duke@435: /*
coleenp@4037:  * Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #ifndef SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP
stefank@2314: #define SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP
stefank@2314: 
stefank@2314: #include "memory/memRegion.hpp"
stefank@2314: #include "runtime/virtualspace.hpp"
stefank@2314: #include "utilities/globalDefinitions.hpp"
stefank@2314: 
duke@435: // The CollectedHeap type requires subtypes to implement a method
duke@435: // "block_start".  For some subtypes, notably generational
duke@435: // systems using card-table-based write barriers, the efficiency of this
duke@435: // operation may be important.  Implementations of the "BlockOffsetArray"
duke@435: // class may be useful in providing such efficient implementations.
duke@435: //
duke@435: // BlockOffsetTable (abstract)
duke@435: //   - BlockOffsetArray (abstract)
duke@435: //     - BlockOffsetArrayNonContigSpace
duke@435: //     - BlockOffsetArrayContigSpace
duke@435: //
duke@435: 
duke@435: class ContiguousSpace;
duke@435: 
duke@435: //////////////////////////////////////////////////////////////////////////
duke@435: // The BlockOffsetTable "interface"
duke@435: //////////////////////////////////////////////////////////////////////////
duke@435: class BlockOffsetTable VALUE_OBJ_CLASS_SPEC {
duke@435:   friend class VMStructs;
duke@435: protected:
duke@435:   // These members describe the region covered by the table.
duke@435: 
duke@435:   // The space this table is covering.
duke@435:   HeapWord* _bottom;    // == reserved.start
duke@435:   HeapWord* _end;       // End of currently allocated region.
duke@435: 
duke@435: public:
duke@435:   // Initialize the table to cover the given space.
duke@435:   // The contents of the initial table are undefined.
duke@435:   BlockOffsetTable(HeapWord* bottom, HeapWord* end):
duke@435:     _bottom(bottom), _end(end) {
duke@435:     assert(_bottom <= _end, "arguments out of order");
duke@435:   }
duke@435: 
duke@435:   // Note that the committed size of the covered space may have changed,
duke@435:   // so the table size might also wish to change.
duke@435:   virtual void resize(size_t new_word_size) = 0;
duke@435: 
duke@435:   virtual void set_bottom(HeapWord* new_bottom) {
duke@435:     assert(new_bottom <= _end, "new_bottom > _end");
duke@435:     _bottom = new_bottom;
duke@435:     resize(pointer_delta(_end, _bottom));
duke@435:   }
duke@435: 
duke@435:   // Requires "addr" to be contained by a block, and returns the address of
duke@435:   // the start of that block.
duke@435:   virtual HeapWord* block_start_unsafe(const void* addr) const = 0;
duke@435: 
duke@435:   // Returns the address of the start of the block containing "addr", or
duke@435:   // else "null" if it is covered by no block.
duke@435:   HeapWord* block_start(const void* addr) const;
duke@435: };
duke@435: 
duke@435: //////////////////////////////////////////////////////////////////////////
duke@435: // One implementation of "BlockOffsetTable," the BlockOffsetArray,
duke@435: // divides the covered region into "N"-word subregions (where
duke@435: // "N" = 2^"LogN".  An array with an entry for each such subregion
duke@435: // indicates how far back one must go to find the start of the
duke@435: // chunk that includes the first word of the subregion.
duke@435: //
duke@435: // Each BlockOffsetArray is owned by a Space.  However, the actual array
duke@435: // may be shared by several BlockOffsetArrays; this is useful
duke@435: // when a single resizable area (such as a generation) is divided up into
duke@435: // several spaces in which contiguous allocation takes place.  (Consider,
duke@435: // for example, the garbage-first generation.)
duke@435: 
duke@435: // Here is the shared array type.
duke@435: //////////////////////////////////////////////////////////////////////////
duke@435: // BlockOffsetSharedArray
duke@435: //////////////////////////////////////////////////////////////////////////
zgu@3900: class BlockOffsetSharedArray: public CHeapObj<mtGC> {
duke@435:   friend class BlockOffsetArray;
duke@435:   friend class BlockOffsetArrayNonContigSpace;
duke@435:   friend class BlockOffsetArrayContigSpace;
duke@435:   friend class VMStructs;
duke@435: 
duke@435:  private:
duke@435:   enum SomePrivateConstants {
duke@435:     LogN = 9,
duke@435:     LogN_words = LogN - LogHeapWordSize,
duke@435:     N_bytes = 1 << LogN,
duke@435:     N_words = 1 << LogN_words
duke@435:   };
duke@435: 
ysr@2071:   bool _init_to_zero;
ysr@2071: 
duke@435:   // The reserved region covered by the shared array.
duke@435:   MemRegion _reserved;
duke@435: 
duke@435:   // End of the current committed region.
duke@435:   HeapWord* _end;
duke@435: 
duke@435:   // Array for keeping offsets for retrieving object start fast given an
duke@435:   // address.
duke@435:   VirtualSpace _vs;
duke@435:   u_char* _offset_array;          // byte array keeping backwards offsets
duke@435: 
duke@435:  protected:
duke@435:   // Bounds checking accessors:
duke@435:   // For performance these have to devolve to array accesses in product builds.
duke@435:   u_char offset_array(size_t index) const {
duke@435:     assert(index < _vs.committed_size(), "index out of range");
duke@435:     return _offset_array[index];
duke@435:   }
ysr@2071:   // An assertion-checking helper method for the set_offset_array() methods below.
ysr@2071:   void check_reducing_assertion(bool reducing);
ysr@2071: 
ysr@2071:   void set_offset_array(size_t index, u_char offset, bool reducing = false) {
ysr@2071:     check_reducing_assertion(reducing);
duke@435:     assert(index < _vs.committed_size(), "index out of range");
ysr@2071:     assert(!reducing || _offset_array[index] >= offset, "Not reducing");
duke@435:     _offset_array[index] = offset;
duke@435:   }
ysr@2071: 
ysr@2071:   void set_offset_array(size_t index, HeapWord* high, HeapWord* low, bool reducing = false) {
ysr@2071:     check_reducing_assertion(reducing);
duke@435:     assert(index < _vs.committed_size(), "index out of range");
duke@435:     assert(high >= low, "addresses out of order");
duke@435:     assert(pointer_delta(high, low) <= N_words, "offset too large");
ysr@2071:     assert(!reducing || _offset_array[index] >=  (u_char)pointer_delta(high, low),
ysr@2071:            "Not reducing");
duke@435:     _offset_array[index] = (u_char)pointer_delta(high, low);
duke@435:   }
ysr@2071: 
ysr@2071:   void set_offset_array(HeapWord* left, HeapWord* right, u_char offset, bool reducing = false) {
ysr@2071:     check_reducing_assertion(reducing);
duke@435:     assert(index_for(right - 1) < _vs.committed_size(),
duke@435:            "right address out of range");
duke@435:     assert(left  < right, "Heap addresses out of order");
duke@435:     size_t num_cards = pointer_delta(right, left) >> LogN_words;
ysr@1873: 
ysr@1873:     // Below, we may use an explicit loop instead of memset()
ysr@1873:     // because on certain platforms memset() can give concurrent
ysr@1873:     // readers "out-of-thin-air," phantom zeros; see 6948537.
ysr@1873:     if (UseMemSetInBOT) {
ysr@1873:       memset(&_offset_array[index_for(left)], offset, num_cards);
ysr@1873:     } else {
ysr@1873:       size_t i = index_for(left);
ysr@1873:       const size_t end = i + num_cards;
ysr@1873:       for (; i < end; i++) {
ysr@2087:         // Elided until CR 6977974 is fixed properly.
ysr@2087:         // assert(!reducing || _offset_array[i] >= offset, "Not reducing");
ysr@1873:         _offset_array[i] = offset;
ysr@1873:       }
ysr@1873:     }
duke@435:   }
duke@435: 
ysr@2071:   void set_offset_array(size_t left, size_t right, u_char offset, bool reducing = false) {
ysr@2071:     check_reducing_assertion(reducing);
duke@435:     assert(right < _vs.committed_size(), "right address out of range");
duke@435:     assert(left  <= right, "indexes out of order");
duke@435:     size_t num_cards = right - left + 1;
ysr@1873: 
ysr@1873:     // Below, we may use an explicit loop instead of memset
ysr@1873:     // because on certain platforms memset() can give concurrent
ysr@1873:     // readers "out-of-thin-air," phantom zeros; see 6948537.
ysr@1873:     if (UseMemSetInBOT) {
ysr@1873:       memset(&_offset_array[left], offset, num_cards);
ysr@1873:     } else {
ysr@1873:       size_t i = left;
ysr@1873:       const size_t end = i + num_cards;
ysr@1873:       for (; i < end; i++) {
ysr@2087:         // Elided until CR 6977974 is fixed properly.
ysr@2087:         // assert(!reducing || _offset_array[i] >= offset, "Not reducing");
ysr@1873:         _offset_array[i] = offset;
ysr@1873:       }
ysr@1873:     }
duke@435:   }
duke@435: 
duke@435:   void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
duke@435:     assert(index < _vs.committed_size(), "index out of range");
duke@435:     assert(high >= low, "addresses out of order");
duke@435:     assert(pointer_delta(high, low) <= N_words, "offset too large");
duke@435:     assert(_offset_array[index] == pointer_delta(high, low),
duke@435:            "Wrong offset");
duke@435:   }
duke@435: 
duke@435:   bool is_card_boundary(HeapWord* p) const;
duke@435: 
duke@435:   // Return the number of slots needed for an offset array
duke@435:   // that covers mem_region_words words.
duke@435:   // We always add an extra slot because if an object
duke@435:   // ends on a card boundary we put a 0 in the next
duke@435:   // offset array slot, so we want that slot always
duke@435:   // to be reserved.
duke@435: 
duke@435:   size_t compute_size(size_t mem_region_words) {
duke@435:     size_t number_of_slots = (mem_region_words / N_words) + 1;
duke@435:     return ReservedSpace::allocation_align_size_up(number_of_slots);
duke@435:   }
duke@435: 
duke@435: public:
duke@435:   // Initialize the table to cover from "base" to (at least)
duke@435:   // "base + init_word_size".  In the future, the table may be expanded
duke@435:   // (see "resize" below) up to the size of "_reserved" (which must be at
duke@435:   // least "init_word_size".)  The contents of the initial table are
duke@435:   // undefined; it is the responsibility of the constituent
duke@435:   // BlockOffsetTable(s) to initialize cards.
duke@435:   BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size);
duke@435: 
duke@435:   // Notes a change in the committed size of the region covered by the
duke@435:   // table.  The "new_word_size" may not be larger than the size of the
duke@435:   // reserved region this table covers.
duke@435:   void resize(size_t new_word_size);
duke@435: 
duke@435:   void set_bottom(HeapWord* new_bottom);
duke@435: 
ysr@2071:   // Whether entries should be initialized to zero. Used currently only for
ysr@2071:   // error checking.
ysr@2071:   void set_init_to_zero(bool val) { _init_to_zero = val; }
ysr@2071:   bool init_to_zero() { return _init_to_zero; }
ysr@2071: 
duke@435:   // Updates all the BlockOffsetArray's sharing this shared array to
duke@435:   // reflect the current "top"'s of their spaces.
duke@435:   void update_offset_arrays();   // Not yet implemented!
duke@435: 
duke@435:   // Return the appropriate index into "_offset_array" for "p".
duke@435:   size_t index_for(const void* p) const;
duke@435: 
duke@435:   // Return the address indicating the start of the region corresponding to
duke@435:   // "index" in "_offset_array".
duke@435:   HeapWord* address_for_index(size_t index) const;
duke@435: 
jmasa@736:   // Return the address "p" incremented by the size of
jmasa@736:   // a region.  This method does not align the address
jmasa@736:   // returned to the start of a region.  It is a simple
jmasa@736:   // primitive.
jmasa@736:   HeapWord* inc_by_region_size(HeapWord* p) const { return p + N_words; }
duke@435: };
duke@435: 
duke@435: //////////////////////////////////////////////////////////////////////////
duke@435: // The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray.
duke@435: //////////////////////////////////////////////////////////////////////////
duke@435: class BlockOffsetArray: public BlockOffsetTable {
duke@435:   friend class VMStructs;
ysr@777:   friend class G1BlockOffsetArray; // temp. until we restructure and cleanup
duke@435:  protected:
duke@435:   // The following enums are used by do_block_internal() below
duke@435:   enum Action {
duke@435:     Action_single,      // BOT records a single block (see single_block())
duke@435:     Action_mark,        // BOT marks the start of a block (see mark_block())
duke@435:     Action_check        // Check that BOT records block correctly
duke@435:                         // (see verify_single_block()).
duke@435:   };
duke@435: 
duke@435:   enum SomePrivateConstants {
duke@435:     N_words = BlockOffsetSharedArray::N_words,
duke@435:     LogN    = BlockOffsetSharedArray::LogN,
duke@435:     // entries "e" of at least N_words mean "go back by Base^(e-N_words)."
duke@435:     // All entries are less than "N_words + N_powers".
duke@435:     LogBase = 4,
duke@435:     Base = (1 << LogBase),
duke@435:     N_powers = 14
duke@435:   };
duke@435: 
duke@435:   static size_t power_to_cards_back(uint i) {
brutisso@4061:     return (size_t)1 << (LogBase * i);
duke@435:   }
duke@435:   static size_t power_to_words_back(uint i) {
duke@435:     return power_to_cards_back(i) * N_words;
duke@435:   }
duke@435:   static size_t entry_to_cards_back(u_char entry) {
duke@435:     assert(entry >= N_words, "Precondition");
duke@435:     return power_to_cards_back(entry - N_words);
duke@435:   }
duke@435:   static size_t entry_to_words_back(u_char entry) {
duke@435:     assert(entry >= N_words, "Precondition");
duke@435:     return power_to_words_back(entry - N_words);
duke@435:   }
duke@435: 
duke@435:   // The shared array, which is shared with other BlockOffsetArray's
duke@435:   // corresponding to different spaces within a generation or span of
duke@435:   // memory.
duke@435:   BlockOffsetSharedArray* _array;
duke@435: 
duke@435:   // The space that owns this subregion.
duke@435:   Space* _sp;
duke@435: 
duke@435:   // If true, array entries are initialized to 0; otherwise, they are
duke@435:   // initialized to point backwards to the beginning of the covered region.
duke@435:   bool _init_to_zero;
duke@435: 
ysr@2071:   // An assertion-checking helper method for the set_remainder*() methods below.
ysr@2071:   void check_reducing_assertion(bool reducing) { _array->check_reducing_assertion(reducing); }
ysr@2071: 
duke@435:   // Sets the entries
duke@435:   // corresponding to the cards starting at "start" and ending at "end"
duke@435:   // to point back to the card before "start": the interval [start, end)
ysr@2071:   // is right-open. The last parameter, reducing, indicates whether the
ysr@2071:   // updates to individual entries always reduce the entry from a higher
ysr@2071:   // to a lower value. (For example this would hold true during a temporal
ysr@2071:   // regime during which only block splits were updating the BOT.
ysr@2071:   void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing = false);
duke@435:   // Same as above, except that the args here are a card _index_ interval
duke@435:   // that is closed: [start_index, end_index]
ysr@2071:   void set_remainder_to_point_to_start_incl(size_t start, size_t end, bool reducing = false);
duke@435: 
duke@435:   // A helper function for BOT adjustment/verification work
ysr@2071:   void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action, bool reducing = false);
duke@435: 
duke@435:  public:
duke@435:   // The space may not have its bottom and top set yet, which is why the
duke@435:   // region is passed as a parameter.  If "init_to_zero" is true, the
duke@435:   // elements of the array are initialized to zero.  Otherwise, they are
duke@435:   // initialized to point backwards to the beginning.
duke@435:   BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr,
ysr@2071:                    bool init_to_zero_);
duke@435: 
duke@435:   // Note: this ought to be part of the constructor, but that would require
duke@435:   // "this" to be passed as a parameter to a member constructor for
duke@435:   // the containing concrete subtype of Space.
duke@435:   // This would be legal C++, but MS VC++ doesn't allow it.
duke@435:   void set_space(Space* sp) { _sp = sp; }
duke@435: 
duke@435:   // Resets the covered region to the given "mr".
duke@435:   void set_region(MemRegion mr) {
duke@435:     _bottom = mr.start();
duke@435:     _end = mr.end();
duke@435:   }
duke@435: 
duke@435:   // Note that the committed size of the covered space may have changed,
duke@435:   // so the table size might also wish to change.
duke@435:   virtual void resize(size_t new_word_size) {
duke@435:     HeapWord* new_end = _bottom + new_word_size;
duke@435:     if (_end < new_end && !init_to_zero()) {
duke@435:       // verify that the old and new boundaries are also card boundaries
duke@435:       assert(_array->is_card_boundary(_end),
duke@435:              "_end not a card boundary");
duke@435:       assert(_array->is_card_boundary(new_end),
duke@435:              "new _end would not be a card boundary");
duke@435:       // set all the newly added cards
duke@435:       _array->set_offset_array(_end, new_end, N_words);
duke@435:     }
duke@435:     _end = new_end;  // update _end
duke@435:   }
duke@435: 
duke@435:   // Adjust the BOT to show that it has a single block in the
duke@435:   // range [blk_start, blk_start + size). All necessary BOT
duke@435:   // cards are adjusted, but _unallocated_block isn't.
duke@435:   void single_block(HeapWord* blk_start, HeapWord* blk_end);
duke@435:   void single_block(HeapWord* blk, size_t size) {
duke@435:     single_block(blk, blk + size);
duke@435:   }
duke@435: 
duke@435:   // When the alloc_block() call returns, the block offset table should
duke@435:   // have enough information such that any subsequent block_start() call
duke@435:   // with an argument equal to an address that is within the range
duke@435:   // [blk_start, blk_end) would return the value blk_start, provided
duke@435:   // there have been no calls in between that reset this information
duke@435:   // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call
duke@435:   // for an appropriate range covering the said interval).
duke@435:   // These methods expect to be called with [blk_start, blk_end)
duke@435:   // representing a block of memory in the heap.
duke@435:   virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
duke@435:   void alloc_block(HeapWord* blk, size_t size) {
duke@435:     alloc_block(blk, blk + size);
duke@435:   }
duke@435: 
duke@435:   // If true, initialize array slots with no allocated blocks to zero.
duke@435:   // Otherwise, make them point back to the front.
duke@435:   bool init_to_zero() { return _init_to_zero; }
ysr@2071:   // Corresponding setter
ysr@2071:   void set_init_to_zero(bool val) {
ysr@2071:     _init_to_zero = val;
ysr@2071:     assert(_array != NULL, "_array should be non-NULL");
ysr@2071:     _array->set_init_to_zero(val);
ysr@2071:   }
duke@435: 
duke@435:   // Debugging
duke@435:   // Return the index of the last entry in the "active" region.
duke@435:   virtual size_t last_active_index() const = 0;
duke@435:   // Verify the block offset table
duke@435:   void verify() const;
duke@435:   void check_all_cards(size_t left_card, size_t right_card) const;
duke@435: };
duke@435: 
duke@435: ////////////////////////////////////////////////////////////////////////////
duke@435: // A subtype of BlockOffsetArray that takes advantage of the fact
duke@435: // that its underlying space is a NonContiguousSpace, so that some
duke@435: // specialized interfaces can be made available for spaces that
duke@435: // manipulate the table.
duke@435: ////////////////////////////////////////////////////////////////////////////
duke@435: class BlockOffsetArrayNonContigSpace: public BlockOffsetArray {
duke@435:   friend class VMStructs;
duke@435:  private:
duke@435:   // The portion [_unallocated_block, _sp.end()) of the space that
duke@435:   // is a single block known not to contain any objects.
duke@435:   // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag.
duke@435:   HeapWord* _unallocated_block;
duke@435: 
duke@435:  public:
duke@435:   BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
duke@435:     BlockOffsetArray(array, mr, false),
duke@435:     _unallocated_block(_bottom) { }
duke@435: 
duke@435:   // accessor
duke@435:   HeapWord* unallocated_block() const {
duke@435:     assert(BlockOffsetArrayUseUnallocatedBlock,
duke@435:            "_unallocated_block is not being maintained");
duke@435:     return _unallocated_block;
duke@435:   }
duke@435: 
duke@435:   void set_unallocated_block(HeapWord* block) {
duke@435:     assert(BlockOffsetArrayUseUnallocatedBlock,
duke@435:            "_unallocated_block is not being maintained");
duke@435:     assert(block >= _bottom && block <= _end, "out of range");
duke@435:     _unallocated_block = block;
duke@435:   }
duke@435: 
duke@435:   // These methods expect to be called with [blk_start, blk_end)
duke@435:   // representing a block of memory in the heap.
duke@435:   void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
duke@435:   void alloc_block(HeapWord* blk, size_t size) {
duke@435:     alloc_block(blk, blk + size);
duke@435:   }
duke@435: 
duke@435:   // The following methods are useful and optimized for a
duke@435:   // non-contiguous space.
duke@435: 
duke@435:   // Given a block [blk_start, blk_start + full_blk_size), and
duke@435:   // a left_blk_size < full_blk_size, adjust the BOT to show two
duke@435:   // blocks [blk_start, blk_start + left_blk_size) and
duke@435:   // [blk_start + left_blk_size, blk_start + full_blk_size).
duke@435:   // It is assumed (and verified in the non-product VM) that the
duke@435:   // BOT was correct for the original block.
duke@435:   void split_block(HeapWord* blk_start, size_t full_blk_size,
duke@435:                            size_t left_blk_size);
duke@435: 
duke@435:   // Adjust BOT to show that it has a block in the range
duke@435:   // [blk_start, blk_start + size). Only the first card
duke@435:   // of BOT is touched. It is assumed (and verified in the
duke@435:   // non-product VM) that the remaining cards of the block
duke@435:   // are correct.
ysr@2071:   void mark_block(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false);
ysr@2071:   void mark_block(HeapWord* blk, size_t size, bool reducing = false) {
ysr@2071:     mark_block(blk, blk + size, reducing);
duke@435:   }
duke@435: 
duke@435:   // Adjust _unallocated_block to indicate that a particular
duke@435:   // block has been newly allocated or freed. It is assumed (and
duke@435:   // verified in the non-product VM) that the BOT is correct for
duke@435:   // the given block.
ysr@2071:   void allocated(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false) {
duke@435:     // Verify that the BOT shows [blk, blk + blk_size) to be one block.
duke@435:     verify_single_block(blk_start, blk_end);
duke@435:     if (BlockOffsetArrayUseUnallocatedBlock) {
duke@435:       _unallocated_block = MAX2(_unallocated_block, blk_end);
duke@435:     }
duke@435:   }
duke@435: 
ysr@2071:   void allocated(HeapWord* blk, size_t size, bool reducing = false) {
ysr@2071:     allocated(blk, blk + size, reducing);
duke@435:   }
duke@435: 
duke@435:   void freed(HeapWord* blk_start, HeapWord* blk_end);
ysr@2071:   void freed(HeapWord* blk, size_t size);
duke@435: 
duke@435:   HeapWord* block_start_unsafe(const void* addr) const;
duke@435: 
duke@435:   // Requires "addr" to be the start of a card and returns the
duke@435:   // start of the block that contains the given address.
duke@435:   HeapWord* block_start_careful(const void* addr) const;
duke@435: 
duke@435:   // Verification & debugging: ensure that the offset table reflects
duke@435:   // the fact that the block [blk_start, blk_end) or [blk, blk + size)
duke@435:   // is a single block of storage. NOTE: can't const this because of
duke@435:   // call to non-const do_block_internal() below.
duke@435:   void verify_single_block(HeapWord* blk_start, HeapWord* blk_end)
duke@435:     PRODUCT_RETURN;
duke@435:   void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN;
duke@435: 
duke@435:   // Verify that the given block is before _unallocated_block
duke@435:   void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end)
duke@435:     const PRODUCT_RETURN;
duke@435:   void verify_not_unallocated(HeapWord* blk, size_t size)
duke@435:     const PRODUCT_RETURN;
duke@435: 
duke@435:   // Debugging support
duke@435:   virtual size_t last_active_index() const;
duke@435: };
duke@435: 
duke@435: ////////////////////////////////////////////////////////////////////////////
duke@435: // A subtype of BlockOffsetArray that takes advantage of the fact
duke@435: // that its underlying space is a ContiguousSpace, so that its "active"
duke@435: // region can be more efficiently tracked (than for a non-contiguous space).
duke@435: ////////////////////////////////////////////////////////////////////////////
duke@435: class BlockOffsetArrayContigSpace: public BlockOffsetArray {
duke@435:   friend class VMStructs;
duke@435:  private:
duke@435:   // allocation boundary at which offset array must be updated
duke@435:   HeapWord* _next_offset_threshold;
duke@435:   size_t    _next_offset_index;      // index corresponding to that boundary
duke@435: 
duke@435:   // Work function when allocation start crosses threshold.
duke@435:   void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end);
duke@435: 
duke@435:  public:
duke@435:   BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
duke@435:     BlockOffsetArray(array, mr, true) {
duke@435:     _next_offset_threshold = NULL;
duke@435:     _next_offset_index = 0;
duke@435:   }
duke@435: 
duke@435:   void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); }
duke@435: 
duke@435:   // Initialize the threshold for an empty heap.
duke@435:   HeapWord* initialize_threshold();
duke@435:   // Zero out the entry for _bottom (offset will be zero)
duke@435:   void      zero_bottom_entry();
duke@435: 
duke@435:   // Return the next threshold, the point at which the table should be
duke@435:   // updated.
duke@435:   HeapWord* threshold() const { return _next_offset_threshold; }
duke@435: 
duke@435:   // In general, these methods expect to be called with
duke@435:   // [blk_start, blk_end) representing a block of memory in the heap.
duke@435:   // In this implementation, however, we are OK even if blk_start and/or
duke@435:   // blk_end are NULL because NULL is represented as 0, and thus
duke@435:   // never exceeds the "_next_offset_threshold".
duke@435:   void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
duke@435:     if (blk_end > _next_offset_threshold) {
duke@435:       alloc_block_work(blk_start, blk_end);
duke@435:     }
duke@435:   }
duke@435:   void alloc_block(HeapWord* blk, size_t size) {
duke@435:     alloc_block(blk, blk + size);
duke@435:   }
duke@435: 
duke@435:   HeapWord* block_start_unsafe(const void* addr) const;
duke@435: 
duke@435:   // Debugging support
duke@435:   virtual size_t last_active_index() const;
duke@435: };
stefank@2314: 
stefank@2314: #endif // SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP