1/* 2 * Copyright (c) 2001, 2017, 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/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 41G1BlockOffsetTable::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 53bool 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((int)BOTConstants::LogN_words)) == (size_t)NoBits; 57} 58 59#ifdef ASSERT 60void G1BlockOffsetTable::check_index(size_t index, const char* msg) const { 61 assert((index) < (_reserved.word_size() >> BOTConstants::LogN_words), 62 "%s - index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT, 63 msg, (index), (_reserved.word_size() >> BOTConstants::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 77G1BlockOffsetTablePart::G1BlockOffsetTablePart(G1BlockOffsetTable* array, G1ContiguousSpace* gsp) : 78 _bot(array), 79 _space(gsp), 80 _next_offset_threshold(NULL), 81 _next_offset_index(0) 82{ 83 debug_only(_object_can_span = false;) 84} 85 86// The arguments follow the normal convention of denoting 87// a right-open interval: [start, end) 88void G1BlockOffsetTablePart:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) { 89 90 if (start >= end) { 91 // The start address is equal to the end address (or to 92 // the right of the end address) so there are not cards 93 // that need to be updated.. 94 return; 95 } 96 97 // Write the backskip value for each region. 98 // 99 // offset 100 // card 2nd 3rd 101 // | +- 1st | | 102 // v v v v 103 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+- 104 // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ... 105 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+- 106 // 11 19 75 107 // 12 108 // 109 // offset card is the card that points to the start of an object 110 // x - offset value of offset card 111 // 1st - start of first logarithmic region 112 // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1 113 // 2nd - start of second logarithmic region 114 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8 115 // 3rd - start of third logarithmic region 116 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64 117 // 118 // integer below the block offset entry is an example of 119 // the index of the entry 120 // 121 // Given an address, 122 // Find the index for the address 123 // Find the block offset table entry 124 // Convert the entry to a back slide 125 // (e.g., with today's, offset = 0x81 => 126 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8 127 // Move back N (e.g., 8) entries and repeat with the 128 // value of the new entry 129 // 130 size_t start_card = _bot->index_for(start); 131 size_t end_card = _bot->index_for(end-1); 132 assert(start ==_bot->address_for_index(start_card), "Precondition"); 133 assert(end ==_bot->address_for_index(end_card)+BOTConstants::N_words, "Precondition"); 134 set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval 135} 136 137// Unlike the normal convention in this code, the argument here denotes 138// a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start() 139// above. 140void G1BlockOffsetTablePart::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) { 141 if (start_card > end_card) { 142 return; 143 } 144 assert(start_card > _bot->index_for(_space->bottom()), "Cannot be first card"); 145 assert(_bot->offset_array(start_card-1) <= BOTConstants::N_words, 146 "Offset card has an unexpected value"); 147 size_t start_card_for_region = start_card; 148 u_char offset = max_jubyte; 149 for (uint i = 0; i < BOTConstants::N_powers; i++) { 150 // -1 so that the the card with the actual offset is counted. Another -1 151 // so that the reach ends in this region and not at the start 152 // of the next. 153 size_t reach = start_card - 1 + (BOTConstants::power_to_cards_back(i+1) - 1); 154 offset = BOTConstants::N_words + i; 155 if (reach >= end_card) { 156 _bot->set_offset_array(start_card_for_region, end_card, offset); 157 start_card_for_region = reach + 1; 158 break; 159 } 160 _bot->set_offset_array(start_card_for_region, reach, offset); 161 start_card_for_region = reach + 1; 162 } 163 assert(start_card_for_region > end_card, "Sanity check"); 164 DEBUG_ONLY(check_all_cards(start_card, end_card);) 165} 166 167// The card-interval [start_card, end_card] is a closed interval; this 168// is an expensive check -- use with care and only under protection of 169// suitable flag. 170void G1BlockOffsetTablePart::check_all_cards(size_t start_card, size_t end_card) const { 171 172 if (end_card < start_card) { 173 return; 174 } 175 guarantee(_bot->offset_array(start_card) == BOTConstants::N_words, "Wrong value in second card"); 176 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) { 177 u_char entry = _bot->offset_array(c); 178 if (c - start_card > BOTConstants::power_to_cards_back(1)) { 179 guarantee(entry > BOTConstants::N_words, 180 "Should be in logarithmic region - " 181 "entry: %u, " 182 "_array->offset_array(c): %u, " 183 "N_words: %u", 184 (uint)entry, (uint)_bot->offset_array(c), BOTConstants::N_words); 185 } 186 size_t backskip = BOTConstants::entry_to_cards_back(entry); 187 size_t landing_card = c - backskip; 188 guarantee(landing_card >= (start_card - 1), "Inv"); 189 if (landing_card >= start_card) { 190 guarantee(_bot->offset_array(landing_card) <= entry, 191 "Monotonicity - landing_card offset: %u, " 192 "entry: %u", 193 (uint)_bot->offset_array(landing_card), (uint)entry); 194 } else { 195 guarantee(landing_card == start_card - 1, "Tautology"); 196 // Note that N_words is the maximum offset value 197 guarantee(_bot->offset_array(landing_card) <= BOTConstants::N_words, 198 "landing card offset: %u, " 199 "N_words: %u", 200 (uint)_bot->offset_array(landing_card), (uint)BOTConstants::N_words); 201 } 202 } 203} 204 205HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr_slow(HeapWord* q, 206 HeapWord* n, 207 const void* addr) { 208 // We're not in the normal case. We need to handle an important subcase 209 // here: LAB allocation. An allocation previously recorded in the 210 // offset table was actually a lab allocation, and was divided into 211 // several objects subsequently. Fix this situation as we answer the 212 // query, by updating entries as we cross them. 213 214 // If the fist object's end q is at the card boundary. Start refining 215 // with the corresponding card (the value of the entry will be basically 216 // set to 0). If the object crosses the boundary -- start from the next card. 217 size_t n_index = _bot->index_for(n); 218 size_t next_index = _bot->index_for(n) + !_bot->is_card_boundary(n); 219 // Calculate a consistent next boundary. If "n" is not at the boundary 220 // already, step to the boundary. 221 HeapWord* next_boundary = _bot->address_for_index(n_index) + 222 (n_index == next_index ? 0 : BOTConstants::N_words); 223 assert(next_boundary <= _bot->_reserved.end(), 224 "next_boundary is beyond the end of the covered region " 225 " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT, 226 p2i(next_boundary), p2i(_bot->_reserved.end())); 227 if (addr >= _space->top()) return _space->top(); 228 while (next_boundary < addr) { 229 while (n <= next_boundary) { 230 q = n; 231 oop obj = oop(q); 232 if (obj->klass_or_null_acquire() == NULL) return q; 233 n += block_size(q); 234 } 235 assert(q <= next_boundary && n > next_boundary, "Consequence of loop"); 236 // [q, n) is the block that crosses the boundary. 237 alloc_block_work(&next_boundary, &next_index, q, n); 238 } 239 return forward_to_block_containing_addr_const(q, n, addr); 240} 241 242// 243// threshold_ 244// | _index_ 245// v v 246// +-------+-------+-------+-------+-------+ 247// | i-1 | i | i+1 | i+2 | i+3 | 248// +-------+-------+-------+-------+-------+ 249// ( ^ ] 250// block-start 251// 252void G1BlockOffsetTablePart::alloc_block_work(HeapWord** threshold_, size_t* index_, 253 HeapWord* blk_start, HeapWord* blk_end) { 254 // For efficiency, do copy-in/copy-out. 255 HeapWord* threshold = *threshold_; 256 size_t index = *index_; 257 258 assert(blk_start != NULL && blk_end > blk_start, 259 "phantom block"); 260 assert(blk_end > threshold, "should be past threshold"); 261 assert(blk_start <= threshold, "blk_start should be at or before threshold"); 262 assert(pointer_delta(threshold, blk_start) <= BOTConstants::N_words, 263 "offset should be <= BlockOffsetSharedArray::N"); 264 assert(G1CollectedHeap::heap()->is_in_reserved(blk_start), 265 "reference must be into the heap"); 266 assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1), 267 "limit must be within the heap"); 268 assert(threshold == _bot->_reserved.start() + index*BOTConstants::N_words, 269 "index must agree with threshold"); 270 271 DEBUG_ONLY(size_t orig_index = index;) 272 273 // Mark the card that holds the offset into the block. Note 274 // that _next_offset_index and _next_offset_threshold are not 275 // updated until the end of this method. 276 _bot->set_offset_array(index, threshold, blk_start); 277 278 // We need to now mark the subsequent cards that this blk spans. 279 280 // Index of card on which blk ends. 281 size_t end_index = _bot->index_for(blk_end - 1); 282 283 // Are there more cards left to be updated? 284 if (index + 1 <= end_index) { 285 HeapWord* rem_st = _bot->address_for_index(index + 1); 286 // Calculate rem_end this way because end_index 287 // may be the last valid index in the covered region. 288 HeapWord* rem_end = _bot->address_for_index(end_index) + BOTConstants::N_words; 289 set_remainder_to_point_to_start(rem_st, rem_end); 290 } 291 292 index = end_index + 1; 293 // Calculate threshold_ this way because end_index 294 // may be the last valid index in the covered region. 295 threshold = _bot->address_for_index(end_index) + BOTConstants::N_words; 296 assert(threshold >= blk_end, "Incorrect offset threshold"); 297 298 // index_ and threshold_ updated here. 299 *threshold_ = threshold; 300 *index_ = index; 301 302#ifdef ASSERT 303 // The offset can be 0 if the block starts on a boundary. That 304 // is checked by an assertion above. 305 size_t start_index = _bot->index_for(blk_start); 306 HeapWord* boundary = _bot->address_for_index(start_index); 307 assert((_bot->offset_array(orig_index) == 0 && blk_start == boundary) || 308 (_bot->offset_array(orig_index) > 0 && _bot->offset_array(orig_index) <= BOTConstants::N_words), 309 "offset array should have been set - " 310 "orig_index offset: %u, " 311 "blk_start: " PTR_FORMAT ", " 312 "boundary: " PTR_FORMAT, 313 (uint)_bot->offset_array(orig_index), 314 p2i(blk_start), p2i(boundary)); 315 for (size_t j = orig_index + 1; j <= end_index; j++) { 316 assert(_bot->offset_array(j) > 0 && 317 _bot->offset_array(j) <= 318 (u_char) (BOTConstants::N_words+BOTConstants::N_powers-1), 319 "offset array should have been set - " 320 "%u not > 0 OR %u not <= %u", 321 (uint) _bot->offset_array(j), 322 (uint) _bot->offset_array(j), 323 (uint) (BOTConstants::N_words+BOTConstants::N_powers-1)); 324 } 325#endif 326} 327 328void G1BlockOffsetTablePart::verify() const { 329 assert(_space->bottom() < _space->top(), "Only non-empty regions should be verified."); 330 size_t start_card = _bot->index_for(_space->bottom()); 331 size_t end_card = _bot->index_for(_space->top() - 1); 332 333 for (size_t current_card = start_card; current_card < end_card; current_card++) { 334 u_char entry = _bot->offset_array(current_card); 335 if (entry < BOTConstants::N_words) { 336 // The entry should point to an object before the current card. Verify that 337 // it is possible to walk from that object in to the current card by just 338 // iterating over the objects following it. 339 HeapWord* card_address = _bot->address_for_index(current_card); 340 HeapWord* obj_end = card_address - entry; 341 while (obj_end < card_address) { 342 HeapWord* obj = obj_end; 343 size_t obj_size = block_size(obj); 344 obj_end = obj + obj_size; 345 guarantee(obj_end > obj && obj_end <= _space->top(), 346 "Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT, 347 p2i(obj), obj_size, p2i(obj_end), p2i(_space->top())); 348 } 349 } else { 350 // Because we refine the BOT based on which cards are dirty there is not much we can verify here. 351 // We need to make sure that we are going backwards and that we don't pass the start of the 352 // corresponding heap region. But that is about all we can verify. 353 size_t backskip = BOTConstants::entry_to_cards_back(entry); 354 guarantee(backskip >= 1, "Must be going back at least one card."); 355 356 size_t max_backskip = current_card - start_card; 357 guarantee(backskip <= max_backskip, 358 "Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT, 359 start_card, current_card, backskip); 360 361 HeapWord* backskip_address = _bot->address_for_index(current_card - backskip); 362 guarantee(backskip_address >= _space->bottom(), 363 "Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT, 364 p2i(_space->bottom()), p2i(backskip_address)); 365 } 366 } 367} 368 369#ifdef ASSERT 370void G1BlockOffsetTablePart::set_object_can_span(bool can_span) { 371 _object_can_span = can_span; 372} 373#endif 374 375#ifndef PRODUCT 376void 377G1BlockOffsetTablePart::print_on(outputStream* out) { 378 size_t from_index = _bot->index_for(_space->bottom()); 379 size_t to_index = _bot->index_for(_space->end()); 380 out->print_cr(">> BOT for area [" PTR_FORMAT "," PTR_FORMAT ") " 381 "cards [" SIZE_FORMAT "," SIZE_FORMAT ")", 382 p2i(_space->bottom()), p2i(_space->end()), from_index, to_index); 383 for (size_t i = from_index; i < to_index; ++i) { 384 out->print_cr(" entry " SIZE_FORMAT_W(8) " | " PTR_FORMAT " : %3u", 385 i, p2i(_bot->address_for_index(i)), 386 (uint) _bot->offset_array(i)); 387 } 388 out->print_cr(" next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold)); 389 out->print_cr(" next offset index: " SIZE_FORMAT, _next_offset_index); 390} 391#endif // !PRODUCT 392 393HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() { 394 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array), 395 "just checking"); 396 _next_offset_index = _bot->index_for_raw(_space->bottom()); 397 _next_offset_index++; 398 _next_offset_threshold = 399 _bot->address_for_index_raw(_next_offset_index); 400 return _next_offset_threshold; 401} 402 403void G1BlockOffsetTablePart::zero_bottom_entry_raw() { 404 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array), 405 "just checking"); 406 size_t bottom_index = _bot->index_for_raw(_space->bottom()); 407 assert(_bot->address_for_index_raw(bottom_index) == _space->bottom(), 408 "Precondition of call"); 409 _bot->set_offset_array_raw(bottom_index, 0); 410} 411 412HeapWord* G1BlockOffsetTablePart::initialize_threshold() { 413 assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array), 414 "just checking"); 415 _next_offset_index = _bot->index_for(_space->bottom()); 416 _next_offset_index++; 417 _next_offset_threshold = 418 _bot->address_for_index(_next_offset_index); 419 return _next_offset_threshold; 420} 421 422void G1BlockOffsetTablePart::set_for_starts_humongous(HeapWord* obj_top, size_t fill_size) { 423 // The first BOT entry should have offset 0. 424 reset_bot(); 425 alloc_block(_space->bottom(), obj_top); 426 if (fill_size > 0) { 427 alloc_block(obj_top, fill_size); 428 } 429} 430