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