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/g1/g1BlockOffsetTable.inline.hpp" 27 #include "gc/g1/g1CollectedHeap.inline.hpp" 28 #include "gc/g1/heapRegion.hpp" 29 #include "gc/shared/space.hpp" 30 #include "logging/log.hpp" 31 #include "oops/oop.inline.hpp" 32 #include "runtime/java.hpp" 33 #include "services/memTracker.hpp" 34 35 36 37 ////////////////////////////////////////////////////////////////////// 38 // G1BlockOffsetSharedArray 39 ////////////////////////////////////////////////////////////////////// 40 41 G1BlockOffsetSharedArray::G1BlockOffsetSharedArray(MemRegion heap, G1RegionToSpaceMapper* storage) : 42 _reserved(), _end(NULL), _listener(), _offset_array(NULL) { 43 44 _reserved = heap; 45 _end = NULL; 46 47 MemRegion bot_reserved = storage->reserved(); 48 49 _offset_array = (u_char*)bot_reserved.start(); 50 _end = _reserved.end(); 51 52 storage->set_mapping_changed_listener(&_listener); 53 54 log_trace(gc, bot)("G1BlockOffsetSharedArray::G1BlockOffsetSharedArray: "); 55 log_trace(gc, bot)(" rs.base(): " PTR_FORMAT " rs.size(): " SIZE_FORMAT " rs end(): " PTR_FORMAT, 56 p2i(bot_reserved.start()), bot_reserved.byte_size(), p2i(bot_reserved.end())); 57 } 58 59 bool G1BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const { 60 assert(p >= _reserved.start(), "just checking"); 61 size_t delta = pointer_delta(p, _reserved.start()); 62 return (delta & right_n_bits(LogN_words)) == (size_t)NoBits; 63 } 64 65 #ifdef ASSERT 66 void G1BlockOffsetSharedArray::check_index(size_t index, const char* msg) const { 67 assert((index) < (_reserved.word_size() >> LogN_words), 68 "%s - index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT, 69 msg, (index), (_reserved.word_size() >> LogN_words)); 70 assert(G1CollectedHeap::heap()->is_in_exact(address_for_index_raw(index)), 71 "Index " SIZE_FORMAT " corresponding to " PTR_FORMAT 72 " (%u) is not in committed area.", 73 (index), 74 p2i(address_for_index_raw(index)), 75 G1CollectedHeap::heap()->addr_to_region(address_for_index_raw(index))); 76 } 77 #endif // ASSERT 78 79 ////////////////////////////////////////////////////////////////////// 80 // G1BlockOffsetArray 81 ////////////////////////////////////////////////////////////////////// 82 83 G1BlockOffsetArray::G1BlockOffsetArray(G1BlockOffsetSharedArray* array, 84 MemRegion mr) : 85 G1BlockOffsetTable(mr.start(), mr.end()), 86 _unallocated_block(_bottom), 87 _array(array), _gsp(NULL) { 88 assert(_bottom <= _end, "arguments out of order"); 89 } 90 91 void G1BlockOffsetArray::set_space(G1OffsetTableContigSpace* sp) { 92 _gsp = sp; 93 } 94 95 // The arguments follow the normal convention of denoting 96 // a right-open interval: [start, end) 97 void 98 G1BlockOffsetArray:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) { 99 100 if (start >= end) { 101 // The start address is equal to the end address (or to 102 // the right of the end address) so there are not cards 103 // that need to be updated.. 104 return; 105 } 106 107 // Write the backskip value for each region. 108 // 109 // offset 110 // card 2nd 3rd 111 // | +- 1st | | 112 // v v v v 113 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+- 114 // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ... 115 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+- 116 // 11 19 75 117 // 12 118 // 120 // x - offset value of offset card 121 // 1st - start of first logarithmic region 122 // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1 123 // 2nd - start of second logarithmic region 124 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8 125 // 3rd - start of third logarithmic region 126 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64 127 // 128 // integer below the block offset entry is an example of 129 // the index of the entry 130 // 131 // Given an address, 132 // Find the index for the address 133 // Find the block offset table entry 134 // Convert the entry to a back slide 135 // (e.g., with today's, offset = 0x81 => 136 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8 137 // Move back N (e.g., 8) entries and repeat with the 138 // value of the new entry 139 // 140 size_t start_card = _array->index_for(start); 141 size_t end_card = _array->index_for(end-1); 142 assert(start ==_array->address_for_index(start_card), "Precondition"); 143 assert(end ==_array->address_for_index(end_card)+N_words, "Precondition"); 144 set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval 145 } 146 147 // Unlike the normal convention in this code, the argument here denotes 148 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start() 149 // above. 150 void 151 G1BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) { 152 if (start_card > end_card) { 153 return; 154 } 155 assert(start_card > _array->index_for(_bottom), "Cannot be first card"); 156 assert(_array->offset_array(start_card-1) <= N_words, 157 "Offset card has an unexpected value"); 158 size_t start_card_for_region = start_card; 159 u_char offset = max_jubyte; 160 for (int i = 0; i < BlockOffsetArray::N_powers; i++) { 161 // -1 so that the the card with the actual offset is counted. Another -1 162 // so that the reach ends in this region and not at the start 163 // of the next. 164 size_t reach = start_card - 1 + (BlockOffsetArray::power_to_cards_back(i+1) - 1); 165 offset = N_words + i; 166 if (reach >= end_card) { 167 _array->set_offset_array(start_card_for_region, end_card, offset); 168 start_card_for_region = reach + 1; 169 break; 170 } 171 _array->set_offset_array(start_card_for_region, reach, offset); 172 start_card_for_region = reach + 1; 173 } 174 assert(start_card_for_region > end_card, "Sanity check"); 175 DEBUG_ONLY(check_all_cards(start_card, end_card);) 176 } 177 178 // The card-interval [start_card, end_card] is a closed interval; this 179 // is an expensive check -- use with care and only under protection of 180 // suitable flag. 181 void G1BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const { 182 183 if (end_card < start_card) { 184 return; 185 } 186 guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card"); 187 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) { 188 u_char entry = _array->offset_array(c); 189 if (c - start_card > BlockOffsetArray::power_to_cards_back(1)) { 190 guarantee(entry > N_words, 191 "Should be in logarithmic region - " 192 "entry: %u, " 193 "_array->offset_array(c): %u, " 194 "N_words: %u", 195 (uint)entry, (uint)_array->offset_array(c), (uint)N_words); 196 } 197 size_t backskip = BlockOffsetArray::entry_to_cards_back(entry); 198 size_t landing_card = c - backskip; 199 guarantee(landing_card >= (start_card - 1), "Inv"); 200 if (landing_card >= start_card) { 201 guarantee(_array->offset_array(landing_card) <= entry, 202 "Monotonicity - landing_card offset: %u, " 203 "entry: %u", 204 (uint)_array->offset_array(landing_card), (uint)entry); 205 } else { 206 guarantee(landing_card == start_card - 1, "Tautology"); 207 // Note that N_words is the maximum offset value 208 guarantee(_array->offset_array(landing_card) <= N_words, 209 "landing card offset: %u, " 210 "N_words: %u", 211 (uint)_array->offset_array(landing_card), (uint)N_words); 212 } 213 } 214 } 215 216 HeapWord* G1BlockOffsetArray::block_start_unsafe(const void* addr) { 217 assert(_bottom <= addr && addr < _end, 218 "addr must be covered by this Array"); 219 // Must read this exactly once because it can be modified by parallel 220 // allocation. 221 HeapWord* ub = _unallocated_block; 222 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) { 223 assert(ub < _end, "tautology (see above)"); 224 return ub; 225 } 226 // Otherwise, find the block start using the table. 227 HeapWord* q = block_at_or_preceding(addr, false, 0); 228 return forward_to_block_containing_addr(q, addr); 229 } 230 231 // This duplicates a little code from the above: unavoidable. 232 HeapWord* 233 G1BlockOffsetArray::block_start_unsafe_const(const void* addr) const { 234 assert(_bottom <= addr && addr < _end, 235 "addr must be covered by this Array"); 236 // Must read this exactly once because it can be modified by parallel 237 // allocation. 238 HeapWord* ub = _unallocated_block; 239 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) { 240 assert(ub < _end, "tautology (see above)"); 241 return ub; 242 } 243 // Otherwise, find the block start using the table. 244 HeapWord* q = block_at_or_preceding(addr, false, 0); 245 HeapWord* n = q + block_size(q); 246 return forward_to_block_containing_addr_const(q, n, addr); 247 } 248 249 250 HeapWord* 251 G1BlockOffsetArray::forward_to_block_containing_addr_slow(HeapWord* q, 252 HeapWord* n, 253 const void* addr) { 254 // We're not in the normal case. We need to handle an important subcase 255 // here: LAB allocation. An allocation previously recorded in the 256 // offset table was actually a lab allocation, and was divided into 257 // several objects subsequently. Fix this situation as we answer the 258 // query, by updating entries as we cross them. 259 260 // If the fist object's end q is at the card boundary. Start refining 261 // with the corresponding card (the value of the entry will be basically 262 // set to 0). If the object crosses the boundary -- start from the next card. 263 size_t n_index = _array->index_for(n); 264 size_t next_index = _array->index_for(n) + !_array->is_card_boundary(n); 265 // Calculate a consistent next boundary. If "n" is not at the boundary 266 // already, step to the boundary. 267 HeapWord* next_boundary = _array->address_for_index(n_index) + 268 (n_index == next_index ? 0 : N_words); 269 assert(next_boundary <= _array->_end, 270 "next_boundary is beyond the end of the covered region " 271 " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT, 272 p2i(next_boundary), p2i(_array->_end)); 273 if (addr >= gsp()->top()) return gsp()->top(); 274 while (next_boundary < addr) { 275 while (n <= next_boundary) { 276 q = n; 277 oop obj = oop(q); 278 if (obj->klass_or_null() == NULL) return q; 279 n += block_size(q); 280 } 281 assert(q <= next_boundary && n > next_boundary, "Consequence of loop"); 282 // [q, n) is the block that crosses the boundary. 283 alloc_block_work2(&next_boundary, &next_index, q, n); 284 } 285 return forward_to_block_containing_addr_const(q, n, addr); 286 } 287 288 // Note that the committed size of the covered space may have changed, 289 // so the table size might also wish to change. 290 void G1BlockOffsetArray::resize(size_t new_word_size) { 291 HeapWord* new_end = _bottom + new_word_size; 292 _end = new_end; // update _end 293 } 294 295 // 296 // threshold_ 297 // | _index_ 298 // v v 299 // +-------+-------+-------+-------+-------+ 300 // | i-1 | i | i+1 | i+2 | i+3 | 301 // +-------+-------+-------+-------+-------+ 302 // ( ^ ] 303 // block-start 304 // 305 void G1BlockOffsetArray::alloc_block_work2(HeapWord** threshold_, size_t* index_, 306 HeapWord* blk_start, HeapWord* blk_end) { 307 // For efficiency, do copy-in/copy-out. 308 HeapWord* threshold = *threshold_; 309 size_t index = *index_; 310 311 assert(blk_start != NULL && blk_end > blk_start, 312 "phantom block"); 313 assert(blk_end > threshold, "should be past threshold"); 314 assert(blk_start <= threshold, "blk_start should be at or before threshold"); 315 assert(pointer_delta(threshold, blk_start) <= N_words, 316 "offset should be <= BlockOffsetSharedArray::N"); 317 assert(G1CollectedHeap::heap()->is_in_reserved(blk_start), 318 "reference must be into the heap"); 319 assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1), 320 "limit must be within the heap"); 321 assert(threshold == _array->_reserved.start() + index*N_words, 322 "index must agree with threshold"); 323 324 DEBUG_ONLY(size_t orig_index = index;) 325 326 // Mark the card that holds the offset into the block. Note 327 // that _next_offset_index and _next_offset_threshold are not 328 // updated until the end of this method. 329 _array->set_offset_array(index, threshold, blk_start); 330 331 // We need to now mark the subsequent cards that this blk spans. 332 333 // Index of card on which blk ends. 334 size_t end_index = _array->index_for(blk_end - 1); 335 336 // Are there more cards left to be updated? 337 if (index + 1 <= end_index) { 338 HeapWord* rem_st = _array->address_for_index(index + 1); 339 // Calculate rem_end this way because end_index 340 // may be the last valid index in the covered region. 341 HeapWord* rem_end = _array->address_for_index(end_index) + N_words; 342 set_remainder_to_point_to_start(rem_st, rem_end); 343 } 344 345 index = end_index + 1; 346 // Calculate threshold_ this way because end_index 347 // may be the last valid index in the covered region. 348 threshold = _array->address_for_index(end_index) + N_words; 349 assert(threshold >= blk_end, "Incorrect offset threshold"); 350 351 // index_ and threshold_ updated here. 352 *threshold_ = threshold; 353 *index_ = index; 354 355 #ifdef ASSERT 356 // The offset can be 0 if the block starts on a boundary. That 357 // is checked by an assertion above. 358 size_t start_index = _array->index_for(blk_start); 359 HeapWord* boundary = _array->address_for_index(start_index); 360 assert((_array->offset_array(orig_index) == 0 && blk_start == boundary) || 361 (_array->offset_array(orig_index) > 0 && _array->offset_array(orig_index) <= N_words), 362 "offset array should have been set - " 363 "orig_index offset: %u, " 364 "blk_start: " PTR_FORMAT ", " 365 "boundary: " PTR_FORMAT, 366 (uint)_array->offset_array(orig_index), 367 p2i(blk_start), p2i(boundary)); 368 for (size_t j = orig_index + 1; j <= end_index; j++) { 369 assert(_array->offset_array(j) > 0 && 370 _array->offset_array(j) <= 371 (u_char) (N_words+BlockOffsetArray::N_powers-1), 372 "offset array should have been set - " 373 "%u not > 0 OR %u not <= %u", 374 (uint) _array->offset_array(j), 375 (uint) _array->offset_array(j), 376 (uint) (N_words+BlockOffsetArray::N_powers-1)); 377 } 378 #endif 379 } 380 381 void G1BlockOffsetArray::verify() const { 382 assert(gsp()->bottom() < gsp()->top(), "Only non-empty regions should be verified."); 383 size_t start_card = _array->index_for(gsp()->bottom()); 384 size_t end_card = _array->index_for(gsp()->top() - 1); 385 386 for (size_t current_card = start_card; current_card < end_card; current_card++) { 387 u_char entry = _array->offset_array(current_card); 388 if (entry < N_words) { 389 // The entry should point to an object before the current card. Verify that 390 // it is possible to walk from that object in to the current card by just 391 // iterating over the objects following it. 392 HeapWord* card_address = _array->address_for_index(current_card); 393 HeapWord* obj_end = card_address - entry; 394 while (obj_end < card_address) { 395 HeapWord* obj = obj_end; 396 size_t obj_size = block_size(obj); 397 obj_end = obj + obj_size; 398 guarantee(obj_end > obj && obj_end <= gsp()->top(), 399 "Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT, 400 p2i(obj), obj_size, p2i(obj_end), p2i(gsp()->top())); 401 } 402 } else { 403 // Because we refine the BOT based on which cards are dirty there is not much we can verify here. 404 // We need to make sure that we are going backwards and that we don't pass the start of the 405 // corresponding heap region. But that is about all we can verify. 406 size_t backskip = BlockOffsetArray::entry_to_cards_back(entry); 407 guarantee(backskip >= 1, "Must be going back at least one card."); 408 409 size_t max_backskip = current_card - start_card; 410 guarantee(backskip <= max_backskip, 411 "Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT, 412 start_card, current_card, backskip); 413 414 HeapWord* backskip_address = _array->address_for_index(current_card - backskip); 415 guarantee(backskip_address >= gsp()->bottom(), 416 "Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT, 417 p2i(gsp()->bottom()), p2i(backskip_address)); 418 } 419 } 420 } 421 422 #ifndef PRODUCT 423 void 424 G1BlockOffsetArray::print_on(outputStream* out) { 425 size_t from_index = _array->index_for(_bottom); 426 size_t to_index = _array->index_for(_end); 427 out->print_cr(">> BOT for area [" PTR_FORMAT "," PTR_FORMAT ") " 428 "cards [" SIZE_FORMAT "," SIZE_FORMAT ")", 429 p2i(_bottom), p2i(_end), from_index, to_index); 430 for (size_t i = from_index; i < to_index; ++i) { 431 out->print_cr(" entry " SIZE_FORMAT_W(8) " | " PTR_FORMAT " : %3u", 432 i, p2i(_array->address_for_index(i)), 433 (uint) _array->offset_array(i)); 434 } 435 } 436 #endif // !PRODUCT 437 438 ////////////////////////////////////////////////////////////////////// 439 // G1BlockOffsetArrayContigSpace 440 ////////////////////////////////////////////////////////////////////// 441 442 HeapWord* 443 G1BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) { 444 assert(_bottom <= addr && addr < _end, 445 "addr must be covered by this Array"); 446 HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1); 447 return forward_to_block_containing_addr(q, addr); 448 } 449 450 HeapWord* 451 G1BlockOffsetArrayContigSpace:: 452 block_start_unsafe_const(const void* addr) const { 453 assert(_bottom <= addr && addr < _end, 454 "addr must be covered by this Array"); 455 HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1); 456 HeapWord* n = q + block_size(q); 457 return forward_to_block_containing_addr_const(q, n, addr); 458 } 459 460 G1BlockOffsetArrayContigSpace:: 461 G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, 462 MemRegion mr) : 463 G1BlockOffsetArray(array, mr) 464 { 465 _next_offset_threshold = NULL; 466 _next_offset_index = 0; 467 } 468 469 HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold_raw() { 470 assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array), 471 "just checking"); 472 _next_offset_index = _array->index_for_raw(_bottom); 473 _next_offset_index++; 474 _next_offset_threshold = 475 _array->address_for_index_raw(_next_offset_index); 476 return _next_offset_threshold; 477 } 478 479 void G1BlockOffsetArrayContigSpace::zero_bottom_entry_raw() { 480 assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array), 481 "just checking"); 482 size_t bottom_index = _array->index_for_raw(_bottom); 483 assert(_array->address_for_index_raw(bottom_index) == _bottom, 484 "Precondition of call"); 485 _array->set_offset_array_raw(bottom_index, 0); 486 } 487 488 HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold() { 489 assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array), 490 "just checking"); 491 _next_offset_index = _array->index_for(_bottom); 492 _next_offset_index++; 493 _next_offset_threshold = 494 _array->address_for_index(_next_offset_index); 495 return _next_offset_threshold; 496 } 497 498 void G1BlockOffsetArrayContigSpace::set_for_starts_humongous(HeapWord* obj_top, size_t fill_size) { 499 // The first BOT entry should have offset 0. 500 reset_bot(); 501 alloc_block(_bottom, obj_top); 502 if (fill_size > 0) { 503 alloc_block(obj_top, fill_size); 504 } 505 } 506 507 #ifndef PRODUCT 508 void G1BlockOffsetArrayContigSpace::print_on(outputStream* out) { 509 G1BlockOffsetArray::print_on(out); 510 out->print_cr(" next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold)); 511 out->print_cr(" next offset index: " SIZE_FORMAT, _next_offset_index); 512 } 513 #endif // !PRODUCT | 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/g1/g1BlockOffsetTable.inline.hpp" 27 #include "gc/g1/g1CollectedHeap.inline.hpp" 28 #include "gc/g1/heapRegion.hpp" 29 #include "gc/shared/space.hpp" 30 #include "logging/log.hpp" 31 #include "oops/oop.inline.hpp" 32 #include "runtime/java.hpp" 33 #include "services/memTracker.hpp" 34 35 36 37 ////////////////////////////////////////////////////////////////////// 38 // G1BlockOffsetTable 39 ////////////////////////////////////////////////////////////////////// 40 41 G1BlockOffsetTable::G1BlockOffsetTable(MemRegion heap, G1RegionToSpaceMapper* storage) : 42 _reserved(heap), _offset_array(NULL) { 43 44 MemRegion bot_reserved = storage->reserved(); 45 46 _offset_array = (u_char*)bot_reserved.start(); 47 48 log_trace(gc, bot)("G1BlockOffsetTable::G1BlockOffsetTable: "); 49 log_trace(gc, bot)(" rs.base(): " PTR_FORMAT " rs.size(): " SIZE_FORMAT " rs end(): " PTR_FORMAT, 50 p2i(bot_reserved.start()), bot_reserved.byte_size(), p2i(bot_reserved.end())); 51 } 52 53 bool G1BlockOffsetTable::is_card_boundary(HeapWord* p) const { 54 assert(p >= _reserved.start(), "just checking"); 55 size_t delta = pointer_delta(p, _reserved.start()); 56 return (delta & right_n_bits(LogN_words)) == (size_t)NoBits; 57 } 58 59 #ifdef ASSERT 60 void G1BlockOffsetTable::check_index(size_t index, const char* msg) const { 61 assert((index) < (_reserved.word_size() >> LogN_words), 62 "%s - index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT, 63 msg, (index), (_reserved.word_size() >> LogN_words)); 64 assert(G1CollectedHeap::heap()->is_in_exact(address_for_index_raw(index)), 65 "Index " SIZE_FORMAT " corresponding to " PTR_FORMAT 66 " (%u) is not in committed area.", 67 (index), 68 p2i(address_for_index_raw(index)), 69 G1CollectedHeap::heap()->addr_to_region(address_for_index_raw(index))); 70 } 71 #endif // ASSERT 72 73 ////////////////////////////////////////////////////////////////////// 74 // G1BlockOffsetTablePart 75 ////////////////////////////////////////////////////////////////////// 76 77 G1BlockOffsetTablePart::G1BlockOffsetTablePart(G1BlockOffsetTable* array, G1ContiguousSpace* gsp) : 78 _bot(array), 79 _space(gsp), 80 _next_offset_threshold(NULL), 81 _next_offset_index(0) 82 { } 83 84 // The arguments follow the normal convention of denoting 85 // a right-open interval: [start, end) 86 void G1BlockOffsetTablePart:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) { 87 88 if (start >= end) { 89 // The start address is equal to the end address (or to 90 // the right of the end address) so there are not cards 91 // that need to be updated.. 92 return; 93 } 94 95 // Write the backskip value for each region. 96 // 97 // offset 98 // card 2nd 3rd 99 // | +- 1st | | 100 // v v v v 101 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+- 102 // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ... 103 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+- 104 // 11 19 75 105 // 12 106 // 108 // x - offset value of offset card 109 // 1st - start of first logarithmic region 110 // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1 111 // 2nd - start of second logarithmic region 112 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8 113 // 3rd - start of third logarithmic region 114 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64 115 // 116 // integer below the block offset entry is an example of 117 // the index of the entry 118 // 119 // Given an address, 120 // Find the index for the address 121 // Find the block offset table entry 122 // Convert the entry to a back slide 123 // (e.g., with today's, offset = 0x81 => 124 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8 125 // Move back N (e.g., 8) entries and repeat with the 126 // value of the new entry 127 // 128 size_t start_card = _bot->index_for(start); 129 size_t end_card = _bot->index_for(end-1); 130 assert(start ==_bot->address_for_index(start_card), "Precondition"); 131 assert(end ==_bot->address_for_index(end_card)+N_words, "Precondition"); 132 set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval 133 } 134 135 // Unlike the normal convention in this code, the argument here denotes 136 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start() 137 // above. 138 void G1BlockOffsetTablePart::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) { 139 if (start_card > end_card) { 140 return; 141 } 142 assert(start_card > _bot->index_for(_space->bottom()), "Cannot be first card"); 143 assert(_bot->offset_array(start_card-1) <= N_words, 144 "Offset card has an unexpected value"); 145 size_t start_card_for_region = start_card; 146 u_char offset = max_jubyte; 147 for (int i = 0; i < BlockOffsetArray::N_powers; i++) { 148 // -1 so that the the card with the actual offset is counted. Another -1 149 // so that the reach ends in this region and not at the start 150 // of the next. 151 size_t reach = start_card - 1 + (BlockOffsetArray::power_to_cards_back(i+1) - 1); 152 offset = N_words + i; 153 if (reach >= end_card) { 154 _bot->set_offset_array(start_card_for_region, end_card, offset); 155 start_card_for_region = reach + 1; 156 break; 157 } 158 _bot->set_offset_array(start_card_for_region, reach, offset); 159 start_card_for_region = reach + 1; 160 } 161 assert(start_card_for_region > end_card, "Sanity check"); 162 DEBUG_ONLY(check_all_cards(start_card, end_card);) 163 } 164 165 // The card-interval [start_card, end_card] is a closed interval; this 166 // is an expensive check -- use with care and only under protection of 167 // suitable flag. 168 void G1BlockOffsetTablePart::check_all_cards(size_t start_card, size_t end_card) const { 169 170 if (end_card < start_card) { 171 return; 172 } 173 guarantee(_bot->offset_array(start_card) == N_words, "Wrong value in second card"); 174 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) { 175 u_char entry = _bot->offset_array(c); 176 if (c - start_card > BlockOffsetArray::power_to_cards_back(1)) { 177 guarantee(entry > N_words, 178 "Should be in logarithmic region - " 179 "entry: %u, " 180 "_array->offset_array(c): %u, " 181 "N_words: %u", 182 (uint)entry, (uint)_bot->offset_array(c), (uint)N_words); 183 } 184 size_t backskip = BlockOffsetArray::entry_to_cards_back(entry); 185 size_t landing_card = c - backskip; 186 guarantee(landing_card >= (start_card - 1), "Inv"); 187 if (landing_card >= start_card) { 188 guarantee(_bot->offset_array(landing_card) <= entry, 189 "Monotonicity - landing_card offset: %u, " 190 "entry: %u", 191 (uint)_bot->offset_array(landing_card), (uint)entry); 192 } else { 193 guarantee(landing_card == start_card - 1, "Tautology"); 194 // Note that N_words is the maximum offset value 195 guarantee(_bot->offset_array(landing_card) <= N_words, 196 "landing card offset: %u, " 197 "N_words: %u", 198 (uint)_bot->offset_array(landing_card), (uint)N_words); 199 } 200 } 201 } 202 203 HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr_slow(HeapWord* q, 204 HeapWord* n, 205 const void* addr) { 206 // We're not in the normal case. We need to handle an important subcase 207 // here: LAB allocation. An allocation previously recorded in the 208 // offset table was actually a lab allocation, and was divided into 209 // several objects subsequently. Fix this situation as we answer the 210 // query, by updating entries as we cross them. 211 212 // If the fist object's end q is at the card boundary. Start refining 213 // with the corresponding card (the value of the entry will be basically 214 // set to 0). If the object crosses the boundary -- start from the next card. 215 size_t n_index = _bot->index_for(n); 216 size_t next_index = _bot->index_for(n) + !_bot->is_card_boundary(n); 217 // Calculate a consistent next boundary. If "n" is not at the boundary 218 // already, step to the boundary. 219 HeapWord* next_boundary = _bot->address_for_index(n_index) + 220 (n_index == next_index ? 0 : N_words); 221 assert(next_boundary <= _bot->_reserved.end(), 222 "next_boundary is beyond the end of the covered region " 223 " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT, 224 p2i(next_boundary), p2i(_bot->_reserved.end())); 225 if (addr >= _space->top()) return _space->top(); 226 while (next_boundary < addr) { 227 while (n <= next_boundary) { 228 q = n; 229 oop obj = oop(q); 230 if (obj->klass_or_null() == NULL) return q; 231 n += block_size(q); 232 } 233 assert(q <= next_boundary && n > next_boundary, "Consequence of loop"); 234 // [q, n) is the block that crosses the boundary. 235 alloc_block_work(&next_boundary, &next_index, q, n); 236 } 237 return forward_to_block_containing_addr_const(q, n, addr); 238 } 239 240 // 241 // threshold_ 242 // | _index_ 243 // v v 244 // +-------+-------+-------+-------+-------+ 245 // | i-1 | i | i+1 | i+2 | i+3 | 246 // +-------+-------+-------+-------+-------+ 247 // ( ^ ] 248 // block-start 249 // 250 void G1BlockOffsetTablePart::alloc_block_work(HeapWord** threshold_, size_t* index_, 251 HeapWord* blk_start, HeapWord* blk_end) { 252 // For efficiency, do copy-in/copy-out. 253 HeapWord* threshold = *threshold_; 254 size_t index = *index_; 255 256 assert(blk_start != NULL && blk_end > blk_start, 257 "phantom block"); 258 assert(blk_end > threshold, "should be past threshold"); 259 assert(blk_start <= threshold, "blk_start should be at or before threshold"); 260 assert(pointer_delta(threshold, blk_start) <= N_words, 261 "offset should be <= BlockOffsetSharedArray::N"); 262 assert(G1CollectedHeap::heap()->is_in_reserved(blk_start), 263 "reference must be into the heap"); 264 assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1), 265 "limit must be within the heap"); 266 assert(threshold == _bot->_reserved.start() + index*N_words, 267 "index must agree with threshold"); 268 269 DEBUG_ONLY(size_t orig_index = index;) 270 271 // Mark the card that holds the offset into the block. Note 272 // that _next_offset_index and _next_offset_threshold are not 273 // updated until the end of this method. 274 _bot->set_offset_array(index, threshold, blk_start); 275 276 // We need to now mark the subsequent cards that this blk spans. 277 278 // Index of card on which blk ends. 279 size_t end_index = _bot->index_for(blk_end - 1); 280 281 // Are there more cards left to be updated? 282 if (index + 1 <= end_index) { 283 HeapWord* rem_st = _bot->address_for_index(index + 1); 284 // Calculate rem_end this way because end_index 285 // may be the last valid index in the covered region. 286 HeapWord* rem_end = _bot->address_for_index(end_index) + N_words; 287 set_remainder_to_point_to_start(rem_st, rem_end); 288 } 289 290 index = end_index + 1; 291 // Calculate threshold_ this way because end_index 292 // may be the last valid index in the covered region. 293 threshold = _bot->address_for_index(end_index) + N_words; 294 assert(threshold >= blk_end, "Incorrect offset threshold"); 295 296 // index_ and threshold_ updated here. 297 *threshold_ = threshold; 298 *index_ = index; 299 300 #ifdef ASSERT 301 // The offset can be 0 if the block starts on a boundary. That 302 // is checked by an assertion above. 303 size_t start_index = _bot->index_for(blk_start); 304 HeapWord* boundary = _bot->address_for_index(start_index); 305 assert((_bot->offset_array(orig_index) == 0 && blk_start == boundary) || 306 (_bot->offset_array(orig_index) > 0 && _bot->offset_array(orig_index) <= N_words), 307 "offset array should have been set - " 308 "orig_index offset: %u, " 309 "blk_start: " PTR_FORMAT ", " 310 "boundary: " PTR_FORMAT, 311 (uint)_bot->offset_array(orig_index), 312 p2i(blk_start), p2i(boundary)); 313 for (size_t j = orig_index + 1; j <= end_index; j++) { 314 assert(_bot->offset_array(j) > 0 && 315 _bot->offset_array(j) <= 316 (u_char) (N_words+BlockOffsetArray::N_powers-1), 317 "offset array should have been set - " 318 "%u not > 0 OR %u not <= %u", 319 (uint) _bot->offset_array(j), 320 (uint) _bot->offset_array(j), 321 (uint) (N_words+BlockOffsetArray::N_powers-1)); 322 } 323 #endif 324 } 325 326 void G1BlockOffsetTablePart::verify() const { 327 assert(_space->bottom() < _space->top(), "Only non-empty regions should be verified."); 328 size_t start_card = _bot->index_for(_space->bottom()); 329 size_t end_card = _bot->index_for(_space->top() - 1); 330 331 for (size_t current_card = start_card; current_card < end_card; current_card++) { 332 u_char entry = _bot->offset_array(current_card); 333 if (entry < N_words) { 334 // The entry should point to an object before the current card. Verify that 335 // it is possible to walk from that object in to the current card by just 336 // iterating over the objects following it. 337 HeapWord* card_address = _bot->address_for_index(current_card); 338 HeapWord* obj_end = card_address - entry; 339 while (obj_end < card_address) { 340 HeapWord* obj = obj_end; 341 size_t obj_size = block_size(obj); 342 obj_end = obj + obj_size; 343 guarantee(obj_end > obj && obj_end <= _space->top(), 344 "Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT, 345 p2i(obj), obj_size, p2i(obj_end), p2i(_space->top())); 346 } 347 } else { 348 // Because we refine the BOT based on which cards are dirty there is not much we can verify here. 349 // We need to make sure that we are going backwards and that we don't pass the start of the 350 // corresponding heap region. But that is about all we can verify. 351 size_t backskip = BlockOffsetArray::entry_to_cards_back(entry); 352 guarantee(backskip >= 1, "Must be going back at least one card."); 353 354 size_t max_backskip = current_card - start_card; 355 guarantee(backskip <= max_backskip, 356 "Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT, 357 start_card, current_card, backskip); 358 359 HeapWord* backskip_address = _bot->address_for_index(current_card - backskip); 360 guarantee(backskip_address >= _space->bottom(), 361 "Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT, 362 p2i(_space->bottom()), p2i(backskip_address)); 363 } 364 } 365 } 366 367 #ifndef PRODUCT 368 void 369 G1BlockOffsetTablePart::print_on(outputStream* out) { 370 size_t from_index = _bot->index_for(_space->bottom()); 371 size_t to_index = _bot->index_for(_space->end()); 372 out->print_cr(">> BOT for area [" PTR_FORMAT "," PTR_FORMAT ") " 373 "cards [" SIZE_FORMAT "," SIZE_FORMAT ")", 374 p2i(_space->bottom()), p2i(_space->end()), from_index, to_index); 375 for (size_t i = from_index; i < to_index; ++i) { 376 out->print_cr(" entry " SIZE_FORMAT_W(8) " | " PTR_FORMAT " : %3u", 377 i, p2i(_bot->address_for_index(i)), 378 (uint) _bot->offset_array(i)); 379 } 380 out->print_cr(" next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold)); 381 out->print_cr(" next offset index: " SIZE_FORMAT, _next_offset_index); 382 } 383 #endif // !PRODUCT 384 385 HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() { 386 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array), 387 "just checking"); 388 _next_offset_index = _bot->index_for_raw(_space->bottom()); 389 _next_offset_index++; 390 _next_offset_threshold = 391 _bot->address_for_index_raw(_next_offset_index); 392 return _next_offset_threshold; 393 } 394 395 void G1BlockOffsetTablePart::zero_bottom_entry_raw() { 396 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array), 397 "just checking"); 398 size_t bottom_index = _bot->index_for_raw(_space->bottom()); 399 assert(_bot->address_for_index_raw(bottom_index) == _space->bottom(), 400 "Precondition of call"); 401 _bot->set_offset_array_raw(bottom_index, 0); 402 } 403 404 HeapWord* G1BlockOffsetTablePart::initialize_threshold() { 405 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array), 406 "just checking"); 407 _next_offset_index = _bot->index_for(_space->bottom()); 408 _next_offset_index++; 409 _next_offset_threshold = 410 _bot->address_for_index(_next_offset_index); 411 return _next_offset_threshold; 412 } 413 414 void G1BlockOffsetTablePart::set_for_starts_humongous(HeapWord* obj_top, size_t fill_size) { 415 // The first BOT entry should have offset 0. 416 reset_bot(); 417 alloc_block(_space->bottom(), obj_top); 418 if (fill_size > 0) { 419 alloc_block(obj_top, fill_size); 420 } 421 } |