jdk8-mips64-public/hotspot: src/share/vm/memory/blockOffsetTable.hpp@710a3c8b516e (annotated)

src/share/vm/memory/blockOffsetTable.hpp@710a3c8b516e (annotated)

src/share/vm/memory/blockOffsetTable.hpp

Tue, 08 Aug 2017 15:57:29 +0800

author: aoqi
date: Tue, 08 Aug 2017 15:57:29 +0800
changeset 6876: 710a3c8b516e
parent 4061: 859cd1a76f8a
parent 0: f90c822e73f8
permissions: -rw-r--r--

merge

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

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/memory/blockOffsetTable.hpp@710a3c8b516e (annotated)

src/share/vm/memory/blockOffsetTable.hpp