jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp@9d7e35a93fad (annotated)

src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp@9d7e35a93fad (annotated)

src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp

Sat, 08 Oct 2016 09:31:28 -0400

author: fujie
date: Sat, 08 Oct 2016 09:31:28 -0400
changeset 124: 9d7e35a93fad
parent 121: fc16fcee952c
child 192: 21e5e0259a4c
permissions: -rw-r--r--

The parallel GC mark-phase should be MT-safe for 3A2000.

 /*
  * Copyright (c) 2005, 2014, 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 "classfile/symbolTable.hpp"
 #include "classfile/systemDictionary.hpp"
 #include "code/codeCache.hpp"
 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.inline.hpp"
 #include "gc_implementation/parallelScavenge/pcTasks.hpp"
 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
 #include "gc_implementation/parallelScavenge/psCompactionManager.inline.hpp"
 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"
 #include "gc_implementation/parallelScavenge/psOldGen.hpp"
 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
 #include "gc_implementation/parallelScavenge/psPromotionManager.inline.hpp"
 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
 #include "gc_implementation/shared/gcHeapSummary.hpp"
 #include "gc_implementation/shared/gcTimer.hpp"
 #include "gc_implementation/shared/gcTrace.hpp"
 #include "gc_implementation/shared/gcTraceTime.hpp"
 #include "gc_implementation/shared/isGCActiveMark.hpp"
 #include "gc_interface/gcCause.hpp"
 #include "memory/gcLocker.inline.hpp"
 #include "memory/referencePolicy.hpp"
 #include "memory/referenceProcessor.hpp"
 #include "oops/methodData.hpp"
 #include "oops/oop.inline.hpp"
 #include "oops/oop.pcgc.inline.hpp"
 #include "runtime/fprofiler.hpp"
 #include "runtime/safepoint.hpp"
 #include "runtime/vmThread.hpp"
 #include "services/management.hpp"
 #include "services/memoryService.hpp"
 #include "services/memTracker.hpp"
 #include "utilities/events.hpp"
 #include "utilities/stack.inline.hpp"
 #include <math.h>
 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
 // 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];
 bool      PSParallelCompact::_print_phases = false;
 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
 Klass*              PSParallelCompact::_updated_int_array_klass_obj = 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()
 {
   tty->print_cr("space  bottom     top        end        new_top");
   tty->print_cr("------ ---------- ---------- ---------- ----------");
   for (unsigned int id = 0; id < last_space_id; ++id) {
     const MutableSpace* space = _space_info[id].space();
     tty->print_cr("%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;
   tty->print_cr(REGION_IDX_FORMAT " " PTR_FORMAT " "
                 REGION_IDX_FORMAT " " PTR_FORMAT " "
                 REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
                 REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
                 i, c->data_location(), dci, 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;
   }
   tty->print_cr("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
 }
 void
 print_generic_summary_data(ParallelCompactData& summary_data,
                            SpaceInfo* space_info)
 {
   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_region(size_t i,
                              const ParallelCompactData::RegionData* c,
                              bool newline = true)
 {
   tty->print(SIZE_FORMAT_W(5) " " PTR_FORMAT " "
              SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " "
              SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
              i, c->destination(),
              c->partial_obj_size(), c->live_obj_size(),
              c->data_size(), c->source_region(), c->destination_count());
   if (newline) tty->cr();
 }
 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) {
     print_initial_summary_region(i, summary_data.region(i));
     ++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;
     }
     print_initial_summary_region(i, c, false);
     tty->print_cr(" %12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
                   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) {
     print_initial_summary_region(i, summary_data.region(i));
   }
   tty->print_cr("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) {
   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(raw_bytes, raw_bytes, 10);
   const size_t granularity = os::vm_allocation_granularity();
   _reserved_byte_size = align_size_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("par compact", 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);
 #ifdef MIPS64
     if (Use3A2000) OrderAccess::fence();
 #endif
     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);
 #ifdef MIPS64
     if (Use3A2000) OrderAccess::fence();
 #endif
 }
 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);
     if (TraceParallelOldGCSummaryPhase) {
         gclog_or_tty->print_cr("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 (TraceParallelOldGCSummaryPhase) {
     const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
     gclog_or_tty->print_cr("%s split:  src=" PTR_FORMAT " src_c=" SIZE_FORMAT
                            " pos=" SIZE_FORMAT,
                            split_type, source_next, split_region,
                            partial_obj_size);
     gclog_or_tty->print_cr("%s split:  dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT
                            " tn=" PTR_FORMAT,
                            split_type, split_destination,
                            addr_to_region_idx(split_destination),
                            *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();
       gclog_or_tty->print_cr("%s split:  "
                              "po_beg=" PTR_FORMAT " " SIZE_FORMAT " "
                              "po_end=" PTR_FORMAT " " SIZE_FORMAT,
                              split_type,
                              po_beg, addr_to_region_idx(po_beg),
                              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)
 {
   if (TraceParallelOldGCSummaryPhase) {
     HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
     tty->print_cr("sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
                   "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
                   source_beg, source_end, source_next_val,
                   target_beg, target_end, *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) {
   assert(addr != NULL, "Should detect NULL oop earlier");
   assert(PSParallelCompact::gc_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(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::KeepAliveClosure::do_oop(oop* p)       { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
 void PSParallelCompact::KeepAliveClosure::do_oop(narrowOop* p) { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
 PSParallelCompact::AdjustPointerClosure PSParallelCompact::_adjust_pointer_closure;
 PSParallelCompact::AdjustKlassClosure PSParallelCompact::_adjust_klass_closure;
 void PSParallelCompact::AdjustPointerClosure::do_oop(oop* p)       { adjust_pointer(p); }
 void PSParallelCompact::AdjustPointerClosure::do_oop(narrowOop* p) { adjust_pointer(p); }
 void PSParallelCompact::FollowStackClosure::do_void() { _compaction_manager->follow_marking_stacks(); }
 void PSParallelCompact::MarkAndPushClosure::do_oop(oop* p)       {
   mark_and_push(_compaction_manager, p);
 }
 void PSParallelCompact::MarkAndPushClosure::do_oop(narrowOop* p) { mark_and_push(_compaction_manager, p); }
 void PSParallelCompact::FollowKlassClosure::do_klass(Klass* klass) {
   klass->oops_do(_mark_and_push_closure);
 }
 void PSParallelCompact::AdjustKlassClosure::do_klass(Klass* klass) {
   klass->oops_do(&PSParallelCompact::_adjust_pointer_closure);
 }
 void PSParallelCompact::post_initialize() {
   ParallelScavengeHeap* heap = gc_heap();
   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
   MemRegion mr = heap->reserved_region();
   _ref_processor =
     new ReferenceProcessor(mr,            // span
                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
                            (int) ParallelGCThreads, // mt processing degree
                            true,          // mt discovery
                            (int) 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 = gc_heap();
   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
   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 = gc_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);
 }
 // Simple class for storing info about the heap at the start of GC, to be used
 // after GC for comparison/printing.
 class PreGCValues {
 public:
   PreGCValues() { }
   PreGCValues(ParallelScavengeHeap* heap) { fill(heap); }
   void fill(ParallelScavengeHeap* heap) {
     _heap_used      = heap->used();
     _young_gen_used = heap->young_gen()->used_in_bytes();
     _old_gen_used   = heap->old_gen()->used_in_bytes();
     _metadata_used  = MetaspaceAux::used_bytes();
   };
   size_t heap_used() const      { return _heap_used; }
   size_t young_gen_used() const { return _young_gen_used; }
   size_t old_gen_used() const   { return _old_gen_used; }
   size_t metadata_used() const  { return _metadata_used; }
 private:
   size_t _heap_used;
   size_t _young_gen_used;
   size_t _old_gen_used;
   size_t _metadata_used;
 };
 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(PreGCValues* pre_gc_values)
 {
   // 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 minor
   // collections will have swapped the spaces an unknown number of times.
   GCTraceTime tm("pre compact", print_phases(), true, &_gc_timer);
   ParallelScavengeHeap* heap = gc_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());
   pre_gc_values->fill(heap);
   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(" VerifyBeforeGC:");
   }
   // 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();
 }
 void PSParallelCompact::post_compact()
 {
   GCTraceTime tm("post compact", print_phases(), true, &_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 = gc_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();
   BarrierSet* bs = heap->barrier_set();
   if (bs->is_a(BarrierSet::ModRef)) {
     ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
     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();
   Threads::gc_epilogue();
   CodeCache::gc_epilogue();
   JvmtiExport::gc_epilogue();
   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
   ref_processor()->enqueue_discovered_references(NULL);
   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=" SIZE_FORMAT_W(8) " " "cdw=" SIZE_FORMAT_W(8),
                     sd.region(cp), region_destination,
                     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, 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)
 {
   if (ParallelOldGCSplitALot) {
     if (_space_info[id].dense_prefix() != _space_info[id].space()->bottom()) {
       // The value was chosen to provoke splitting a young gen space; use it.
       return _space_info[id].dense_prefix();
     }
   }
   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, %d)=%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;
     }
   }
 #if     0
   // Something to consider:  if the region with the best ratio is 'close to' the
   // first region w/free space, choose the first region with free space
   // ("first-free").  The first-free region is usually near the start of the
   // heap, which means we are copying most of the heap already, so copy a bit
   // more to get complete compaction.
   if (pointer_delta(best_cp, full_cp, sizeof(RegionData)) < 4) {
     _maximum_compaction_gc_num = total_invocations();
     best_cp = full_cp;
   }
 #endif  // #if 0
   return sd.region_to_addr(best_cp);
 }
 #ifndef PRODUCT
 void
 PSParallelCompact::fill_with_live_objects(SpaceId id, HeapWord* const start,
                                           size_t words)
 {
   if (TraceParallelOldGCSummaryPhase) {
     tty->print_cr("fill_with_live_objects [" PTR_FORMAT " " PTR_FORMAT ") "
                   SIZE_FORMAT, start, start + words, words);
   }
   ObjectStartArray* const start_array = _space_info[id].start_array();
   CollectedHeap::fill_with_objects(start, words);
   for (HeapWord* p = start; p < start + words; p += oop(p)->size()) {
     _mark_bitmap.mark_obj(p, words);
     _summary_data.add_obj(p, words);
     start_array->allocate_block(p);
   }
 }
 void
 PSParallelCompact::summarize_new_objects(SpaceId id, HeapWord* start)
 {
   ParallelCompactData& sd = summary_data();
   MutableSpace* space = _space_info[id].space();
   // Find the source and destination start addresses.
   HeapWord* const src_addr = sd.region_align_down(start);
   HeapWord* dst_addr;
   if (src_addr < start) {
     dst_addr = sd.addr_to_region_ptr(src_addr)->destination();
   } else if (src_addr > space->bottom()) {
     // The start (the original top() value) is aligned to a region boundary so
     // the associated region does not have a destination.  Compute the
     // destination from the previous region.
     RegionData* const cp = sd.addr_to_region_ptr(src_addr) - 1;
     dst_addr = cp->destination() + cp->data_size();
   } else {
     // Filling the entire space.
     dst_addr = space->bottom();
   }
   assert(dst_addr != NULL, "sanity");
   // Update the summary data.
   bool result = _summary_data.summarize(_space_info[id].split_info(),
                                         src_addr, space->top(), NULL,
                                         dst_addr, space->end(),
                                         _space_info[id].new_top_addr());
   assert(result, "should not fail:  bad filler object size");
 }
 void
 PSParallelCompact::provoke_split_fill_survivor(SpaceId id)
 {
   if (total_invocations() % (ParallelOldGCSplitInterval * 3) != 0) {
     return;
   }
   MutableSpace* const space = _space_info[id].space();
   if (space->is_empty()) {
     HeapWord* b = space->bottom();
     HeapWord* t = b + space->capacity_in_words() / 2;
     space->set_top(t);
     if (ZapUnusedHeapArea) {
       space->set_top_for_allocations();
     }
     size_t min_size = CollectedHeap::min_fill_size();
     size_t obj_len = min_size;
     while (b + obj_len <= t) {
       CollectedHeap::fill_with_object(b, obj_len);
       mark_bitmap()->mark_obj(b, obj_len);
       summary_data().add_obj(b, obj_len);
       b += obj_len;
       obj_len = (obj_len & (min_size*3)) + min_size; // 8 16 24 32 8 16 24 32 ...
     }
     if (b < t) {
       // The loop didn't completely fill to t (top); adjust top downward.
       space->set_top(b);
       if (ZapUnusedHeapArea) {
         space->set_top_for_allocations();
       }
     }
     HeapWord** nta = _space_info[id].new_top_addr();
     bool result = summary_data().summarize(_space_info[id].split_info(),
                                            space->bottom(), space->top(), NULL,
                                            space->bottom(), space->end(), nta);
     assert(result, "space must fit into itself");
   }
 }
 void
 PSParallelCompact::provoke_split(bool & max_compaction)
 {
   if (total_invocations() % ParallelOldGCSplitInterval != 0) {
     return;
   }
   const size_t region_size = ParallelCompactData::RegionSize;
   ParallelCompactData& sd = summary_data();
   MutableSpace* const eden_space = _space_info[eden_space_id].space();
   MutableSpace* const from_space = _space_info[from_space_id].space();
   const size_t eden_live = pointer_delta(eden_space->top(),
                                          _space_info[eden_space_id].new_top());
   const size_t from_live = pointer_delta(from_space->top(),
                                          _space_info[from_space_id].new_top());
   const size_t min_fill_size = CollectedHeap::min_fill_size();
   const size_t eden_free = pointer_delta(eden_space->end(), eden_space->top());
   const size_t eden_fillable = eden_free >= min_fill_size ? eden_free : 0;
   const size_t from_free = pointer_delta(from_space->end(), from_space->top());
   const size_t from_fillable = from_free >= min_fill_size ? from_free : 0;
   // Choose the space to split; need at least 2 regions live (or fillable).
   SpaceId id;
   MutableSpace* space;
   size_t live_words;
   size_t fill_words;
   if (eden_live + eden_fillable >= region_size * 2) {
     id = eden_space_id;
     space = eden_space;
     live_words = eden_live;
     fill_words = eden_fillable;
   } else if (from_live + from_fillable >= region_size * 2) {
     id = from_space_id;
     space = from_space;
     live_words = from_live;
     fill_words = from_fillable;
   } else {
     return; // Give up.
   }
   assert(fill_words == 0 || fill_words >= min_fill_size, "sanity");
   if (live_words < region_size * 2) {
     // Fill from top() to end() w/live objects of mixed sizes.
     HeapWord* const fill_start = space->top();
     live_words += fill_words;
     space->set_top(fill_start + fill_words);
     if (ZapUnusedHeapArea) {
       space->set_top_for_allocations();
     }
     HeapWord* cur_addr = fill_start;
     while (fill_words > 0) {
       const size_t r = (size_t)os::random() % (region_size / 2) + min_fill_size;
       size_t cur_size = MIN2(align_object_size_(r), fill_words);
       if (fill_words - cur_size < min_fill_size) {
         cur_size = fill_words; // Avoid leaving a fragment too small to fill.
       }
       CollectedHeap::fill_with_object(cur_addr, cur_size);
       mark_bitmap()->mark_obj(cur_addr, cur_size);
       sd.add_obj(cur_addr, cur_size);
       cur_addr += cur_size;
       fill_words -= cur_size;
     }
     summarize_new_objects(id, fill_start);
   }
   max_compaction = false;
   // Manipulate the old gen so that it has room for about half of the live data
   // in the target young gen space (live_words / 2).
   id = old_space_id;
   space = _space_info[id].space();
   const size_t free_at_end = space->free_in_words();
   const size_t free_target = align_object_size(live_words / 2);
   const size_t dead = pointer_delta(space->top(), _space_info[id].new_top());
   if (free_at_end >= free_target + min_fill_size) {
     // Fill space above top() and set the dense prefix so everything survives.
     HeapWord* const fill_start = space->top();
     const size_t fill_size = free_at_end - free_target;
     space->set_top(space->top() + fill_size);
     if (ZapUnusedHeapArea) {
       space->set_top_for_allocations();
     }
     fill_with_live_objects(id, fill_start, fill_size);
     summarize_new_objects(id, fill_start);
     _space_info[id].set_dense_prefix(sd.region_align_down(space->top()));
   } else if (dead + free_at_end > free_target) {
     // Find a dense prefix that makes the right amount of space available.
     HeapWord* cur = sd.region_align_down(space->top());
     HeapWord* cur_destination = sd.addr_to_region_ptr(cur)->destination();
     size_t dead_to_right = pointer_delta(space->end(), cur_destination);
     while (dead_to_right < free_target) {
       cur -= region_size;
       cur_destination = sd.addr_to_region_ptr(cur)->destination();
       dead_to_right = pointer_delta(space->end(), cur_destination);
     }
     _space_info[id].set_dense_prefix(cur);
   }
 }
 #endif // #ifndef PRODUCT
 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());
   }
 #ifndef PRODUCT
   if (ParallelOldGCSplitALot) {
     provoke_split_fill_survivor(to_space_id);
   }
 #endif // #ifndef PRODUCT
 }
 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::clear_source_region(HeapWord* beg_addr, HeapWord* end_addr)
 {
   RegionData* const beg_ptr = _summary_data.addr_to_region_ptr(beg_addr);
   HeapWord* const end_aligned_up = _summary_data.region_align_up(end_addr);
   RegionData* const end_ptr = _summary_data.addr_to_region_ptr(end_aligned_up);
   for (RegionData* cur = beg_ptr; cur < end_ptr; ++cur) {
     cur->set_source_region(0);
   }
 }
 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() ||
          ParallelOldGCSplitALot && id == old_space_id,
          "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 (TraceParallelOldGCSummaryPhase) {
     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);
     tty->print_cr("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(), dense_prefix_end,
                   dp_region, dp_words / region_size,
                   cr_words / region_size, 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)
 {
   if (TraceParallelOldGCSummaryPhase) {
     tty->print_cr("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],
                   src_beg, src_end,
                   _summary_data.addr_to_region_idx(src_beg),
                   _summary_data.addr_to_region_idx(src_end),
                   dst_beg, 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 tm("summary phase", print_phases(), true, &_gc_timer);
   // trace("2");
 #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();
   if (TraceParallelOldGCSummaryPhase) {
     tty->print_cr("summary_phase:  after summarizing each space to self");
     Universe::print();
     NOT_PRODUCT(print_region_ranges());
     if (Verbose) {
       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;
   }
 #ifndef PRODUCT
   if (ParallelOldGCSplitALot && old_space_total_live < old_capacity) {
     provoke_split(maximum_compaction);
   }
 #endif // #ifndef PRODUCT
   // 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");
     }
   }
   if (TraceParallelOldGCSummaryPhase) {
     tty->print_cr("summary_phase:  after final summarization");
     Universe::print();
     NOT_PRODUCT(print_region_ranges());
     if (Verbose) {
       NOT_PRODUCT(print_generic_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 = gc_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 (GC_locker::check_active_before_gc()) {
     return false;
   }
   ParallelScavengeHeap* heap = gc_heap();
   _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();
   }
   heap->pre_full_gc_dump(&_gc_timer);
   _print_phases = PrintGCDetails && PrintParallelOldGCPhaseTimes;
   // Make sure data structures are sane, make the heap parsable, and do other
   // miscellaneous bookkeeping.
   PreGCValues pre_gc_values;
   pre_compact(&pre_gc_values);
   // Get the compaction manager reserved for the VM thread.
   ParCompactionManager* const vmthread_cm =
     ParCompactionManager::manager_array(gc_task_manager()->workers());
   // Place after pre_compact() where the number of invocations is incremented.
   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
   {
     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();
     heap->set_par_threads(gc_task_manager()->active_workers());
     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
     GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
     TraceCollectorStats tcs(counters());
     TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);
     if (TraceGen1Time) accumulated_time()->start();
     // Let the size policy know we're starting
     size_policy->major_collection_begin();
     CodeCache::gc_prologue();
     Threads::gc_prologue();
     COMPILER2_PRESENT(DerivedPointerTable::clear());
     ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
     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
       && gc_cause == GCCause::_java_lang_system_gc;
     summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
     COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
     COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
     // adjust_roots() updates Universe::_intArrayKlassObj which is
     // needed by the compaction for filling holes in the dense prefix.
     adjust_roots();
     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) {
       if (PrintAdaptiveSizePolicy) {
         gclog_or_tty->print("AdaptiveSizeStart: ");
         gclog_or_tty->stamp();
         gclog_or_tty->print_cr(" collection: %d ",
                        heap->total_collections());
         if (Verbose) {
           gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
             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 &&
           ((gc_cause != GCCause::_java_lang_system_gc) ||
             UseAdaptiveSizePolicyWithSystemGC)) {
         // 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());
         // Don't resize the young generation at an major collection.  A
         // desired young generation size may have been calculated but
         // resizing the young generation complicates the code because the
         // resizing of the old generation may have moved the boundary
         // between the young generation and the old generation.  Let the
         // young generation resizing happen at the minor collections.
       }
       if (PrintAdaptiveSizePolicy) {
         gclog_or_tty->print_cr("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 capactiy after a collection
     MetaspaceGC::compute_new_size();
     if (TraceGen1Time) accumulated_time()->stop();
     if (PrintGC) {
       if (PrintGCDetails) {
         // No GC timestamp here.  This is after GC so it would be confusing.
         young_gen->print_used_change(pre_gc_values.young_gen_used());
         old_gen->print_used_change(pre_gc_values.old_gen_used());
         heap->print_heap_change(pre_gc_values.heap_used());
         MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used());
       } else {
         heap->print_heap_change(pre_gc_values.heap_used());
       }
     }
     // Track memory usage and detect low memory
     MemoryService::track_memory_usage();
     heap->update_counters();
     gc_task_manager()->release_idle_workers();
   }
 #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(ParCompactionManager::region_list(int(i))->is_empty(), "should be empty");
   }
 #endif // ASSERT
   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
     HandleMark hm;  // Discard invalid handles created during verification
     Universe::verify(" VerifyAfterGC:");
   }
   // 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);
   if (PrintGCTaskTimeStamps) {
     gclog_or_tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " "
                            INT64_FORMAT,
                            marking_start.ticks(), compaction_start.ticks(),
                            collection_exit.ticks());
     gc_task_manager()->print_task_time_stamps();
   }
   heap->post_full_gc_dump(&_gc_timer);
 #ifdef TRACESPINNING
   ParallelTaskTerminator::print_termination_counts();
 #endif
   _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_size_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.
   }
   if (TraceAdaptiveGCBoundary && Verbose) {
     gclog_or_tty->print(" 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 tm("marking phase", print_phases(), true, &_gc_timer);
   ParallelScavengeHeap* heap = gc_heap();
   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);
   PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
   PSParallelCompact::FollowStackClosure follow_stack_closure(cm);
   // Need new claim bits before marking starts.
   ClassLoaderDataGraph::clear_claimed_marks();
   {
     GCTraceTime tm_m("par mark", print_phases(), true, &_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::flat_profiler));
     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 tm_r("reference processing", print_phases(), true, &_gc_timer);
     ReferenceProcessorStats stats;
     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, &_gc_timer);
     } else {
       stats = ref_processor()->process_discovered_references(
         is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
         &_gc_timer);
     }
     gc_tracer->report_gc_reference_stats(stats);
   }
   GCTraceTime tm_c("class unloading", print_phases(), true, &_gc_timer);
   // This is the point where the entire marking should have completed.
   assert(cm->marking_stacks_empty(), "Marking should have completed");
   // Follow system dictionary roots and unload classes.
   bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
   // 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());
   // Delete entries for dead interned strings.
   StringTable::unlink(is_alive_closure());
   // Clean up unreferenced symbols in symbol table.
   SymbolTable::unlink();
   _gc_tracer.report_object_count_after_gc(is_alive_closure());
 }
 void PSParallelCompact::follow_class_loader(ParCompactionManager* cm,
                                             ClassLoaderData* cld) {
   PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
   PSParallelCompact::FollowKlassClosure follow_klass_closure(&mark_and_push_closure);
   cld->oops_do(&mark_and_push_closure, &follow_klass_closure, true);
 }
 // This should be moved to the shared markSweep code!
 class PSAlwaysTrueClosure: public BoolObjectClosure {
 public:
   bool do_object_b(oop p) { return true; }
 };
 static PSAlwaysTrueClosure always_true;
 void PSParallelCompact::adjust_roots() {
   // Adjust the pointers to reflect the new locations
   GCTraceTime tm("adjust roots", print_phases(), true, &_gc_timer);
   // Need new claim bits when tracing through and adjusting pointers.
   ClassLoaderDataGraph::clear_claimed_marks();
   // General strong roots.
   Universe::oops_do(adjust_pointer_closure());
   JNIHandles::oops_do(adjust_pointer_closure());   // Global (strong) JNI handles
   CLDToOopClosure adjust_from_cld(adjust_pointer_closure());
   Threads::oops_do(adjust_pointer_closure(), &adjust_from_cld, NULL);
   ObjectSynchronizer::oops_do(adjust_pointer_closure());
   FlatProfiler::oops_do(adjust_pointer_closure());
   Management::oops_do(adjust_pointer_closure());
   JvmtiExport::oops_do(adjust_pointer_closure());
   // SO_AllClasses
   SystemDictionary::oops_do(adjust_pointer_closure());
   ClassLoaderDataGraph::oops_do(adjust_pointer_closure(), adjust_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(&always_true, adjust_pointer_closure());
   CodeCache::oops_do(adjust_pointer_closure());
   StringTable::oops_do(adjust_pointer_closure());
   ref_processor()->weak_oops_do(adjust_pointer_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(adjust_pointer_closure());
 }
 void PSParallelCompact::enqueue_region_draining_tasks(GCTaskQueue* q,
                                                       uint parallel_gc_threads)
 {
   GCTraceTime tm("drain task setup", print_phases(), true, &_gc_timer);
   // Find the threads that are active
   unsigned int which = 0;
   const uint task_count = MAX2(parallel_gc_threads, 1U);
   for (uint j = 0; j < task_count; j++) {
     q->enqueue(new DrainStacksCompactionTask(j));
     ParCompactionManager::verify_region_list_empty(j);
     // Set the region stacks variables to "no" region stack values
     // so that they will be recognized and needing a region stack
     // in the stealing tasks if they do not get one by executing
     // a draining stack.
     ParCompactionManager* cm = ParCompactionManager::manager_array(j);
     cm->set_region_stack(NULL);
     cm->set_region_stack_index((uint)max_uintx);
   }
   ParCompactionManager::reset_recycled_stack_index();
   // 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();
   size_t fillable_regions = 0;   // A count for diagnostic purposes.
   // A region index which corresponds to the tasks created above.
   // "which" must be 0 <= which < task_count
   which = 0;
   // id + 1 is used to test termination so unsigned  can
   // be used with an old_space_id == 0.
   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::region_list_push(which, cur);
         if (TraceParallelOldGCCompactionPhase && Verbose) {
           const size_t count_mod_8 = fillable_regions & 7;
           if (count_mod_8 == 0) gclog_or_tty->print("fillable: ");
           gclog_or_tty->print(" " SIZE_FORMAT_W(7), cur);
           if (count_mod_8 == 7) gclog_or_tty->cr();
         }
         NOT_PRODUCT(++fillable_regions;)
         // Assign regions to tasks in round-robin fashion.
         if (++which == task_count) {
           assert(which <= parallel_gc_threads,
             "Inconsistent number of workers");
           which = 0;
         }
       }
     }
   }
   if (TraceParallelOldGCCompactionPhase) {
     if (Verbose && (fillable_regions & 7) != 0) gclog_or_tty->cr();
     gclog_or_tty->print_cr("%u initially fillable regions", fillable_regions);
   }
 }
 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
                                                     uint parallel_gc_threads) {
   GCTraceTime tm("dense prefix task setup", print_phases(), true, &_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 tm("steal task setup", print_phases(), true, &_gc_timer);
   // Once a thread has drained it's stack, it should try to steal regions from
   // other threads.
   if (parallel_gc_threads > 1) {
     for (uint j = 0; j < parallel_gc_threads; j++) {
       q->enqueue(new StealRegionCompactionTask(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(outputStream* const out)
 {
   if (!TraceParallelOldGCCompactionPhase) return;
   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("%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() {
   // trace("5");
   GCTraceTime tm("compaction phase", print_phases(), true, &_gc_timer);
   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
   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();
   enqueue_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 tm_pc("par compact", print_phases(), true, &_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 tm_du("deferred updates", print_phases(), true, &_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(gclog_or_tty));
 }
 #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()) {
       warning("region " SIZE_FORMAT " not filled:  "
               "destination_count=" SIZE_FORMAT,
               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()) {
       warning("region " SIZE_FORMAT " not empty:   "
               "destination_count=" SIZE_FORMAT,
               cur_region, c->destination_count());
       issued_a_warning = true;
     }
   }
   if (issued_a_warning) {
     print_region_ranges();
   }
 }
 #endif  // #ifdef ASSERT
 // 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(Universe::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);
       }
       oop(addr)->update_contents(cm);
       assert(oop(addr)->is_oop_or_null(), "should be an oop now");
     }
   }
 }
 // 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;
 #ifdef MIPS64
       /* 2016/5/4 Jin: On 3A2000-B, when multiple threads write to
          the same memory location without explict synchronization,
          sync is required for access correctness. */
       if (Use3A2000) OrderAccess::fence();
 #endif
       sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
 #ifdef MIPS64
       if (Use3A2000) OrderAccess::fence();
 #endif
     }
     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-deccreasing 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(warning("time warp: "INT64_FORMAT, ret_val);)
     return 0;
   }
   return ret_val;
 }
 void PSParallelCompact::reset_millis_since_last_gc() {
   // We need a monotonically non-deccreasing 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);
 }
 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()) ==
          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();
   moved_oop->update_contents(compaction_manager());
   assert(moved_oop->is_oop_or_null(), "Object should be whole at this point");
   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;
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp@9d7e35a93fad (annotated)

src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.cpp