t ParallelCompactData::RegionSize      = (size_t)1 << Log2RegionSize;
+const size_t ParallelCompactData::RegionSizeBytes =
+  RegionSize << LogHeapWordSize;
+const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
+const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
+const size_t ParallelCompactData::RegionAddrMask       = ~RegionAddrOffsetMask;
+
+const size_t ParallelCompactData::Log2BlockSize   = 7; // 128 words
+const size_t ParallelCompactData::BlockSize       = (size_t)1 << Log2BlockSize;
+const size_t ParallelCompactData::BlockSizeBytes  =
+  BlockSize << LogHeapWordSize;
+const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
+const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
+const size_t ParallelCompactData::BlockAddrMask       = ~BlockAddrOffsetMask;
+
+const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
+const size_t ParallelCompactData::Log2BlocksPerRegion =
+  Log2RegionSize - Log2BlockSize;
+
+const ParallelCompactData::RegionData::region_sz_t
+ParallelCompactData::RegionData::dc_shift = 27;
+
+const ParallelCompactData::RegionData::region_sz_t
+ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
+
+const ParallelCompactData::RegionData::region_sz_t
+ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
+
+const ParallelCompactData::RegionData::region_sz_t
+ParallelCompactData::RegionData::los_mask = ~dc_mask;
+
+const ParallelCompactData::RegionData::region_sz_t
+ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
+
+const ParallelCompactData::RegionData::region_sz_t
+ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
+
+SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
+
+ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
+
+double PSParallelCompact::_dwl_mean;
+double PSParallelCompact::_dwl_std_dev;
+double PSParallelCompact::_dwl_first_term;
+double PSParallelCompact::_dwl_adjustment;
+#ifdef  ASSERT
+bool   PSParallelCompact::_dwl_initialized = false;
+#endif  // #ifdef ASSERT
+
+void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
+                       HeapWord* destination)
+{
+  assert(src_region_idx != 0, "invalid src_region_idx");
+  assert(partial_obj_size != 0, "invalid partial_obj_size argument");
+  assert(destination != NULL, "invalid destination argument");
+
+  _src_region_idx = src_region_idx;
+  _partial_obj_size = partial_obj_size;
+  _destination = destination;
+
+  // These fields may not be updated below, so make sure they're clear.
+  assert(_dest_region_addr == NULL, "should have been cleared");
+  assert(_first_src_addr == NULL, "should have been cleared");
+
+  // Determine the number of destination regions for the partial object.
+  HeapWord* const last_word = destination + partial_obj_size - 1;
+  const ParallelCompactData& sd = PSParallelCompact::summary_data();
+  HeapWord* const beg_region_addr = sd.region_align_down(destination);
+  HeapWord* const end_region_addr = sd.region_align_down(last_word);
+
+  if (beg_region_addr == end_region_addr) {
+    // One destination region.
+    _destination_count = 1;
+    if (end_region_addr == destination) {
+      // The destination falls on a region boundary, thus the first word of the
+      // partial object will be the first word copied to the destination region.
+      _dest_region_addr = end_region_addr;
+      _first_src_addr = sd.region_to_addr(src_region_idx);
+    }
+  } else {
+    // Two destination regions.  When copied, the partial object will cross a
+    // destination region boundary, so a word somewhere within the partial
+    // object will be the first word copied to the second destination region.
+    _destination_count = 2;
+    _dest_region_addr = end_region_addr;
+    const size_t ofs = pointer_delta(end_region_addr, destination);
+    assert(ofs < _partial_obj_size, "sanity");
+    _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
+  }
+}
+
+void SplitInfo::clear()
+{
+  _src_region_idx = 0;
+  _partial_obj_size = 0;
+  _destination = NULL;
+  _destination_count = 0;
+  _dest_region_addr = NULL;
+  _first_src_addr = NULL;
+  assert(!is_valid(), "sanity");
+}
+
+#ifdef  ASSERT
+void SplitInfo::verify_clear()
+{
+  assert(_src_region_idx == 0, "not clear");
+  assert(_partial_obj_size == 0, "not clear");
+  assert(_destination == NULL, "not clear");
+  assert(_destination_count == 0, "not clear");
+  assert(_dest_region_addr == NULL, "not clear");
+  assert(_first_src_addr == NULL, "not clear");
+}
+#endif  // #ifdef ASSERT
+
+
+void PSParallelCompact::print_on_error(outputStream* st) {
+  _mark_bitmap.print_on_error(st);
+}
+
+#ifndef PRODUCT
+const char* PSParallelCompact::space_names[] = {
+  "old ", "eden", "from", "to  "
+};
+
+void PSParallelCompact::print_region_ranges() {
+  if (!log_develop_is_enabled(Trace, gc, compaction)) {
+    return;
+  }
+  Log(gc, compaction) log;
+  ResourceMark rm;
+  LogStream ls(log.trace());
+  Universe::print_on(&ls);
+  log.trace("space  bottom     top        end        new_top");
+  log.trace("------ ---------- ---------- ---------- ----------");
+
+  for (unsigned int id = 0; id < last_space_id; ++id) {
+    const MutableSpace* space = _space_info[id].space();
+    log.trace("%u %s "
+              SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
+              SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
+              id, space_names[id],
+              summary_data().addr_to_region_idx(space->bottom()),
+              summary_data().addr_to_region_idx(space->top()),
+              summary_data().addr_to_region_idx(space->end()),
+              summary_data().addr_to_region_idx(_space_info[id].new_top()));
+  }
+}
+
+void
+print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
+{
+#define REGION_IDX_FORMAT        SIZE_FORMAT_W(7)
+#define REGION_DATA_FORMAT       SIZE_FORMAT_W(5)
+
+  ParallelCompactData& sd = PSParallelCompact::summary_data();
+  size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
+  log_develop_trace(gc, compaction)(
+      REGION_IDX_FORMAT " " PTR_FORMAT " "
+      REGION_IDX_FORMAT " " PTR_FORMAT " "
+      REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
+      REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
+      i, p2i(c->data_location()), dci, p2i(c->destination()),
+      c->partial_obj_size(), c->live_obj_size(),
+      c->data_size(), c->source_region(), c->destination_count());
+
+#undef  REGION_IDX_FORMAT
+#undef  REGION_DATA_FORMAT
+}
+
+void
+print_generic_summary_data(ParallelCompactData& summary_data,
+                           HeapWord* const beg_addr,
+                           HeapWord* const end_addr)
+{
+  size_t total_words = 0;
+  size_t i = summary_data.addr_to_region_idx(beg_addr);
+  const size_t last = summary_data.addr_to_region_idx(end_addr);
+  HeapWord* pdest = 0;
+
+  while (i < last) {
+    ParallelCompactData::RegionData* c = summary_data.region(i);
+    if (c->data_size() != 0 || c->destination() != pdest) {
+      print_generic_summary_region(i, c);
+      total_words += c->data_size();
+      pdest = c->destination();
+    }
+    ++i;
+  }
+
+  log_develop_trace(gc, compaction)("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
+}
+
+void
+PSParallelCompact::print_generic_summary_data(ParallelCompactData& summary_data,
+                                              HeapWord* const beg_addr,
+                                              HeapWord* const end_addr) {
+  ::print_generic_summary_data(summary_data,beg_addr, end_addr);
+}
+
+void
+print_generic_summary_data(ParallelCompactData& summary_data,
+                           SpaceInfo* space_info)
+{
+  if (!log_develop_is_enabled(Trace, gc, compaction)) {
+    return;
+  }
+
+  for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
+    const MutableSpace* space = space_info[id].space();
+    print_generic_summary_data(summary_data, space->bottom(),
+                               MAX2(space->top(), space_info[id].new_top()));
+  }
+}
+
+void
+print_initial_summary_data(ParallelCompactData& summary_data,
+                           const MutableSpace* space) {
+  if (space->top() == space->bottom()) {
+    return;
+  }
+
+  const size_t region_size = ParallelCompactData::RegionSize;
+  typedef ParallelCompactData::RegionData RegionData;
+  HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
+  const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
+  const RegionData* c = summary_data.region(end_region - 1);
+  HeapWord* end_addr = c->destination() + c->data_size();
+  const size_t live_in_space = pointer_delta(end_addr, space->bottom());
+
+  // Print (and count) the full regions at the beginning of the space.
+  size_t full_region_count = 0;
+  size_t i = summary_data.addr_to_region_idx(space->bottom());
+  while (i < end_region && summary_data.region(i)->data_size() == region_size) {
+    ParallelCompactData::RegionData* c = summary_data.region(i);
+    log_develop_trace(gc, compaction)(
+        SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
+        i, p2i(c->destination()),
+        c->partial_obj_size(), c->live_obj_size(),
+        c->data_size(), c->source_region(), c->destination_count());
+    ++full_region_count;
+    ++i;
+  }
+
+  size_t live_to_right = live_in_space - full_region_count * region_size;
+
+  double max_reclaimed_ratio = 0.0;
+  size_t max_reclaimed_ratio_region = 0;
+  size_t max_dead_to_right = 0;
+  size_t max_live_to_right = 0;
+
+  // Print the 'reclaimed ratio' for regions while there is something live in
+  // the region or to the right of it.  The remaining regions are empty (and
+  // uninteresting), and computing the ratio will result in division by 0.
+  while (i < end_region && live_to_right > 0) {
+    c = summary_data.region(i);
+    HeapWord* const region_addr = summary_data.region_to_addr(i);
+    const size_t used_to_right = pointer_delta(space->top(), region_addr);
+    const size_t dead_to_right = used_to_right - live_to_right;
+    const double reclaimed_ratio = double(dead_to_right) / live_to_right;
+
+    if (reclaimed_ratio > max_reclaimed_ratio) {
+            max_reclaimed_ratio = reclaimed_ratio;
+            max_reclaimed_ratio_region = i;
+            max_dead_to_right = dead_to_right;
+            max_live_to_right = live_to_right;
+    }
+
+    ParallelCompactData::RegionData* c = summary_data.region(i);
+    log_develop_trace(gc, compaction)(
+        SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d"
+        "%12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
+        i, p2i(c->destination()),
+        c->partial_obj_size(), c->live_obj_size(),
+        c->data_size(), c->source_region(), c->destination_count(),
+        reclaimed_ratio, dead_to_right, live_to_right);
+
+
+    live_to_right -= c->data_size();
+    ++i;
+  }
+
+  // Any remaining regions are empty.  Print one more if there is one.
+  if (i < end_region) {
+    ParallelCompactData::RegionData* c = summary_data.region(i);
+    log_develop_trace(gc, compaction)(
+        SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
+         i, p2i(c->destination()),
+         c->partial_obj_size(), c->live_obj_size(),
+         c->data_size(), c->source_region(), c->destination_count());
+  }
+
+  log_develop_trace(gc, compaction)("max:  " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
+                                    max_reclaimed_ratio_region, max_dead_to_right, max_live_to_right, max_reclaimed_ratio);
+}
+
+void
+print_initial_summary_data(ParallelCompactData& summary_data,
+                           SpaceInfo* space_info) {
+  if (!log_develop_is_enabled(Trace, gc, compaction)) {
+    return;
+  }
+
+  unsigned int id = PSParallelCompact::old_space_id;
+  const MutableSpace* space;
+  do {
+    space = space_info[id].space();
+    print_initial_summary_data(summary_data, space);
+  } while (++id < PSParallelCompact::eden_space_id);
+
+  do {
+    space = space_info[id].space();
+    print_generic_summary_data(summary_data, space->bottom(), space->top());
+  } while (++id < PSParallelCompact::last_space_id);
+}
+#endif  // #ifndef PRODUCT
+
+#ifdef  ASSERT
+size_t add_obj_count;
+size_t add_obj_size;
+size_t mark_bitmap_count;
+size_t mark_bitmap_size;
+#endif  // #ifdef ASSERT
+
+ParallelCompactData::ParallelCompactData()
+{
+  _region_start = 0;
+
+  _region_vspace = 0;
+  _reserved_byte_size = 0;
+  _region_data = 0;
+  _region_count = 0;
+
+  _block_vspace = 0;
+  _block_data = 0;
+  _block_count = 0;
+}
+
+bool ParallelCompactData::initialize(MemRegion covered_region)
+{
+  _region_start = covered_region.start();
+  const size_t region_size = covered_region.word_size();
+  DEBUG_ONLY(_region_end = _region_start + region_size;)
+
+  assert(region_align_down(_region_start) == _region_start,
+         "region start not aligned");
+  assert((region_size & RegionSizeOffsetMask) == 0,
+         "region size not a multiple of RegionSize");
+
+  bool result = initialize_region_data(region_size) && initialize_block_data();
+  return result;
+}
+
+PSVirtualSpace*
+ParallelCompactData::create_vspace(size_t count, size_t element_size)
+{
+  const size_t raw_bytes = count * element_size;
+  const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
+  const size_t granularity = os::vm_allocation_granularity();
+  _reserved_byte_size = align_up(raw_bytes, MAX2(page_sz, granularity));
+
+  const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
+    MAX2(page_sz, granularity);
+  ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
+  os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, page_sz, rs.base(),
+                       rs.size());
+
+  MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
+
+  PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
+  if (vspace != 0) {
+    if (vspace->expand_by(_reserved_byte_size)) {
+      return vspace;
+    }
+    delete vspace;
+    // Release memory reserved in the space.
+    rs.release();
+  }
+
+  return 0;
+}
+
+bool ParallelCompactData::initialize_region_data(size_t region_size)
+{
+  const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
+  _region_vspace = create_vspace(count, sizeof(RegionData));
+  if (_region_vspace != 0) {
+    _region_data = (RegionData*)_region_vspace->reserved_low_addr();
+    _region_count = count;
+    return true;
+  }
+  return false;
+}
+
+bool ParallelCompactData::initialize_block_data()
+{
+  assert(_region_count != 0, "region data must be initialized first");
+  const size_t count = _region_count << Log2BlocksPerRegion;
+  _block_vspace = create_vspace(count, sizeof(BlockData));
+  if (_block_vspace != 0) {
+    _block_data = (BlockData*)_block_vspace->reserved_low_addr();
+    _block_count = count;
+    return true;
+  }
+  return false;
+}
+
+void ParallelCompactData::clear()
+{
+  memset(_region_data, 0, _region_vspace->committed_size());
+  memset(_block_data, 0, _block_vspace->committed_size());
+}
+
+void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
+  assert(beg_region <= _region_count, "beg_region out of range");
+  assert(end_region <= _region_count, "end_region out of range");
+  assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
+
+  const size_t region_cnt = end_region - beg_region;
+  memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
+
+  const size_t beg_block = beg_region * BlocksPerRegion;
+  const size_t block_cnt = region_cnt * BlocksPerRegion;
+  memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
+}
+
+HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
+{
+  const RegionData* cur_cp = region(region_idx);
+  const RegionData* const end_cp = region(region_count() - 1);
+
+  HeapWord* result = region_to_addr(region_idx);
+  if (cur_cp < end_cp) {
+    do {
+      result += cur_cp->partial_obj_size();
+    } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
+  }
+  return result;
+}
+
+void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
+{
+  const size_t obj_ofs = pointer_delta(addr, _region_start);
+  const size_t beg_region = obj_ofs >> Log2RegionSize;
+  const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
+
+  DEBUG_ONLY(Atomic::inc_ptr(&add_obj_count);)
+  DEBUG_ONLY(Atomic::add_ptr(len, &add_obj_size);)
+
+  if (beg_region == end_region) {
+    // All in one region.
+    _region_data[beg_region].add_live_obj(len);
+    return;
+  }
+
+  // First region.
+  const size_t beg_ofs = region_offset(addr);
+  _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
+
+  Klass* klass = ((oop)addr)->klass();
+  // Middle regions--completely spanned by this object.
+  for (size_t region = beg_region + 1; region < end_region; ++region) {
+    _region_data[region].set_partial_obj_size(RegionSize);
+    _region_data[region].set_partial_obj_addr(addr);
+  }
+
+  // Last region.
+  const size_t end_ofs = region_offset(addr + len - 1);
+  _region_data[end_region].set_partial_obj_size(end_ofs + 1);
+  _region_data[end_region].set_partial_obj_addr(addr);
+}
+
+void
+ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
+{
+  assert(region_offset(beg) == 0, "not RegionSize aligned");
+  assert(region_offset(end) == 0, "not RegionSize aligned");
+
+  size_t cur_region = addr_to_region_idx(beg);
+  const size_t end_region = addr_to_region_idx(end);
+  HeapWord* addr = beg;
+  while (cur_region < end_region) {
+    _region_data[cur_region].set_destination(addr);
+    _region_data[cur_region].set_destination_count(0);
+    _region_data[cur_region].set_source_region(cur_region);
+    _region_data[cur_region].set_data_location(addr);
+
+    // Update live_obj_size so the region appears completely full.
+    size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
+    _region_data[cur_region].set_live_obj_size(live_size);
+
+    ++cur_region;
+    addr += RegionSize;
+  }
+}
+
+// Find the point at which a space can be split and, if necessary, record the
+// split point.
+//
+// If the current src region (which overflowed the destination space) doesn't
+// have a partial object, the split point is at the beginning of the current src
+// region (an "easy" split, no extra bookkeeping required).
+//
+// If the current src region has a partial object, the split point is in the
+// region where that partial object starts (call it the split_region).  If
+// split_region has a partial object, then the split point is just after that
+// partial object (a "hard" split where we have to record the split data and
+// zero the partial_obj_size field).  With a "hard" split, we know that the
+// partial_obj ends within split_region because the partial object that caused
+// the overflow starts in split_region.  If split_region doesn't have a partial
+// obj, then the split is at the beginning of split_region (another "easy"
+// split).
+HeapWord*
+ParallelCompactData::summarize_split_space(size_t src_region,
+                                           SplitInfo& split_info,
+                                           HeapWord* destination,
+                                           HeapWord* target_end,
+                                           HeapWord** target_next)
+{
+  assert(destination <= target_end, "sanity");
+  assert(destination + _region_data[src_region].data_size() > target_end,
+    "region should not fit into target space");
+  assert(is_region_aligned(target_end), "sanity");
+
+  size_t split_region = src_region;
+  HeapWord* split_destination = destination;
+  size_t partial_obj_size = _region_data[src_region].partial_obj_size();
+
+  if (destination + partial_obj_size > target_end) {
+    // The split point is just after the partial object (if any) in the
+    // src_region that contains the start of the object that overflowed the
+    // destination space.
+    //
+    // Find the start of the "overflow" object and set split_region to the
+    // region containing it.
+    HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
+    split_region = addr_to_region_idx(overflow_obj);
+
+    // Clear the source_region field of all destination regions whose first word
+    // came from data after the split point (a non-null source_region field
+    // implies a region must be filled).
+    //
+    // An alternative to the simple loop below:  clear during post_compact(),
+    // which uses memcpy instead of individual stores, and is easy to
+    // parallelize.  (The downside is that it clears the entire RegionData
+    // object as opposed to just one field.)
+    //
+    // post_compact() would have to clear the summary data up to the highest
+    // address that was written during the summary phase, which would be
+    //
+    //         max(top, max(new_top, clear_top))
+    //
+    // where clear_top is a new field in SpaceInfo.  Would have to set clear_top
+    // to target_end.
+    const RegionData* const sr = region(split_region);
+    const size_t beg_idx =
+      addr_to_region_idx(region_align_up(sr->destination() +
+                                         sr->partial_obj_size()));
+    const size_t end_idx = addr_to_region_idx(target_end);
+
+    log_develop_trace(gc, compaction)("split:  clearing source_region field in [" SIZE_FORMAT ", " SIZE_FORMAT ")", beg_idx, end_idx);
+    for (size_t idx = beg_idx; idx < end_idx; ++idx) {
+      _region_data[idx].set_source_region(0);
+    }
+
+    // Set split_destination and partial_obj_size to reflect the split region.
+    split_destination = sr->destination();
+    partial_obj_size = sr->partial_obj_size();
+  }
+
+  // The split is recorded only if a partial object extends onto the region.
+  if (partial_obj_size != 0) {
+    _region_data[split_region].set_partial_obj_size(0);
+    split_info.record(split_region, partial_obj_size, split_destination);
+  }
+
+  // Setup the continuation addresses.
+  *target_next = split_destination + partial_obj_size;
+  HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
+
+  if (log_develop_is_enabled(Trace, gc, compaction)) {
+    const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
+    log_develop_trace(gc, compaction)("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT " pos=" SIZE_FORMAT,
+                                      split_type, p2i(source_next), split_region, partial_obj_size);
+    log_develop_trace(gc, compaction)("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT " tn=" PTR_FORMAT,
+                                      split_type, p2i(split_destination),
+                                      addr_to_region_idx(split_destination),
+                                      p2i(*target_next));
+
+    if (partial_obj_size != 0) {
+      HeapWord* const po_beg = split_info.destination();
+      HeapWord* const po_end = po_beg + split_info.partial_obj_size();
+      log_develop_trace(gc, compaction)("%s split:  po_beg=" PTR_FORMAT " " SIZE_FORMAT " po_end=" PTR_FORMAT " " SIZE_FORMAT,
+                                        split_type,
+                                        p2i(po_beg), addr_to_region_idx(po_beg),
+                                        p2i(po_end), addr_to_region_idx(po_end));
+    }
+  }
+
+  return source_next;
+}
+
+bool ParallelCompactData::summarize(SplitInfo& split_info,
+                                    HeapWord* source_beg, HeapWord* source_end,
+                                    HeapWord** source_next,
+                                    HeapWord* target_beg, HeapWord* target_end,
+                                    HeapWord** target_next)
+{
+  HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
+  log_develop_trace(gc, compaction)(
+      "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
+      "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
+      p2i(source_beg), p2i(source_end), p2i(source_next_val),
+      p2i(target_beg), p2i(target_end), p2i(*target_next));
+
+  size_t cur_region = addr_to_region_idx(source_beg);
+  const size_t end_region = addr_to_region_idx(region_align_up(source_end));
+
+  HeapWord *dest_addr = target_beg;
+  while (cur_region < end_region) {
+    // The destination must be set even if the region has no data.
+    _region_data[cur_region].set_destination(dest_addr);
+
+    size_t words = _region_data[cur_region].data_size();
+    if (words > 0) {
+      // If cur_region does not fit entirely into the target space, find a point
+      // at which the source space can be 'split' so that part is copied to the
+      // target space and the rest is copied elsewhere.
+      if (dest_addr + words > target_end) {
+        assert(source_next != NULL, "source_next is NULL when splitting");
+        *source_next = summarize_split_space(cur_region, split_info, dest_addr,
+                                             target_end, target_next);
+        return false;
+      }
+
+      // Compute the destination_count for cur_region, and if necessary, update
+      // source_region for a destination region.  The source_region field is
+      // updated if cur_region is the first (left-most) region to be copied to a
+      // destination region.
+      //
+      // The destination_count calculation is a bit subtle.  A region that has
+      // data that compacts into itself does not count itself as a destination.
+      // This maintains the invariant that a zero count means the region is
+      // available and can be claimed and then filled.
+      uint destination_count = 0;
+      if (split_info.is_split(cur_region)) {
+        // The current region has been split:  the partial object will be copied
+        // to one destination space and the remaining data will be copied to
+        // another destination space.  Adjust the initial destination_count and,
+        // if necessary, set the source_region field if the partial object will
+        // cross a destination region boundary.
+        destination_count = split_info.destination_count();
+        if (destination_count == 2) {
+          size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
+          _region_data[dest_idx].set_source_region(cur_region);
+        }
+      }
+
+      HeapWord* const last_addr = dest_addr + words - 1;
+      const size_t dest_region_1 = addr_to_region_idx(dest_addr);
+      const size_t dest_region_2 = addr_to_region_idx(last_addr);
+
+      // Initially assume that the destination regions will be the same and
+      // adjust the value below if necessary.  Under this assumption, if
+      // cur_region == dest_region_2, then cur_region will be compacted
+      // completely into itself.
+      destination_count += cur_region == dest_region_2 ? 0 : 1;
+      if (dest_region_1 != dest_region_2) {
+        // Destination regions differ; adjust destination_count.
+        destination_count += 1;
+        // Data from cur_region will be copied to the start of dest_region_2.
+        _region_data[dest_region_2].set_source_region(cur_region);
+      } else if (region_offset(dest_addr) == 0) {
+        // Data from cur_region will be copied to the start of the destination
+        // region.
+        _region_data[dest_region_1].set_source_region(cur_region);
+      }
+
+      _region_data[cur_region].set_destination_count(destination_count);
+      _region_data[cur_region].set_data_location(region_to_addr(cur_region));
+      dest_addr += words;
+    }
+
+    ++cur_region;
+  }
+
+  *target_next = dest_addr;
+  return true;
+}
+
+HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr, ParCompactionManager* cm) {
+  assert(addr != NULL, "Should detect NULL oop earlier");
+  assert(ParallelScavengeHeap::heap()->is_in(addr), "not in heap");
+  assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
+
+  // Region covering the object.
+  RegionData* const region_ptr = addr_to_region_ptr(addr);
+  HeapWord* result = region_ptr->destination();
+
+  // If the entire Region is live, the new location is region->destination + the
+  // offset of the object within in the Region.
+
+  // Run some performance tests to determine if this special case pays off.  It
+  // is worth it for pointers into the dense prefix.  If the optimization to
+  // avoid pointer updates in regions that only point to the dense prefix is
+  // ever implemented, this should be revisited.
+  if (region_ptr->data_size() == RegionSize) {
+    result += region_offset(addr);
+    return result;
+  }
+
+  // Otherwise, the new location is region->destination + block offset + the
+  // number of live words in the Block that are (a) to the left of addr and (b)
+  // due to objects that start in the Block.
+
+  // Fill in the block table if necessary.  This is unsynchronized, so multiple
+  // threads may fill the block table for a region (harmless, since it is
+  // idempotent).
+  if (!region_ptr->blocks_filled()) {
+    PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
+    region_ptr->set_blocks_filled();
+  }
+
+  HeapWord* const search_start = block_align_down(addr);
+  const size_t block_offset = addr_to_block_ptr(addr)->offset();
+
+  const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
+  const size_t live = bitmap->live_words_in_range(cm, search_start, oop(addr));
+  result += block_offset + live;
+  DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
+  return result;
+}
+
+#ifdef ASSERT
+void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
+{
+  const size_t* const beg = (const size_t*)vspace->committed_low_addr();
+  const size_t* const end = (const size_t*)vspace->committed_high_addr();
+  for (const size_t* p = beg; p < end; ++p) {
+    assert(*p == 0, "not zero");
+  }
+}
+
+void ParallelCompactData::verify_clear()
+{
+  verify_clear(_region_vspace);
+  verify_clear(_block_vspace);
+}
+#endif  // #ifdef ASSERT
+
+STWGCTimer          PSParallelCompact::_gc_timer;
+ParallelOldTracer   PSParallelCompact::_gc_tracer;
+elapsedTimer        PSParallelCompact::_accumulated_time;
+unsigned int        PSParallelCompact::_total_invocations = 0;
+unsigned int        PSParallelCompact::_maximum_compaction_gc_num = 0;
+jlong               PSParallelCompact::_time_of_last_gc = 0;
+CollectorCounters*  PSParallelCompact::_counters = NULL;
+ParMarkBitMap       PSParallelCompact::_mark_bitmap;
+ParallelCompactData PSParallelCompact::_summary_data;
+
+PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
+
+bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
+
+void PSParallelCompact::AdjustKlassClosure::do_klass(Klass* klass) {
+  PSParallelCompact::AdjustPointerClosure closure(_cm);
+  klass->oops_do(&closure);
+}
+
+void PSParallelCompact::post_initialize() {
+  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
+  MemRegion mr = heap->reserved_region();
+  _ref_processor =
+    new ReferenceProcessor(mr,            // span
+                           ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
+                           ParallelGCThreads, // mt processing degree
+                           true,              // mt discovery
+                           ParallelGCThreads, // mt discovery degree
+                           true,              // atomic_discovery
+                           &_is_alive_closure); // non-header is alive closure
+  _counters = new CollectorCounters("PSParallelCompact", 1);
+
+  // Initialize static fields in ParCompactionManager.
+  ParCompactionManager::initialize(mark_bitmap());
+}
+
+bool PSParallelCompact::initialize() {
+  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
+  MemRegion mr = heap->reserved_region();
+
+  // Was the old gen get allocated successfully?
+  if (!heap->old_gen()->is_allocated()) {
+    return false;
+  }
+
+  initialize_space_info();
+  initialize_dead_wood_limiter();
+
+  if (!_mark_bitmap.initialize(mr)) {
+    vm_shutdown_during_initialization(
+      err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
+      "garbage collection for the requested " SIZE_FORMAT "KB heap.",
+      _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
+    return false;
+  }
+
+  if (!_summary_data.initialize(mr)) {
+    vm_shutdown_during_initialization(
+      err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
+      "garbage collection for the requested " SIZE_FORMAT "KB heap.",
+      _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
+    return false;
+  }
+
+  return true;
+}
+
+void PSParallelCompact::initialize_space_info()
+{
+  memset(&_space_info, 0, sizeof(_space_info));
+
+  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
+  PSYoungGen* young_gen = heap->young_gen();
+
+  _space_info[old_space_id].set_space(heap->old_gen()->object_space());
+  _space_info[eden_space_id].set_space(young_gen->eden_space());
+  _space_info[from_space_id].set_space(young_gen->from_space());
+  _space_info[to_space_id].set_space(young_gen->to_space());
+
+  _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
+}
+
+void PSParallelCompact::initialize_dead_wood_limiter()
+{
+  const size_t max = 100;
+  _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
+  _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
+  _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
+  DEBUG_ONLY(_dwl_initialized = true;)
+  _dwl_adjustment = normal_distribution(1.0);
+}
+
+void
+PSParallelCompact::clear_data_covering_space(SpaceId id)
+{
+  // At this point, top is the value before GC, new_top() is the value that will
+  // be set at the end of GC.  The marking bitmap is cleared to top; nothing
+  // should be marked above top.  The summary data is cleared to the larger of
+  // top & new_top.
+  MutableSpace* const space = _space_info[id].space();
+  HeapWord* const bot = space->bottom();
+  HeapWord* const top = space->top();
+  HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
+
+  const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
+  const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
+  _mark_bitmap.clear_range(beg_bit, end_bit);
+
+  const size_t beg_region = _summary_data.addr_to_region_idx(bot);
+  const size_t end_region =
+    _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
+  _summary_data.clear_range(beg_region, end_region);
+
+  // Clear the data used to 'split' regions.
+  SplitInfo& split_info = _space_info[id].split_info();
+  if (split_info.is_valid()) {
+    split_info.clear();
+  }
+  DEBUG_ONLY(split_info.verify_clear();)
+}
+
+void PSParallelCompact::pre_compact()
+{
+  // Update the from & to space pointers in space_info, since they are swapped
+  // at each young gen gc.  Do the update unconditionally (even though a
+  // promotion failure does not swap spaces) because an unknown number of young
+  // collections will have swapped the spaces an unknown number of times.
+  GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
+  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
+  _space_info[from_space_id].set_space(heap->young_gen()->from_space());
+  _space_info[to_space_id].set_space(heap->young_gen()->to_space());
+
+  DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
+  DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
+
+  // Increment the invocation count
+  heap->increment_total_collections(true);
+
+  // We need to track unique mark sweep invocations as well.
+  _total_invocations++;
+
+  heap->print_heap_before_gc();
+  heap->trace_heap_before_gc(&_gc_tracer);
+
+  // Fill in TLABs
+  heap->accumulate_statistics_all_tlabs();
+  heap->ensure_parsability(true);  // retire TLABs
+
+  if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
+    HandleMark hm;  // Discard invalid handles created during verification
+    Universe::verify("Before GC");
+  }
+
+  // Verify object start arrays
+  if (VerifyObjectStartArray &&
+      VerifyBeforeGC) {
+    heap->old_gen()->verify_object_start_array();
+  }
+
+  DEBUG_ONLY(mark_bitmap()->verify_clear();)
+  DEBUG_ONLY(summary_data().verify_clear();)
+
+  // Have worker threads release resources the next time they run a task.
+  gc_task_manager()->release_all_resources();
+
+  ParCompactionManager::reset_all_bitmap_query_caches();
+}
+
+void PSParallelCompact::post_compact()
+{
+  GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
+
+  for (unsigned int id = old_space_id; id < last_space_id; ++id) {
+    // Clear the marking bitmap, summary data and split info.
+    clear_data_covering_space(SpaceId(id));
+    // Update top().  Must be done after clearing the bitmap and summary data.
+    _space_info[id].publish_new_top();
+  }
+
+  MutableSpace* const eden_space = _space_info[eden_space_id].space();
+  MutableSpace* const from_space = _space_info[from_space_id].space();
+  MutableSpace* const to_space   = _space_info[to_space_id].space();
+
+  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
+  bool eden_empty = eden_space->is_empty();
+  if (!eden_empty) {
+    eden_empty = absorb_live_data_from_eden(heap->size_policy(),
+                                            heap->young_gen(), heap->old_gen());
+  }
+
+  // Update heap occupancy information which is used as input to the soft ref
+  // clearing policy at the next gc.
+  Universe::update_heap_info_at_gc();
+
+  bool young_gen_empty = eden_empty && from_space->is_empty() &&
+    to_space->is_empty();
+
+  ModRefBarrierSet* modBS = barrier_set_cast<ModRefBarrierSet>(heap->barrier_set());
+  MemRegion old_mr = heap->old_gen()->reserved();
+  if (young_gen_empty) {
+    modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
+  } else {
+    modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
+  }
+
+  // Delete metaspaces for unloaded class loaders and clean up loader_data graph
+  ClassLoaderDataGraph::purge();
+  MetaspaceAux::verify_metrics();
+
+  CodeCache::gc_epilogue();
+  JvmtiExport::gc_epilogue();
+
+#if defined(COMPILER2) || INCLUDE_JVMCI
+  DerivedPointerTable::update_pointers();
+#endif
+
+  ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->num_q());
+
+  ref_processor()->enqueue_discovered_references(NULL, &pt);
+
+  pt.print_enqueue_phase();
+
+  if (ZapUnusedHeapArea) {
+    heap->gen_mangle_unused_area();
+  }
+
+  // Update time of last GC
+  reset_millis_since_last_gc();
+}
+
+HeapWord*
+PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
+                                                    bool maximum_compaction)
+{
+  const size_t region_size = ParallelCompactData::RegionSize;
+  const ParallelCompactData& sd = summary_data();
+
+  const MutableSpace* const space = _space_info[id].space();
+  HeapWord* const top_aligned_up = sd.region_align_up(space->top());
+  const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
+  const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
+
+  // Skip full regions at the beginning of the space--they are necessarily part
+  // of the dense prefix.
+  size_t full_count = 0;
+  const RegionData* cp;
+  for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
+    ++full_count;
+  }
+
+  assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
+  const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
+  const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
+  if (maximum_compaction || cp == end_cp || interval_ended) {
+    _maximum_compaction_gc_num = total_invocations();
+    return sd.region_to_addr(cp);
+  }
+
+  HeapWord* const new_top = _space_info[id].new_top();
+  const size_t space_live = pointer_delta(new_top, space->bottom());
+  const size_t space_used = space->used_in_words();
+  const size_t space_capacity = space->capacity_in_words();
+
+  const double cur_density = double(space_live) / space_capacity;
+  const double deadwood_density =
+    (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
+  const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
+
+  if (TraceParallelOldGCDensePrefix) {
+    tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
+                  cur_density, deadwood_density, deadwood_goal);
+    tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
+                  "space_cap=" SIZE_FORMAT,
+                  space_live, space_used,
+                  space_capacity);
+  }
+
+  // XXX - Use binary search?
+  HeapWord* dense_prefix = sd.region_to_addr(cp);
+  const RegionData* full_cp = cp;
+  const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
+  while (cp < end_cp) {
+    HeapWord* region_destination = cp->destination();
+    const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
+    if (TraceParallelOldGCDensePrefix && Verbose) {
+      tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
+                    "dp=" PTR_FORMAT " " "cdw=" SIZE_FORMAT_W(8),
+                    sd.region(cp), p2i(region_destination),
+                    p2i(dense_prefix), cur_deadwood);
+    }
+
+    if (cur_deadwood >= deadwood_goal) {
+      // Found the region that has the correct amount of deadwood to the left.
+      // This typically occurs after crossing a fairly sparse set of regions, so
+      // iterate backwards over those sparse regions, looking for the region
+      // that has the lowest density of live objects 'to the right.'
+      size_t space_to_left = sd.region(cp) * region_size;
+      size_t live_to_left = space_to_left - cur_deadwood;
+      size_t space_to_right = space_capacity - space_to_left;
+      size_t live_to_right = space_live - live_to_left;
+      double density_to_right = double(live_to_right) / space_to_right;
+      while (cp > full_cp) {
+        --cp;
+        const size_t prev_region_live_to_right = live_to_right -
+          cp->data_size();
+        const size_t prev_region_space_to_right = space_to_right + region_size;
+        double prev_region_density_to_right =
+          double(prev_region_live_to_right) / prev_region_space_to_right;
+        if (density_to_right <= prev_region_density_to_right) {
+          return dense_prefix;
+        }
+        if (TraceParallelOldGCDensePrefix && Verbose) {
+          tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
+                        "pc_d2r=%10.8f", sd.region(cp), density_to_right,
+                        prev_region_density_to_right);
+        }
+        dense_prefix -= region_size;
+        live_to_right = prev_region_live_to_right;
+        space_to_right = prev_region_space_to_right;
+        density_to_right = prev_region_density_to_right;
+      }
+      return dense_prefix;
+    }
+
+    dense_prefix += region_size;
+    ++cp;
+  }
+
+  return dense_prefix;
+}
+
+#ifndef PRODUCT
+void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
+                                                 const SpaceId id,
+                                                 const bool maximum_compaction,
+                                                 HeapWord* const addr)
+{
+  const size_t region_idx = summary_data().addr_to_region_idx(addr);
+  RegionData* const cp = summary_data().region(region_idx);
+  const MutableSpace* const space = _space_info[id].space();
+  HeapWord* const new_top = _space_info[id].new_top();
+
+  const size_t space_live = pointer_delta(new_top, space->bottom());
+  const size_t dead_to_left = pointer_delta(addr, cp->destination());
+  const size_t space_cap = space->capacity_in_words();
+  const double dead_to_left_pct = double(dead_to_left) / space_cap;
+  const size_t live_to_right = new_top - cp->destination();
+  const size_t dead_to_right = space->top() - addr - live_to_right;
+
+  tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
+                "spl=" SIZE_FORMAT " "
+                "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
+                "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
+                " ratio=%10.8f",
+                algorithm, p2i(addr), region_idx,
+                space_live,
+                dead_to_left, dead_to_left_pct,
+                dead_to_right, live_to_right,
+                double(dead_to_right) / live_to_right);
+}
+#endif  // #ifndef PRODUCT
+
+// Return a fraction indicating how much of the generation can be treated as
+// "dead wood" (i.e., not reclaimed).  The function uses a normal distribution
+// based on the density of live objects in the generation to determine a limit,
+// which is then adjusted so the return value is min_percent when the density is
+// 1.
+//
+// The following table shows some return values for a different values of the
+// standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
+// min_percent is 1.
+//
+//                          fraction allowed as dead wood
+//         -----------------------------------------------------------------
+// density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
+// ------- ---------- ---------- ---------- ---------- ---------- ----------
+// 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
+// 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
+// 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
+// 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
+// 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
+// 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
+// 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
+// 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
+// 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
+// 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
+// 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
+// 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
+// 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
+// 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
+// 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
+// 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
+// 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
+// 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
+// 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
+// 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
+// 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
+
+double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
+{
+  assert(_dwl_initialized, "uninitialized");
+
+  // The raw limit is the value of the normal distribution at x = density.
+  const double raw_limit = normal_distribution(density);
+
+  // Adjust the raw limit so it becomes the minimum when the density is 1.
+  //
+  // First subtract the adjustment value (which is simply the precomputed value
+  // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
+  // Then add the minimum value, so the minimum is returned when the density is
+  // 1.  Finally, prevent negative values, which occur when the mean is not 0.5.
+  const double min = double(min_percent) / 100.0;
+  const double limit = raw_limit - _dwl_adjustment + min;
+  return MAX2(limit, 0.0);
+}
+
+ParallelCompactData::RegionData*
+PSParallelCompact::first_dead_space_region(const RegionData* beg,
+                                           const RegionData* end)
+{
+  const size_t region_size = ParallelCompactData::RegionSize;
+  ParallelCompactData& sd = summary_data();
+  size_t left = sd.region(beg);
+  size_t right = end > beg ? sd.region(end) - 1 : left;
+
+  // Binary search.
+  while (left < right) {
+    // Equivalent to (left + right) / 2, but does not overflow.
+    const size_t middle = left + (right - left) / 2;
+    RegionData* const middle_ptr = sd.region(middle);
+    HeapWord* const dest = middle_ptr->destination();
+    HeapWord* const addr = sd.region_to_addr(middle);
+    assert(dest != NULL, "sanity");
+    assert(dest <= addr, "must move left");
+
+    if (middle > left && dest < addr) {
+      right = middle - 1;
+    } else if (middle < right && middle_ptr->data_size() == region_size) {
+      left = middle + 1;
+    } else {
+      return middle_ptr;
+    }
+  }
+  return sd.region(left);
+}
+
+ParallelCompactData::RegionData*
+PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
+                                          const RegionData* end,
+                                          size_t dead_words)
+{
+  ParallelCompactData& sd = summary_data();
+  size_t left = sd.region(beg);
+  size_t right = end > beg ? sd.region(end) - 1 : left;
+
+  // Binary search.
+  while (left < right) {
+    // Equivalent to (left + right) / 2, but does not overflow.
+    const size_t middle = left + (right - left) / 2;
+    RegionData* const middle_ptr = sd.region(middle);
+    HeapWord* const dest = middle_ptr->destination();
+    HeapWord* const addr = sd.region_to_addr(middle);
+    assert(dest != NULL, "sanity");
+    assert(dest <= addr, "must move left");
+
+    const size_t dead_to_left = pointer_delta(addr, dest);
+    if (middle > left && dead_to_left > dead_words) {
+      right = middle - 1;
+    } else if (middle < right && dead_to_left < dead_words) {
+      left = middle + 1;
+    } else {
+      return middle_ptr;
+    }
+  }
+  return sd.region(left);
+}
+
+// The result is valid during the summary phase, after the initial summarization
+// of each space into itself, and before final summarization.
+inline double
+PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
+                                   HeapWord* const bottom,
+                                   HeapWord* const top,
+                                   HeapWord* const new_top)
+{
+  ParallelCompactData& sd = summary_data();
+
+  assert(cp != NULL, "sanity");
+  assert(bottom != NULL, "sanity");
+  assert(top != NULL, "sanity");
+  assert(new_top != NULL, "sanity");
+  assert(top >= new_top, "summary data problem?");
+  assert(new_top > bottom, "space is empty; should not be here");
+  assert(new_top >= cp->destination(), "sanity");
+  assert(top >= sd.region_to_addr(cp), "sanity");
+
+  HeapWord* const destination = cp->destination();
+  const size_t dense_prefix_live  = pointer_delta(destination, bottom);
+  const size_t compacted_region_live = pointer_delta(new_top, destination);
+  const size_t compacted_region_used = pointer_delta(top,
+                                                     sd.region_to_addr(cp));
+  const size_t reclaimable = compacted_region_used - compacted_region_live;
+
+  const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
+  return double(reclaimable) / divisor;
+}
+
+// Return the address of the end of the dense prefix, a.k.a. the start of the
+// compacted region.  The address is always on a region boundary.
+//
+// Completely full regions at the left are skipped, since no compaction can
+// occur in those regions.  Then the maximum amount of dead wood to allow is
+// computed, based on the density (amount live / capacity) of the generation;
+// the region with approximately that amount of dead space to the left is
+// identified as the limit region.  Regions between the last completely full
+// region and the limit region are scanned and the one that has the best
+// (maximum) reclaimed_ratio() is selected.
+HeapWord*
+PSParallelCompact::compute_dense_prefix(const SpaceId id,
+                                        bool maximum_compaction)
+{
+  const size_t region_size = ParallelCompactData::RegionSize;
+  const ParallelCompactData& sd = summary_data();
+
+  const MutableSpace* const space = _space_info[id].space();
+  HeapWord* const top = space->top();
+  HeapWord* const top_aligned_up = sd.region_align_up(top);
+  HeapWord* const new_top = _space_info[id].new_top();
+  HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
+  HeapWord* const bottom = space->bottom();
+  const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
+  const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
+  const RegionData* const new_top_cp =
+    sd.addr_to_region_ptr(new_top_aligned_up);
+
+  // Skip full regions at the beginning of the space--they are necessarily part
+  // of the dense prefix.
+  const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
+  assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
+         space->is_empty(), "no dead space allowed to the left");
+  assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
+         "region must have dead space");
+
+  // The gc number is saved whenever a maximum compaction is done, and used to
+  // determine when the maximum compaction interval has expired.  This avoids
+  // successive max compactions for different reasons.
+  assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
+  const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
+  const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
+    total_invocations() == HeapFirstMaximumCompactionCount;
+  if (maximum_compaction || full_cp == top_cp || interval_ended) {
+    _maximum_compaction_gc_num = total_invocations();
+    return sd.region_to_addr(full_cp);
+  }
+
+  const size_t space_live = pointer_delta(new_top, bottom);
+  const size_t space_used = space->used_in_words();
+  const size_t space_capacity = space->capacity_in_words();
+
+  const double density = double(space_live) / double(space_capacity);
+  const size_t min_percent_free = MarkSweepDeadRatio;
+  const double limiter = dead_wood_limiter(density, min_percent_free);
+  const size_t dead_wood_max = space_used - space_live;
+  const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
+                                      dead_wood_max);
+
+  if (TraceParallelOldGCDensePrefix) {
+    tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
+                  "space_cap=" SIZE_FORMAT,
+                  space_live, space_used,
+                  space_capacity);
+    tty->print_cr("dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
+                  "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
+                  density, min_percent_free, limiter,
+                  dead_wood_max, dead_wood_limit);
+  }
+
+  // Locate the region with the desired amount of dead space to the left.
+  const RegionData* const limit_cp =
+    dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
+
+  // Scan from the first region with dead space to the limit region and find the
+  // one with the best (largest) reclaimed ratio.
+  double best_ratio = 0.0;
+  const RegionData* best_cp = full_cp;
+  for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
+    double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
+    if (tmp_ratio > best_ratio) {
+      best_cp = cp;
+      best_ratio = tmp_ratio;
+    }
+  }
+
+  return sd.region_to_addr(best_cp);
+}
+
+void PSParallelCompact::summarize_spaces_quick()
+{
+  for (unsigned int i = 0; i < last_space_id; ++i) {
+    const MutableSpace* space = _space_info[i].space();
+    HeapWord** nta = _space_info[i].new_top_addr();
+    bool result = _summary_data.summarize(_space_info[i].split_info(),
+                                          space->bottom(), space->top(), NULL,
+                                          space->bottom(), space->end(), nta);
+    assert(result, "space must fit into itself");
+    _space_info[i].set_dense_prefix(space->bottom());
+  }
+}
+
+void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
+{
+  HeapWord* const dense_prefix_end = dense_prefix(id);
+  const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
+  const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
+  if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
+    // Only enough dead space is filled so that any remaining dead space to the
+    // left is larger than the minimum filler object.  (The remainder is filled
+    // during the copy/update phase.)
+    //
+    // The size of the dead space to the right of the boundary is not a
+    // concern, since compaction will be able to use whatever space is
+    // available.
+    //
+    // Here '||' is the boundary, 'x' represents a don't care bit and a box
+    // surrounds the space to be filled with an object.
+    //
+    // In the 32-bit VM, each bit represents two 32-bit words:
+    //                              +---+
+    // a) beg_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
+    //    end_bits:  ...  x   x   x | 0 | ||   0   x  x  ...
+    //                              +---+
+    //
+    // In the 64-bit VM, each bit represents one 64-bit word:
+    //                              +------------+
+    // b) beg_bits:  ...  x   x   x | 0   ||   0 | x  x  ...
+    //    end_bits:  ...  x   x   1 | 0   ||   0 | x  x  ...
+    //                              +------------+
+    //                          +-------+
+    // c) beg_bits:  ...  x   x | 0   0 | ||   0   x  x  ...
+    //    end_bits:  ...  x   1 | 0   0 | ||   0   x  x  ...
+    //                          +-------+
+    //                      +-----------+
+    // d) beg_bits:  ...  x | 0   0   0 | ||   0   x  x  ...
+    //    end_bits:  ...  1 | 0   0   0 | ||   0   x  x  ...
+    //                      +-----------+
+    //                          +-------+
+    // e) beg_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
+    //    end_bits:  ...  0   0 | 0   0 | ||   0   x  x  ...
+    //                          +-------+
+
+    // Initially assume case a, c or e will apply.
+    size_t obj_len = CollectedHeap::min_fill_size();
+    HeapWord* obj_beg = dense_prefix_end - obj_len;
+
+#ifdef  _LP64
+    if (MinObjAlignment > 1) { // object alignment > heap word size
+      // Cases a, c or e.
+    } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
+      // Case b above.
+      obj_beg = dense_prefix_end - 1;
+    } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
+               _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
+      // Case d above.
+      obj_beg = dense_prefix_end - 3;
+      obj_len = 3;
+    }
+#endif  // #ifdef _LP64
+
+    CollectedHeap::fill_with_object(obj_beg, obj_len);
+    _mark_bitmap.mark_obj(obj_beg, obj_len);
+    _summary_data.add_obj(obj_beg, obj_len);
+    assert(start_array(id) != NULL, "sanity");
+    start_array(id)->allocate_block(obj_beg);
+  }
+}
+
+void
+PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
+{
+  assert(id < last_space_id, "id out of range");
+  assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
+         "should have been reset in summarize_spaces_quick()");
+
+  const MutableSpace* space = _space_info[id].space();
+  if (_space_info[id].new_top() != space->bottom()) {
+    HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
+    _space_info[id].set_dense_prefix(dense_prefix_end);
+
+#ifndef PRODUCT
+    if (TraceParallelOldGCDensePrefix) {
+      print_dense_prefix_stats("ratio", id, maximum_compaction,
+                               dense_prefix_end);
+      HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
+      print_dense_prefix_stats("density", id, maximum_compaction, addr);
+    }
+#endif  // #ifndef PRODUCT
+
+    // Recompute the summary data, taking into account the dense prefix.  If
+    // every last byte will be reclaimed, then the existing summary data which
+    // compacts everything can be left in place.
+    if (!maximum_compaction && dense_prefix_end != space->bottom()) {
+      // If dead space crosses the dense prefix boundary, it is (at least
+      // partially) filled with a dummy object, marked live and added to the
+      // summary data.  This simplifies the copy/update phase and must be done
+      // before the final locations of objects are determined, to prevent
+      // leaving a fragment of dead space that is too small to fill.
+      fill_dense_prefix_end(id);
+
+      // Compute the destination of each Region, and thus each object.
+      _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
+      _summary_data.summarize(_space_info[id].split_info(),
+                              dense_prefix_end, space->top(), NULL,
+                              dense_prefix_end, space->end(),
+                              _space_info[id].new_top_addr());
+    }
+  }
+
+  if (log_develop_is_enabled(Trace, gc, compaction)) {
+    const size_t region_size = ParallelCompactData::RegionSize;
+    HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
+    const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
+    const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
+    HeapWord* const new_top = _space_info[id].new_top();
+    const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
+    const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
+    log_develop_trace(gc, compaction)(
+        "id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
+        "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
+        "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
+        id, space->capacity_in_words(), p2i(dense_prefix_end),
+        dp_region, dp_words / region_size,
+        cr_words / region_size, p2i(new_top));
+  }
+}
+
+#ifndef PRODUCT
+void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
+                                          HeapWord* dst_beg, HeapWord* dst_end,
+                                          SpaceId src_space_id,
+                                          HeapWord* src_beg, HeapWord* src_end)
+{
+  log_develop_trace(gc, compaction)(
+      "Summarizing %d [%s] into %d [%s]:  "
+      "src=" PTR_FORMAT "-" PTR_FORMAT " "
+      SIZE_FORMAT "-" SIZE_FORMAT " "
+      "dst=" PTR_FORMAT "-" PTR_FORMAT " "
+      SIZE_FORMAT "-" SIZE_FORMAT,
+      src_space_id, space_names[src_space_id],
+      dst_space_id, space_names[dst_space_id],
+      p2i(src_beg), p2i(src_end),
+      _summary_data.addr_to_region_idx(src_beg),
+      _summary_data.addr_to_region_idx(src_end),
+      p2i(dst_beg), p2i(dst_end),
+      _summary_data.addr_to_region_idx(dst_beg),
+      _summary_data.addr_to_region_idx(dst_end));
+}
+#endif  // #ifndef PRODUCT
+
+void PSParallelCompact::summary_phase(ParCompactionManager* cm,
+                                      bool maximum_compaction)
+{
+  GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
+
+#ifdef  ASSERT
+  if (TraceParallelOldGCMarkingPhase) {
+    tty->print_cr("add_obj_count=" SIZE_FORMAT " "
+                  "add_obj_bytes=" SIZE_FORMAT,
+                  add_obj_count, add_obj_size * HeapWordSize);
+    tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
+                  "mark_bitmap_bytes=" SIZE_FORMAT,
+                  mark_bitmap_count, mark_bitmap_size * HeapWordSize);
+  }
+#endif  // #ifdef ASSERT
+
+  // Quick summarization of each space into itself, to see how much is live.
+  summarize_spaces_quick();
+
+  log_develop_trace(gc, compaction)("summary phase:  after summarizing each space to self");
+  NOT_PRODUCT(print_region_ranges());
+  NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
+
+  // The amount of live data that will end up in old space (assuming it fits).
+  size_t old_space_total_live = 0;
+  for (unsigned int id = old_space_id; id < last_space_id; ++id) {
+    old_space_total_live += pointer_delta(_space_info[id].new_top(),
+                                          _space_info[id].space()->bottom());
+  }
+
+  MutableSpace* const old_space = _space_info[old_space_id].space();
+  const size_t old_capacity = old_space->capacity_in_words();
+  if (old_space_total_live > old_capacity) {
+    // XXX - should also try to expand
+    maximum_compaction = true;
+  }
+
+  // Old generations.
+  summarize_space(old_space_id, maximum_compaction);
+
+  // Summarize the remaining spaces in the young gen.  The initial target space
+  // is the old gen.  If a space does not fit entirely into the target, then the
+  // remainder is compacted into the space itself and that space becomes the new
+  // target.
+  SpaceId dst_space_id = old_space_id;
+  HeapWord* dst_space_end = old_space->end();
+  HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
+  for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
+    const MutableSpace* space = _space_info[id].space();
+    const size_t live = pointer_delta(_space_info[id].new_top(),
+                                      space->bottom());
+    const size_t available = pointer_delta(dst_space_end, *new_top_addr);
+
+    NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
+                                  SpaceId(id), space->bottom(), space->top());)
+    if (live > 0 && live <= available) {
+      // All the live data will fit.
+      bool done = _summary_data.summarize(_space_info[id].split_info(),
+                                          space->bottom(), space->top(),
+                                          NULL,
+                                          *new_top_addr, dst_space_end,
+                                          new_top_addr);
+      assert(done, "space must fit into old gen");
+
+      // Reset the new_top value for the space.
+      _space_info[id].set_new_top(space->bottom());
+    } else if (live > 0) {
+      // Attempt to fit part of the source space into the target space.
+      HeapWord* next_src_addr = NULL;
+      bool done = _summary_data.summarize(_space_info[id].split_info(),
+                                          space->bottom(), space->top(),
+                                          &next_src_addr,
+                                          *new_top_addr, dst_space_end,
+                                          new_top_addr);
+      assert(!done, "space should not fit into old gen");
+      assert(next_src_addr != NULL, "sanity");
+
+      // The source space becomes the new target, so the remainder is compacted
+      // within the space itself.
+      dst_space_id = SpaceId(id);
+      dst_space_end = space->end();
+      new_top_addr = _space_info[id].new_top_addr();
+      NOT_PRODUCT(summary_phase_msg(dst_space_id,
+                                    space->bottom(), dst_space_end,
+                                    SpaceId(id), next_src_addr, space->top());)
+      done = _summary_data.summarize(_space_info[id].split_info(),
+                                     next_src_addr, space->top(),
+                                     NULL,
+                                     space->bottom(), dst_space_end,
+                                     new_top_addr);
+      assert(done, "space must fit when compacted into itself");
+      assert(*new_top_addr <= space->top(), "usage should not grow");
+    }
+  }
+
+  log_develop_trace(gc, compaction)("Summary_phase:  after final summarization");
+  NOT_PRODUCT(print_region_ranges());
+  NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
+}
+
+// This method should contain all heap-specific policy for invoking a full
+// collection.  invoke_no_policy() will only attempt to compact the heap; it
+// will do nothing further.  If we need to bail out for policy reasons, scavenge
+// before full gc, or any other specialized behavior, it needs to be added here.
+//
+// Note that this method should only be called from the vm_thread while at a
+// safepoint.
+//
+// Note that the all_soft_refs_clear flag in the collector policy
+// may be true because this method can be called without intervening
+// activity.  For example when the heap space is tight and full measure
+// are being taken to free space.
+void PSParallelCompact::invoke(bool maximum_heap_compaction) {
+  assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
+  assert(Thread::current() == (Thread*)VMThread::vm_thread(),
+         "should be in vm thread");
+
+  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
+  GCCause::Cause gc_cause = heap->gc_cause();
+  assert(!heap->is_gc_active(), "not reentrant");
+
+  PSAdaptiveSizePolicy* policy = heap->size_policy();
+  IsGCActiveMark mark;
+
+  if (ScavengeBeforeFullGC) {
+    PSScavenge::invoke_no_policy();
+  }
+
+  const bool clear_all_soft_refs =
+    heap->collector_policy()->should_clear_all_soft_refs();
+
+  PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
+                                      maximum_heap_compaction);
+}
+
+// This method contains no policy. You should probably
+// be calling invoke() instead.
+bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
+  assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
+  assert(ref_processor() != NULL, "Sanity");
+
+  if (GCLocker::check_active_before_gc()) {
+    return false;
+  }
+
+  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
+
+  GCIdMark gc_id_mark;
+  _gc_timer.register_gc_start();
+  _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
+
+  TimeStamp marking_start;
+  TimeStamp compaction_start;
+  TimeStamp collection_exit;
+
+  GCCause::Cause gc_cause = heap->gc_cause();
+  PSYoungGen* young_gen = heap->young_gen();
+  PSOldGen* old_gen = heap->old_gen();
+  PSAdaptiveSizePolicy* size_policy = heap->size_policy();
+
+  // The scope of casr should end after code that can change
+  // CollectorPolicy::_should_clear_all_soft_refs.
+  ClearedAllSoftRefs casr(maximum_heap_compaction,
+                          heap->collector_policy());
+
+  if (ZapUnusedHeapArea) {
+    // Save information needed to minimize mangling
+    heap->record_gen_tops_before_GC();
+  }
+
+  // Make sure data structures are sane, make the heap parsable, and do other
+  // miscellaneous bookkeeping.
+  pre_compact();
+
+  PreGCValues pre_gc_values(heap);
+
+  // Get the compaction manager reserved for the VM thread.
+  ParCompactionManager* const vmthread_cm =
+    ParCompactionManager::manager_array(gc_task_manager()->workers());
+
+  {
+    ResourceMark rm;
+    HandleMark hm;
+
+    // Set the number of GC threads to be used in this collection
+    gc_task_manager()->set_active_gang();
+    gc_task_manager()->task_idle_workers();
+
+    GCTraceCPUTime tcpu;
+    GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause, true);
+
+    heap->pre_full_gc_dump(&_gc_timer);
+
+    TraceCollectorStats tcs(counters());
+    TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);
+
+    if (TraceOldGenTime) accumulated_time()->start();
+
+    // Let the size policy know we're starting
+    size_policy->major_collection_begin();
+
+    CodeCache::gc_prologue();
+
+#if defined(COMPILER2) || INCLUDE_JVMCI
+    DerivedPointerTable::clear();
+#endif
+
+    ref_processor()->enable_discovery();
+    ref_processor()->setup_policy(maximum_heap_compaction);
+
+    bool marked_for_unloading = false;
+
+    marking_start.update();
+    marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
+
+    bool max_on_system_gc = UseMaximumCompactionOnSystemGC
+      && GCCause::is_user_requested_gc(gc_cause);
+    summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
+
+#if defined(COMPILER2) || INCLUDE_JVMCI
+    assert(DerivedPointerTable::is_active(), "Sanity");
+    DerivedPointerTable::set_active(false);
+#endif
+
+    // adjust_roots() updates Universe::_intArrayKlassObj which is
+    // needed by the compaction for filling holes in the dense prefix.
+    adjust_roots(vmthread_cm);
+
+    compaction_start.update();
+    compact();
+
+    // Reset the mark bitmap, summary data, and do other bookkeeping.  Must be
+    // done before resizing.
+    post_compact();
+
+    // Let the size policy know we're done
+    size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
+
+    if (UseAdaptiveSizePolicy) {
+      log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
+      log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
+                          old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
+
+      // Don't check if the size_policy is ready here.  Let
+      // the size_policy check that internally.
+      if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
+          AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
+        // Swap the survivor spaces if from_space is empty. The
+        // resize_young_gen() called below is normally used after
+        // a successful young GC and swapping of survivor spaces;
+        // otherwise, it will fail to resize the young gen with
+        // the current implementation.
+        if (young_gen->from_space()->is_empty()) {
+          young_gen->from_space()->clear(SpaceDecorator::Mangle);
+          young_gen->swap_spaces();
+        }
+
+        // Calculate optimal free space amounts
+        assert(young_gen->max_size() >
+          young_gen->from_space()->capacity_in_bytes() +
+          young_gen->to_space()->capacity_in_bytes(),
+          "Sizes of space in young gen are out-of-bounds");
+
+        size_t young_live = young_gen->used_in_bytes();
+        size_t eden_live = young_gen->eden_space()->used_in_bytes();
+        size_t old_live = old_gen->used_in_bytes();
+        size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
+        size_t max_old_gen_size = old_gen->max_gen_size();
+        size_t max_eden_size = young_gen->max_size() -
+          young_gen->from_space()->capacity_in_bytes() -
+          young_gen->to_space()->capacity_in_bytes();
+
+        // Used for diagnostics
+        size_policy->clear_generation_free_space_flags();
+
+        size_policy->compute_generations_free_space(young_live,
+                                                    eden_live,
+                                                    old_live,
+                                                    cur_eden,
+                                                    max_old_gen_size,
+                                                    max_eden_size,
+                                                    true /* full gc*/);
+
+        size_policy->check_gc_overhead_limit(young_live,
+                                             eden_live,
+                                             max_old_gen_size,
+                                             max_eden_size,
+                                             true /* full gc*/,
+                                             gc_cause,
+                                             heap->collector_policy());
+
+        size_policy->decay_supplemental_growth(true /* full gc*/);
+
+        heap->resize_old_gen(
+          size_policy->calculated_old_free_size_in_bytes());
+
+        heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
+                               size_policy->calculated_survivor_size_in_bytes());
+      }
+
+      log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
+    }
+
+    if (UsePerfData) {
+      PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
+      counters->update_counters();
+      counters->update_old_capacity(old_gen->capacity_in_bytes());
+      counters->update_young_capacity(young_gen->capacity_in_bytes());
+    }
+
+    heap->resize_all_tlabs();
+
+    // Resize the metaspace capacity after a collection
+    MetaspaceGC::compute_new_size();
+
+    if (TraceOldGenTime) {
+      accumulated_time()->stop();
+    }
+
+    young_gen->print_used_change(pre_gc_values.young_gen_used());
+    old_gen->print_used_change(pre_gc_values.old_gen_used());
+    MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used());
+
+    // Track memory usage and detect low memory
+    MemoryService::track_memory_usage();
+    heap->update_counters();
+    gc_task_manager()->release_idle_workers();
+
+    heap->post_full_gc_dump(&_gc_timer);
+  }
+
+#ifdef ASSERT
+  for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
+    ParCompactionManager* const cm =
+      ParCompactionManager::manager_array(int(i));
+    assert(cm->marking_stack()->is_empty(),       "should be empty");
+    assert(cm->region_stack()->is_empty(), "Region stack " SIZE_FORMAT " is not empty", i);
+  }
+#endif // ASSERT
+
+  if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
+    HandleMark hm;  // Discard invalid handles created during verification
+    Universe::verify("After GC");
+  }
+
+  // Re-verify object start arrays
+  if (VerifyObjectStartArray &&
+      VerifyAfterGC) {
+    old_gen->verify_object_start_array();
+  }
+
+  if (ZapUnusedHeapArea) {
+    old_gen->object_space()->check_mangled_unused_area_complete();
+  }
+
+  NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
+
+  collection_exit.update();
+
+  heap->print_heap_after_gc();
+  heap->trace_heap_after_gc(&_gc_tracer);
+
+  log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
+                         marking_start.ticks(), compaction_start.ticks(),
+                         collection_exit.ticks());
+  gc_task_manager()->print_task_time_stamps();
+
+#ifdef TRACESPINNING
+  ParallelTaskTerminator::print_termination_counts();
+#endif
+
+  AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
+
+  _gc_timer.register_gc_end();
+
+  _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
+  _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
+
+  return true;
+}
+
+bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
+                                             PSYoungGen* young_gen,
+                                             PSOldGen* old_gen) {
+  MutableSpace* const eden_space = young_gen->eden_space();
+  assert(!eden_space->is_empty(), "eden must be non-empty");
+  assert(young_gen->virtual_space()->alignment() ==
+         old_gen->virtual_space()->alignment(), "alignments do not match");
+
+  if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
+    return false;
+  }
+
+  // Both generations must be completely committed.
+  if (young_gen->virtual_space()->uncommitted_size() != 0) {
+    return false;
+  }
+  if (old_gen->virtual_space()->uncommitted_size() != 0) {
+    return false;
+  }
+
+  // Figure out how much to take from eden.  Include the average amount promoted
+  // in the total; otherwise the next young gen GC will simply bail out to a
+  // full GC.
+  const size_t alignment = old_gen->virtual_space()->alignment();
+  const size_t eden_used = eden_space->used_in_bytes();
+  const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
+  const size_t absorb_size = align_up(eden_used + promoted, alignment);
+  const size_t eden_capacity = eden_space->capacity_in_bytes();
+
+  if (absorb_size >= eden_capacity) {
+    return false; // Must leave some space in eden.
+  }
+
+  const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
+  if (new_young_size < young_gen->min_gen_size()) {
+    return false; // Respect young gen minimum size.
+  }
+
+  log_trace(heap, ergo)(" absorbing " SIZE_FORMAT "K:  "
+                        "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
+                        "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
+                        "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
+                        absorb_size / K,
+                        eden_capacity / K, (eden_capacity - absorb_size) / K,
+                        young_gen->from_space()->used_in_bytes() / K,
+                        young_gen->to_space()->used_in_bytes() / K,
+                        young_gen->capacity_in_bytes() / K, new_young_size / K);
+
+  // Fill the unused part of the old gen.
+  MutableSpace* const old_space = old_gen->object_space();
+  HeapWord* const unused_start = old_space->top();
+  size_t const unused_words = pointer_delta(old_space->end(), unused_start);
+
+  if (unused_words > 0) {
+    if (unused_words < CollectedHeap::min_fill_size()) {
+      return false;  // If the old gen cannot be filled, must give up.
+    }
+    CollectedHeap::fill_with_objects(unused_start, unused_words);
+  }
+
+  // Take the live data from eden and set both top and end in the old gen to
+  // eden top.  (Need to set end because reset_after_change() mangles the region
+  // from end to virtual_space->high() in debug builds).
+  HeapWord* const new_top = eden_space->top();
+  old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
+                                        absorb_size);
+  young_gen->reset_after_change();
+  old_space->set_top(new_top);
+  old_space->set_end(new_top);
+  old_gen->reset_after_change();
+
+  // Update the object start array for the filler object and the data from eden.
+  ObjectStartArray* const start_array = old_gen->start_array();
+  for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
+    start_array->allocate_block(p);
+  }
+
+  // Could update the promoted average here, but it is not typically updated at
+  // full GCs and the value to use is unclear.  Something like
+  //
+  // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
+
+  size_policy->set_bytes_absorbed_from_eden(absorb_size);
+  return true;
+}
+
+GCTaskManager* const PSParallelCompact::gc_task_manager() {
+  assert(ParallelScavengeHeap::gc_task_manager() != NULL,
+    "shouldn't return NULL");
+  return ParallelScavengeHeap::gc_task_manager();
+}
+
+void PSParallelCompact::marking_phase(ParCompactionManager* cm,
+                                      bool maximum_heap_compaction,
+                                      ParallelOldTracer *gc_tracer) {
+  // Recursively traverse all live objects and mark them
+  GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
+
+  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
+  uint parallel_gc_threads = heap->gc_task_manager()->workers();
+  uint active_gc_threads = heap->gc_task_manager()->active_workers();
+  TaskQueueSetSuper* qset = ParCompactionManager::stack_array();
+  ParallelTaskTerminator terminator(active_gc_threads, qset);
+
+  ParCompactionManager::MarkAndPushClosure mark_and_push_closure(cm);
+  ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
+
+  // Need new claim bits before marking starts.
+  ClassLoaderDataGraph::clear_claimed_marks();
+
+  {
+    GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
+
+    ParallelScavengeHeap::ParStrongRootsScope psrs;
+
+    GCTaskQueue* q = GCTaskQueue::create();
+
+    q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
+    q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
+    // We scan the thread roots in parallel
+    Threads::create_thread_roots_marking_tasks(q);
+    q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
+    q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
+    q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
+    q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data));
+    q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
+    q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
+
+    if (active_gc_threads > 1) {
+      for (uint j = 0; j < active_gc_threads; j++) {
+        q->enqueue(new StealMarkingTask(&terminator));
+      }
+    }
+
+    gc_task_manager()->execute_and_wait(q);
+  }
+
+  // Process reference objects found during marking
+  {
+    GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
+
+    ReferenceProcessorStats stats;
+    ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->num_q());
+    if (ref_processor()->processing_is_mt()) {
+      RefProcTaskExecutor task_executor;
+      stats = ref_processor()->process_discovered_references(
+        is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
+        &task_executor, &pt);
+    } else {
+      stats = ref_processor()->process_discovered_references(
+        is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
+        &pt);
+    }
+
+    gc_tracer->report_gc_reference_stats(stats);
+    pt.print_all_references();
+  }
+
+  // This is the point where the entire marking should have completed.
+  assert(cm->marking_stacks_empty(), "Marking should have completed");
+
+  {
+    GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
+
+    // Follow system dictionary roots and unload classes.
+    bool purged_class = SystemDictionary::do_unloading(is_alive_closure(), &_gc_timer);
+
+    // Unload nmethods.
+    CodeCache::do_unloading(is_alive_closure(), purged_class);
+
+    // Prune dead klasses from subklass/sibling/implementor lists.
+    Klass::clean_weak_klass_links(is_alive_closure());
+  }
+
+  {
+    GCTraceTime(Debug, gc, phases) t("Scrub String Table", &_gc_timer);
+    // Delete entries for dead interned strings.
+    StringTable::unlink(is_alive_closure());
+  }
+
+  {
+    GCTraceTime(Debug, gc, phases) t("Scrub Symbol Table", &_gc_timer);
+    // Clean up unreferenced symbols in symbol table.
+    SymbolTable::unlink();
+  }
+
+  _gc_tracer.report_object_count_after_gc(is_alive_closure());
+}
+
+void PSParallelCompact::adjust_roots(ParCompactionManager* cm) {
+  // Adjust the pointers to reflect the new locations
+  GCTraceTime(Info, gc, phases) tm("Adjust Roots", &_gc_timer);
+
+  // Need new claim bits when tracing through and adjusting pointers.
+  ClassLoaderDataGraph::clear_claimed_marks();
+
+  PSParallelCompact::AdjustPointerClosure oop_closure(cm);
+  PSParallelCompact::AdjustKlassClosure klass_closure(cm);
+
+  // General strong roots.
+  Universe::oops_do(&oop_closure);
+  JNIHandles::oops_do(&oop_closure);   // Global (strong) JNI handles
+  Threads::oops_do(&oop_closure, NULL);
+  ObjectSynchronizer::oops_do(&oop_closure);
+  Management::oops_do(&oop_closure);
+  JvmtiExport::oops_do(&oop_closure);
+  SystemDictionary::oops_do(&oop_closure);
+  ClassLoaderDataGraph::oops_do(&oop_closure, &klass_closure, true);
+
+  // Now adjust pointers in remaining weak roots.  (All of which should
+  // have been cleared if they pointed to non-surviving objects.)
+  // Global (weak) JNI handles
+  JNIHandles::weak_oops_do(&oop_closure);
+
+  CodeBlobToOopClosure adjust_from_blobs(&oop_closure, CodeBlobToOopClosure::FixRelocations);
+  CodeCache::blobs_do(&adjust_from_blobs);
+  AOTLoader::oops_do(&oop_closure);
+  StringTable::oops_do(&oop_closure);
+  ref_processor()->weak_oops_do(&oop_closure);
+  // Roots were visited so references into the young gen in roots
+  // may have been scanned.  Process them also.
+  // Should the reference processor have a span that excludes
+  // young gen objects?
+  PSScavenge::reference_processor()->weak_oops_do(&oop_closure);
+}
+
+// Helper class to print 8 region numbers per line and then print the total at the end.
+class FillableRegionLogger : public StackObj {
+private:
+  Log(gc, compaction) log;
+  static const int LineLength = 8;
+  size_t _regions[LineLength];
+  int _next_index;
+  bool _enabled;
+  size_t _total_regions;
+public:
+  FillableRegionLogger() : _next_index(0), _total_regions(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)) { }
+  ~FillableRegionLogger() {
+    log.trace(SIZE_FORMAT " initially fillable regions", _total_regions);
+  }
+
+  void print_line() {
+    if (!_enabled || _next_index == 0) {
+      return;
+    }
+    FormatBuffer<> line("Fillable: ");
+    for (int i = 0; i < _next_index; i++) {
+      line.append(" " SIZE_FORMAT_W(7), _regions[i]);
+    }
+    log.trace("%s", line.buffer());
+    _next_index = 0;
+  }
+
+  void handle(size_t region) {
+    if (!_enabled) {
+      return;
+    }
+    _regions[_next_index++] = region;
+    if (_next_index == LineLength) {
+      print_line();
+    }
+    _total_regions++;
+  }
+};
+
+void PSParallelCompact::prepare_region_draining_tasks(GCTaskQueue* q,
+                                                      uint parallel_gc_threads)
+{
+  GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
+
+  // Find the threads that are active
+  unsigned int which = 0;
+
+  // Find all regions that are available (can be filled immediately) and
+  // distribute them to the thread stacks.  The iteration is done in reverse
+  // order (high to low) so the regions will be removed in ascending order.
+
+  const ParallelCompactData& sd = PSParallelCompact::summary_data();
+
+  which = 0;
+  // id + 1 is used to test termination so unsigned  can
+  // be used with an old_space_id == 0.
+  FillableRegionLogger region_logger;
+  for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
+    SpaceInfo* const space_info = _space_info + id;
+    MutableSpace* const space = space_info->space();
+    HeapWord* const new_top = space_info->new_top();
+
+    const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
+    const size_t end_region =
+      sd.addr_to_region_idx(sd.region_align_up(new_top));
+
+    for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
+      if (sd.region(cur)->claim_unsafe()) {
+        ParCompactionManager* cm = ParCompactionManager::manager_array(which);
+        cm->region_stack()->push(cur);
+        region_logger.handle(cur);
+        // Assign regions to tasks in round-robin fashion.
+        if (++which == parallel_gc_threads) {
+          which = 0;
+        }
+      }
+    }
+    region_logger.print_line();
+  }
+}
+
+#define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
+
+void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
+                                                    uint parallel_gc_threads) {
+  GCTraceTime(Trace, gc, phases) tm("Dense Prefix Task Setup", &_gc_timer);
+
+  ParallelCompactData& sd = PSParallelCompact::summary_data();
+
+  // Iterate over all the spaces adding tasks for updating
+  // regions in the dense prefix.  Assume that 1 gc thread
+  // will work on opening the gaps and the remaining gc threads
+  // will work on the dense prefix.
+  unsigned int space_id;
+  for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
+    HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
+    const MutableSpace* const space = _space_info[space_id].space();
+
+    if (dense_prefix_end == space->bottom()) {
+      // There is no dense prefix for this space.
+      continue;
+    }
+
+    // The dense prefix is before this region.
+    size_t region_index_end_dense_prefix =
+        sd.addr_to_region_idx(dense_prefix_end);
+    RegionData* const dense_prefix_cp =
+      sd.region(region_index_end_dense_prefix);
+    assert(dense_prefix_end == space->end() ||
+           dense_prefix_cp->available() ||
+           dense_prefix_cp->claimed(),
+           "The region after the dense prefix should always be ready to fill");
+
+    size_t region_index_start = sd.addr_to_region_idx(space->bottom());
+
+    // Is there dense prefix work?
+    size_t total_dense_prefix_regions =
+      region_index_end_dense_prefix - region_index_start;
+    // How many regions of the dense prefix should be given to
+    // each thread?
+    if (total_dense_prefix_regions > 0) {
+      uint tasks_for_dense_prefix = 1;
+      if (total_dense_prefix_regions <=
+          (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
+        // Don't over partition.  This assumes that
+        // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
+        // so there are not many regions to process.
+        tasks_for_dense_prefix = parallel_gc_threads;
+      } else {
+        // Over partition
+        tasks_for_dense_prefix = parallel_gc_threads *
+          PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
+      }
+      size_t regions_per_thread = total_dense_prefix_regions /
+        tasks_for_dense_prefix;
+      // Give each thread at least 1 region.
+      if (regions_per_thread == 0) {
+        regions_per_thread = 1;
+      }
+
+      for (uint k = 0; k < tasks_for_dense_prefix; k++) {
+        if (region_index_start >= region_index_end_dense_prefix) {
+          break;
+        }
+        // region_index_end is not processed
+        size_t region_index_end = MIN2(region_index_start + regions_per_thread,
+                                       region_index_end_dense_prefix);
+        q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
+                                             region_index_start,
+                                             region_index_end));
+        region_index_start = region_index_end;
+      }
+    }
+    // This gets any part of the dense prefix that did not
+    // fit evenly.
+    if (region_index_start < region_index_end_dense_prefix) {
+      q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
+                                           region_index_start,
+                                           region_index_end_dense_prefix));
+    }
+  }
+}
+
+void PSParallelCompact::enqueue_region_stealing_tasks(
+                                     GCTaskQueue* q,
+                                     ParallelTaskTerminator* terminator_ptr,
+                                     uint parallel_gc_threads) {
+  GCTraceTime(Trace, gc, phases) tm("Steal Task Setup", &_gc_timer);
+
+  // Once a thread has drained it's stack, it should try to steal regions from
+  // other threads.
+  for (uint j = 0; j < parallel_gc_threads; j++) {
+    q->enqueue(new CompactionWithStealingTask(terminator_ptr));
+  }
+}
+
+#ifdef ASSERT
+// Write a histogram of the number of times the block table was filled for a
+// region.
+void PSParallelCompact::write_block_fill_histogram()
+{
+  if (!log_develop_is_enabled(Trace, gc, compaction)) {
+    return;
+  }
+
+  Log(gc, compaction) log;
+  ResourceMark rm;
+  LogStream ls(log.trace());
+  outputStream* out = &ls;
+
+  typedef ParallelCompactData::RegionData rd_t;
+  ParallelCompactData& sd = summary_data();
+
+  for (unsigned int id = old_space_id; id < last_space_id; ++id) {
+    MutableSpace* const spc = _space_info[id].space();
+    if (spc->bottom() != spc->top()) {
+      const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
+      HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
+      const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
+
+      size_t histo[5] = { 0, 0, 0, 0, 0 };
+      const size_t histo_len = sizeof(histo) / sizeof(size_t);
+      const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
+
+      for (const rd_t* cur = beg; cur < end; ++cur) {
+        ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
+      }
+      out->print("Block fill histogram: %u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
+      for (size_t i = 0; i < histo_len; ++i) {
+        out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
+                   histo[i], 100.0 * histo[i] / region_cnt);
+      }
+      out->cr();
+    }
+  }
+}
+#endif // #ifdef ASSERT
+
+void PSParallelCompact::compact() {
+  GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
+
+  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
+  PSOldGen* old_gen = heap->old_gen();
+  old_gen->start_array()->reset();
+  uint parallel_gc_threads = heap->gc_task_manager()->workers();
+  uint active_gc_threads = heap->gc_task_manager()->active_workers();
+  TaskQueueSetSuper* qset = ParCompactionManager::region_array();
+  ParallelTaskTerminator terminator(active_gc_threads, qset);
+
+  GCTaskQueue* q = GCTaskQueue::create();
+  prepare_region_draining_tasks(q, active_gc_threads);
+  enqueue_dense_prefix_tasks(q, active_gc_threads);
+  enqueue_region_stealing_tasks(q, &terminator, active_gc_threads);
+
+  {
+    GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
+
+    gc_task_manager()->execute_and_wait(q);
+
+#ifdef  ASSERT
+    // Verify that all regions have been processed before the deferred updates.
+    for (unsigned int id = old_space_id; id < last_space_id; ++id) {
+      verify_complete(SpaceId(id));
+    }
+#endif
+  }
+
+  {
+    // Update the deferred objects, if any.  Any compaction manager can be used.
+    GCTraceTime(Trace, gc, phases) tm("Deferred Updates", &_gc_timer);
+    ParCompactionManager* cm = ParCompactionManager::manager_array(0);
+    for (unsigned int id = old_space_id; id < last_space_id; ++id) {
+      update_deferred_objects(cm, SpaceId(id));
+    }
+  }
+
+  DEBUG_ONLY(write_block_fill_histogram());
+}
+
+#ifdef  ASSERT
+void PSParallelCompact::verify_complete(SpaceId space_id) {
+  // All Regions between space bottom() to new_top() should be marked as filled
+  // and all Regions between new_top() and top() should be available (i.e.,
+  // should have been emptied).
+  ParallelCompactData& sd = summary_data();
+  SpaceInfo si = _space_info[space_id];
+  HeapWord* new_top_addr = sd.region_align_up(si.new_top());
+  HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
+  const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
+  const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
+  const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
+
+  bool issued_a_warning = false;
+
+  size_t cur_region;
+  for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
+    const RegionData* const c = sd.region(cur_region);
+    if (!c->completed()) {
+      log_warning(gc)("region " SIZE_FORMAT " not filled: destination_count=%u",
+                      cur_region, c->destination_count());
+      issued_a_warning = true;
+    }
+  }
+
+  for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
+    const RegionData* const c = sd.region(cur_region);
+    if (!c->available()) {
+      log_warning(gc)("region " SIZE_FORMAT " not empty: destination_count=%u",
+                      cur_region, c->destination_count());
+      issued_a_warning = true;
+    }
+  }
+
+  if (issued_a_warning) {
+    print_region_ranges();
+  }
+}
+#endif  // #ifdef ASSERT
+
+inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
+  _start_array->allocate_block(addr);
+  compaction_manager()->update_contents(oop(addr));
+}
+
+// Update interior oops in the ranges of regions [beg_region, end_region).
+void
+PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
+                                                       SpaceId space_id,
+                                                       size_t beg_region,
+                                                       size_t end_region) {
+  ParallelCompactData& sd = summary_data();
+  ParMarkBitMap* const mbm = mark_bitmap();
+
+  HeapWord* beg_addr = sd.region_to_addr(beg_region);
+  HeapWord* const end_addr = sd.region_to_addr(end_region);
+  assert(beg_region <= end_region, "bad region range");
+  assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
+
+#ifdef  ASSERT
+  // Claim the regions to avoid triggering an assert when they are marked as
+  // filled.
+  for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
+    assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
+  }
+#endif  // #ifdef ASSERT
+
+  if (beg_addr != space(space_id)->bottom()) {
+    // Find the first live object or block of dead space that *starts* in this
+    // range of regions.  If a partial object crosses onto the region, skip it;
+    // it will be marked for 'deferred update' when the object head is
+    // processed.  If dead space crosses onto the region, it is also skipped; it
+    // will be filled when the prior region is processed.  If neither of those
+    // apply, the first word in the region is the start of a live object or dead
+    // space.
+    assert(beg_addr > space(space_id)->bottom(), "sanity");
+    const RegionData* const cp = sd.region(beg_region);
+    if (cp->partial_obj_size() != 0) {
+      beg_addr = sd.partial_obj_end(beg_region);
+    } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
+      beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
+    }
+  }
+
+  if (beg_addr < end_addr) {
+    // A live object or block of dead space starts in this range of Regions.
+     HeapWord* const dense_prefix_end = dense_prefix(space_id);
+
+    // Create closures and iterate.
+    UpdateOnlyClosure update_closure(mbm, cm, space_id);
+    FillClosure fill_closure(cm, space_id);
+    ParMarkBitMap::IterationStatus status;
+    status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
+                          dense_prefix_end);
+    if (status == ParMarkBitMap::incomplete) {
+      update_closure.do_addr(update_closure.source());
+    }
+  }
+
+  // Mark the regions as filled.
+  RegionData* const beg_cp = sd.region(beg_region);
+  RegionData* const end_cp = sd.region(end_region);
+  for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
+    cp->set_completed();
+  }
+}
+
+// Return the SpaceId for the space containing addr.  If addr is not in the
+// heap, last_space_id is returned.  In debug mode it expects the address to be
+// in the heap and asserts such.
+PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
+  assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
+
+  for (unsigned int id = old_space_id; id < last_space_id; ++id) {
+    if (_space_info[id].space()->contains(addr)) {
+      return SpaceId(id);
+    }
+  }
+
+  assert(false, "no space contains the addr");
+  return last_space_id;
+}
+
+void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
+                                                SpaceId id) {
+  assert(id < last_space_id, "bad space id");
+
+  ParallelCompactData& sd = summary_data();
+  const SpaceInfo* const space_info = _space_info + id;
+  ObjectStartArray* const start_array = space_info->start_array();
+
+  const MutableSpace* const space = space_info->space();
+  assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
+  HeapWord* const beg_addr = space_info->dense_prefix();
+  HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
+
+  const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
+  const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
+  const RegionData* cur_region;
+  for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
+    HeapWord* const addr = cur_region->deferred_obj_addr();
+    if (addr != NULL) {
+      if (start_array != NULL) {
+        start_array->allocate_block(addr);
+      }
+      cm->update_contents(oop(addr));
+      assert(oopDesc::is_oop_or_null(oop(addr)), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr)));
+    }
+  }
+}
+
+// Skip over count live words starting from beg, and return the address of the
+// next live word.  Unless marked, the word corresponding to beg is assumed to
+// be dead.  Callers must either ensure beg does not correspond to the middle of
+// an object, or account for those live words in some other way.  Callers must
+// also ensure that there are enough live words in the range [beg, end) to skip.
+HeapWord*
+PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
+{
+  assert(count > 0, "sanity");
+
+  ParMarkBitMap* m = mark_bitmap();
+  idx_t bits_to_skip = m->words_to_bits(count);
+  idx_t cur_beg = m->addr_to_bit(beg);
+  const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
+
+  do {
+    cur_beg = m->find_obj_beg(cur_beg, search_end);
+    idx_t cur_end = m->find_obj_end(cur_beg, search_end);
+    const size_t obj_bits = cur_end - cur_beg + 1;
+    if (obj_bits > bits_to_skip) {
+      return m->bit_to_addr(cur_beg + bits_to_skip);
+    }
+    bits_to_skip -= obj_bits;
+    cur_beg = cur_end + 1;
+  } while (bits_to_skip > 0);
+
+  // Skipping the desired number of words landed just past the end of an object.
+  // Find the start of the next object.
+  cur_beg = m->find_obj_beg(cur_beg, search_end);
+  assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
+  return m->bit_to_addr(cur_beg);
+}
+
+HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
+                                            SpaceId src_space_id,
+                                            size_t src_region_idx)
+{
+  assert(summary_data().is_region_aligned(dest_addr), "not aligned");
+
+  const SplitInfo& split_info = _space_info[src_space_id].split_info();
+  if (split_info.dest_region_addr() == dest_addr) {
+    // The partial object ending at the split point contains the first word to
+    // be copied to dest_addr.
+    return split_info.first_src_addr();
+  }
+
+  const ParallelCompactData& sd = summary_data();
+  ParMarkBitMap* const bitmap = mark_bitmap();
+  const size_t RegionSize = ParallelCompactData::RegionSize;
+
+  assert(sd.is_region_aligned(dest_addr), "not aligned");
+  const RegionData* const src_region_ptr = sd.region(src_region_idx);
+  const size_t partial_obj_size = src_region_ptr->partial_obj_size();
+  HeapWord* const src_region_destination = src_region_ptr->destination();
+
+  assert(dest_addr >= src_region_destination, "wrong src region");
+  assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
+
+  HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
+  HeapWord* const src_region_end = src_region_beg + RegionSize;
+
+  HeapWord* addr = src_region_beg;
+  if (dest_addr == src_region_destination) {
+    // Return the first live word in the source region.
+    if (partial_obj_size == 0) {
+      addr = bitmap->find_obj_beg(addr, src_region_end);
+      assert(addr < src_region_end, "no objects start in src region");
+    }
+    return addr;
+  }
+
+  // Must skip some live data.
+  size_t words_to_skip = dest_addr - src_region_destination;
+  assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
+
+  if (partial_obj_size >= words_to_skip) {
+    // All the live words to skip are part of the partial object.
+    addr += words_to_skip;
+    if (partial_obj_size == words_to_skip) {
+      // Find the first live word past the partial object.
+      addr = bitmap->find_obj_beg(addr, src_region_end);
+      assert(addr < src_region_end, "wrong src region");
+    }
+    return addr;
+  }
+
+  // Skip over the partial object (if any).
+  if (partial_obj_size != 0) {
+    words_to_skip -= partial_obj_size;
+    addr += partial_obj_size;
+  }
+
+  // Skip over live words due to objects that start in the region.
+  addr = skip_live_words(addr, src_region_end, words_to_skip);
+  assert(addr < src_region_end, "wrong src region");
+  return addr;
+}
+
+void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
+                                                     SpaceId src_space_id,
+                                                     size_t beg_region,
+                                                     HeapWord* end_addr)
+{
+  ParallelCompactData& sd = summary_data();
+
+#ifdef ASSERT
+  MutableSpace* const src_space = _space_info[src_space_id].space();
+  HeapWord* const beg_addr = sd.region_to_addr(beg_region);
+  assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
+         "src_space_id does not match beg_addr");
+  assert(src_space->contains(end_addr) || end_addr == src_space->end(),
+         "src_space_id does not match end_addr");
+#endif // #ifdef ASSERT
+
+  RegionData* const beg = sd.region(beg_region);
+  RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
+
+  // Regions up to new_top() are enqueued if they become available.
+  HeapWord* const new_top = _space_info[src_space_id].new_top();
+  RegionData* const enqueue_end =
+    sd.addr_to_region_ptr(sd.region_align_up(new_top));
+
+  for (RegionData* cur = beg; cur < end; ++cur) {
+    assert(cur->data_size() > 0, "region must have live data");
+    cur->decrement_destination_count();
+    if (cur < enqueue_end && cur->available() && cur->claim()) {
+      cm->push_region(sd.region(cur));
+    }
+  }
+}
+
+size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
+                                          SpaceId& src_space_id,
+                                          HeapWord*& src_space_top,
+                                          HeapWord* end_addr)
+{
+  typedef ParallelCompactData::RegionData RegionData;
+
+  ParallelCompactData& sd = PSParallelCompact::summary_data();
+  const size_t region_size = ParallelCompactData::RegionSize;
+
+  size_t src_region_idx = 0;
+
+  // Skip empty regions (if any) up to the top of the space.
+  HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
+  RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
+  HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
+  const RegionData* const top_region_ptr =
+    sd.addr_to_region_ptr(top_aligned_up);
+  while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
+    ++src_region_ptr;
+  }
+
+  if (src_region_ptr < top_region_ptr) {
+    // The next source region is in the current space.  Update src_region_idx
+    // and the source address to match src_region_ptr.
+    src_region_idx = sd.region(src_region_ptr);
+    HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
+    if (src_region_addr > closure.source()) {
+      closure.set_source(src_region_addr);
+    }
+    return src_region_idx;
+  }
+
+  // Switch to a new source space and find the first non-empty region.
+  unsigned int space_id = src_space_id + 1;
+  assert(space_id < last_space_id, "not enough spaces");
+
+  HeapWord* const destination = closure.destination();
+
+  do {
+    MutableSpace* space = _space_info[space_id].space();
+    HeapWord* const bottom = space->bottom();
+    const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
+
+    // Iterate over the spaces that do not compact into themselves.
+    if (bottom_cp->destination() != bottom) {
+      HeapWord* const top_aligned_up = sd.region_align_up(space->top());
+      const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
+
+      for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
+        if (src_cp->live_obj_size() > 0) {
+          // Found it.
+          assert(src_cp->destination() == destination,
+                 "first live obj in the space must match the destination");
+          assert(src_cp->partial_obj_size() == 0,
+                 "a space cannot begin with a partial obj");
+
+          src_space_id = SpaceId(space_id);
+          src_space_top = space->top();
+          const size_t src_region_idx = sd.region(src_cp);
+          closure.set_source(sd.region_to_addr(src_region_idx));
+          return src_region_idx;
+        } else {
+          assert(src_cp->data_size() == 0, "sanity");
+        }
+      }
+    }
+  } while (++space_id < last_space_id);
+
+  assert(false, "no source region was found");
+  return 0;
+}
+
+void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
+{
+  typedef ParMarkBitMap::IterationStatus IterationStatus;
+  const size_t RegionSize = ParallelCompactData::RegionSize;
+  ParMarkBitMap* const bitmap = mark_bitmap();
+  ParallelCompactData& sd = summary_data();
+  RegionData* const region_ptr = sd.region(region_idx);
+
+  // Get the items needed to construct the closure.
+  HeapWord* dest_addr = sd.region_to_addr(region_idx);
+  SpaceId dest_space_id = space_id(dest_addr);
+  ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
+  HeapWord* new_top = _space_info[dest_space_id].new_top();
+  assert(dest_addr < new_top, "sanity");
+  const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
+
+  // Get the source region and related info.
+  size_t src_region_idx = region_ptr->source_region();
+  SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
+  HeapWord* src_space_top = _space_info[src_space_id].space()->top();
+
+  MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
+  closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
+
+  // Adjust src_region_idx to prepare for decrementing destination counts (the
+  // destination count is not decremented when a region is copied to itself).
+  if (src_region_idx == region_idx) {
+    src_region_idx += 1;
+  }
+
+  if (bitmap->is_unmarked(closure.source())) {
+    // The first source word is in the middle of an object; copy the remainder
+    // of the object or as much as will fit.  The fact that pointer updates were
+    // deferred will be noted when the object header is processed.
+    HeapWord* const old_src_addr = closure.source();
+    closure.copy_partial_obj();
+    if (closure.is_full()) {
+      decrement_destination_counts(cm, src_space_id, src_region_idx,
+                                   closure.source());
+      region_ptr->set_deferred_obj_addr(NULL);
+      region_ptr->set_completed();
+      return;
+    }
+
+    HeapWord* const end_addr = sd.region_align_down(closure.source());
+    if (sd.region_align_down(old_src_addr) != end_addr) {
+      // The partial object was copied from more than one source region.
+      decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
+
+      // Move to the next source region, possibly switching spaces as well.  All
+      // args except end_addr may be modified.
+      src_region_idx = next_src_region(closure, src_space_id, src_space_top,
+                                       end_addr);
+    }
+  }
+
+  do {
+    HeapWord* const cur_addr = closure.source();
+    HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
+                                    src_space_top);
+    IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
+
+    if (status == ParMarkBitMap::incomplete) {
+      // The last obj that starts in the source region does not end in the
+      // region.
+      assert(closure.source() < end_addr, "sanity");
+      HeapWord* const obj_beg = closure.source();
+      HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
+                                       src_space_top);
+      HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
+      if (obj_end < range_end) {
+        // The end was found; the entire object will fit.
+        status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
+        assert(status != ParMarkBitMap::would_overflow, "sanity");
+      } else {
+        // The end was not found; the object will not fit.
+        assert(range_end < src_space_top, "obj cannot cross space boundary");
+        status = ParMarkBitMap::would_overflow;
+      }
+    }
+
+    if (status == ParMarkBitMap::would_overflow) {
+      // The last object did not fit.  Note that interior oop updates were
+      // deferred, then copy enough of the object to fill the region.
+      region_ptr->set_deferred_obj_addr(closure.destination());
+      status = closure.copy_until_full(); // copies from closure.source()
+
+      decrement_destination_counts(cm, src_space_id, src_region_idx,
+                                   closure.source());
+      region_ptr->set_completed();
+      return;
+    }
+
+    if (status == ParMarkBitMap::full) {
+      decrement_destination_counts(cm, src_space_id, src_region_idx,
+                                   closure.source());
+      region_ptr->set_deferred_obj_addr(NULL);
+      region_ptr->set_completed();
+      return;
+    }
+
+    decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
+
+    // Move to the next source region, possibly switching spaces as well.  All
+    // args except end_addr may be modified.
+    src_region_idx = next_src_region(closure, src_space_id, src_space_top,
+                                     end_addr);
+  } while (true);
+}
+
+void PSParallelCompact::fill_blocks(size_t region_idx)
+{
+  // Fill in the block table elements for the specified region.  Each block
+  // table element holds the number of live words in the region that are to the
+  // left of the first object that starts in the block.  Thus only blocks in
+  // which an object starts need to be filled.
+  //
+  // The algorithm scans the section of the bitmap that corresponds to the
+  // region, keeping a running total of the live words.  When an object start is
+  // found, if it's the first to start in the block that contains it, the
+  // current total is written to the block table element.
+  const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
+  const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
+  const size_t RegionSize = ParallelCompactData::RegionSize;
+
+  ParallelCompactData& sd = summary_data();
+  const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
+  if (partial_obj_size >= RegionSize) {
+    return; // No objects start in this region.
+  }
+
+  // Ensure the first loop iteration decides that the block has changed.
+  size_t cur_block = sd.block_count();
+
+  const ParMarkBitMap* const bitmap = mark_bitmap();
+
+  const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
+  assert((size_t)1 << Log2BitsPerBlock ==
+         bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
+
+  size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
+  const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
+  size_t live_bits = bitmap->words_to_bits(partial_obj_size);
+  beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
+  while (beg_bit < range_end) {
+    const size_t new_block = beg_bit >> Log2BitsPerBlock;
+    if (new_block != cur_block) {
+      cur_block = new_block;
+      sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
+    }
+
+    const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
+    if (end_bit < range_end - 1) {
+      live_bits += end_bit - beg_bit + 1;
+      beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
+    } else {
+      return;
+    }
+  }
+}
+
+void
+PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
+  const MutableSpace* sp = space(space_id);
+  if (sp->is_empty()) {
+    return;
+  }
+
+  ParallelCompactData& sd = PSParallelCompact::summary_data();
+  ParMarkBitMap* const bitmap = mark_bitmap();
+  HeapWord* const dp_addr = dense_prefix(space_id);
+  HeapWord* beg_addr = sp->bottom();
+  HeapWord* end_addr = sp->top();
+
+  assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
+
+  const size_t beg_region = sd.addr_to_region_idx(beg_addr);
+  const size_t dp_region = sd.addr_to_region_idx(dp_addr);
+  if (beg_region < dp_region) {
+    update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
+  }
+
+  // The destination of the first live object that starts in the region is one
+  // past the end of the partial object entering the region (if any).
+  HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
+  HeapWord* const new_top = _space_info[space_id].new_top();
+  assert(new_top >= dest_addr, "bad new_top value");
+  const size_t words = pointer_delta(new_top, dest_addr);
+
+  if (words > 0) {
+    ObjectStartArray* start_array = _space_info[space_id].start_array();
+    MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
+
+    ParMarkBitMap::IterationStatus status;
+    status = bitmap->iterate(&closure, dest_addr, end_addr);
+    assert(status == ParMarkBitMap::full, "iteration not complete");
+    assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
+           "live objects skipped because closure is full");
+  }
+}
+
+jlong PSParallelCompact::millis_since_last_gc() {
+  // We need a monotonically non-decreasing time in ms but
+  // os::javaTimeMillis() does not guarantee monotonicity.
+  jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
+  jlong ret_val = now - _time_of_last_gc;
+  // XXX See note in genCollectedHeap::millis_since_last_gc().
+  if (ret_val < 0) {
+    NOT_PRODUCT(log_warning(gc)("time warp: " JLONG_FORMAT, ret_val);)
+    return 0;
+  }
+  return ret_val;
+}
+
+void PSParallelCompact::reset_millis_since_last_gc() {
+  // We need a monotonically non-decreasing time in ms but
+  // os::javaTimeMillis() does not guarantee monotonicity.
+  _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
+}
+
+ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
+{
+  if (source() != destination()) {
+    DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
+    Copy::aligned_conjoint_words(source(), destination(), words_remaining());
+  }
+  update_state(words_remaining());
+  assert(is_full(), "sanity");
+  return ParMarkBitMap::full;
+}
+
+void MoveAndUpdateClosure::copy_partial_obj()
+{
+  size_t words = words_remaining();
+
+  HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
+  HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
+  if (end_addr < range_end) {
+    words = bitmap()->obj_size(source(), end_addr);
+  }
+
+  // This test is necessary; if omitted, the pointer updates to a partial object
+  // that crosses the dense prefix boundary could be overwritten.
+  if (source() != destination()) {
+    DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
+    Copy::aligned_conjoint_words(source(), destination(), words);
+  }
+  update_state(words);
+}
+
+void InstanceKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
+  PSParallelCompact::AdjustPointerClosure closure(cm);
+  oop_oop_iterate_oop_maps<true>(obj, &closure);
+}
+
+void InstanceMirrorKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
+  InstanceKlass::oop_pc_update_pointers(obj, cm);
+
+  PSParallelCompact::AdjustPointerClosure closure(cm);
+  oop_oop_iterate_statics<true>(obj, &closure);
+}
+
+void InstanceClassLoaderKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
+  InstanceKlass::oop_pc_update_pointers(obj, cm);
+}
+
+#ifdef ASSERT
+template <class T> static void trace_reference_gc(const char *s, oop obj,
+                                                  T* referent_addr,
+                                                  T* next_addr,
+                                                  T* discovered_addr) {
+  log_develop_trace(gc, ref)("%s obj " PTR_FORMAT, s, p2i(obj));
+  log_develop_trace(gc, ref)("     referent_addr/* " PTR_FORMAT " / " PTR_FORMAT,
+                             p2i(referent_addr), referent_addr ? p2i(oopDesc::load_decode_heap_oop(referent_addr)) : NULL);
+  log_develop_trace(gc, ref)("     next_addr/* " PTR_FORMAT " / " PTR_FORMAT,
+                             p2i(next_addr), next_addr ? p2i(oopDesc::load_decode_heap_oop(next_addr)) : NULL);
+  log_develop_trace(gc, ref)("     discovered_addr/* " PTR_FORMAT " / " PTR_FORMAT,
+                             p2i(discovered_addr), discovered_addr ? p2i(oopDesc::load_decode_heap_oop(discovered_addr)) : NULL);
+}
+#endif
+
+template <class T>
+static void oop_pc_update_pointers_specialized(oop obj, ParCompactionManager* cm) {
+  T* referent_addr = (T*)java_lang_ref_Reference::referent_addr(obj);
+  PSParallelCompact::adjust_pointer(referent_addr, cm);
+  T* next_addr = (T*)java_lang_ref_Reference::next_addr(obj);
+  PSParallelCompact::adjust_pointer(next_addr, cm);
+  T* discovered_addr = (T*)java_lang_ref_Reference::discovered_addr(obj);
+  PSParallelCompact::adjust_pointer(discovered_addr, cm);
+  debug_only(trace_reference_gc("InstanceRefKlass::oop_update_ptrs", obj,
+                                referent_addr, next_addr, discovered_addr);)
+}
+
+void InstanceRefKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
+  InstanceKlass::oop_pc_update_pointers(obj, cm);
+
+  if (UseCompressedOops) {
+    oop_pc_update_pointers_specialized<narrowOop>(obj, cm);
+  } else {
+    oop_pc_update_pointers_specialized<oop>(obj, cm);
+  }
+}
+
+void ObjArrayKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
+  assert(obj->is_objArray(), "obj must be obj array");
+  PSParallelCompact::AdjustPointerClosure closure(cm);
+  oop_oop_iterate_elements<true>(objArrayOop(obj), &closure);
+}
+
+void TypeArrayKlass::oop_pc_update_pointers(oop obj, ParCompactionManager* cm) {
+  assert(obj->is_typeArray(),"must be a type array");
+}
+
+ParMarkBitMapClosure::IterationStatus
+MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
+  assert(destination() != NULL, "sanity");
+  assert(bitmap()->obj_size(addr) == words, "bad size");
+
+  _source = addr;
+  assert(PSParallelCompact::summary_data().calc_new_pointer(source(), compaction_manager()) ==
+         destination(), "wrong destination");
+
+  if (words > words_remaining()) {
+    return ParMarkBitMap::would_overflow;
+  }
+
+  // The start_array must be updated even if the object is not moving.
+  if (_start_array != NULL) {
+    _start_array->allocate_block(destination());
+  }
+
+  if (destination() != source()) {
+    DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
+    Copy::aligned_conjoint_words(source(), destination(), words);
+  }
+
+  oop moved_oop = (oop) destination();
+  compaction_manager()->update_contents(moved_oop);
+  assert(oopDesc::is_oop_or_null(moved_oop), "Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop));
+
+  update_state(words);
+  assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
+  return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
+}
+
+UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
+                                     ParCompactionManager* cm,
+                                     PSParallelCompact::SpaceId space_id) :
+  ParMarkBitMapClosure(mbm, cm),
+  _space_id(space_id),
+  _start_array(PSParallelCompact::start_array(space_id))
+{
+}
+
+// Updates the references in the object to their new values.
+ParMarkBitMapClosure::IterationStatus
+UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
+  do_addr(addr);
+  return ParMarkBitMap::incomplete;
+}
+
+FillClosure::FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :
+  ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),
+  _start_array(PSParallelCompact::start_array(space_id))
+{
+  assert(space_id == PSParallelCompact::old_space_id,
+         "cannot use FillClosure in the young gen");
+}
+
+ParMarkBitMapClosure::IterationStatus
+FillClosure::do_addr(HeapWord* addr, size_t size) {
+  CollectedHeap::fill_with_objects(addr, size);
+  HeapWord* const end = addr + size;
+  do {
+    _start_array->allocate_block(addr);
+    addr += oop(addr)->size();
+  } while (addr < end);
+  return ParMarkBitMap::incomplete;
+}