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 /*

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * 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.

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSPARALLELCOMPACT_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSPARALLELCOMPACT_HPP

 #include "gc_implementation/parallelScavenge/objectStartArray.hpp"

 #include "gc_implementation/parallelScavenge/parMarkBitMap.hpp"

 #include "gc_implementation/parallelScavenge/psCompactionManager.hpp"

 #include "gc_implementation/shared/collectorCounters.hpp"

 #include "gc_implementation/shared/markSweep.hpp"

 #include "gc_implementation/shared/mutableSpace.hpp"

 #include "memory/sharedHeap.hpp"

 #include "oops/oop.hpp"

 class ParallelScavengeHeap;

 class PSAdaptiveSizePolicy;

 class PSYoungGen;

 class PSOldGen;

 class PSPermGen;

 class ParCompactionManager;

 class ParallelTaskTerminator;

 class PSParallelCompact;

 class GCTaskManager;

 class GCTaskQueue;

 class PreGCValues;

 class MoveAndUpdateClosure;

 class RefProcTaskExecutor;

 // The SplitInfo class holds the information needed to 'split' a source region

 // so that the live data can be copied to two destination *spaces*.  Normally,

 // all the live data in a region is copied to a single destination space (e.g.,

 // everything live in a region in eden is copied entirely into the old gen).

 // However, when the heap is nearly full, all the live data in eden may not fit

 // into the old gen.  Copying only some of the regions from eden to old gen

 // requires finding a region that does not contain a partial object (i.e., no

 // live object crosses the region boundary) somewhere near the last object that

 // does fit into the old gen.  Since it's not always possible to find such a

 // region, splitting is necessary for predictable behavior.

 //

 // A region is always split at the end of the partial object.  This avoids

 // additional tests when calculating the new location of a pointer, which is a

 // very hot code path.  The partial object and everything to its left will be

 // copied to another space (call it dest_space_1).  The live data to the right

 // of the partial object will be copied either within the space itself, or to a

 // different destination space (distinct from dest_space_1).

 //

 // Split points are identified during the summary phase, when region

 // destinations are computed:  data about the split, including the

 // partial_object_size, is recorded in a SplitInfo record and the

 // partial_object_size field in the summary data is set to zero.  The zeroing is

 // possible (and necessary) since the partial object will move to a different

 // destination space than anything to its right, thus the partial object should

 // not affect the locations of any objects to its right.

 //

 // The recorded data is used during the compaction phase, but only rarely:  when

 // the partial object on the split region will be copied across a destination

 // region boundary.  This test is made once each time a region is filled, and is

 // a simple address comparison, so the overhead is negligible (see

 // PSParallelCompact::first_src_addr()).

 //

 // Notes:

 //

 // Only regions with partial objects are split; a region without a partial

 // object does not need any extra bookkeeping.

 //

 // At most one region is split per space, so the amount of data required is

 // constant.

 //

 // A region is split only when the destination space would overflow.  Once that

 // happens, the destination space is abandoned and no other data (even from

 // other source spaces) is targeted to that destination space.  Abandoning the

 // destination space may leave a somewhat large unused area at the end, if a

 // large object caused the overflow.

 //

 // Future work:

 //

 // More bookkeeping would be required to continue to use the destination space.

 // The most general solution would allow data from regions in two different

 // source spaces to be "joined" in a single destination region.  At the very

 // least, additional code would be required in next_src_region() to detect the

 // join and skip to an out-of-order source region.  If the join region was also

 // the last destination region to which a split region was copied (the most

 // likely case), then additional work would be needed to get fill_region() to

 // stop iteration and switch to a new source region at the right point.  Basic

 // idea would be to use a fake value for the top of the source space.  It is

 // doable, if a bit tricky.

 //

 // A simpler (but less general) solution would fill the remainder of the

 // destination region with a dummy object and continue filling the next

 // destination region.

 class SplitInfo

 {

 public:

   // Return true if this split info is valid (i.e., if a split has been

   // recorded).  The very first region cannot have a partial object and thus is

   // never split, so 0 is the 'invalid' value.

   bool is_valid() const { return _src_region_idx > 0; }

   // Return true if this split holds data for the specified source region.

   inline bool is_split(size_t source_region) const;

   // The index of the split region, the size of the partial object on that

   // region and the destination of the partial object.

   size_t    src_region_idx() const   { return _src_region_idx; }

   size_t    partial_obj_size() const { return _partial_obj_size; }

   HeapWord* destination() const      { return _destination; }

   // The destination count of the partial object referenced by this split

   // (either 1 or 2).  This must be added to the destination count of the

   // remainder of the source region.

   unsigned int destination_count() const { return _destination_count; }

   // If a word within the partial object will be written to the first word of a

   // destination region, this is the address of the destination region;

   // otherwise this is NULL.

   HeapWord* dest_region_addr() const     { return _dest_region_addr; }

   // If a word within the partial object will be written to the first word of a

   // destination region, this is the address of that word within the partial

   // object; otherwise this is NULL.

   HeapWord* first_src_addr() const       { return _first_src_addr; }

   // Record the data necessary to split the region src_region_idx.

   void record(size_t src_region_idx, size_t partial_obj_size,

               HeapWord* destination);

   void clear();

   DEBUG_ONLY(void verify_clear();)

 private:

   size_t       _src_region_idx;

   size_t       _partial_obj_size;

   HeapWord*    _destination;

   unsigned int _destination_count;

   HeapWord*    _dest_region_addr;

   HeapWord*    _first_src_addr;

 };

 inline bool SplitInfo::is_split(size_t region_idx) const

 {

   return _src_region_idx == region_idx && is_valid();

 }

 class SpaceInfo

 {

  public:

   MutableSpace* space() const { return _space; }

   // Where the free space will start after the collection.  Valid only after the

   // summary phase completes.

   HeapWord* new_top() const { return _new_top; }

   // Allows new_top to be set.

   HeapWord** new_top_addr() { return &_new_top; }

   // Where the smallest allowable dense prefix ends (used only for perm gen).

   HeapWord* min_dense_prefix() const { return _min_dense_prefix; }

   // Where the dense prefix ends, or the compacted region begins.

   HeapWord* dense_prefix() const { return _dense_prefix; }

   // The start array for the (generation containing the) space, or NULL if there

   // is no start array.

   ObjectStartArray* start_array() const { return _start_array; }

   SplitInfo& split_info() { return _split_info; }

   void set_space(MutableSpace* s)           { _space = s; }

   void set_new_top(HeapWord* addr)          { _new_top = addr; }

   void set_min_dense_prefix(HeapWord* addr) { _min_dense_prefix = addr; }

   void set_dense_prefix(HeapWord* addr)     { _dense_prefix = addr; }

   void set_start_array(ObjectStartArray* s) { _start_array = s; }

   void publish_new_top() const              { _space->set_top(_new_top); }

  private:

   MutableSpace*     _space;

   HeapWord*         _new_top;

   HeapWord*         _min_dense_prefix;

   HeapWord*         _dense_prefix;

   ObjectStartArray* _start_array;

   SplitInfo         _split_info;

 };

 class ParallelCompactData

 {

 public:

   // Sizes are in HeapWords, unless indicated otherwise.

   static const size_t Log2RegionSize;

   static const size_t RegionSize;

   static const size_t RegionSizeBytes;

   // Mask for the bits in a size_t to get an offset within a region.

   static const size_t RegionSizeOffsetMask;

   // Mask for the bits in a pointer to get an offset within a region.

   static const size_t RegionAddrOffsetMask;

   // Mask for the bits in a pointer to get the address of the start of a region.

   static const size_t RegionAddrMask;

   class RegionData

   {

   public:

     // Destination address of the region.

     HeapWord* destination() const { return _destination; }

     // The first region containing data destined for this region.

     size_t source_region() const { return _source_region; }

     // The object (if any) starting in this region and ending in a different

     // region that could not be updated during the main (parallel) compaction

     // phase.  This is different from _partial_obj_addr, which is an object that

     // extends onto a source region.  However, the two uses do not overlap in

     // time, so the same field is used to save space.

     HeapWord* deferred_obj_addr() const { return _partial_obj_addr; }

     // The starting address of the partial object extending onto the region.

     HeapWord* partial_obj_addr() const { return _partial_obj_addr; }

     // Size of the partial object extending onto the region (words).

     size_t partial_obj_size() const { return _partial_obj_size; }

     // Size of live data that lies within this region due to objects that start

     // in this region (words).  This does not include the partial object

     // extending onto the region (if any), or the part of an object that extends

     // onto the next region (if any).

     size_t live_obj_size() const { return _dc_and_los & los_mask; }

     // Total live data that lies within the region (words).

     size_t data_size() const { return partial_obj_size() + live_obj_size(); }

     // The destination_count is the number of other regions to which data from

     // this region will be copied.  At the end of the summary phase, the valid

     // values of destination_count are

     //

     // 0 - data from the region will be compacted completely into itself, or the

     //     region is empty.  The region can be claimed and then filled.

     // 1 - data from the region will be compacted into 1 other region; some

     //     data from the region may also be compacted into the region itself.

     // 2 - data from the region will be copied to 2 other regions.

     //

     // During compaction as regions are emptied, the destination_count is

     // decremented (atomically) and when it reaches 0, it can be claimed and

     // then filled.

     //

     // A region is claimed for processing by atomically changing the

     // destination_count to the claimed value (dc_claimed).  After a region has

     // been filled, the destination_count should be set to the completed value

     // (dc_completed).

     inline uint destination_count() const;

     inline uint destination_count_raw() const;

     // The location of the java heap data that corresponds to this region.

     inline HeapWord* data_location() const;

     // The highest address referenced by objects in this region.

     inline HeapWord* highest_ref() const;

     // Whether this region is available to be claimed, has been claimed, or has

     // been completed.

     //

     // Minor subtlety:  claimed() returns true if the region is marked

     // completed(), which is desirable since a region must be claimed before it

     // can be completed.

     bool available() const { return _dc_and_los < dc_one; }

     bool claimed() const   { return _dc_and_los >= dc_claimed; }

     bool completed() const { return _dc_and_los >= dc_completed; }

     // These are not atomic.

     void set_destination(HeapWord* addr)       { _destination = addr; }

     void set_source_region(size_t region)      { _source_region = region; }

     void set_deferred_obj_addr(HeapWord* addr) { _partial_obj_addr = addr; }

     void set_partial_obj_addr(HeapWord* addr)  { _partial_obj_addr = addr; }

     void set_partial_obj_size(size_t words)    {

       _partial_obj_size = (region_sz_t) words;

     }

     inline void set_destination_count(uint count);

     inline void set_live_obj_size(size_t words);

     inline void set_data_location(HeapWord* addr);

     inline void set_completed();

     inline bool claim_unsafe();

     // These are atomic.

     inline void add_live_obj(size_t words);

     inline void set_highest_ref(HeapWord* addr);

     inline void decrement_destination_count();

     inline bool claim();

   private:

     // The type used to represent object sizes within a region.

     typedef uint region_sz_t;

     // Constants for manipulating the _dc_and_los field, which holds both the

     // destination count and live obj size.  The live obj size lives at the

     // least significant end so no masking is necessary when adding.

     static const region_sz_t dc_shift;           // Shift amount.

     static const region_sz_t dc_mask;            // Mask for destination count.

     static const region_sz_t dc_one;             // 1, shifted appropriately.

     static const region_sz_t dc_claimed;         // Region has been claimed.

     static const region_sz_t dc_completed;       // Region has been completed.

     static const region_sz_t los_mask;           // Mask for live obj size.

     HeapWord*            _destination;

     size_t               _source_region;

     HeapWord*            _partial_obj_addr;

     region_sz_t          _partial_obj_size;

     region_sz_t volatile _dc_and_los;

 #ifdef ASSERT

     // These enable optimizations that are only partially implemented.  Use

     // debug builds to prevent the code fragments from breaking.

     HeapWord*            _data_location;

     HeapWord*            _highest_ref;

 #endif  // #ifdef ASSERT

 #ifdef ASSERT

    public:

     uint            _pushed;   // 0 until region is pushed onto a worker's stack

    private:

 #endif

   };

 public:

   ParallelCompactData();

   bool initialize(MemRegion covered_region);

   size_t region_count() const { return _region_count; }

   // Convert region indices to/from RegionData pointers.

   inline RegionData* region(size_t region_idx) const;

   inline size_t     region(const RegionData* const region_ptr) const;

   // Returns true if the given address is contained within the region

   bool region_contains(size_t region_index, HeapWord* addr);

   void add_obj(HeapWord* addr, size_t len);

   void add_obj(oop p, size_t len) { add_obj((HeapWord*)p, len); }

   // Fill in the regions covering [beg, end) so that no data moves; i.e., the

   // destination of region n is simply the start of region n.  The argument beg

   // must be region-aligned; end need not be.

   void summarize_dense_prefix(HeapWord* beg, HeapWord* end);

   HeapWord* summarize_split_space(size_t src_region, SplitInfo& split_info,

                                   HeapWord* destination, HeapWord* target_end,

                                   HeapWord** target_next);

   bool summarize(SplitInfo& split_info,

                  HeapWord* source_beg, HeapWord* source_end,

                  HeapWord** source_next,

                  HeapWord* target_beg, HeapWord* target_end,

                  HeapWord** target_next);

   void clear();

   void clear_range(size_t beg_region, size_t end_region);

   void clear_range(HeapWord* beg, HeapWord* end) {

     clear_range(addr_to_region_idx(beg), addr_to_region_idx(end));

   }

   // Return the number of words between addr and the start of the region

   // containing addr.

   inline size_t     region_offset(const HeapWord* addr) const;

   // Convert addresses to/from a region index or region pointer.

   inline size_t     addr_to_region_idx(const HeapWord* addr) const;

   inline RegionData* addr_to_region_ptr(const HeapWord* addr) const;

   inline HeapWord*  region_to_addr(size_t region) const;

   inline HeapWord*  region_to_addr(size_t region, size_t offset) const;

   inline HeapWord*  region_to_addr(const RegionData* region) const;

   inline HeapWord*  region_align_down(HeapWord* addr) const;

   inline HeapWord*  region_align_up(HeapWord* addr) const;

   inline bool       is_region_aligned(HeapWord* addr) const;

   // Return the address one past the end of the partial object.

   HeapWord* partial_obj_end(size_t region_idx) const;

   // Return the new location of the object p after the

   // the compaction.

   HeapWord* calc_new_pointer(HeapWord* addr);

   HeapWord* calc_new_pointer(oop p) {

     return calc_new_pointer((HeapWord*) p);

   }

   // Return the updated address for the given klass

   klassOop calc_new_klass(klassOop);

 #ifdef  ASSERT

   void verify_clear(const PSVirtualSpace* vspace);

   void verify_clear();

 #endif  // #ifdef ASSERT

 private:

   bool initialize_region_data(size_t region_size);

   PSVirtualSpace* create_vspace(size_t count, size_t element_size);

 private:

   HeapWord*       _region_start;

 #ifdef  ASSERT

   HeapWord*       _region_end;

 #endif  // #ifdef ASSERT

   PSVirtualSpace* _region_vspace;

   RegionData*     _region_data;

   size_t          _region_count;

 };

 inline uint

 ParallelCompactData::RegionData::destination_count_raw() const

 {

   return _dc_and_los & dc_mask;

 }

 inline uint

 ParallelCompactData::RegionData::destination_count() const

 {

   return destination_count_raw() >> dc_shift;

 }

 inline void

 ParallelCompactData::RegionData::set_destination_count(uint count)

 {

   assert(count <= (dc_completed >> dc_shift), "count too large");

   const region_sz_t live_sz = (region_sz_t) live_obj_size();

   _dc_and_los = (count << dc_shift) | live_sz;

 }

 inline void ParallelCompactData::RegionData::set_live_obj_size(size_t words)

 {

   assert(words <= los_mask, "would overflow");

   _dc_and_los = destination_count_raw() | (region_sz_t)words;

 }

 inline void ParallelCompactData::RegionData::decrement_destination_count()

 {

   assert(_dc_and_los < dc_claimed, "already claimed");

   assert(_dc_and_los >= dc_one, "count would go negative");

   Atomic::add((int)dc_mask, (volatile int*)&_dc_and_los);

 }

 inline HeapWord* ParallelCompactData::RegionData::data_location() const

 {

   DEBUG_ONLY(return _data_location;)

   NOT_DEBUG(return NULL;)

 }

 inline HeapWord* ParallelCompactData::RegionData::highest_ref() const

 {

   DEBUG_ONLY(return _highest_ref;)

   NOT_DEBUG(return NULL;)

 }

 inline void ParallelCompactData::RegionData::set_data_location(HeapWord* addr)

 {

   DEBUG_ONLY(_data_location = addr;)

 }

 inline void ParallelCompactData::RegionData::set_completed()

 {

   assert(claimed(), "must be claimed first");

   _dc_and_los = dc_completed | (region_sz_t) live_obj_size();

 }

 // MT-unsafe claiming of a region.  Should only be used during single threaded

 // execution.

 inline bool ParallelCompactData::RegionData::claim_unsafe()

 {

   if (available()) {

     _dc_and_los |= dc_claimed;

     return true;

   }

   return false;

 }

 inline void ParallelCompactData::RegionData::add_live_obj(size_t words)

 {

   assert(words <= (size_t)los_mask - live_obj_size(), "overflow");

   Atomic::add((int) words, (volatile int*) &_dc_and_los);

 }

 inline void ParallelCompactData::RegionData::set_highest_ref(HeapWord* addr)

 {

 #ifdef ASSERT

   HeapWord* tmp = _highest_ref;

   while (addr > tmp) {

     tmp = (HeapWord*)Atomic::cmpxchg_ptr(addr, &_highest_ref, tmp);

   }

 #endif  // #ifdef ASSERT

 }

 inline bool ParallelCompactData::RegionData::claim()

 {

   const int los = (int) live_obj_size();

   const int old = Atomic::cmpxchg(dc_claimed | los,

                                   (volatile int*) &_dc_and_los, los);

   return old == los;

 }

 inline ParallelCompactData::RegionData*

 ParallelCompactData::region(size_t region_idx) const

 {

   assert(region_idx <= region_count(), "bad arg");

   return _region_data + region_idx;

 }

 inline size_t

 ParallelCompactData::region(const RegionData* const region_ptr) const

 {

   assert(region_ptr >= _region_data, "bad arg");

   assert(region_ptr <= _region_data + region_count(), "bad arg");

   return pointer_delta(region_ptr, _region_data, sizeof(RegionData));

 }

 inline size_t

 ParallelCompactData::region_offset(const HeapWord* addr) const

 {

   assert(addr >= _region_start, "bad addr");

   assert(addr <= _region_end, "bad addr");

   return (size_t(addr) & RegionAddrOffsetMask) >> LogHeapWordSize;

 }

 inline size_t

 ParallelCompactData::addr_to_region_idx(const HeapWord* addr) const

 {

   assert(addr >= _region_start, "bad addr");

   assert(addr <= _region_end, "bad addr");

   return pointer_delta(addr, _region_start) >> Log2RegionSize;

 }

 inline ParallelCompactData::RegionData*

 ParallelCompactData::addr_to_region_ptr(const HeapWord* addr) const

 {

   return region(addr_to_region_idx(addr));

 }

 inline HeapWord*

 ParallelCompactData::region_to_addr(size_t region) const

 {

   assert(region <= _region_count, "region out of range");

   return _region_start + (region << Log2RegionSize);

 }

 inline HeapWord*

 ParallelCompactData::region_to_addr(const RegionData* region) const

 {

   return region_to_addr(pointer_delta(region, _region_data,

                                       sizeof(RegionData)));

 }

 inline HeapWord*

 ParallelCompactData::region_to_addr(size_t region, size_t offset) const

 {

   assert(region <= _region_count, "region out of range");

   assert(offset < RegionSize, "offset too big");  // This may be too strict.

   return region_to_addr(region) + offset;

 }

 inline HeapWord*

 ParallelCompactData::region_align_down(HeapWord* addr) const

 {

   assert(addr >= _region_start, "bad addr");

   assert(addr < _region_end + RegionSize, "bad addr");

   return (HeapWord*)(size_t(addr) & RegionAddrMask);

 }

 inline HeapWord*

 ParallelCompactData::region_align_up(HeapWord* addr) const

 {

   assert(addr >= _region_start, "bad addr");

   assert(addr <= _region_end, "bad addr");

   return region_align_down(addr + RegionSizeOffsetMask);

 }

 inline bool

 ParallelCompactData::is_region_aligned(HeapWord* addr) const

 {

   return region_offset(addr) == 0;

 }

 // Abstract closure for use with ParMarkBitMap::iterate(), which will invoke the

 // do_addr() method.

 //

 // The closure is initialized with the number of heap words to process

 // (words_remaining()), and becomes 'full' when it reaches 0.  The do_addr()

 // methods in subclasses should update the total as words are processed.  Since

 // only one subclass actually uses this mechanism to terminate iteration, the

 // default initial value is > 0.  The implementation is here and not in the

 // single subclass that uses it to avoid making is_full() virtual, and thus

 // adding a virtual call per live object.

 class ParMarkBitMapClosure: public StackObj {

  public:

   typedef ParMarkBitMap::idx_t idx_t;

   typedef ParMarkBitMap::IterationStatus IterationStatus;

  public:

   inline ParMarkBitMapClosure(ParMarkBitMap* mbm, ParCompactionManager* cm,

                               size_t words = max_uintx);

   inline ParCompactionManager* compaction_manager() const;

   inline ParMarkBitMap*        bitmap() const;

   inline size_t                words_remaining() const;

   inline bool                  is_full() const;

   inline HeapWord*             source() const;

   inline void                  set_source(HeapWord* addr);

   virtual IterationStatus do_addr(HeapWord* addr, size_t words) = 0;

  protected:

   inline void decrement_words_remaining(size_t words);

  private:

   ParMarkBitMap* const        _bitmap;

   ParCompactionManager* const _compaction_manager;

   DEBUG_ONLY(const size_t     _initial_words_remaining;) // Useful in debugger.

   size_t                      _words_remaining; // Words left to copy.

  protected:

   HeapWord*                   _source;          // Next addr that would be read.

 };

 inline

 ParMarkBitMapClosure::ParMarkBitMapClosure(ParMarkBitMap* bitmap,

                                            ParCompactionManager* cm,

                                            size_t words):

   _bitmap(bitmap), _compaction_manager(cm)

 #ifdef  ASSERT

   , _initial_words_remaining(words)

 #endif

 {

   _words_remaining = words;

   _source = NULL;

 }

 inline ParCompactionManager* ParMarkBitMapClosure::compaction_manager() const {

   return _compaction_manager;

 }

 inline ParMarkBitMap* ParMarkBitMapClosure::bitmap() const {

   return _bitmap;

 }

 inline size_t ParMarkBitMapClosure::words_remaining() const {

   return _words_remaining;

 }

 inline bool ParMarkBitMapClosure::is_full() const {

   return words_remaining() == 0;

 }

 inline HeapWord* ParMarkBitMapClosure::source() const {

   return _source;

 }

 inline void ParMarkBitMapClosure::set_source(HeapWord* addr) {

   _source = addr;

 }

 inline void ParMarkBitMapClosure::decrement_words_remaining(size_t words) {

   assert(_words_remaining >= words, "processed too many words");

   _words_remaining -= words;

 }

 // The UseParallelOldGC collector is a stop-the-world garbage collector that

 // does parts of the collection using parallel threads.  The collection includes

 // the tenured generation and the young generation.  The permanent generation is

 // collected at the same time as the other two generations but the permanent

 // generation is collect by a single GC thread.  The permanent generation is

 // collected serially because of the requirement that during the processing of a

 // klass AAA, any objects reference by AAA must already have been processed.

 // This requirement is enforced by a left (lower address) to right (higher

 // address) sliding compaction.

 //

 // There are four phases of the collection.

 //

 //      - marking phase

 //      - summary phase

 //      - compacting phase

 //      - clean up phase

 //

 // Roughly speaking these phases correspond, respectively, to

 //      - mark all the live objects

 //      - calculate the destination of each object at the end of the collection

 //      - move the objects to their destination

 //      - update some references and reinitialize some variables

 //

 // These three phases are invoked in PSParallelCompact::invoke_no_policy().  The

 // marking phase is implemented in PSParallelCompact::marking_phase() and does a

 // complete marking of the heap.  The summary phase is implemented in

 // PSParallelCompact::summary_phase().  The move and update phase is implemented

 // in PSParallelCompact::compact().

 //

 // A space that is being collected is divided into regions and with each region

 // is associated an object of type ParallelCompactData.  Each region is of a

 // fixed size and typically will contain more than 1 object and may have parts

 // of objects at the front and back of the region.

 //

 // region            -----+---------------------+----------

 // objects covered   [ AAA  )[ BBB )[ CCC   )[ DDD     )

 //

 // The marking phase does a complete marking of all live objects in the heap.

 // The marking also compiles the size of the data for all live objects covered

 // by the region.  This size includes the part of any live object spanning onto

 // the region (part of AAA if it is live) from the front, all live objects

 // contained in the region (BBB and/or CCC if they are live), and the part of

 // any live objects covered by the region that extends off the region (part of

 // DDD if it is live).  The marking phase uses multiple GC threads and marking

 // is done in a bit array of type ParMarkBitMap.  The marking of the bit map is

 // done atomically as is the accumulation of the size of the live objects

 // covered by a region.

 //

 // The summary phase calculates the total live data to the left of each region

 // XXX.  Based on that total and the bottom of the space, it can calculate the

 // starting location of the live data in XXX.  The summary phase calculates for

 // each region XXX quantites such as

 //

 //      - the amount of live data at the beginning of a region from an object

 //        entering the region.

 //      - the location of the first live data on the region

 //      - a count of the number of regions receiving live data from XXX.

 //

 // See ParallelCompactData for precise details.  The summary phase also

 // calculates the dense prefix for the compaction.  The dense prefix is a

 // portion at the beginning of the space that is not moved.  The objects in the

 // dense prefix do need to have their object references updated.  See method

 // summarize_dense_prefix().

 //

 // The summary phase is done using 1 GC thread.

 //

 // The compaction phase moves objects to their new location and updates all

 // references in the object.

 //

 // A current exception is that objects that cross a region boundary are moved

 // but do not have their references updated.  References are not updated because

 // it cannot easily be determined if the klass pointer KKK for the object AAA

 // has been updated.  KKK likely resides in a region to the left of the region

 // containing AAA.  These AAA's have there references updated at the end in a

 // clean up phase.  See the method PSParallelCompact::update_deferred_objects().

 // An alternate strategy is being investigated for this deferral of updating.

 //

 // Compaction is done on a region basis.  A region that is ready to be filled is

 // put on a ready list and GC threads take region off the list and fill them.  A

 // region is ready to be filled if it empty of live objects.  Such a region may

 // have been initially empty (only contained dead objects) or may have had all

 // its live objects copied out already.  A region that compacts into itself is

 // also ready for filling.  The ready list is initially filled with empty

 // regions and regions compacting into themselves.  There is always at least 1

 // region that can be put on the ready list.  The regions are atomically added

 // and removed from the ready list.

 class PSParallelCompact : AllStatic {

  public:

   // Convenient access to type names.

   typedef ParMarkBitMap::idx_t idx_t;

   typedef ParallelCompactData::RegionData RegionData;

   typedef enum {

     perm_space_id, old_space_id, eden_space_id,

     from_space_id, to_space_id, last_space_id

   } SpaceId;

  public:

   // Inline closure decls

   //

   class IsAliveClosure: public BoolObjectClosure {

    public:

     virtual void do_object(oop p);

     virtual bool do_object_b(oop p);

   };

   class KeepAliveClosure: public OopClosure {

    private:

     ParCompactionManager* _compaction_manager;

    protected:

     template <class T> inline void do_oop_work(T* p);

    public:

     KeepAliveClosure(ParCompactionManager* cm) : _compaction_manager(cm) { }

     virtual void do_oop(oop* p);

     virtual void do_oop(narrowOop* p);

   };

   // Current unused

   class FollowRootClosure: public OopsInGenClosure {

    private:

     ParCompactionManager* _compaction_manager;

    public:

     FollowRootClosure(ParCompactionManager* cm) : _compaction_manager(cm) { }

     virtual void do_oop(oop* p);

     virtual void do_oop(narrowOop* p);

  };

   class FollowStackClosure: public VoidClosure {

    private:

     ParCompactionManager* _compaction_manager;

    public:

     FollowStackClosure(ParCompactionManager* cm) : _compaction_manager(cm) { }

     virtual void do_void();

   };

   class AdjustPointerClosure: public OopsInGenClosure {

    private:

     bool _is_root;

    public:

     AdjustPointerClosure(bool is_root) : _is_root(is_root) { }

     virtual void do_oop(oop* p);

     virtual void do_oop(narrowOop* p);

     // do not walk from thread stacks to the code cache on this phase

     virtual void do_code_blob(CodeBlob* cb) const { }

   };

   friend class KeepAliveClosure;

   friend class FollowStackClosure;

   friend class AdjustPointerClosure;

   friend class FollowRootClosure;

   friend class instanceKlassKlass;

   friend class RefProcTaskProxy;

  private:

   static elapsedTimer         _accumulated_time;

   static unsigned int         _total_invocations;

   static unsigned int         _maximum_compaction_gc_num;

   static jlong                _time_of_last_gc;   // ms

   static CollectorCounters*   _counters;

   static ParMarkBitMap        _mark_bitmap;

   static ParallelCompactData  _summary_data;

   static IsAliveClosure       _is_alive_closure;

   static SpaceInfo            _space_info[last_space_id];

   static bool                 _print_phases;

   static AdjustPointerClosure _adjust_root_pointer_closure;

   static AdjustPointerClosure _adjust_pointer_closure;

   // Reference processing (used in ...follow_contents)

   static ReferenceProcessor*  _ref_processor;

   // Updated location of intArrayKlassObj.

   static klassOop _updated_int_array_klass_obj;

   // Values computed at initialization and used by dead_wood_limiter().

   static double _dwl_mean;

   static double _dwl_std_dev;

   static double _dwl_first_term;

   static double _dwl_adjustment;

 #ifdef  ASSERT

   static bool   _dwl_initialized;

 #endif  // #ifdef ASSERT

  private:

   // Closure accessors

   static OopClosure* adjust_pointer_closure()      { return (OopClosure*)&_adjust_pointer_closure; }

   static OopClosure* adjust_root_pointer_closure() { return (OopClosure*)&_adjust_root_pointer_closure; }

   static BoolObjectClosure* is_alive_closure()     { return (BoolObjectClosure*)&_is_alive_closure; }

   static void initialize_space_info();

   // Return true if details about individual phases should be printed.

   static inline bool print_phases();

   // Clear the marking bitmap and summary data that cover the specified space.

   static void clear_data_covering_space(SpaceId id);

   static void pre_compact(PreGCValues* pre_gc_values);

   static void post_compact();

   // Mark live objects

   static void marking_phase(ParCompactionManager* cm,

                             bool maximum_heap_compaction);

   static void follow_weak_klass_links();

   static void follow_mdo_weak_refs();

   template <class T> static inline void adjust_pointer(T* p, bool is_root);

   static void adjust_root_pointer(oop* p) { adjust_pointer(p, true); }

   template <class T>

   static inline void follow_root(ParCompactionManager* cm, T* p);

   // Compute the dense prefix for the designated space.  This is an experimental

   // implementation currently not used in production.

   static HeapWord* compute_dense_prefix_via_density(const SpaceId id,

                                                     bool maximum_compaction);

   // Methods used to compute the dense prefix.

   // Compute the value of the normal distribution at x = density.  The mean and

   // standard deviation are values saved by initialize_dead_wood_limiter().

   static inline double normal_distribution(double density);

   // Initialize the static vars used by dead_wood_limiter().

   static void initialize_dead_wood_limiter();

   // Return the percentage of space that can be treated as "dead wood" (i.e.,

   // not reclaimed).

   static double dead_wood_limiter(double density, size_t min_percent);

   // Find the first (left-most) region in the range [beg, end) that has at least

   // dead_words of dead space to the left.  The argument beg must be the first

   // region in the space that is not completely live.

   static RegionData* dead_wood_limit_region(const RegionData* beg,

                                             const RegionData* end,

                                             size_t dead_words);

   // Return a pointer to the first region in the range [beg, end) that is not

   // completely full.

   static RegionData* first_dead_space_region(const RegionData* beg,

                                              const RegionData* end);

   // Return a value indicating the benefit or 'yield' if the compacted region

   // were to start (or equivalently if the dense prefix were to end) at the

   // candidate region.  Higher values are better.

   //

   // The value is based on the amount of space reclaimed vs. the costs of (a)

   // updating references in the dense prefix plus (b) copying objects and

   // updating references in the compacted region.

   static inline double reclaimed_ratio(const RegionData* const candidate,

                                        HeapWord* const bottom,

                                        HeapWord* const top,

                                        HeapWord* const new_top);

   // Compute the dense prefix for the designated space.

   static HeapWord* compute_dense_prefix(const SpaceId id,

                                         bool maximum_compaction);

   // Return true if dead space crosses onto the specified Region; bit must be

   // the bit index corresponding to the first word of the Region.

   static inline bool dead_space_crosses_boundary(const RegionData* region,

                                                  idx_t bit);

   // Summary phase utility routine to fill dead space (if any) at the dense

   // prefix boundary.  Should only be called if the the dense prefix is

   // non-empty.

   static void fill_dense_prefix_end(SpaceId id);

   // Clear the summary data source_region field for the specified addresses.

   static void clear_source_region(HeapWord* beg_addr, HeapWord* end_addr);

 #ifndef PRODUCT

   // Routines to provoke splitting a young gen space (ParallelOldGCSplitALot).

   // Fill the region [start, start + words) with live object(s).  Only usable

   // for the old and permanent generations.

   static void fill_with_live_objects(SpaceId id, HeapWord* const start,

                                      size_t words);

   // Include the new objects in the summary data.

   static void summarize_new_objects(SpaceId id, HeapWord* start);

   // Add live objects to a survivor space since it's rare that both survivors

   // are non-empty.

   static void provoke_split_fill_survivor(SpaceId id);

   // Add live objects and/or choose the dense prefix to provoke splitting.

   static void provoke_split(bool & maximum_compaction);

 #endif

   static void summarize_spaces_quick();

   static void summarize_space(SpaceId id, bool maximum_compaction);

   static void summary_phase(ParCompactionManager* cm, bool maximum_compaction);

   // Adjust addresses in roots.  Does not adjust addresses in heap.

   static void adjust_roots();

   // Serial code executed in preparation for the compaction phase.

   static void compact_prologue();

   // Move objects to new locations.

   static void compact_perm(ParCompactionManager* cm);

   static void compact();

   // Add available regions to the stack and draining tasks to the task queue.

   static void enqueue_region_draining_tasks(GCTaskQueue* q,

                                             uint parallel_gc_threads);

   // Add dense prefix update tasks to the task queue.

   static void enqueue_dense_prefix_tasks(GCTaskQueue* q,

                                          uint parallel_gc_threads);

   // Add region stealing tasks to the task queue.

   static void enqueue_region_stealing_tasks(

                                        GCTaskQueue* q,

                                        ParallelTaskTerminator* terminator_ptr,

                                        uint parallel_gc_threads);

   // If objects are left in eden after a collection, try to move the boundary

   // and absorb them into the old gen.  Returns true if eden was emptied.

   static bool absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,

                                          PSYoungGen* young_gen,

                                          PSOldGen* old_gen);

   // Reset time since last full gc

   static void reset_millis_since_last_gc();

  protected:

 #ifdef VALIDATE_MARK_SWEEP

   static GrowableArray<void*>*           _root_refs_stack;

   static GrowableArray<oop> *            _live_oops;

   static GrowableArray<oop> *            _live_oops_moved_to;

   static GrowableArray<size_t>*          _live_oops_size;

   static size_t                          _live_oops_index;

   static size_t                          _live_oops_index_at_perm;

   static GrowableArray<void*>*           _other_refs_stack;

   static GrowableArray<void*>*           _adjusted_pointers;

   static bool                            _pointer_tracking;

   static bool                            _root_tracking;

   // The following arrays are saved since the time of the last GC and

   // assist in tracking down problems where someone has done an errant

   // store into the heap, usually to an oop that wasn't properly

   // handleized across a GC. If we crash or otherwise fail before the

   // next GC, we can query these arrays to find out the object we had

   // intended to do the store to (assuming it is still alive) and the

   // offset within that object. Covered under RecordMarkSweepCompaction.

   static GrowableArray<HeapWord*> *      _cur_gc_live_oops;

   static GrowableArray<HeapWord*> *      _cur_gc_live_oops_moved_to;

   static GrowableArray<size_t>*          _cur_gc_live_oops_size;

   static GrowableArray<HeapWord*> *      _last_gc_live_oops;

   static GrowableArray<HeapWord*> *      _last_gc_live_oops_moved_to;

   static GrowableArray<size_t>*          _last_gc_live_oops_size;

 #endif

  public:

   class MarkAndPushClosure: public OopClosure {

    private:

     ParCompactionManager* _compaction_manager;

    public:

     MarkAndPushClosure(ParCompactionManager* cm) : _compaction_manager(cm) { }

     virtual void do_oop(oop* p);

     virtual void do_oop(narrowOop* p);

   };

   PSParallelCompact();

   // Convenient accessor for Universe::heap().

   static ParallelScavengeHeap* gc_heap() {

     return (ParallelScavengeHeap*)Universe::heap();

   }

   static void invoke(bool maximum_heap_compaction);

   static bool invoke_no_policy(bool maximum_heap_compaction);

   static void post_initialize();

   // Perform initialization for PSParallelCompact that requires

   // allocations.  This should be called during the VM initialization

   // at a pointer where it would be appropriate to return a JNI_ENOMEM

   // in the event of a failure.

   static bool initialize();

   // Public accessors

   static elapsedTimer* accumulated_time() { return &_accumulated_time; }

   static unsigned int total_invocations() { return _total_invocations; }

   static CollectorCounters* counters()    { return _counters; }

   // Used to add tasks

   static GCTaskManager* const gc_task_manager();

   static klassOop updated_int_array_klass_obj() {

     return _updated_int_array_klass_obj;

   }

   // Marking support

   static inline bool mark_obj(oop obj);

   // Check mark and maybe push on marking stack

   template <class T> static inline void mark_and_push(ParCompactionManager* cm,

                                                       T* p);

   // Compaction support.

   // Return true if p is in the range [beg_addr, end_addr).

   static inline bool is_in(HeapWord* p, HeapWord* beg_addr, HeapWord* end_addr);

   static inline bool is_in(oop* p, HeapWord* beg_addr, HeapWord* end_addr);

   // Convenience wrappers for per-space data kept in _space_info.

   static inline MutableSpace*     space(SpaceId space_id);

   static inline HeapWord*         new_top(SpaceId space_id);

   static inline HeapWord*         dense_prefix(SpaceId space_id);

   static inline ObjectStartArray* start_array(SpaceId space_id);

   // Return true if the klass should be updated.

   static inline bool should_update_klass(klassOop k);

   // Move and update the live objects in the specified space.

   static void move_and_update(ParCompactionManager* cm, SpaceId space_id);

   // Process the end of the given region range in the dense prefix.

   // This includes saving any object not updated.

   static void dense_prefix_regions_epilogue(ParCompactionManager* cm,

                                             size_t region_start_index,

                                             size_t region_end_index,

                                             idx_t exiting_object_offset,

                                             idx_t region_offset_start,

                                             idx_t region_offset_end);

   // Update a region in the dense prefix.  For each live object

   // in the region, update it's interior references.  For each

   // dead object, fill it with deadwood. Dead space at the end

   // of a region range will be filled to the start of the next

   // live object regardless of the region_index_end.  None of the

   // objects in the dense prefix move and dead space is dead

   // (holds only dead objects that don't need any processing), so

   // dead space can be filled in any order.

   static void update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,

                                                   SpaceId space_id,

                                                   size_t region_index_start,

                                                   size_t region_index_end);

   // Return the address of the count + 1st live word in the range [beg, end).

   static HeapWord* skip_live_words(HeapWord* beg, HeapWord* end, size_t count);

   // Return the address of the word to be copied to dest_addr, which must be

   // aligned to a region boundary.

   static HeapWord* first_src_addr(HeapWord* const dest_addr,

                                   SpaceId src_space_id,

                                   size_t src_region_idx);

   // Determine the next source region, set closure.source() to the start of the

   // new region return the region index.  Parameter end_addr is the address one

   // beyond the end of source range just processed.  If necessary, switch to a

   // new source space and set src_space_id (in-out parameter) and src_space_top

   // (out parameter) accordingly.

   static size_t next_src_region(MoveAndUpdateClosure& closure,

                                 SpaceId& src_space_id,

                                 HeapWord*& src_space_top,

                                 HeapWord* end_addr);

   // Decrement the destination count for each non-empty source region in the

   // range [beg_region, region(region_align_up(end_addr))).  If the destination

   // count for a region goes to 0 and it needs to be filled, enqueue it.

   static void decrement_destination_counts(ParCompactionManager* cm,

                                            SpaceId src_space_id,

                                            size_t beg_region,

                                            HeapWord* end_addr);

   // Fill a region, copying objects from one or more source regions.

   static void fill_region(ParCompactionManager* cm, size_t region_idx);

   static void fill_and_update_region(ParCompactionManager* cm, size_t region) {

     fill_region(cm, region);

   }

   // Update the deferred objects in the space.

   static void update_deferred_objects(ParCompactionManager* cm, SpaceId id);

   static ParMarkBitMap* mark_bitmap() { return &_mark_bitmap; }

   static ParallelCompactData& summary_data() { return _summary_data; }

   static inline void adjust_pointer(oop* p)       { adjust_pointer(p, false); }

   static inline void adjust_pointer(narrowOop* p) { adjust_pointer(p, false); }

   // Reference Processing

   static ReferenceProcessor* const ref_processor() { return _ref_processor; }

   // Return the SpaceId for the given address.

   static SpaceId space_id(HeapWord* addr);

   // Time since last full gc (in milliseconds).

   static jlong millis_since_last_gc();

 #ifdef VALIDATE_MARK_SWEEP

   static void track_adjusted_pointer(void* p, bool isroot);

   static void check_adjust_pointer(void* p);

   static void track_interior_pointers(oop obj);

   static void check_interior_pointers();

   static void reset_live_oop_tracking(bool at_perm);

   static void register_live_oop(oop p, size_t size);

   static void validate_live_oop(oop p, size_t size);

   static void live_oop_moved_to(HeapWord* q, size_t size, HeapWord* compaction_top);

   static void compaction_complete();

   // Querying operation of RecordMarkSweepCompaction results.

   // Finds and prints the current base oop and offset for a word

   // within an oop that was live during the last GC. Helpful for

   // tracking down heap stomps.

   static void print_new_location_of_heap_address(HeapWord* q);

 #endif  // #ifdef VALIDATE_MARK_SWEEP

   // Call backs for class unloading

   // Update subklass/sibling/implementor links at end of marking.

   static void revisit_weak_klass_link(ParCompactionManager* cm, Klass* k);

   // Clear unmarked oops in MDOs at the end of marking.

   static void revisit_mdo(ParCompactionManager* cm, DataLayout* p);

 #ifndef PRODUCT

   // Debugging support.

   static const char* space_names[last_space_id];

   static void print_region_ranges();

   static void print_dense_prefix_stats(const char* const algorithm,

                                        const SpaceId id,

                                        const bool maximum_compaction,

                                        HeapWord* const addr);

   static void summary_phase_msg(SpaceId dst_space_id,

                                 HeapWord* dst_beg, HeapWord* dst_end,

                                 SpaceId src_space_id,

                                 HeapWord* src_beg, HeapWord* src_end);

 #endif  // #ifndef PRODUCT

 #ifdef  ASSERT

   // Sanity check the new location of a word in the heap.

   static inline void check_new_location(HeapWord* old_addr, HeapWord* new_addr);

   // Verify that all the regions have been emptied.

   static void verify_complete(SpaceId space_id);

 #endif  // #ifdef ASSERT

 };

 inline bool PSParallelCompact::mark_obj(oop obj) {

   const int obj_size = obj->size();

   if (mark_bitmap()->mark_obj(obj, obj_size)) {

     _summary_data.add_obj(obj, obj_size);

     return true;

   } else {

     return false;

   }

 }

 template <class T>

 inline void PSParallelCompact::follow_root(ParCompactionManager* cm, T* p) {

   assert(!Universe::heap()->is_in_reserved(p),

          "roots shouldn't be things within the heap");

 #ifdef VALIDATE_MARK_SWEEP

   if (ValidateMarkSweep) {

     guarantee(!_root_refs_stack->contains(p), "should only be in here once");

     _root_refs_stack->push(p);

   }

 #endif

   T heap_oop = oopDesc::load_heap_oop(p);

   if (!oopDesc::is_null(heap_oop)) {

     oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);

     if (mark_bitmap()->is_unmarked(obj)) {

       if (mark_obj(obj)) {

         obj->follow_contents(cm);

       }

     }

   }

   cm->follow_marking_stacks();

 }

 template <class T>

 inline void PSParallelCompact::mark_and_push(ParCompactionManager* cm, T* p) {

   T heap_oop = oopDesc::load_heap_oop(p);

   if (!oopDesc::is_null(heap_oop)) {

     oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);

     if (mark_bitmap()->is_unmarked(obj) && mark_obj(obj)) {

       cm->push(obj);

     }

   }

 }

 template <class T>

 inline void PSParallelCompact::adjust_pointer(T* p, bool isroot) {

   T heap_oop = oopDesc::load_heap_oop(p);

   if (!oopDesc::is_null(heap_oop)) {

     oop obj     = oopDesc::decode_heap_oop_not_null(heap_oop);

     oop new_obj = (oop)summary_data().calc_new_pointer(obj);

     assert(new_obj != NULL ||                     // is forwarding ptr?

            obj->is_shared(),                      // never forwarded?

            "should be forwarded");

     // Just always do the update unconditionally?

     if (new_obj != NULL) {

       assert(Universe::heap()->is_in_reserved(new_obj),

              "should be in object space");

       oopDesc::encode_store_heap_oop_not_null(p, new_obj);

     }

   }

   VALIDATE_MARK_SWEEP_ONLY(track_adjusted_pointer(p, isroot));

 }

 template <class T>

 inline void PSParallelCompact::KeepAliveClosure::do_oop_work(T* p) {

 #ifdef VALIDATE_MARK_SWEEP

   if (ValidateMarkSweep) {

     if (!Universe::heap()->is_in_reserved(p)) {

       _root_refs_stack->push(p);

     } else {

       _other_refs_stack->push(p);

     }

   }

 #endif

   mark_and_push(_compaction_manager, p);

 }

 inline bool PSParallelCompact::print_phases() {

   return _print_phases;

 }

 inline double PSParallelCompact::normal_distribution(double density) {

   assert(_dwl_initialized, "uninitialized");

   const double squared_term = (density - _dwl_mean) / _dwl_std_dev;

   return _dwl_first_term * exp(-0.5 * squared_term * squared_term);

 }

 inline bool

 PSParallelCompact::dead_space_crosses_boundary(const RegionData* region,

                                                idx_t bit)

 {

   assert(bit > 0, "cannot call this for the first bit/region");

   assert(_summary_data.region_to_addr(region) == _mark_bitmap.bit_to_addr(bit),

          "sanity check");

   // Dead space crosses the boundary if (1) a partial object does not extend

   // onto the region, (2) an object does not start at the beginning of the

   // region, and (3) an object does not end at the end of the prior region.

   return region->partial_obj_size() == 0 &&

     !_mark_bitmap.is_obj_beg(bit) &&

     !_mark_bitmap.is_obj_end(bit - 1);

 }

 inline bool

 PSParallelCompact::is_in(HeapWord* p, HeapWord* beg_addr, HeapWord* end_addr) {

   return p >= beg_addr && p < end_addr;

 }

 inline bool

 PSParallelCompact::is_in(oop* p, HeapWord* beg_addr, HeapWord* end_addr) {

   return is_in((HeapWord*)p, beg_addr, end_addr);

 }

 inline MutableSpace* PSParallelCompact::space(SpaceId id) {

   assert(id < last_space_id, "id out of range");

   return _space_info[id].space();

 }

 inline HeapWord* PSParallelCompact::new_top(SpaceId id) {

   assert(id < last_space_id, "id out of range");

   return _space_info[id].new_top();

 }

 inline HeapWord* PSParallelCompact::dense_prefix(SpaceId id) {

   assert(id < last_space_id, "id out of range");

   return _space_info[id].dense_prefix();

 }

 inline ObjectStartArray* PSParallelCompact::start_array(SpaceId id) {

   assert(id < last_space_id, "id out of range");

   return _space_info[id].start_array();

 }

 inline bool PSParallelCompact::should_update_klass(klassOop k) {

   return ((HeapWord*) k) >= dense_prefix(perm_space_id);

 }

 #ifdef ASSERT

 inline void

 PSParallelCompact::check_new_location(HeapWord* old_addr, HeapWord* new_addr)

 {

   assert(old_addr >= new_addr || space_id(old_addr) != space_id(new_addr),

          "must move left or to a different space");

   assert(is_object_aligned((intptr_t)old_addr) && is_object_aligned((intptr_t)new_addr),

          "checking alignment");

 }

 #endif // ASSERT

 class MoveAndUpdateClosure: public ParMarkBitMapClosure {

  public:

   inline MoveAndUpdateClosure(ParMarkBitMap* bitmap, ParCompactionManager* cm,

                               ObjectStartArray* start_array,

                               HeapWord* destination, size_t words);

   // Accessors.

   HeapWord* destination() const         { return _destination; }

   // If the object will fit (size <= words_remaining()), copy it to the current

   // destination, update the interior oops and the start array and return either

   // full (if the closure is full) or incomplete.  If the object will not fit,

   // return would_overflow.

   virtual IterationStatus do_addr(HeapWord* addr, size_t size);

   // Copy enough words to fill this closure, starting at source().  Interior

   // oops and the start array are not updated.  Return full.

   IterationStatus copy_until_full();

   // Copy enough words to fill this closure or to the end of an object,

   // whichever is smaller, starting at source().  Interior oops and the start

   // array are not updated.

   void copy_partial_obj();

  protected:

   // Update variables to indicate that word_count words were processed.

   inline void update_state(size_t word_count);

  protected:

   ObjectStartArray* const _start_array;

   HeapWord*               _destination;         // Next addr to be written.

 };

 inline

 MoveAndUpdateClosure::MoveAndUpdateClosure(ParMarkBitMap* bitmap,

                                            ParCompactionManager* cm,

                                            ObjectStartArray* start_array,

                                            HeapWord* destination,

                                            size_t words) :

   ParMarkBitMapClosure(bitmap, cm, words), _start_array(start_array)

 {

   _destination = destination;

 }

 inline void MoveAndUpdateClosure::update_state(size_t words)

 {

   decrement_words_remaining(words);

   _source += words;

   _destination += words;

 }

 class UpdateOnlyClosure: public ParMarkBitMapClosure {

  private:

   const PSParallelCompact::SpaceId _space_id;

   ObjectStartArray* const          _start_array;

  public:

   UpdateOnlyClosure(ParMarkBitMap* mbm,

                     ParCompactionManager* cm,

                     PSParallelCompact::SpaceId space_id);

   // Update the object.

   virtual IterationStatus do_addr(HeapWord* addr, size_t words);

   inline void do_addr(HeapWord* addr);

 };

 inline void UpdateOnlyClosure::do_addr(HeapWord* addr)

 {

   _start_array->allocate_block(addr);

   oop(addr)->update_contents(compaction_manager());

 }

 class FillClosure: public ParMarkBitMapClosure

 {

 public:

   FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :

     ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),

     _start_array(PSParallelCompact::start_array(space_id))

   {

     assert(space_id == PSParallelCompact::perm_space_id ||

            space_id == PSParallelCompact::old_space_id,

            "cannot use FillClosure in the young gen");

   }

   virtual IterationStatus do_addr(HeapWord* addr, size_t size) {

     CollectedHeap::fill_with_objects(addr, size);

     HeapWord* const end = addr + size;

     do {

       _start_array->allocate_block(addr);

       addr += oop(addr)->size();

     } while (addr < end);

     return ParMarkBitMap::incomplete;

   }

 private:

   ObjectStartArray* const _start_array;

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSPARALLELCOMPACT_HPP