1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/memory/blockOffsetTable.hpp Wed Apr 27 01:25:04 2016 +0800
1.3 @@ -0,0 +1,566 @@
1.4 +/*
1.5 + * Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.23 + * or visit www.oracle.com if you need additional information or have any
1.24 + * questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#ifndef SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP
1.29 +#define SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP
1.30 +
1.31 +#include "memory/memRegion.hpp"
1.32 +#include "runtime/virtualspace.hpp"
1.33 +#include "utilities/globalDefinitions.hpp"
1.34 +
1.35 +// The CollectedHeap type requires subtypes to implement a method
1.36 +// "block_start". For some subtypes, notably generational
1.37 +// systems using card-table-based write barriers, the efficiency of this
1.38 +// operation may be important. Implementations of the "BlockOffsetArray"
1.39 +// class may be useful in providing such efficient implementations.
1.40 +//
1.41 +// BlockOffsetTable (abstract)
1.42 +// - BlockOffsetArray (abstract)
1.43 +// - BlockOffsetArrayNonContigSpace
1.44 +// - BlockOffsetArrayContigSpace
1.45 +//
1.46 +
1.47 +class ContiguousSpace;
1.48 +
1.49 +//////////////////////////////////////////////////////////////////////////
1.50 +// The BlockOffsetTable "interface"
1.51 +//////////////////////////////////////////////////////////////////////////
1.52 +class BlockOffsetTable VALUE_OBJ_CLASS_SPEC {
1.53 + friend class VMStructs;
1.54 +protected:
1.55 + // These members describe the region covered by the table.
1.56 +
1.57 + // The space this table is covering.
1.58 + HeapWord* _bottom; // == reserved.start
1.59 + HeapWord* _end; // End of currently allocated region.
1.60 +
1.61 +public:
1.62 + // Initialize the table to cover the given space.
1.63 + // The contents of the initial table are undefined.
1.64 + BlockOffsetTable(HeapWord* bottom, HeapWord* end):
1.65 + _bottom(bottom), _end(end) {
1.66 + assert(_bottom <= _end, "arguments out of order");
1.67 + }
1.68 +
1.69 + // Note that the committed size of the covered space may have changed,
1.70 + // so the table size might also wish to change.
1.71 + virtual void resize(size_t new_word_size) = 0;
1.72 +
1.73 + virtual void set_bottom(HeapWord* new_bottom) {
1.74 + assert(new_bottom <= _end, "new_bottom > _end");
1.75 + _bottom = new_bottom;
1.76 + resize(pointer_delta(_end, _bottom));
1.77 + }
1.78 +
1.79 + // Requires "addr" to be contained by a block, and returns the address of
1.80 + // the start of that block.
1.81 + virtual HeapWord* block_start_unsafe(const void* addr) const = 0;
1.82 +
1.83 + // Returns the address of the start of the block containing "addr", or
1.84 + // else "null" if it is covered by no block.
1.85 + HeapWord* block_start(const void* addr) const;
1.86 +};
1.87 +
1.88 +//////////////////////////////////////////////////////////////////////////
1.89 +// One implementation of "BlockOffsetTable," the BlockOffsetArray,
1.90 +// divides the covered region into "N"-word subregions (where
1.91 +// "N" = 2^"LogN". An array with an entry for each such subregion
1.92 +// indicates how far back one must go to find the start of the
1.93 +// chunk that includes the first word of the subregion.
1.94 +//
1.95 +// Each BlockOffsetArray is owned by a Space. However, the actual array
1.96 +// may be shared by several BlockOffsetArrays; this is useful
1.97 +// when a single resizable area (such as a generation) is divided up into
1.98 +// several spaces in which contiguous allocation takes place. (Consider,
1.99 +// for example, the garbage-first generation.)
1.100 +
1.101 +// Here is the shared array type.
1.102 +//////////////////////////////////////////////////////////////////////////
1.103 +// BlockOffsetSharedArray
1.104 +//////////////////////////////////////////////////////////////////////////
1.105 +class BlockOffsetSharedArray: public CHeapObj<mtGC> {
1.106 + friend class BlockOffsetArray;
1.107 + friend class BlockOffsetArrayNonContigSpace;
1.108 + friend class BlockOffsetArrayContigSpace;
1.109 + friend class VMStructs;
1.110 +
1.111 + private:
1.112 + enum SomePrivateConstants {
1.113 + LogN = 9,
1.114 + LogN_words = LogN - LogHeapWordSize,
1.115 + N_bytes = 1 << LogN,
1.116 + N_words = 1 << LogN_words
1.117 + };
1.118 +
1.119 + bool _init_to_zero;
1.120 +
1.121 + // The reserved region covered by the shared array.
1.122 + MemRegion _reserved;
1.123 +
1.124 + // End of the current committed region.
1.125 + HeapWord* _end;
1.126 +
1.127 + // Array for keeping offsets for retrieving object start fast given an
1.128 + // address.
1.129 + VirtualSpace _vs;
1.130 + u_char* _offset_array; // byte array keeping backwards offsets
1.131 +
1.132 + protected:
1.133 + // Bounds checking accessors:
1.134 + // For performance these have to devolve to array accesses in product builds.
1.135 + u_char offset_array(size_t index) const {
1.136 + assert(index < _vs.committed_size(), "index out of range");
1.137 + return _offset_array[index];
1.138 + }
1.139 + // An assertion-checking helper method for the set_offset_array() methods below.
1.140 + void check_reducing_assertion(bool reducing);
1.141 +
1.142 + void set_offset_array(size_t index, u_char offset, bool reducing = false) {
1.143 + check_reducing_assertion(reducing);
1.144 + assert(index < _vs.committed_size(), "index out of range");
1.145 + assert(!reducing || _offset_array[index] >= offset, "Not reducing");
1.146 + _offset_array[index] = offset;
1.147 + }
1.148 +
1.149 + void set_offset_array(size_t index, HeapWord* high, HeapWord* low, bool reducing = false) {
1.150 + check_reducing_assertion(reducing);
1.151 + assert(index < _vs.committed_size(), "index out of range");
1.152 + assert(high >= low, "addresses out of order");
1.153 + assert(pointer_delta(high, low) <= N_words, "offset too large");
1.154 + assert(!reducing || _offset_array[index] >= (u_char)pointer_delta(high, low),
1.155 + "Not reducing");
1.156 + _offset_array[index] = (u_char)pointer_delta(high, low);
1.157 + }
1.158 +
1.159 + void set_offset_array(HeapWord* left, HeapWord* right, u_char offset, bool reducing = false) {
1.160 + check_reducing_assertion(reducing);
1.161 + assert(index_for(right - 1) < _vs.committed_size(),
1.162 + "right address out of range");
1.163 + assert(left < right, "Heap addresses out of order");
1.164 + size_t num_cards = pointer_delta(right, left) >> LogN_words;
1.165 +
1.166 + // Below, we may use an explicit loop instead of memset()
1.167 + // because on certain platforms memset() can give concurrent
1.168 + // readers "out-of-thin-air," phantom zeros; see 6948537.
1.169 + if (UseMemSetInBOT) {
1.170 + memset(&_offset_array[index_for(left)], offset, num_cards);
1.171 + } else {
1.172 + size_t i = index_for(left);
1.173 + const size_t end = i + num_cards;
1.174 + for (; i < end; i++) {
1.175 + // Elided until CR 6977974 is fixed properly.
1.176 + // assert(!reducing || _offset_array[i] >= offset, "Not reducing");
1.177 + _offset_array[i] = offset;
1.178 + }
1.179 + }
1.180 + }
1.181 +
1.182 + void set_offset_array(size_t left, size_t right, u_char offset, bool reducing = false) {
1.183 + check_reducing_assertion(reducing);
1.184 + assert(right < _vs.committed_size(), "right address out of range");
1.185 + assert(left <= right, "indexes out of order");
1.186 + size_t num_cards = right - left + 1;
1.187 +
1.188 + // Below, we may use an explicit loop instead of memset
1.189 + // because on certain platforms memset() can give concurrent
1.190 + // readers "out-of-thin-air," phantom zeros; see 6948537.
1.191 + if (UseMemSetInBOT) {
1.192 + memset(&_offset_array[left], offset, num_cards);
1.193 + } else {
1.194 + size_t i = left;
1.195 + const size_t end = i + num_cards;
1.196 + for (; i < end; i++) {
1.197 + // Elided until CR 6977974 is fixed properly.
1.198 + // assert(!reducing || _offset_array[i] >= offset, "Not reducing");
1.199 + _offset_array[i] = offset;
1.200 + }
1.201 + }
1.202 + }
1.203 +
1.204 + void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
1.205 + assert(index < _vs.committed_size(), "index out of range");
1.206 + assert(high >= low, "addresses out of order");
1.207 + assert(pointer_delta(high, low) <= N_words, "offset too large");
1.208 + assert(_offset_array[index] == pointer_delta(high, low),
1.209 + "Wrong offset");
1.210 + }
1.211 +
1.212 + bool is_card_boundary(HeapWord* p) const;
1.213 +
1.214 + // Return the number of slots needed for an offset array
1.215 + // that covers mem_region_words words.
1.216 + // We always add an extra slot because if an object
1.217 + // ends on a card boundary we put a 0 in the next
1.218 + // offset array slot, so we want that slot always
1.219 + // to be reserved.
1.220 +
1.221 + size_t compute_size(size_t mem_region_words) {
1.222 + size_t number_of_slots = (mem_region_words / N_words) + 1;
1.223 + return ReservedSpace::allocation_align_size_up(number_of_slots);
1.224 + }
1.225 +
1.226 +public:
1.227 + // Initialize the table to cover from "base" to (at least)
1.228 + // "base + init_word_size". In the future, the table may be expanded
1.229 + // (see "resize" below) up to the size of "_reserved" (which must be at
1.230 + // least "init_word_size".) The contents of the initial table are
1.231 + // undefined; it is the responsibility of the constituent
1.232 + // BlockOffsetTable(s) to initialize cards.
1.233 + BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size);
1.234 +
1.235 + // Notes a change in the committed size of the region covered by the
1.236 + // table. The "new_word_size" may not be larger than the size of the
1.237 + // reserved region this table covers.
1.238 + void resize(size_t new_word_size);
1.239 +
1.240 + void set_bottom(HeapWord* new_bottom);
1.241 +
1.242 + // Whether entries should be initialized to zero. Used currently only for
1.243 + // error checking.
1.244 + void set_init_to_zero(bool val) { _init_to_zero = val; }
1.245 + bool init_to_zero() { return _init_to_zero; }
1.246 +
1.247 + // Updates all the BlockOffsetArray's sharing this shared array to
1.248 + // reflect the current "top"'s of their spaces.
1.249 + void update_offset_arrays(); // Not yet implemented!
1.250 +
1.251 + // Return the appropriate index into "_offset_array" for "p".
1.252 + size_t index_for(const void* p) const;
1.253 +
1.254 + // Return the address indicating the start of the region corresponding to
1.255 + // "index" in "_offset_array".
1.256 + HeapWord* address_for_index(size_t index) const;
1.257 +
1.258 + // Return the address "p" incremented by the size of
1.259 + // a region. This method does not align the address
1.260 + // returned to the start of a region. It is a simple
1.261 + // primitive.
1.262 + HeapWord* inc_by_region_size(HeapWord* p) const { return p + N_words; }
1.263 +};
1.264 +
1.265 +//////////////////////////////////////////////////////////////////////////
1.266 +// The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray.
1.267 +//////////////////////////////////////////////////////////////////////////
1.268 +class BlockOffsetArray: public BlockOffsetTable {
1.269 + friend class VMStructs;
1.270 + friend class G1BlockOffsetArray; // temp. until we restructure and cleanup
1.271 + protected:
1.272 + // The following enums are used by do_block_internal() below
1.273 + enum Action {
1.274 + Action_single, // BOT records a single block (see single_block())
1.275 + Action_mark, // BOT marks the start of a block (see mark_block())
1.276 + Action_check // Check that BOT records block correctly
1.277 + // (see verify_single_block()).
1.278 + };
1.279 +
1.280 + enum SomePrivateConstants {
1.281 + N_words = BlockOffsetSharedArray::N_words,
1.282 + LogN = BlockOffsetSharedArray::LogN,
1.283 + // entries "e" of at least N_words mean "go back by Base^(e-N_words)."
1.284 + // All entries are less than "N_words + N_powers".
1.285 + LogBase = 4,
1.286 + Base = (1 << LogBase),
1.287 + N_powers = 14
1.288 + };
1.289 +
1.290 + static size_t power_to_cards_back(uint i) {
1.291 + return (size_t)1 << (LogBase * i);
1.292 + }
1.293 + static size_t power_to_words_back(uint i) {
1.294 + return power_to_cards_back(i) * N_words;
1.295 + }
1.296 + static size_t entry_to_cards_back(u_char entry) {
1.297 + assert(entry >= N_words, "Precondition");
1.298 + return power_to_cards_back(entry - N_words);
1.299 + }
1.300 + static size_t entry_to_words_back(u_char entry) {
1.301 + assert(entry >= N_words, "Precondition");
1.302 + return power_to_words_back(entry - N_words);
1.303 + }
1.304 +
1.305 + // The shared array, which is shared with other BlockOffsetArray's
1.306 + // corresponding to different spaces within a generation or span of
1.307 + // memory.
1.308 + BlockOffsetSharedArray* _array;
1.309 +
1.310 + // The space that owns this subregion.
1.311 + Space* _sp;
1.312 +
1.313 + // If true, array entries are initialized to 0; otherwise, they are
1.314 + // initialized to point backwards to the beginning of the covered region.
1.315 + bool _init_to_zero;
1.316 +
1.317 + // An assertion-checking helper method for the set_remainder*() methods below.
1.318 + void check_reducing_assertion(bool reducing) { _array->check_reducing_assertion(reducing); }
1.319 +
1.320 + // Sets the entries
1.321 + // corresponding to the cards starting at "start" and ending at "end"
1.322 + // to point back to the card before "start": the interval [start, end)
1.323 + // is right-open. The last parameter, reducing, indicates whether the
1.324 + // updates to individual entries always reduce the entry from a higher
1.325 + // to a lower value. (For example this would hold true during a temporal
1.326 + // regime during which only block splits were updating the BOT.
1.327 + void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing = false);
1.328 + // Same as above, except that the args here are a card _index_ interval
1.329 + // that is closed: [start_index, end_index]
1.330 + void set_remainder_to_point_to_start_incl(size_t start, size_t end, bool reducing = false);
1.331 +
1.332 + // A helper function for BOT adjustment/verification work
1.333 + void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action, bool reducing = false);
1.334 +
1.335 + public:
1.336 + // The space may not have its bottom and top set yet, which is why the
1.337 + // region is passed as a parameter. If "init_to_zero" is true, the
1.338 + // elements of the array are initialized to zero. Otherwise, they are
1.339 + // initialized to point backwards to the beginning.
1.340 + BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr,
1.341 + bool init_to_zero_);
1.342 +
1.343 + // Note: this ought to be part of the constructor, but that would require
1.344 + // "this" to be passed as a parameter to a member constructor for
1.345 + // the containing concrete subtype of Space.
1.346 + // This would be legal C++, but MS VC++ doesn't allow it.
1.347 + void set_space(Space* sp) { _sp = sp; }
1.348 +
1.349 + // Resets the covered region to the given "mr".
1.350 + void set_region(MemRegion mr) {
1.351 + _bottom = mr.start();
1.352 + _end = mr.end();
1.353 + }
1.354 +
1.355 + // Note that the committed size of the covered space may have changed,
1.356 + // so the table size might also wish to change.
1.357 + virtual void resize(size_t new_word_size) {
1.358 + HeapWord* new_end = _bottom + new_word_size;
1.359 + if (_end < new_end && !init_to_zero()) {
1.360 + // verify that the old and new boundaries are also card boundaries
1.361 + assert(_array->is_card_boundary(_end),
1.362 + "_end not a card boundary");
1.363 + assert(_array->is_card_boundary(new_end),
1.364 + "new _end would not be a card boundary");
1.365 + // set all the newly added cards
1.366 + _array->set_offset_array(_end, new_end, N_words);
1.367 + }
1.368 + _end = new_end; // update _end
1.369 + }
1.370 +
1.371 + // Adjust the BOT to show that it has a single block in the
1.372 + // range [blk_start, blk_start + size). All necessary BOT
1.373 + // cards are adjusted, but _unallocated_block isn't.
1.374 + void single_block(HeapWord* blk_start, HeapWord* blk_end);
1.375 + void single_block(HeapWord* blk, size_t size) {
1.376 + single_block(blk, blk + size);
1.377 + }
1.378 +
1.379 + // When the alloc_block() call returns, the block offset table should
1.380 + // have enough information such that any subsequent block_start() call
1.381 + // with an argument equal to an address that is within the range
1.382 + // [blk_start, blk_end) would return the value blk_start, provided
1.383 + // there have been no calls in between that reset this information
1.384 + // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call
1.385 + // for an appropriate range covering the said interval).
1.386 + // These methods expect to be called with [blk_start, blk_end)
1.387 + // representing a block of memory in the heap.
1.388 + virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
1.389 + void alloc_block(HeapWord* blk, size_t size) {
1.390 + alloc_block(blk, blk + size);
1.391 + }
1.392 +
1.393 + // If true, initialize array slots with no allocated blocks to zero.
1.394 + // Otherwise, make them point back to the front.
1.395 + bool init_to_zero() { return _init_to_zero; }
1.396 + // Corresponding setter
1.397 + void set_init_to_zero(bool val) {
1.398 + _init_to_zero = val;
1.399 + assert(_array != NULL, "_array should be non-NULL");
1.400 + _array->set_init_to_zero(val);
1.401 + }
1.402 +
1.403 + // Debugging
1.404 + // Return the index of the last entry in the "active" region.
1.405 + virtual size_t last_active_index() const = 0;
1.406 + // Verify the block offset table
1.407 + void verify() const;
1.408 + void check_all_cards(size_t left_card, size_t right_card) const;
1.409 +};
1.410 +
1.411 +////////////////////////////////////////////////////////////////////////////
1.412 +// A subtype of BlockOffsetArray that takes advantage of the fact
1.413 +// that its underlying space is a NonContiguousSpace, so that some
1.414 +// specialized interfaces can be made available for spaces that
1.415 +// manipulate the table.
1.416 +////////////////////////////////////////////////////////////////////////////
1.417 +class BlockOffsetArrayNonContigSpace: public BlockOffsetArray {
1.418 + friend class VMStructs;
1.419 + private:
1.420 + // The portion [_unallocated_block, _sp.end()) of the space that
1.421 + // is a single block known not to contain any objects.
1.422 + // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag.
1.423 + HeapWord* _unallocated_block;
1.424 +
1.425 + public:
1.426 + BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
1.427 + BlockOffsetArray(array, mr, false),
1.428 + _unallocated_block(_bottom) { }
1.429 +
1.430 + // accessor
1.431 + HeapWord* unallocated_block() const {
1.432 + assert(BlockOffsetArrayUseUnallocatedBlock,
1.433 + "_unallocated_block is not being maintained");
1.434 + return _unallocated_block;
1.435 + }
1.436 +
1.437 + void set_unallocated_block(HeapWord* block) {
1.438 + assert(BlockOffsetArrayUseUnallocatedBlock,
1.439 + "_unallocated_block is not being maintained");
1.440 + assert(block >= _bottom && block <= _end, "out of range");
1.441 + _unallocated_block = block;
1.442 + }
1.443 +
1.444 + // These methods expect to be called with [blk_start, blk_end)
1.445 + // representing a block of memory in the heap.
1.446 + void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
1.447 + void alloc_block(HeapWord* blk, size_t size) {
1.448 + alloc_block(blk, blk + size);
1.449 + }
1.450 +
1.451 + // The following methods are useful and optimized for a
1.452 + // non-contiguous space.
1.453 +
1.454 + // Given a block [blk_start, blk_start + full_blk_size), and
1.455 + // a left_blk_size < full_blk_size, adjust the BOT to show two
1.456 + // blocks [blk_start, blk_start + left_blk_size) and
1.457 + // [blk_start + left_blk_size, blk_start + full_blk_size).
1.458 + // It is assumed (and verified in the non-product VM) that the
1.459 + // BOT was correct for the original block.
1.460 + void split_block(HeapWord* blk_start, size_t full_blk_size,
1.461 + size_t left_blk_size);
1.462 +
1.463 + // Adjust BOT to show that it has a block in the range
1.464 + // [blk_start, blk_start + size). Only the first card
1.465 + // of BOT is touched. It is assumed (and verified in the
1.466 + // non-product VM) that the remaining cards of the block
1.467 + // are correct.
1.468 + void mark_block(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false);
1.469 + void mark_block(HeapWord* blk, size_t size, bool reducing = false) {
1.470 + mark_block(blk, blk + size, reducing);
1.471 + }
1.472 +
1.473 + // Adjust _unallocated_block to indicate that a particular
1.474 + // block has been newly allocated or freed. It is assumed (and
1.475 + // verified in the non-product VM) that the BOT is correct for
1.476 + // the given block.
1.477 + void allocated(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false) {
1.478 + // Verify that the BOT shows [blk, blk + blk_size) to be one block.
1.479 + verify_single_block(blk_start, blk_end);
1.480 + if (BlockOffsetArrayUseUnallocatedBlock) {
1.481 + _unallocated_block = MAX2(_unallocated_block, blk_end);
1.482 + }
1.483 + }
1.484 +
1.485 + void allocated(HeapWord* blk, size_t size, bool reducing = false) {
1.486 + allocated(blk, blk + size, reducing);
1.487 + }
1.488 +
1.489 + void freed(HeapWord* blk_start, HeapWord* blk_end);
1.490 + void freed(HeapWord* blk, size_t size);
1.491 +
1.492 + HeapWord* block_start_unsafe(const void* addr) const;
1.493 +
1.494 + // Requires "addr" to be the start of a card and returns the
1.495 + // start of the block that contains the given address.
1.496 + HeapWord* block_start_careful(const void* addr) const;
1.497 +
1.498 + // Verification & debugging: ensure that the offset table reflects
1.499 + // the fact that the block [blk_start, blk_end) or [blk, blk + size)
1.500 + // is a single block of storage. NOTE: can't const this because of
1.501 + // call to non-const do_block_internal() below.
1.502 + void verify_single_block(HeapWord* blk_start, HeapWord* blk_end)
1.503 + PRODUCT_RETURN;
1.504 + void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN;
1.505 +
1.506 + // Verify that the given block is before _unallocated_block
1.507 + void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end)
1.508 + const PRODUCT_RETURN;
1.509 + void verify_not_unallocated(HeapWord* blk, size_t size)
1.510 + const PRODUCT_RETURN;
1.511 +
1.512 + // Debugging support
1.513 + virtual size_t last_active_index() const;
1.514 +};
1.515 +
1.516 +////////////////////////////////////////////////////////////////////////////
1.517 +// A subtype of BlockOffsetArray that takes advantage of the fact
1.518 +// that its underlying space is a ContiguousSpace, so that its "active"
1.519 +// region can be more efficiently tracked (than for a non-contiguous space).
1.520 +////////////////////////////////////////////////////////////////////////////
1.521 +class BlockOffsetArrayContigSpace: public BlockOffsetArray {
1.522 + friend class VMStructs;
1.523 + private:
1.524 + // allocation boundary at which offset array must be updated
1.525 + HeapWord* _next_offset_threshold;
1.526 + size_t _next_offset_index; // index corresponding to that boundary
1.527 +
1.528 + // Work function when allocation start crosses threshold.
1.529 + void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end);
1.530 +
1.531 + public:
1.532 + BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
1.533 + BlockOffsetArray(array, mr, true) {
1.534 + _next_offset_threshold = NULL;
1.535 + _next_offset_index = 0;
1.536 + }
1.537 +
1.538 + void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); }
1.539 +
1.540 + // Initialize the threshold for an empty heap.
1.541 + HeapWord* initialize_threshold();
1.542 + // Zero out the entry for _bottom (offset will be zero)
1.543 + void zero_bottom_entry();
1.544 +
1.545 + // Return the next threshold, the point at which the table should be
1.546 + // updated.
1.547 + HeapWord* threshold() const { return _next_offset_threshold; }
1.548 +
1.549 + // In general, these methods expect to be called with
1.550 + // [blk_start, blk_end) representing a block of memory in the heap.
1.551 + // In this implementation, however, we are OK even if blk_start and/or
1.552 + // blk_end are NULL because NULL is represented as 0, and thus
1.553 + // never exceeds the "_next_offset_threshold".
1.554 + void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
1.555 + if (blk_end > _next_offset_threshold) {
1.556 + alloc_block_work(blk_start, blk_end);
1.557 + }
1.558 + }
1.559 + void alloc_block(HeapWord* blk, size_t size) {
1.560 + alloc_block(blk, blk + size);
1.561 + }
1.562 +
1.563 + HeapWord* block_start_unsafe(const void* addr) const;
1.564 +
1.565 + // Debugging support
1.566 + virtual size_t last_active_index() const;
1.567 +};
1.568 +
1.569 +#endif // SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP
