1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/memory/blockOffsetTable.hpp Sat Dec 01 00:00:00 2007 +0000
1.3 @@ -0,0 +1,500 @@
1.4 +/*
1.5 + * Copyright 2000-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
1.23 + * CA 95054 USA or visit www.sun.com if you need additional information or
1.24 + * have any questions.
1.25 + *
1.26 + */
1.27 +
1.28 +// The CollectedHeap type requires subtypes to implement a method
1.29 +// "block_start". For some subtypes, notably generational
1.30 +// systems using card-table-based write barriers, the efficiency of this
1.31 +// operation may be important. Implementations of the "BlockOffsetArray"
1.32 +// class may be useful in providing such efficient implementations.
1.33 +//
1.34 +// BlockOffsetTable (abstract)
1.35 +// - BlockOffsetArray (abstract)
1.36 +// - BlockOffsetArrayNonContigSpace
1.37 +// - BlockOffsetArrayContigSpace
1.38 +//
1.39 +
1.40 +class ContiguousSpace;
1.41 +class SerializeOopClosure;
1.42 +
1.43 +//////////////////////////////////////////////////////////////////////////
1.44 +// The BlockOffsetTable "interface"
1.45 +//////////////////////////////////////////////////////////////////////////
1.46 +class BlockOffsetTable VALUE_OBJ_CLASS_SPEC {
1.47 + friend class VMStructs;
1.48 +protected:
1.49 + // These members describe the region covered by the table.
1.50 +
1.51 + // The space this table is covering.
1.52 + HeapWord* _bottom; // == reserved.start
1.53 + HeapWord* _end; // End of currently allocated region.
1.54 +
1.55 +public:
1.56 + // Initialize the table to cover the given space.
1.57 + // The contents of the initial table are undefined.
1.58 + BlockOffsetTable(HeapWord* bottom, HeapWord* end):
1.59 + _bottom(bottom), _end(end) {
1.60 + assert(_bottom <= _end, "arguments out of order");
1.61 + }
1.62 +
1.63 + // Note that the committed size of the covered space may have changed,
1.64 + // so the table size might also wish to change.
1.65 + virtual void resize(size_t new_word_size) = 0;
1.66 +
1.67 + virtual void set_bottom(HeapWord* new_bottom) {
1.68 + assert(new_bottom <= _end, "new_bottom > _end");
1.69 + _bottom = new_bottom;
1.70 + resize(pointer_delta(_end, _bottom));
1.71 + }
1.72 +
1.73 + // Requires "addr" to be contained by a block, and returns the address of
1.74 + // the start of that block.
1.75 + virtual HeapWord* block_start_unsafe(const void* addr) const = 0;
1.76 +
1.77 + // Returns the address of the start of the block containing "addr", or
1.78 + // else "null" if it is covered by no block.
1.79 + HeapWord* block_start(const void* addr) const;
1.80 +};
1.81 +
1.82 +//////////////////////////////////////////////////////////////////////////
1.83 +// One implementation of "BlockOffsetTable," the BlockOffsetArray,
1.84 +// divides the covered region into "N"-word subregions (where
1.85 +// "N" = 2^"LogN". An array with an entry for each such subregion
1.86 +// indicates how far back one must go to find the start of the
1.87 +// chunk that includes the first word of the subregion.
1.88 +//
1.89 +// Each BlockOffsetArray is owned by a Space. However, the actual array
1.90 +// may be shared by several BlockOffsetArrays; this is useful
1.91 +// when a single resizable area (such as a generation) is divided up into
1.92 +// several spaces in which contiguous allocation takes place. (Consider,
1.93 +// for example, the garbage-first generation.)
1.94 +
1.95 +// Here is the shared array type.
1.96 +//////////////////////////////////////////////////////////////////////////
1.97 +// BlockOffsetSharedArray
1.98 +//////////////////////////////////////////////////////////////////////////
1.99 +class BlockOffsetSharedArray: public CHeapObj {
1.100 + friend class BlockOffsetArray;
1.101 + friend class BlockOffsetArrayNonContigSpace;
1.102 + friend class BlockOffsetArrayContigSpace;
1.103 + friend class VMStructs;
1.104 +
1.105 + private:
1.106 + enum SomePrivateConstants {
1.107 + LogN = 9,
1.108 + LogN_words = LogN - LogHeapWordSize,
1.109 + N_bytes = 1 << LogN,
1.110 + N_words = 1 << LogN_words
1.111 + };
1.112 +
1.113 + // The reserved region covered by the shared array.
1.114 + MemRegion _reserved;
1.115 +
1.116 + // End of the current committed region.
1.117 + HeapWord* _end;
1.118 +
1.119 + // Array for keeping offsets for retrieving object start fast given an
1.120 + // address.
1.121 + VirtualSpace _vs;
1.122 + u_char* _offset_array; // byte array keeping backwards offsets
1.123 +
1.124 + protected:
1.125 + // Bounds checking accessors:
1.126 + // For performance these have to devolve to array accesses in product builds.
1.127 + u_char offset_array(size_t index) const {
1.128 + assert(index < _vs.committed_size(), "index out of range");
1.129 + return _offset_array[index];
1.130 + }
1.131 + void set_offset_array(size_t index, u_char offset) {
1.132 + assert(index < _vs.committed_size(), "index out of range");
1.133 + _offset_array[index] = offset;
1.134 + }
1.135 + void set_offset_array(size_t index, HeapWord* high, HeapWord* low) {
1.136 + assert(index < _vs.committed_size(), "index out of range");
1.137 + assert(high >= low, "addresses out of order");
1.138 + assert(pointer_delta(high, low) <= N_words, "offset too large");
1.139 + _offset_array[index] = (u_char)pointer_delta(high, low);
1.140 + }
1.141 + void set_offset_array(HeapWord* left, HeapWord* right, u_char offset) {
1.142 + assert(index_for(right - 1) < _vs.committed_size(),
1.143 + "right address out of range");
1.144 + assert(left < right, "Heap addresses out of order");
1.145 + size_t num_cards = pointer_delta(right, left) >> LogN_words;
1.146 + memset(&_offset_array[index_for(left)], offset, num_cards);
1.147 + }
1.148 +
1.149 + void set_offset_array(size_t left, size_t right, u_char offset) {
1.150 + assert(right < _vs.committed_size(), "right address out of range");
1.151 + assert(left <= right, "indexes out of order");
1.152 + size_t num_cards = right - left + 1;
1.153 + memset(&_offset_array[left], offset, num_cards);
1.154 + }
1.155 +
1.156 + void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
1.157 + assert(index < _vs.committed_size(), "index out of range");
1.158 + assert(high >= low, "addresses out of order");
1.159 + assert(pointer_delta(high, low) <= N_words, "offset too large");
1.160 + assert(_offset_array[index] == pointer_delta(high, low),
1.161 + "Wrong offset");
1.162 + }
1.163 +
1.164 + bool is_card_boundary(HeapWord* p) const;
1.165 +
1.166 + // Return the number of slots needed for an offset array
1.167 + // that covers mem_region_words words.
1.168 + // We always add an extra slot because if an object
1.169 + // ends on a card boundary we put a 0 in the next
1.170 + // offset array slot, so we want that slot always
1.171 + // to be reserved.
1.172 +
1.173 + size_t compute_size(size_t mem_region_words) {
1.174 + size_t number_of_slots = (mem_region_words / N_words) + 1;
1.175 + return ReservedSpace::allocation_align_size_up(number_of_slots);
1.176 + }
1.177 +
1.178 +public:
1.179 + // Initialize the table to cover from "base" to (at least)
1.180 + // "base + init_word_size". In the future, the table may be expanded
1.181 + // (see "resize" below) up to the size of "_reserved" (which must be at
1.182 + // least "init_word_size".) The contents of the initial table are
1.183 + // undefined; it is the responsibility of the constituent
1.184 + // BlockOffsetTable(s) to initialize cards.
1.185 + BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size);
1.186 +
1.187 + // Notes a change in the committed size of the region covered by the
1.188 + // table. The "new_word_size" may not be larger than the size of the
1.189 + // reserved region this table covers.
1.190 + void resize(size_t new_word_size);
1.191 +
1.192 + void set_bottom(HeapWord* new_bottom);
1.193 +
1.194 + // Updates all the BlockOffsetArray's sharing this shared array to
1.195 + // reflect the current "top"'s of their spaces.
1.196 + void update_offset_arrays(); // Not yet implemented!
1.197 +
1.198 + // Return the appropriate index into "_offset_array" for "p".
1.199 + size_t index_for(const void* p) const;
1.200 +
1.201 + // Return the address indicating the start of the region corresponding to
1.202 + // "index" in "_offset_array".
1.203 + HeapWord* address_for_index(size_t index) const;
1.204 +
1.205 + // Shared space support
1.206 + void serialize(SerializeOopClosure* soc, HeapWord* start, HeapWord* end);
1.207 +};
1.208 +
1.209 +//////////////////////////////////////////////////////////////////////////
1.210 +// The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray.
1.211 +//////////////////////////////////////////////////////////////////////////
1.212 +class BlockOffsetArray: public BlockOffsetTable {
1.213 + friend class VMStructs;
1.214 + protected:
1.215 + // The following enums are used by do_block_internal() below
1.216 + enum Action {
1.217 + Action_single, // BOT records a single block (see single_block())
1.218 + Action_mark, // BOT marks the start of a block (see mark_block())
1.219 + Action_check // Check that BOT records block correctly
1.220 + // (see verify_single_block()).
1.221 + };
1.222 +
1.223 + enum SomePrivateConstants {
1.224 + N_words = BlockOffsetSharedArray::N_words,
1.225 + LogN = BlockOffsetSharedArray::LogN,
1.226 + // entries "e" of at least N_words mean "go back by Base^(e-N_words)."
1.227 + // All entries are less than "N_words + N_powers".
1.228 + LogBase = 4,
1.229 + Base = (1 << LogBase),
1.230 + N_powers = 14
1.231 + };
1.232 +
1.233 + static size_t power_to_cards_back(uint i) {
1.234 + return 1 << (LogBase * i);
1.235 + }
1.236 + static size_t power_to_words_back(uint i) {
1.237 + return power_to_cards_back(i) * N_words;
1.238 + }
1.239 + static size_t entry_to_cards_back(u_char entry) {
1.240 + assert(entry >= N_words, "Precondition");
1.241 + return power_to_cards_back(entry - N_words);
1.242 + }
1.243 + static size_t entry_to_words_back(u_char entry) {
1.244 + assert(entry >= N_words, "Precondition");
1.245 + return power_to_words_back(entry - N_words);
1.246 + }
1.247 +
1.248 + // The shared array, which is shared with other BlockOffsetArray's
1.249 + // corresponding to different spaces within a generation or span of
1.250 + // memory.
1.251 + BlockOffsetSharedArray* _array;
1.252 +
1.253 + // The space that owns this subregion.
1.254 + Space* _sp;
1.255 +
1.256 + // If true, array entries are initialized to 0; otherwise, they are
1.257 + // initialized to point backwards to the beginning of the covered region.
1.258 + bool _init_to_zero;
1.259 +
1.260 + // Sets the entries
1.261 + // corresponding to the cards starting at "start" and ending at "end"
1.262 + // to point back to the card before "start": the interval [start, end)
1.263 + // is right-open.
1.264 + void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end);
1.265 + // Same as above, except that the args here are a card _index_ interval
1.266 + // that is closed: [start_index, end_index]
1.267 + void set_remainder_to_point_to_start_incl(size_t start, size_t end);
1.268 +
1.269 + // A helper function for BOT adjustment/verification work
1.270 + void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action);
1.271 +
1.272 + public:
1.273 + // The space may not have its bottom and top set yet, which is why the
1.274 + // region is passed as a parameter. If "init_to_zero" is true, the
1.275 + // elements of the array are initialized to zero. Otherwise, they are
1.276 + // initialized to point backwards to the beginning.
1.277 + BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr,
1.278 + bool init_to_zero);
1.279 +
1.280 + // Note: this ought to be part of the constructor, but that would require
1.281 + // "this" to be passed as a parameter to a member constructor for
1.282 + // the containing concrete subtype of Space.
1.283 + // This would be legal C++, but MS VC++ doesn't allow it.
1.284 + void set_space(Space* sp) { _sp = sp; }
1.285 +
1.286 + // Resets the covered region to the given "mr".
1.287 + void set_region(MemRegion mr) {
1.288 + _bottom = mr.start();
1.289 + _end = mr.end();
1.290 + }
1.291 +
1.292 + // Note that the committed size of the covered space may have changed,
1.293 + // so the table size might also wish to change.
1.294 + virtual void resize(size_t new_word_size) {
1.295 + HeapWord* new_end = _bottom + new_word_size;
1.296 + if (_end < new_end && !init_to_zero()) {
1.297 + // verify that the old and new boundaries are also card boundaries
1.298 + assert(_array->is_card_boundary(_end),
1.299 + "_end not a card boundary");
1.300 + assert(_array->is_card_boundary(new_end),
1.301 + "new _end would not be a card boundary");
1.302 + // set all the newly added cards
1.303 + _array->set_offset_array(_end, new_end, N_words);
1.304 + }
1.305 + _end = new_end; // update _end
1.306 + }
1.307 +
1.308 + // Adjust the BOT to show that it has a single block in the
1.309 + // range [blk_start, blk_start + size). All necessary BOT
1.310 + // cards are adjusted, but _unallocated_block isn't.
1.311 + void single_block(HeapWord* blk_start, HeapWord* blk_end);
1.312 + void single_block(HeapWord* blk, size_t size) {
1.313 + single_block(blk, blk + size);
1.314 + }
1.315 +
1.316 + // When the alloc_block() call returns, the block offset table should
1.317 + // have enough information such that any subsequent block_start() call
1.318 + // with an argument equal to an address that is within the range
1.319 + // [blk_start, blk_end) would return the value blk_start, provided
1.320 + // there have been no calls in between that reset this information
1.321 + // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call
1.322 + // for an appropriate range covering the said interval).
1.323 + // These methods expect to be called with [blk_start, blk_end)
1.324 + // representing a block of memory in the heap.
1.325 + virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
1.326 + void alloc_block(HeapWord* blk, size_t size) {
1.327 + alloc_block(blk, blk + size);
1.328 + }
1.329 +
1.330 + // If true, initialize array slots with no allocated blocks to zero.
1.331 + // Otherwise, make them point back to the front.
1.332 + bool init_to_zero() { return _init_to_zero; }
1.333 +
1.334 + // Debugging
1.335 + // Return the index of the last entry in the "active" region.
1.336 + virtual size_t last_active_index() const = 0;
1.337 + // Verify the block offset table
1.338 + void verify() const;
1.339 + void check_all_cards(size_t left_card, size_t right_card) const;
1.340 +};
1.341 +
1.342 +////////////////////////////////////////////////////////////////////////////
1.343 +// A subtype of BlockOffsetArray that takes advantage of the fact
1.344 +// that its underlying space is a NonContiguousSpace, so that some
1.345 +// specialized interfaces can be made available for spaces that
1.346 +// manipulate the table.
1.347 +////////////////////////////////////////////////////////////////////////////
1.348 +class BlockOffsetArrayNonContigSpace: public BlockOffsetArray {
1.349 + friend class VMStructs;
1.350 + private:
1.351 + // The portion [_unallocated_block, _sp.end()) of the space that
1.352 + // is a single block known not to contain any objects.
1.353 + // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag.
1.354 + HeapWord* _unallocated_block;
1.355 +
1.356 + public:
1.357 + BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
1.358 + BlockOffsetArray(array, mr, false),
1.359 + _unallocated_block(_bottom) { }
1.360 +
1.361 + // accessor
1.362 + HeapWord* unallocated_block() const {
1.363 + assert(BlockOffsetArrayUseUnallocatedBlock,
1.364 + "_unallocated_block is not being maintained");
1.365 + return _unallocated_block;
1.366 + }
1.367 +
1.368 + void set_unallocated_block(HeapWord* block) {
1.369 + assert(BlockOffsetArrayUseUnallocatedBlock,
1.370 + "_unallocated_block is not being maintained");
1.371 + assert(block >= _bottom && block <= _end, "out of range");
1.372 + _unallocated_block = block;
1.373 + }
1.374 +
1.375 + // These methods expect to be called with [blk_start, blk_end)
1.376 + // representing a block of memory in the heap.
1.377 + void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
1.378 + void alloc_block(HeapWord* blk, size_t size) {
1.379 + alloc_block(blk, blk + size);
1.380 + }
1.381 +
1.382 + // The following methods are useful and optimized for a
1.383 + // non-contiguous space.
1.384 +
1.385 + // Given a block [blk_start, blk_start + full_blk_size), and
1.386 + // a left_blk_size < full_blk_size, adjust the BOT to show two
1.387 + // blocks [blk_start, blk_start + left_blk_size) and
1.388 + // [blk_start + left_blk_size, blk_start + full_blk_size).
1.389 + // It is assumed (and verified in the non-product VM) that the
1.390 + // BOT was correct for the original block.
1.391 + void split_block(HeapWord* blk_start, size_t full_blk_size,
1.392 + size_t left_blk_size);
1.393 +
1.394 + // Adjust BOT to show that it has a block in the range
1.395 + // [blk_start, blk_start + size). Only the first card
1.396 + // of BOT is touched. It is assumed (and verified in the
1.397 + // non-product VM) that the remaining cards of the block
1.398 + // are correct.
1.399 + void mark_block(HeapWord* blk_start, HeapWord* blk_end);
1.400 + void mark_block(HeapWord* blk, size_t size) {
1.401 + mark_block(blk, blk + size);
1.402 + }
1.403 +
1.404 + // Adjust _unallocated_block to indicate that a particular
1.405 + // block has been newly allocated or freed. It is assumed (and
1.406 + // verified in the non-product VM) that the BOT is correct for
1.407 + // the given block.
1.408 + void allocated(HeapWord* blk_start, HeapWord* blk_end) {
1.409 + // Verify that the BOT shows [blk, blk + blk_size) to be one block.
1.410 + verify_single_block(blk_start, blk_end);
1.411 + if (BlockOffsetArrayUseUnallocatedBlock) {
1.412 + _unallocated_block = MAX2(_unallocated_block, blk_end);
1.413 + }
1.414 + }
1.415 +
1.416 + void allocated(HeapWord* blk, size_t size) {
1.417 + allocated(blk, blk + size);
1.418 + }
1.419 +
1.420 + void freed(HeapWord* blk_start, HeapWord* blk_end);
1.421 + void freed(HeapWord* blk, size_t size) {
1.422 + freed(blk, blk + size);
1.423 + }
1.424 +
1.425 + HeapWord* block_start_unsafe(const void* addr) const;
1.426 +
1.427 + // Requires "addr" to be the start of a card and returns the
1.428 + // start of the block that contains the given address.
1.429 + HeapWord* block_start_careful(const void* addr) const;
1.430 +
1.431 +
1.432 + // Verification & debugging: ensure that the offset table reflects
1.433 + // the fact that the block [blk_start, blk_end) or [blk, blk + size)
1.434 + // is a single block of storage. NOTE: can't const this because of
1.435 + // call to non-const do_block_internal() below.
1.436 + void verify_single_block(HeapWord* blk_start, HeapWord* blk_end)
1.437 + PRODUCT_RETURN;
1.438 + void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN;
1.439 +
1.440 + // Verify that the given block is before _unallocated_block
1.441 + void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end)
1.442 + const PRODUCT_RETURN;
1.443 + void verify_not_unallocated(HeapWord* blk, size_t size)
1.444 + const PRODUCT_RETURN;
1.445 +
1.446 + // Debugging support
1.447 + virtual size_t last_active_index() const;
1.448 +};
1.449 +
1.450 +////////////////////////////////////////////////////////////////////////////
1.451 +// A subtype of BlockOffsetArray that takes advantage of the fact
1.452 +// that its underlying space is a ContiguousSpace, so that its "active"
1.453 +// region can be more efficiently tracked (than for a non-contiguous space).
1.454 +////////////////////////////////////////////////////////////////////////////
1.455 +class BlockOffsetArrayContigSpace: public BlockOffsetArray {
1.456 + friend class VMStructs;
1.457 + private:
1.458 + // allocation boundary at which offset array must be updated
1.459 + HeapWord* _next_offset_threshold;
1.460 + size_t _next_offset_index; // index corresponding to that boundary
1.461 +
1.462 + // Work function when allocation start crosses threshold.
1.463 + void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end);
1.464 +
1.465 + public:
1.466 + BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
1.467 + BlockOffsetArray(array, mr, true) {
1.468 + _next_offset_threshold = NULL;
1.469 + _next_offset_index = 0;
1.470 + }
1.471 +
1.472 + void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); }
1.473 +
1.474 + // Initialize the threshold for an empty heap.
1.475 + HeapWord* initialize_threshold();
1.476 + // Zero out the entry for _bottom (offset will be zero)
1.477 + void zero_bottom_entry();
1.478 +
1.479 + // Return the next threshold, the point at which the table should be
1.480 + // updated.
1.481 + HeapWord* threshold() const { return _next_offset_threshold; }
1.482 +
1.483 + // In general, these methods expect to be called with
1.484 + // [blk_start, blk_end) representing a block of memory in the heap.
1.485 + // In this implementation, however, we are OK even if blk_start and/or
1.486 + // blk_end are NULL because NULL is represented as 0, and thus
1.487 + // never exceeds the "_next_offset_threshold".
1.488 + void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
1.489 + if (blk_end > _next_offset_threshold) {
1.490 + alloc_block_work(blk_start, blk_end);
1.491 + }
1.492 + }
1.493 + void alloc_block(HeapWord* blk, size_t size) {
1.494 + alloc_block(blk, blk + size);
1.495 + }
1.496 +
1.497 + HeapWord* block_start_unsafe(const void* addr) const;
1.498 +
1.499 + void serialize(SerializeOopClosure* soc);
1.500 +
1.501 + // Debugging support
1.502 + virtual size_t last_active_index() const;
1.503 +};
