1 /* 2 * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "gc/shared/blockOffsetTable.inline.hpp" 27 #include "gc/shared/collectedHeap.inline.hpp" 28 #include "gc/shared/space.inline.hpp" 29 #include "memory/iterator.hpp" 30 #include "memory/universe.hpp" 31 #include "oops/oop.inline.hpp" 32 #include "runtime/java.hpp" 33 #include "services/memTracker.hpp" 34 35 ////////////////////////////////////////////////////////////////////// 36 // BlockOffsetSharedArray 37 ////////////////////////////////////////////////////////////////////// 38 39 BlockOffsetSharedArray::BlockOffsetSharedArray(MemRegion reserved, 40 size_t init_word_size): 41 _reserved(reserved), _end(NULL) 42 { 43 size_t size = compute_size(reserved.word_size()); 44 ReservedSpace rs(size); 45 if (!rs.is_reserved()) { 46 vm_exit_during_initialization("Could not reserve enough space for heap offset array"); 47 } 48 49 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC); 50 51 if (!_vs.initialize(rs, 0)) { 52 vm_exit_during_initialization("Could not reserve enough space for heap offset array"); 53 } 54 _offset_array = (u_char*)_vs.low_boundary(); 55 resize(init_word_size); 56 if (TraceBlockOffsetTable) { 57 gclog_or_tty->print_cr("BlockOffsetSharedArray::BlockOffsetSharedArray: "); 58 gclog_or_tty->print_cr(" " 59 " rs.base(): " INTPTR_FORMAT 60 " rs.size(): " INTPTR_FORMAT 61 " rs end(): " INTPTR_FORMAT, 62 p2i(rs.base()), rs.size(), p2i(rs.base() + rs.size())); 63 gclog_or_tty->print_cr(" " 64 " _vs.low_boundary(): " INTPTR_FORMAT 65 " _vs.high_boundary(): " INTPTR_FORMAT, 66 p2i(_vs.low_boundary()), 67 p2i(_vs.high_boundary())); 68 } 69 } 70 71 void BlockOffsetSharedArray::resize(size_t new_word_size) { 72 assert(new_word_size <= _reserved.word_size(), "Resize larger than reserved"); 73 size_t new_size = compute_size(new_word_size); 74 size_t old_size = _vs.committed_size(); 75 size_t delta; 76 char* high = _vs.high(); 77 _end = _reserved.start() + new_word_size; 78 if (new_size > old_size) { 79 delta = ReservedSpace::page_align_size_up(new_size - old_size); 80 assert(delta > 0, "just checking"); 81 if (!_vs.expand_by(delta)) { 82 // Do better than this for Merlin 83 vm_exit_out_of_memory(delta, OOM_MMAP_ERROR, "offset table expansion"); 84 } 85 assert(_vs.high() == high + delta, "invalid expansion"); 86 } else { 87 delta = ReservedSpace::page_align_size_down(old_size - new_size); 88 if (delta == 0) return; 89 _vs.shrink_by(delta); 90 assert(_vs.high() == high - delta, "invalid expansion"); 91 } 92 } 93 94 bool BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const { 95 assert(p >= _reserved.start(), "just checking"); 96 size_t delta = pointer_delta(p, _reserved.start()); 97 return (delta & right_n_bits(LogN_words)) == (size_t)NoBits; 98 } 99 100 101 ////////////////////////////////////////////////////////////////////// 102 // BlockOffsetArray 103 ////////////////////////////////////////////////////////////////////// 104 105 BlockOffsetArray::BlockOffsetArray(BlockOffsetSharedArray* array, 106 MemRegion mr, bool init_to_zero_) : 107 BlockOffsetTable(mr.start(), mr.end()), 108 _array(array) 109 { 110 assert(_bottom <= _end, "arguments out of order"); 111 set_init_to_zero(init_to_zero_); 112 if (!init_to_zero_) { 113 // initialize cards to point back to mr.start() 114 set_remainder_to_point_to_start(mr.start() + N_words, mr.end()); 115 _array->set_offset_array(0, 0); // set first card to 0 116 } 117 } 118 119 120 // The arguments follow the normal convention of denoting 121 // a right-open interval: [start, end) 122 void 123 BlockOffsetArray:: 124 set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing) { 125 126 check_reducing_assertion(reducing); 127 if (start >= end) { 128 // The start address is equal to the end address (or to 129 // the right of the end address) so there are not cards 130 // that need to be updated.. 131 return; 132 } 133 134 // Write the backskip value for each region. 135 // 136 // offset 137 // card 2nd 3rd 138 // | +- 1st | | 139 // v v v v 140 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+- 141 // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ... 142 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+- 143 // 11 19 75 144 // 12 145 // 146 // offset card is the card that points to the start of an object 147 // x - offset value of offset card 148 // 1st - start of first logarithmic region 149 // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1 150 // 2nd - start of second logarithmic region 151 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8 152 // 3rd - start of third logarithmic region 153 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64 154 // 155 // integer below the block offset entry is an example of 156 // the index of the entry 157 // 158 // Given an address, 159 // Find the index for the address 160 // Find the block offset table entry 161 // Convert the entry to a back slide 162 // (e.g., with today's, offset = 0x81 => 163 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8 164 // Move back N (e.g., 8) entries and repeat with the 165 // value of the new entry 166 // 167 size_t start_card = _array->index_for(start); 168 size_t end_card = _array->index_for(end-1); 169 assert(start ==_array->address_for_index(start_card), "Precondition"); 170 assert(end ==_array->address_for_index(end_card)+N_words, "Precondition"); 171 set_remainder_to_point_to_start_incl(start_card, end_card, reducing); // closed interval 172 } 173 174 175 // Unlike the normal convention in this code, the argument here denotes 176 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start() 177 // above. 178 void 179 BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card, bool reducing) { 180 181 check_reducing_assertion(reducing); 182 if (start_card > end_card) { 183 return; 184 } 185 assert(start_card > _array->index_for(_bottom), "Cannot be first card"); 186 assert(_array->offset_array(start_card-1) <= N_words, 187 "Offset card has an unexpected value"); 188 size_t start_card_for_region = start_card; 189 u_char offset = max_jubyte; 190 for (int i = 0; i < N_powers; i++) { 191 // -1 so that the the card with the actual offset is counted. Another -1 192 // so that the reach ends in this region and not at the start 193 // of the next. 194 size_t reach = start_card - 1 + (power_to_cards_back(i+1) - 1); 195 offset = N_words + i; 196 if (reach >= end_card) { 197 _array->set_offset_array(start_card_for_region, end_card, offset, reducing); 198 start_card_for_region = reach + 1; 199 break; 200 } 201 _array->set_offset_array(start_card_for_region, reach, offset, reducing); 202 start_card_for_region = reach + 1; 203 } 204 assert(start_card_for_region > end_card, "Sanity check"); 205 DEBUG_ONLY(check_all_cards(start_card, end_card);) 206 } 207 208 // The card-interval [start_card, end_card] is a closed interval; this 209 // is an expensive check -- use with care and only under protection of 210 // suitable flag. 211 void BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const { 212 213 if (end_card < start_card) { 214 return; 215 } 216 guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card"); 217 u_char last_entry = N_words; 218 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) { 219 u_char entry = _array->offset_array(c); 220 guarantee(entry >= last_entry, "Monotonicity"); 221 if (c - start_card > power_to_cards_back(1)) { 222 guarantee(entry > N_words, "Should be in logarithmic region"); 223 } 224 size_t backskip = entry_to_cards_back(entry); 225 size_t landing_card = c - backskip; 226 guarantee(landing_card >= (start_card - 1), "Inv"); 227 if (landing_card >= start_card) { 228 guarantee(_array->offset_array(landing_card) <= entry, "Monotonicity"); 229 } else { 230 guarantee(landing_card == (start_card - 1), "Tautology"); 231 // Note that N_words is the maximum offset value 232 guarantee(_array->offset_array(landing_card) <= N_words, "Offset value"); 233 } 234 last_entry = entry; // remember for monotonicity test 235 } 236 } 237 238 239 void 240 BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) { 241 assert(blk_start != NULL && blk_end > blk_start, 242 "phantom block"); 243 single_block(blk_start, blk_end); 244 } 245 246 // Action_mark - update the BOT for the block [blk_start, blk_end). 247 // Current typical use is for splitting a block. 248 // Action_single - udpate the BOT for an allocation. 249 // Action_verify - BOT verification. 250 void 251 BlockOffsetArray::do_block_internal(HeapWord* blk_start, 252 HeapWord* blk_end, 253 Action action, bool reducing) { 254 assert(Universe::heap()->is_in_reserved(blk_start), 255 "reference must be into the heap"); 256 assert(Universe::heap()->is_in_reserved(blk_end-1), 257 "limit must be within the heap"); 258 // This is optimized to make the test fast, assuming we only rarely 259 // cross boundaries. 260 uintptr_t end_ui = (uintptr_t)(blk_end - 1); 261 uintptr_t start_ui = (uintptr_t)blk_start; 262 // Calculate the last card boundary preceding end of blk 263 intptr_t boundary_before_end = (intptr_t)end_ui; 264 clear_bits(boundary_before_end, right_n_bits(LogN)); 265 if (start_ui <= (uintptr_t)boundary_before_end) { 266 // blk starts at or crosses a boundary 267 // Calculate index of card on which blk begins 268 size_t start_index = _array->index_for(blk_start); 269 // Index of card on which blk ends 270 size_t end_index = _array->index_for(blk_end - 1); 271 // Start address of card on which blk begins 272 HeapWord* boundary = _array->address_for_index(start_index); 273 assert(boundary <= blk_start, "blk should start at or after boundary"); 274 if (blk_start != boundary) { 275 // blk starts strictly after boundary 276 // adjust card boundary and start_index forward to next card 277 boundary += N_words; 278 start_index++; 279 } 280 assert(start_index <= end_index, "monotonicity of index_for()"); 281 assert(boundary <= (HeapWord*)boundary_before_end, "tautology"); 282 switch (action) { 283 case Action_mark: { 284 if (init_to_zero()) { 285 _array->set_offset_array(start_index, boundary, blk_start, reducing); 286 break; 287 } // Else fall through to the next case 288 } 289 case Action_single: { 290 _array->set_offset_array(start_index, boundary, blk_start, reducing); 291 // We have finished marking the "offset card". We need to now 292 // mark the subsequent cards that this blk spans. 293 if (start_index < end_index) { 294 HeapWord* rem_st = _array->address_for_index(start_index) + N_words; 295 HeapWord* rem_end = _array->address_for_index(end_index) + N_words; 296 set_remainder_to_point_to_start(rem_st, rem_end, reducing); 297 } 298 break; 299 } 300 case Action_check: { 301 _array->check_offset_array(start_index, boundary, blk_start); 302 // We have finished checking the "offset card". We need to now 303 // check the subsequent cards that this blk spans. 304 check_all_cards(start_index + 1, end_index); 305 break; 306 } 307 default: 308 ShouldNotReachHere(); 309 } 310 } 311 } 312 313 // The range [blk_start, blk_end) represents a single contiguous block 314 // of storage; modify the block offset table to represent this 315 // information; Right-open interval: [blk_start, blk_end) 316 // NOTE: this method does _not_ adjust _unallocated_block. 317 void 318 BlockOffsetArray::single_block(HeapWord* blk_start, 319 HeapWord* blk_end) { 320 do_block_internal(blk_start, blk_end, Action_single); 321 } 322 323 void BlockOffsetArray::verify() const { 324 // For each entry in the block offset table, verify that 325 // the entry correctly finds the start of an object at the 326 // first address covered by the block or to the left of that 327 // first address. 328 329 size_t next_index = 1; 330 size_t last_index = last_active_index(); 331 332 // Use for debugging. Initialize to NULL to distinguish the 333 // first iteration through the while loop. 334 HeapWord* last_p = NULL; 335 HeapWord* last_start = NULL; 336 oop last_o = NULL; 337 338 while (next_index <= last_index) { 339 // Use an address past the start of the address for 340 // the entry. 341 HeapWord* p = _array->address_for_index(next_index) + 1; 342 if (p >= _end) { 343 // That's all of the allocated block table. 344 return; 345 } 346 // block_start() asserts that start <= p. 347 HeapWord* start = block_start(p); 348 // First check if the start is an allocated block and only 349 // then if it is a valid object. 350 oop o = oop(start); 351 assert(!Universe::is_fully_initialized() || 352 _sp->is_free_block(start) || 353 o->is_oop_or_null(), "Bad object was found"); 354 next_index++; 355 last_p = p; 356 last_start = start; 357 last_o = o; 358 } 359 } 360 361 ////////////////////////////////////////////////////////////////////// 362 // BlockOffsetArrayNonContigSpace 363 ////////////////////////////////////////////////////////////////////// 364 365 // The block [blk_start, blk_end) has been allocated; 366 // adjust the block offset table to represent this information; 367 // NOTE: Clients of BlockOffsetArrayNonContigSpace: consider using 368 // the somewhat more lightweight split_block() or 369 // (when init_to_zero()) mark_block() wherever possible. 370 // right-open interval: [blk_start, blk_end) 371 void 372 BlockOffsetArrayNonContigSpace::alloc_block(HeapWord* blk_start, 373 HeapWord* blk_end) { 374 assert(blk_start != NULL && blk_end > blk_start, 375 "phantom block"); 376 single_block(blk_start, blk_end); 377 allocated(blk_start, blk_end); 378 } 379 380 // Adjust BOT to show that a previously whole block has been split 381 // into two. We verify the BOT for the first part (prefix) and 382 // update the BOT for the second part (suffix). 383 // blk is the start of the block 384 // blk_size is the size of the original block 385 // left_blk_size is the size of the first part of the split 386 void BlockOffsetArrayNonContigSpace::split_block(HeapWord* blk, 387 size_t blk_size, 388 size_t left_blk_size) { 389 // Verify that the BOT shows [blk, blk + blk_size) to be one block. 390 verify_single_block(blk, blk_size); 391 // Update the BOT to indicate that [blk + left_blk_size, blk + blk_size) 392 // is one single block. 393 assert(blk_size > 0, "Should be positive"); 394 assert(left_blk_size > 0, "Should be positive"); 395 assert(left_blk_size < blk_size, "Not a split"); 396 397 // Start addresses of prefix block and suffix block. 398 HeapWord* pref_addr = blk; 399 HeapWord* suff_addr = blk + left_blk_size; 400 HeapWord* end_addr = blk + blk_size; 401 402 // Indices for starts of prefix block and suffix block. 403 size_t pref_index = _array->index_for(pref_addr); 404 if (_array->address_for_index(pref_index) != pref_addr) { 405 // pref_addr does not begin pref_index 406 pref_index++; 407 } 408 409 size_t suff_index = _array->index_for(suff_addr); 410 if (_array->address_for_index(suff_index) != suff_addr) { 411 // suff_addr does not begin suff_index 412 suff_index++; 413 } 414 415 // Definition: A block B, denoted [B_start, B_end) __starts__ 416 // a card C, denoted [C_start, C_end), where C_start and C_end 417 // are the heap addresses that card C covers, iff 418 // B_start <= C_start < B_end. 419 // 420 // We say that a card C "is started by" a block B, iff 421 // B "starts" C. 422 // 423 // Note that the cardinality of the set of cards {C} 424 // started by a block B can be 0, 1, or more. 425 // 426 // Below, pref_index and suff_index are, respectively, the 427 // first (least) card indices that the prefix and suffix of 428 // the split start; end_index is one more than the index of 429 // the last (greatest) card that blk starts. 430 size_t end_index = _array->index_for(end_addr - 1) + 1; 431 432 // Calculate the # cards that the prefix and suffix affect. 433 size_t num_pref_cards = suff_index - pref_index; 434 435 size_t num_suff_cards = end_index - suff_index; 436 // Change the cards that need changing 437 if (num_suff_cards > 0) { 438 HeapWord* boundary = _array->address_for_index(suff_index); 439 // Set the offset card for suffix block 440 _array->set_offset_array(suff_index, boundary, suff_addr, true /* reducing */); 441 // Change any further cards that need changing in the suffix 442 if (num_pref_cards > 0) { 443 if (num_pref_cards >= num_suff_cards) { 444 // Unilaterally fix all of the suffix cards: closed card 445 // index interval in args below. 446 set_remainder_to_point_to_start_incl(suff_index + 1, end_index - 1, true /* reducing */); 447 } else { 448 // Unilaterally fix the first (num_pref_cards - 1) following 449 // the "offset card" in the suffix block. 450 const size_t right_most_fixed_index = suff_index + num_pref_cards - 1; 451 set_remainder_to_point_to_start_incl(suff_index + 1, 452 right_most_fixed_index, true /* reducing */); 453 // Fix the appropriate cards in the remainder of the 454 // suffix block -- these are the last num_pref_cards 455 // cards in each power block of the "new" range plumbed 456 // from suff_addr. 457 bool more = true; 458 uint i = 1; 459 // Fix the first power block with back_by > num_pref_cards. 460 while (more && (i < N_powers)) { 461 size_t back_by = power_to_cards_back(i); 462 size_t right_index = suff_index + back_by - 1; 463 size_t left_index = right_index - num_pref_cards + 1; 464 if (right_index >= end_index - 1) { // last iteration 465 right_index = end_index - 1; 466 more = false; 467 } 468 if (left_index <= right_most_fixed_index) { 469 left_index = right_most_fixed_index + 1; 470 } 471 if (back_by > num_pref_cards) { 472 // Fill in the remainder of this "power block", if it 473 // is non-null. 474 if (left_index <= right_index) { 475 _array->set_offset_array(left_index, right_index, 476 N_words + i - 1, true /* reducing */); 477 } else { 478 more = false; // we are done 479 assert((end_index - 1) == right_index, "Must be at the end."); 480 } 481 i++; 482 break; 483 } 484 i++; 485 } 486 // Fix the rest of the power blocks. 487 while (more && (i < N_powers)) { 488 size_t back_by = power_to_cards_back(i); 489 size_t right_index = suff_index + back_by - 1; 490 size_t left_index = right_index - num_pref_cards + 1; 491 if (right_index >= end_index - 1) { // last iteration 492 right_index = end_index - 1; 493 if (left_index > right_index) { 494 break; 495 } 496 more = false; 497 } 498 assert(left_index <= right_index, "Error"); 499 _array->set_offset_array(left_index, right_index, N_words + i - 1, true /* reducing */); 500 i++; 501 } 502 } 503 } // else no more cards to fix in suffix 504 } // else nothing needs to be done 505 // Verify that we did the right thing 506 verify_single_block(pref_addr, left_blk_size); 507 verify_single_block(suff_addr, blk_size - left_blk_size); 508 } 509 510 511 // Mark the BOT such that if [blk_start, blk_end) straddles a card 512 // boundary, the card following the first such boundary is marked 513 // with the appropriate offset. 514 // NOTE: this method does _not_ adjust _unallocated_block or 515 // any cards subsequent to the first one. 516 void 517 BlockOffsetArrayNonContigSpace::mark_block(HeapWord* blk_start, 518 HeapWord* blk_end, bool reducing) { 519 do_block_internal(blk_start, blk_end, Action_mark, reducing); 520 } 521 522 HeapWord* BlockOffsetArrayNonContigSpace::block_start_unsafe( 523 const void* addr) const { 524 assert(_array->offset_array(0) == 0, "objects can't cross covered areas"); 525 assert(_bottom <= addr && addr < _end, 526 "addr must be covered by this Array"); 527 // Must read this exactly once because it can be modified by parallel 528 // allocation. 529 HeapWord* ub = _unallocated_block; 530 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) { 531 assert(ub < _end, "tautology (see above)"); 532 return ub; 533 } 534 535 // Otherwise, find the block start using the table. 536 size_t index = _array->index_for(addr); 537 HeapWord* q = _array->address_for_index(index); 538 539 uint offset = _array->offset_array(index); // Extend u_char to uint. 540 while (offset >= N_words) { 541 // The excess of the offset from N_words indicates a power of Base 542 // to go back by. 543 size_t n_cards_back = entry_to_cards_back(offset); 544 q -= (N_words * n_cards_back); 545 assert(q >= _sp->bottom(), 546 err_msg("q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT, 547 p2i(q), p2i(_sp->bottom()))); 548 assert(q < _sp->end(), 549 err_msg("q = " PTR_FORMAT " crossed above end = " PTR_FORMAT, 550 p2i(q), p2i(_sp->end()))); 551 index -= n_cards_back; 552 offset = _array->offset_array(index); 553 } 554 assert(offset < N_words, "offset too large"); 555 index--; 556 q -= offset; 557 assert(q >= _sp->bottom(), 558 err_msg("q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT, 559 p2i(q), p2i(_sp->bottom()))); 560 assert(q < _sp->end(), 561 err_msg("q = " PTR_FORMAT " crossed above end = " PTR_FORMAT, 562 p2i(q), p2i(_sp->end()))); 563 HeapWord* n = q; 564 565 while (n <= addr) { 566 debug_only(HeapWord* last = q); // for debugging 567 q = n; 568 n += _sp->block_size(n); 569 assert(n > q, 570 err_msg("Looping at n = " PTR_FORMAT " with last = " PTR_FORMAT"," 571 " while querying blk_start(" PTR_FORMAT ")" 572 " on _sp = [" PTR_FORMAT "," PTR_FORMAT ")", 573 p2i(n), p2i(last), p2i(addr), p2i(_sp->bottom()), p2i(_sp->end()))); 574 } 575 assert(q <= addr, 576 err_msg("wrong order for current (" INTPTR_FORMAT ")" " <= arg (" INTPTR_FORMAT ")", 577 p2i(q), p2i(addr))); 578 assert(addr <= n, 579 err_msg("wrong order for arg (" INTPTR_FORMAT ") <= next (" INTPTR_FORMAT ")", 580 p2i(addr), p2i(n))); 581 return q; 582 } 583 584 HeapWord* BlockOffsetArrayNonContigSpace::block_start_careful( 585 const void* addr) const { 586 assert(_array->offset_array(0) == 0, "objects can't cross covered areas"); 587 588 assert(_bottom <= addr && addr < _end, 589 "addr must be covered by this Array"); 590 // Must read this exactly once because it can be modified by parallel 591 // allocation. 592 HeapWord* ub = _unallocated_block; 593 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) { 594 assert(ub < _end, "tautology (see above)"); 595 return ub; 596 } 597 598 // Otherwise, find the block start using the table, but taking 599 // care (cf block_start_unsafe() above) not to parse any objects/blocks 600 // on the cards themselves. 601 size_t index = _array->index_for(addr); 602 assert(_array->address_for_index(index) == addr, 603 "arg should be start of card"); 604 605 HeapWord* q = (HeapWord*)addr; 606 uint offset; 607 do { 608 offset = _array->offset_array(index); 609 if (offset < N_words) { 610 q -= offset; 611 } else { 612 size_t n_cards_back = entry_to_cards_back(offset); 613 q -= (n_cards_back * N_words); 614 index -= n_cards_back; 615 } 616 } while (offset >= N_words); 617 assert(q <= addr, "block start should be to left of arg"); 618 return q; 619 } 620 621 #ifndef PRODUCT 622 // Verification & debugging - ensure that the offset table reflects the fact 623 // that the block [blk_start, blk_end) or [blk, blk + size) is a 624 // single block of storage. NOTE: can't const this because of 625 // call to non-const do_block_internal() below. 626 void BlockOffsetArrayNonContigSpace::verify_single_block( 627 HeapWord* blk_start, HeapWord* blk_end) { 628 if (VerifyBlockOffsetArray) { 629 do_block_internal(blk_start, blk_end, Action_check); 630 } 631 } 632 633 void BlockOffsetArrayNonContigSpace::verify_single_block( 634 HeapWord* blk, size_t size) { 635 verify_single_block(blk, blk + size); 636 } 637 638 // Verify that the given block is before _unallocated_block 639 void BlockOffsetArrayNonContigSpace::verify_not_unallocated( 640 HeapWord* blk_start, HeapWord* blk_end) const { 641 if (BlockOffsetArrayUseUnallocatedBlock) { 642 assert(blk_start < blk_end, "Block inconsistency?"); 643 assert(blk_end <= _unallocated_block, "_unallocated_block problem"); 644 } 645 } 646 647 void BlockOffsetArrayNonContigSpace::verify_not_unallocated( 648 HeapWord* blk, size_t size) const { 649 verify_not_unallocated(blk, blk + size); 650 } 651 #endif // PRODUCT 652 653 size_t BlockOffsetArrayNonContigSpace::last_active_index() const { 654 if (_unallocated_block == _bottom) { 655 return 0; 656 } else { 657 return _array->index_for(_unallocated_block - 1); 658 } 659 } 660 661 ////////////////////////////////////////////////////////////////////// 662 // BlockOffsetArrayContigSpace 663 ////////////////////////////////////////////////////////////////////// 664 665 HeapWord* BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) const { 666 assert(_array->offset_array(0) == 0, "objects can't cross covered areas"); 667 668 // Otherwise, find the block start using the table. 669 assert(_bottom <= addr && addr < _end, 670 "addr must be covered by this Array"); 671 size_t index = _array->index_for(addr); 672 // We must make sure that the offset table entry we use is valid. If 673 // "addr" is past the end, start at the last known one and go forward. 674 index = MIN2(index, _next_offset_index-1); 675 HeapWord* q = _array->address_for_index(index); 676 677 uint offset = _array->offset_array(index); // Extend u_char to uint. 678 while (offset > N_words) { 679 // The excess of the offset from N_words indicates a power of Base 680 // to go back by. 681 size_t n_cards_back = entry_to_cards_back(offset); 682 q -= (N_words * n_cards_back); 683 assert(q >= _sp->bottom(), "Went below bottom!"); 684 index -= n_cards_back; 685 offset = _array->offset_array(index); 686 } 687 while (offset == N_words) { 688 assert(q >= _sp->bottom(), "Went below bottom!"); 689 q -= N_words; 690 index--; 691 offset = _array->offset_array(index); 692 } 693 assert(offset < N_words, "offset too large"); 694 q -= offset; 695 HeapWord* n = q; 696 697 while (n <= addr) { 698 debug_only(HeapWord* last = q); // for debugging 699 q = n; 700 n += _sp->block_size(n); 701 } 702 assert(q <= addr, "wrong order for current and arg"); 703 assert(addr <= n, "wrong order for arg and next"); 704 return q; 705 } 706 707 // 708 // _next_offset_threshold 709 // | _next_offset_index 710 // v v 711 // +-------+-------+-------+-------+-------+ 712 // | i-1 | i | i+1 | i+2 | i+3 | 713 // +-------+-------+-------+-------+-------+ 714 // ( ^ ] 715 // block-start 716 // 717 718 void BlockOffsetArrayContigSpace::alloc_block_work(HeapWord* blk_start, 719 HeapWord* blk_end) { 720 assert(blk_start != NULL && blk_end > blk_start, 721 "phantom block"); 722 assert(blk_end > _next_offset_threshold, 723 "should be past threshold"); 724 assert(blk_start <= _next_offset_threshold, 725 "blk_start should be at or before threshold"); 726 assert(pointer_delta(_next_offset_threshold, blk_start) <= N_words, 727 "offset should be <= BlockOffsetSharedArray::N"); 728 assert(Universe::heap()->is_in_reserved(blk_start), 729 "reference must be into the heap"); 730 assert(Universe::heap()->is_in_reserved(blk_end-1), 731 "limit must be within the heap"); 732 assert(_next_offset_threshold == 733 _array->_reserved.start() + _next_offset_index*N_words, 734 "index must agree with threshold"); 735 736 debug_only(size_t orig_next_offset_index = _next_offset_index;) 737 738 // Mark the card that holds the offset into the block. Note 739 // that _next_offset_index and _next_offset_threshold are not 740 // updated until the end of this method. 741 _array->set_offset_array(_next_offset_index, 742 _next_offset_threshold, 743 blk_start); 744 745 // We need to now mark the subsequent cards that this blk spans. 746 747 // Index of card on which blk ends. 748 size_t end_index = _array->index_for(blk_end - 1); 749 750 // Are there more cards left to be updated? 751 if (_next_offset_index + 1 <= end_index) { 752 HeapWord* rem_st = _array->address_for_index(_next_offset_index + 1); 753 // Calculate rem_end this way because end_index 754 // may be the last valid index in the covered region. 755 HeapWord* rem_end = _array->address_for_index(end_index) + N_words; 756 set_remainder_to_point_to_start(rem_st, rem_end); 757 } 758 759 // _next_offset_index and _next_offset_threshold updated here. 760 _next_offset_index = end_index + 1; 761 // Calculate _next_offset_threshold this way because end_index 762 // may be the last valid index in the covered region. 763 _next_offset_threshold = _array->address_for_index(end_index) + N_words; 764 assert(_next_offset_threshold >= blk_end, "Incorrect offset threshold"); 765 766 #ifdef ASSERT 767 // The offset can be 0 if the block starts on a boundary. That 768 // is checked by an assertion above. 769 size_t start_index = _array->index_for(blk_start); 770 HeapWord* boundary = _array->address_for_index(start_index); 771 assert((_array->offset_array(orig_next_offset_index) == 0 && 772 blk_start == boundary) || 773 (_array->offset_array(orig_next_offset_index) > 0 && 774 _array->offset_array(orig_next_offset_index) <= N_words), 775 "offset array should have been set"); 776 for (size_t j = orig_next_offset_index + 1; j <= end_index; j++) { 777 assert(_array->offset_array(j) > 0 && 778 _array->offset_array(j) <= (u_char) (N_words+N_powers-1), 779 "offset array should have been set"); 780 } 781 #endif 782 } 783 784 HeapWord* BlockOffsetArrayContigSpace::initialize_threshold() { 785 assert(!Universe::heap()->is_in_reserved(_array->_offset_array), 786 "just checking"); 787 _next_offset_index = _array->index_for(_bottom); 788 _next_offset_index++; 789 _next_offset_threshold = 790 _array->address_for_index(_next_offset_index); 791 return _next_offset_threshold; 792 } 793 794 void BlockOffsetArrayContigSpace::zero_bottom_entry() { 795 assert(!Universe::heap()->is_in_reserved(_array->_offset_array), 796 "just checking"); 797 size_t bottom_index = _array->index_for(_bottom); 798 _array->set_offset_array(bottom_index, 0); 799 } 800 801 size_t BlockOffsetArrayContigSpace::last_active_index() const { 802 return _next_offset_index == 0 ? 0 : _next_offset_index - 1; 803 }