1 /* 2 * Copyright (c) 2016, 2019, 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/g1CollectedHeap.inline.hpp" 27 #include "gc/g1/g1CollectionSet.hpp" 28 #include "gc/g1/g1CollectionSetCandidates.hpp" 29 #include "gc/g1/g1CollectorState.hpp" 30 #include "gc/g1/g1HotCardCache.hpp" 31 #include "gc/g1/g1ParScanThreadState.hpp" 32 #include "gc/g1/g1Policy.hpp" 33 #include "gc/g1/heapRegion.inline.hpp" 34 #include "gc/g1/heapRegionRemSet.hpp" 35 #include "gc/g1/heapRegionSet.hpp" 36 #include "logging/logStream.hpp" 37 #include "utilities/debug.hpp" 38 #include "utilities/globalDefinitions.hpp" 39 #include "utilities/quickSort.hpp" 40 41 G1CollectorState* G1CollectionSet::collector_state() { 42 return _g1h->collector_state(); 43 } 44 45 G1GCPhaseTimes* G1CollectionSet::phase_times() { 46 return _policy->phase_times(); 47 } 48 49 double G1CollectionSet::predict_region_elapsed_time_ms(HeapRegion* hr) { 50 return _policy->predict_region_elapsed_time_ms(hr, collector_state()->in_young_only_phase()); 51 } 52 53 G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) : 54 _g1h(g1h), 55 _policy(policy), 56 _candidates(NULL), 57 _eden_region_length(0), 58 _survivor_region_length(0), 59 _old_region_length(0), 60 _collection_set_regions(NULL), 61 _collection_set_cur_length(0), 62 _collection_set_max_length(0), 63 _num_optional_regions(0), 64 _bytes_used_before(0), 65 _recorded_rs_length(0), 66 _inc_build_state(Inactive), 67 _inc_part_start(0), 68 _inc_bytes_used_before(0), 69 _inc_recorded_rs_length(0), 70 _inc_recorded_rs_length_diff(0), 71 _inc_predicted_elapsed_time_ms(0.0), 72 _inc_predicted_elapsed_time_ms_diff(0.0) { 73 } 74 75 G1CollectionSet::~G1CollectionSet() { 76 FREE_C_HEAP_ARRAY(uint, _collection_set_regions); 77 free_optional_regions(); 78 clear_candidates(); 79 } 80 81 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length, 82 uint survivor_cset_region_length) { 83 assert_at_safepoint_on_vm_thread(); 84 85 _eden_region_length = eden_cset_region_length; 86 _survivor_region_length = survivor_cset_region_length; 87 88 assert((size_t) young_region_length() == _collection_set_cur_length, 89 "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_cur_length); 90 91 _old_region_length = 0; 92 free_optional_regions(); 93 } 94 95 void G1CollectionSet::initialize(uint max_region_length) { 96 guarantee(_collection_set_regions == NULL, "Must only initialize once."); 97 _collection_set_max_length = max_region_length; 98 _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC); 99 } 100 101 void G1CollectionSet::free_optional_regions() { 102 _num_optional_regions = 0; 103 } 104 105 void G1CollectionSet::clear_candidates() { 106 delete _candidates; 107 _candidates = NULL; 108 } 109 110 void G1CollectionSet::set_recorded_rs_length(size_t rs_length) { 111 _recorded_rs_length = rs_length; 112 } 113 114 // Add the heap region at the head of the non-incremental collection set 115 void G1CollectionSet::add_old_region(HeapRegion* hr) { 116 assert_at_safepoint_on_vm_thread(); 117 118 assert(_inc_build_state == Active, 119 "Precondition, actively building cset or adding optional later on"); 120 assert(hr->is_old(), "the region should be old"); 121 122 assert(!hr->in_collection_set(), "should not already be in the collection set"); 123 _g1h->register_old_region_with_region_attr(hr); 124 125 _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index(); 126 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size."); 127 128 _bytes_used_before += hr->used(); 129 _recorded_rs_length += hr->rem_set()->occupied(); 130 _old_region_length++; 131 132 _g1h->old_set_remove(hr); 133 } 134 135 void G1CollectionSet::add_optional_region(HeapRegion* hr) { 136 assert(hr->is_old(), "the region should be old"); 137 assert(!hr->in_collection_set(), "should not already be in the CSet"); 138 139 _g1h->register_optional_region_with_region_attr(hr); 140 141 hr->set_index_in_opt_cset(_num_optional_regions++); 142 } 143 144 void G1CollectionSet::start_incremental_building() { 145 assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set."); 146 assert(_inc_build_state == Inactive, "Precondition"); 147 148 _inc_bytes_used_before = 0; 149 150 _inc_recorded_rs_length = 0; 151 _inc_recorded_rs_length_diff = 0; 152 _inc_predicted_elapsed_time_ms = 0.0; 153 _inc_predicted_elapsed_time_ms_diff = 0.0; 154 155 update_incremental_marker(); 156 } 157 158 void G1CollectionSet::finalize_incremental_building() { 159 assert(_inc_build_state == Active, "Precondition"); 160 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint"); 161 162 // The two "main" fields, _inc_recorded_rs_length and 163 // _inc_predicted_elapsed_time_ms, are updated by the thread 164 // that adds a new region to the CSet. Further updates by the 165 // concurrent refinement thread that samples the young RSet lengths 166 // are accumulated in the *_diff fields. Here we add the diffs to 167 // the "main" fields. 168 169 if (_inc_recorded_rs_length_diff >= 0) { 170 _inc_recorded_rs_length += _inc_recorded_rs_length_diff; 171 } else { 172 // This is defensive. The diff should in theory be always positive 173 // as RSets can only grow between GCs. However, given that we 174 // sample their size concurrently with other threads updating them 175 // it's possible that we might get the wrong size back, which 176 // could make the calculations somewhat inaccurate. 177 size_t diffs = (size_t) (-_inc_recorded_rs_length_diff); 178 if (_inc_recorded_rs_length >= diffs) { 179 _inc_recorded_rs_length -= diffs; 180 } else { 181 _inc_recorded_rs_length = 0; 182 } 183 } 184 _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diff; 185 186 _inc_recorded_rs_length_diff = 0; 187 _inc_predicted_elapsed_time_ms_diff = 0.0; 188 } 189 190 void G1CollectionSet::clear() { 191 assert_at_safepoint_on_vm_thread(); 192 _collection_set_cur_length = 0; 193 } 194 195 void G1CollectionSet::iterate(HeapRegionClosure* cl) const { 196 size_t len = _collection_set_cur_length; 197 OrderAccess::loadload(); 198 199 for (uint i = 0; i < len; i++) { 200 HeapRegion* r = _g1h->region_at(_collection_set_regions[i]); 201 bool result = cl->do_heap_region(r); 202 if (result) { 203 cl->set_incomplete(); 204 return; 205 } 206 } 207 } 208 209 void G1CollectionSet::iterate_optional(HeapRegionClosure* cl) const { 210 assert_at_safepoint(); 211 212 for (uint i = 0; i < _num_optional_regions; i++) { 213 HeapRegion* r = _candidates->at(i); 214 bool result = cl->do_heap_region(r); 215 guarantee(!result, "Must not cancel iteration"); 216 } 217 } 218 219 void G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure* cl, 220 HeapRegionClaimer* hr_claimer, 221 uint worker_id, 222 uint total_workers) const { 223 assert_at_safepoint(); 224 225 size_t len = increment_length(); 226 if (len == 0) { 227 return; 228 } 229 230 size_t start_pos = (worker_id * len) / total_workers; 231 size_t cur_pos = start_pos; 232 233 do { 234 uint region_idx = _collection_set_regions[cur_pos + _inc_part_start]; 235 if (hr_claimer == NULL || hr_claimer->claim_region(region_idx)) { 236 HeapRegion* r = _g1h->region_at(region_idx); 237 bool result = cl->do_heap_region(r); 238 guarantee(!result, "Must not cancel iteration"); 239 } 240 241 cur_pos++; 242 if (cur_pos == len) { 243 cur_pos = 0; 244 } 245 } while (cur_pos != start_pos); 246 } 247 248 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr, 249 size_t new_rs_length) { 250 // Update the CSet information that is dependent on the new RS length 251 assert(hr->is_young(), "Precondition"); 252 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint"); 253 254 // We could have updated _inc_recorded_rs_length and 255 // _inc_predicted_elapsed_time_ms directly but we'd need to do 256 // that atomically, as this code is executed by a concurrent 257 // refinement thread, potentially concurrently with a mutator thread 258 // allocating a new region and also updating the same fields. To 259 // avoid the atomic operations we accumulate these updates on two 260 // separate fields (*_diff) and we'll just add them to the "main" 261 // fields at the start of a GC. 262 263 ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length(); 264 ssize_t rs_length_diff = (ssize_t) new_rs_length - old_rs_length; 265 _inc_recorded_rs_length_diff += rs_length_diff; 266 267 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms(); 268 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr); 269 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms; 270 _inc_predicted_elapsed_time_ms_diff += elapsed_ms_diff; 271 272 hr->set_recorded_rs_length(new_rs_length); 273 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms); 274 } 275 276 void G1CollectionSet::add_young_region_common(HeapRegion* hr) { 277 assert(hr->is_young(), "invariant"); 278 assert(_inc_build_state == Active, "Precondition"); 279 280 size_t collection_set_length = _collection_set_cur_length; 281 // We use UINT_MAX as "invalid" marker in verification. 282 assert(collection_set_length < (UINT_MAX - 1), 283 "Collection set is too large with " SIZE_FORMAT " entries", collection_set_length); 284 hr->set_young_index_in_cset((uint)collection_set_length + 1); 285 286 _collection_set_regions[collection_set_length] = hr->hrm_index(); 287 // Concurrent readers must observe the store of the value in the array before an 288 // update to the length field. 289 OrderAccess::storestore(); 290 _collection_set_cur_length++; 291 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed."); 292 293 // This routine is used when: 294 // * adding survivor regions to the incremental cset at the end of an 295 // evacuation pause or 296 // * adding the current allocation region to the incremental cset 297 // when it is retired. 298 // Therefore this routine may be called at a safepoint by the 299 // VM thread, or in-between safepoints by mutator threads (when 300 // retiring the current allocation region) 301 // We need to clear and set the cached recorded/cached collection set 302 // information in the heap region here (before the region gets added 303 // to the collection set). An individual heap region's cached values 304 // are calculated, aggregated with the policy collection set info, 305 // and cached in the heap region here (initially) and (subsequently) 306 // by the Young List sampling code. 307 // Ignore calls to this due to retirement during full gc. 308 309 if (!_g1h->collector_state()->in_full_gc()) { 310 size_t rs_length = hr->rem_set()->occupied(); 311 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr); 312 313 // Cache the values we have added to the aggregated information 314 // in the heap region in case we have to remove this region from 315 // the incremental collection set, or it is updated by the 316 // rset sampling code 317 hr->set_recorded_rs_length(rs_length); 318 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms); 319 320 _inc_recorded_rs_length += rs_length; 321 _inc_predicted_elapsed_time_ms += region_elapsed_time_ms; 322 _inc_bytes_used_before += hr->used(); 323 } 324 325 assert(!hr->in_collection_set(), "invariant"); 326 _g1h->register_young_region_with_region_attr(hr); 327 } 328 329 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) { 330 assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str()); 331 add_young_region_common(hr); 332 } 333 334 void G1CollectionSet::add_eden_region(HeapRegion* hr) { 335 assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str()); 336 add_young_region_common(hr); 337 } 338 339 #ifndef PRODUCT 340 class G1VerifyYoungAgesClosure : public HeapRegionClosure { 341 public: 342 bool _valid; 343 public: 344 G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { } 345 346 virtual bool do_heap_region(HeapRegion* r) { 347 guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str()); 348 349 SurvRateGroup* group = r->surv_rate_group(); 350 351 if (group == NULL) { 352 log_error(gc, verify)("## encountered NULL surv_rate_group in young region"); 353 _valid = false; 354 } 355 356 if (r->age_in_surv_rate_group() < 0) { 357 log_error(gc, verify)("## encountered negative age in young region"); 358 _valid = false; 359 } 360 361 return false; 362 } 363 364 bool valid() const { return _valid; } 365 }; 366 367 bool G1CollectionSet::verify_young_ages() { 368 assert_at_safepoint_on_vm_thread(); 369 370 G1VerifyYoungAgesClosure cl; 371 iterate(&cl); 372 373 if (!cl.valid()) { 374 LogStreamHandle(Error, gc, verify) log; 375 print(&log); 376 } 377 378 return cl.valid(); 379 } 380 381 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure { 382 outputStream* _st; 383 public: 384 G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { } 385 386 virtual bool do_heap_region(HeapRegion* r) { 387 assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index()); 388 _st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d", 389 HR_FORMAT_PARAMS(r), 390 p2i(r->prev_top_at_mark_start()), 391 p2i(r->next_top_at_mark_start()), 392 r->age_in_surv_rate_group_cond()); 393 return false; 394 } 395 }; 396 397 void G1CollectionSet::print(outputStream* st) { 398 st->print_cr("\nCollection_set:"); 399 400 G1PrintCollectionSetDetailClosure cl(st); 401 iterate(&cl); 402 } 403 #endif // !PRODUCT 404 405 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) { 406 double young_start_time_sec = os::elapsedTime(); 407 408 finalize_incremental_building(); 409 410 guarantee(target_pause_time_ms > 0.0, 411 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms); 412 413 size_t pending_cards = _policy->pending_cards_at_gc_start() + _g1h->hot_card_cache()->num_entries(); 414 double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards); 415 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0); 416 417 log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms", 418 pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms); 419 420 // The young list is laid with the survivor regions from the previous 421 // pause are appended to the RHS of the young list, i.e. 422 // [Newly Young Regions ++ Survivors from last pause]. 423 424 uint survivor_region_length = survivors->length(); 425 uint eden_region_length = _g1h->eden_regions_count(); 426 init_region_lengths(eden_region_length, survivor_region_length); 427 428 verify_young_cset_indices(); 429 430 // Clear the fields that point to the survivor list - they are all young now. 431 survivors->convert_to_eden(); 432 433 _bytes_used_before = _inc_bytes_used_before; 434 time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0); 435 436 log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms", 437 eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms); 438 439 // The number of recorded young regions is the incremental 440 // collection set's current size 441 set_recorded_rs_length(_inc_recorded_rs_length); 442 443 double young_end_time_sec = os::elapsedTime(); 444 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0); 445 446 return time_remaining_ms; 447 } 448 449 static int compare_region_idx(const uint a, const uint b) { 450 if (a > b) { 451 return 1; 452 } else if (a == b) { 453 return 0; 454 } else { 455 return -1; 456 } 457 } 458 459 void G1CollectionSet::finalize_old_part(double time_remaining_ms) { 460 double non_young_start_time_sec = os::elapsedTime(); 461 462 if (collector_state()->in_mixed_phase()) { 463 candidates()->verify(); 464 465 uint num_initial_old_regions; 466 uint num_optional_old_regions; 467 468 _policy->calculate_old_collection_set_regions(candidates(), 469 time_remaining_ms, 470 num_initial_old_regions, 471 num_optional_old_regions); 472 473 // Prepare initial old regions. 474 move_candidates_to_collection_set(num_initial_old_regions); 475 476 // Prepare optional old regions for evacuation. 477 uint candidate_idx = candidates()->cur_idx(); 478 for (uint i = 0; i < num_optional_old_regions; i++) { 479 add_optional_region(candidates()->at(candidate_idx + i)); 480 } 481 482 candidates()->verify(); 483 } 484 485 stop_incremental_building(); 486 487 double non_young_end_time_sec = os::elapsedTime(); 488 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0); 489 490 QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true); 491 } 492 493 void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) { 494 if (num_old_candidate_regions == 0) { 495 return; 496 } 497 uint candidate_idx = candidates()->cur_idx(); 498 for (uint i = 0; i < num_old_candidate_regions; i++) { 499 HeapRegion* r = candidates()->at(candidate_idx + i); 500 // This potentially optional candidate region is going to be an actual collection 501 // set region. Clear cset marker. 502 _g1h->clear_region_attr(r); 503 add_old_region(r); 504 } 505 candidates()->remove(num_old_candidate_regions); 506 507 candidates()->verify(); 508 } 509 510 void G1CollectionSet::finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) { 511 double time_remaining_ms = finalize_young_part(target_pause_time_ms, survivor); 512 finalize_old_part(time_remaining_ms); 513 } 514 515 bool G1CollectionSet::finalize_optional_for_evacuation(double remaining_pause_time) { 516 update_incremental_marker(); 517 518 uint num_selected_regions; 519 _policy->calculate_optional_collection_set_regions(candidates(), 520 _num_optional_regions, 521 remaining_pause_time, 522 num_selected_regions); 523 524 move_candidates_to_collection_set(num_selected_regions); 525 526 _num_optional_regions -= num_selected_regions; 527 528 stop_incremental_building(); 529 530 _g1h->verify_region_attr_remset_update(); 531 532 return num_selected_regions > 0; 533 } 534 535 void G1CollectionSet::abandon_optional_collection_set(G1ParScanThreadStateSet* pss) { 536 for (uint i = 0; i < _num_optional_regions; i++) { 537 HeapRegion* r = candidates()->at(candidates()->cur_idx() + i); 538 pss->record_unused_optional_region(r); 539 // Clear collection set marker and make sure that the remembered set information 540 // is correct as we still need it later. 541 _g1h->clear_region_attr(r); 542 _g1h->register_region_with_region_attr(r); 543 r->clear_index_in_opt_cset(); 544 } 545 free_optional_regions(); 546 547 _g1h->verify_region_attr_remset_update(); 548 } 549 550 #ifdef ASSERT 551 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure { 552 private: 553 size_t _young_length; 554 uint* _heap_region_indices; 555 public: 556 G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) { 557 _heap_region_indices = NEW_C_HEAP_ARRAY(uint, young_length + 1, mtGC); 558 for (size_t i = 0; i < young_length + 1; i++) { 559 _heap_region_indices[i] = UINT_MAX; 560 } 561 } 562 ~G1VerifyYoungCSetIndicesClosure() { 563 FREE_C_HEAP_ARRAY(int, _heap_region_indices); 564 } 565 566 virtual bool do_heap_region(HeapRegion* r) { 567 const uint idx = r->young_index_in_cset(); 568 569 assert(idx > 0, "Young index must be set for all regions in the incremental collection set but is not for region %u.", r->hrm_index()); 570 assert(idx <= _young_length, "Young cset index %u too large for region %u", idx, r->hrm_index()); 571 572 assert(_heap_region_indices[idx] == UINT_MAX, 573 "Index %d used by multiple regions, first use by region %u, second by region %u", 574 idx, _heap_region_indices[idx], r->hrm_index()); 575 576 _heap_region_indices[idx] = r->hrm_index(); 577 578 return false; 579 } 580 }; 581 582 void G1CollectionSet::verify_young_cset_indices() const { 583 assert_at_safepoint_on_vm_thread(); 584 585 G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length); 586 iterate(&cl); 587 } 588 #endif