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_lengths(0), 65 _inc_build_state(Inactive), 66 _inc_bytes_used_before(0), 67 _inc_recorded_rs_lengths(0), 68 _inc_recorded_rs_lengths_diffs(0), 69 _inc_predicted_elapsed_time_ms(0.0), 70 _inc_predicted_elapsed_time_ms_diffs(0.0) { 71 } 72 73 G1CollectionSet::~G1CollectionSet() { 74 if (_collection_set_regions != NULL) { 75 FREE_C_HEAP_ARRAY(uint, _collection_set_regions); 76 } 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 _num_optional_regions = 0; 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_lengths(size_t rs_lengths) { 111 _recorded_rs_lengths = rs_lengths; 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_cset(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_lengths += 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_cset(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_lengths = 0; 151 _inc_recorded_rs_lengths_diffs = 0; 152 _inc_predicted_elapsed_time_ms = 0.0; 153 _inc_predicted_elapsed_time_ms_diffs = 0.0; 154 155 update_incremental_marker(); 156 } 157 158 void G1CollectionSet::finalize_young_increment() { 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_lengths 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 *_diffs fields. Here we add the diffs to 167 // the "main" fields. 168 169 if (_inc_recorded_rs_lengths_diffs >= 0) { 170 _inc_recorded_rs_lengths += _inc_recorded_rs_lengths_diffs; 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_lengths_diffs); 178 if (_inc_recorded_rs_lengths >= diffs) { 179 _inc_recorded_rs_lengths -= diffs; 180 } else { 181 _inc_recorded_rs_lengths = 0; 182 } 183 } 184 _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diffs; 185 186 _inc_recorded_rs_lengths_diffs = 0; 187 _inc_predicted_elapsed_time_ms_diffs = 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, uint worker_id, uint total_workers) const { 220 assert_at_safepoint(); 221 222 size_t len = _collection_set_cur_length - _inc_part_start; 223 if (len == 0) { 224 return; 225 } 226 227 size_t start_pos = (worker_id * len) / total_workers; 228 size_t cur_pos = start_pos; 229 230 do { 231 HeapRegion* r = _g1h->region_at(_collection_set_regions[cur_pos + _inc_part_start]); 232 bool result = cl->do_heap_region(r); 233 guarantee(!result, "Must not cancel iteration"); 234 235 cur_pos++; 236 if (cur_pos == len) { 237 cur_pos = 0; 238 } 239 } while (cur_pos != start_pos); 240 } 241 242 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr, 243 size_t new_rs_length) { 244 // Update the CSet information that is dependent on the new RS length 245 assert(hr->is_young(), "Precondition"); 246 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint"); 247 248 // We could have updated _inc_recorded_rs_lengths and 249 // _inc_predicted_elapsed_time_ms directly but we'd need to do 250 // that atomically, as this code is executed by a concurrent 251 // refinement thread, potentially concurrently with a mutator thread 252 // allocating a new region and also updating the same fields. To 253 // avoid the atomic operations we accumulate these updates on two 254 // separate fields (*_diffs) and we'll just add them to the "main" 255 // fields at the start of a GC. 256 257 ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length(); 258 ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length; 259 _inc_recorded_rs_lengths_diffs += rs_lengths_diff; 260 261 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms(); 262 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr); 263 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms; 264 _inc_predicted_elapsed_time_ms_diffs += elapsed_ms_diff; 265 266 hr->set_recorded_rs_length(new_rs_length); 267 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms); 268 } 269 270 void G1CollectionSet::add_young_region_common(HeapRegion* hr) { 271 assert(hr->is_young(), "invariant"); 272 assert(_inc_build_state == Active, "Precondition"); 273 274 size_t collection_set_length = _collection_set_cur_length; 275 assert(collection_set_length <= INT_MAX, "Collection set is too large with %d entries", (int)collection_set_length); 276 hr->set_young_index_in_cset((int)collection_set_length); 277 278 _collection_set_regions[collection_set_length] = hr->hrm_index(); 279 // Concurrent readers must observe the store of the value in the array before an 280 // update to the length field. 281 OrderAccess::storestore(); 282 _collection_set_cur_length++; 283 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed."); 284 285 // This routine is used when: 286 // * adding survivor regions to the incremental cset at the end of an 287 // evacuation pause or 288 // * adding the current allocation region to the incremental cset 289 // when it is retired. 290 // Therefore this routine may be called at a safepoint by the 291 // VM thread, or in-between safepoints by mutator threads (when 292 // retiring the current allocation region) 293 // We need to clear and set the cached recorded/cached collection set 294 // information in the heap region here (before the region gets added 295 // to the collection set). An individual heap region's cached values 296 // are calculated, aggregated with the policy collection set info, 297 // and cached in the heap region here (initially) and (subsequently) 298 // by the Young List sampling code. 299 // Ignore calls to this due to retirement during full gc. 300 301 if (!_g1h->collector_state()->in_full_gc()) { 302 size_t rs_length = hr->rem_set()->occupied(); 303 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr); 304 305 // Cache the values we have added to the aggregated information 306 // in the heap region in case we have to remove this region from 307 // the incremental collection set, or it is updated by the 308 // rset sampling code 309 hr->set_recorded_rs_length(rs_length); 310 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms); 311 312 _inc_recorded_rs_lengths += rs_length; 313 _inc_predicted_elapsed_time_ms += region_elapsed_time_ms; 314 _inc_bytes_used_before += hr->used(); 315 } 316 317 assert(!hr->in_collection_set(), "invariant"); 318 _g1h->register_young_region_with_cset(hr); 319 } 320 321 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) { 322 assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str()); 323 add_young_region_common(hr); 324 } 325 326 void G1CollectionSet::add_eden_region(HeapRegion* hr) { 327 assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str()); 328 add_young_region_common(hr); 329 } 330 331 #ifndef PRODUCT 332 class G1VerifyYoungAgesClosure : public HeapRegionClosure { 333 public: 334 bool _valid; 335 public: 336 G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { } 337 338 virtual bool do_heap_region(HeapRegion* r) { 339 guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str()); 340 341 SurvRateGroup* group = r->surv_rate_group(); 342 343 if (group == NULL) { 344 log_error(gc, verify)("## encountered NULL surv_rate_group in young region"); 345 _valid = false; 346 } 347 348 if (r->age_in_surv_rate_group() < 0) { 349 log_error(gc, verify)("## encountered negative age in young region"); 350 _valid = false; 351 } 352 353 return false; 354 } 355 356 bool valid() const { return _valid; } 357 }; 358 359 bool G1CollectionSet::verify_young_ages() { 360 assert_at_safepoint_on_vm_thread(); 361 362 G1VerifyYoungAgesClosure cl; 363 iterate(&cl); 364 365 if (!cl.valid()) { 366 LogStreamHandle(Error, gc, verify) log; 367 print(&log); 368 } 369 370 return cl.valid(); 371 } 372 373 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure { 374 outputStream* _st; 375 public: 376 G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { } 377 378 virtual bool do_heap_region(HeapRegion* r) { 379 assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index()); 380 _st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d", 381 HR_FORMAT_PARAMS(r), 382 p2i(r->prev_top_at_mark_start()), 383 p2i(r->next_top_at_mark_start()), 384 r->age_in_surv_rate_group_cond()); 385 return false; 386 } 387 }; 388 389 void G1CollectionSet::print(outputStream* st) { 390 st->print_cr("\nCollection_set:"); 391 392 G1PrintCollectionSetDetailClosure cl(st); 393 iterate(&cl); 394 } 395 #endif // !PRODUCT 396 397 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) { 398 double young_start_time_sec = os::elapsedTime(); 399 400 finalize_young_increment(); 401 402 guarantee(target_pause_time_ms > 0.0, 403 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms); 404 405 size_t pending_cards = _policy->pending_cards(); 406 double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards); 407 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0); 408 409 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", 410 pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms); 411 412 // The young list is laid with the survivor regions from the previous 413 // pause are appended to the RHS of the young list, i.e. 414 // [Newly Young Regions ++ Survivors from last pause]. 415 416 uint survivor_region_length = survivors->length(); 417 uint eden_region_length = _g1h->eden_regions_count(); 418 init_region_lengths(eden_region_length, survivor_region_length); 419 420 verify_young_cset_indices(); 421 422 // Clear the fields that point to the survivor list - they are all young now. 423 survivors->convert_to_eden(); 424 425 _bytes_used_before = _inc_bytes_used_before; 426 time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0); 427 428 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", 429 eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms); 430 431 // The number of recorded young regions is the incremental 432 // collection set's current size 433 set_recorded_rs_lengths(_inc_recorded_rs_lengths); 434 435 double young_end_time_sec = os::elapsedTime(); 436 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0); 437 438 return time_remaining_ms; 439 } 440 441 static int compare_region_idx(const uint a, const uint b) { 442 if (a > b) { 443 return 1; 444 } else if (a == b) { 445 return 0; 446 } else { 447 return -1; 448 } 449 } 450 451 void G1CollectionSet::finalize_old_part(double time_remaining_ms) { 452 double non_young_start_time_sec = os::elapsedTime(); 453 454 uint num_expensive_regions = 0; 455 456 if (collector_state()->in_mixed_phase()) { 457 candidates()->verify(); 458 459 uint num_initial_regions; 460 uint num_optional_regions; 461 462 _policy->select_old_collection_set_regions(candidates(), 463 time_remaining_ms, 464 num_expensive_regions, 465 num_initial_regions, 466 num_optional_regions); 467 468 // Prepare initial old regions. 469 move_candidates_to_collection_set(num_initial_regions); 470 471 // Prepare optional regions for evacuation. 472 uint candidate_idx = candidates()->cur_idx(); 473 for (uint i = 0; i < num_optional_regions; i++) { 474 add_optional_region(candidates()->at(candidate_idx + i)); 475 } 476 477 candidates()->verify(); 478 } 479 480 stop_incremental_building(); 481 482 double non_young_end_time_sec = os::elapsedTime(); 483 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0); 484 485 QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true); 486 } 487 488 void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) { 489 if (num_old_candidate_regions == 0) { 490 return; 491 } 492 uint candidate_idx = candidates()->cur_idx(); 493 for (uint i = 0; i < num_old_candidate_regions; i++) { 494 HeapRegion* r = candidates()->at(candidate_idx + i); 495 // This potentially optional candidate region is going to be an actual collection 496 // set region. Clear cset marker. 497 _g1h->clear_in_cset(r); 498 add_old_region(r); 499 } 500 candidates()->remove(num_old_candidate_regions); 501 502 candidates()->verify(); 503 } 504 505 void G1CollectionSet::finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) { 506 double time_remaining_ms = finalize_young_part(target_pause_time_ms, survivor); 507 finalize_old_part(time_remaining_ms); 508 } 509 510 bool G1CollectionSet::finalize_optional_for_evacuation(double remaining_pause_time) { 511 update_incremental_marker(); 512 513 uint num_selected_regions; 514 _policy->select_optional_collection_set_regions(candidates(), 515 _num_optional_regions, 516 remaining_pause_time, 517 num_selected_regions); 518 519 move_candidates_to_collection_set(num_selected_regions); 520 521 _num_optional_regions -= num_selected_regions; 522 523 stop_incremental_building(); 524 return num_selected_regions > 0; 525 } 526 527 void G1CollectionSet::abandon_optional_collection_set(G1ParScanThreadStateSet* pss) { 528 for (uint i = 0; i < _num_optional_regions; i++) { 529 HeapRegion* r = candidates()->at(candidates()->cur_idx() + i); 530 pss->record_unused_optional_region(r); 531 _g1h->clear_in_cset(r); 532 r->clear_index_in_opt_cset(); 533 } 534 _num_optional_regions = 0; 535 } 536 537 #ifdef ASSERT 538 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure { 539 private: 540 size_t _young_length; 541 int* _heap_region_indices; 542 public: 543 G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) { 544 _heap_region_indices = NEW_C_HEAP_ARRAY(int, young_length, mtGC); 545 for (size_t i = 0; i < young_length; i++) { 546 _heap_region_indices[i] = -1; 547 } 548 } 549 ~G1VerifyYoungCSetIndicesClosure() { 550 FREE_C_HEAP_ARRAY(int, _heap_region_indices); 551 } 552 553 virtual bool do_heap_region(HeapRegion* r) { 554 const int idx = r->young_index_in_cset(); 555 556 assert(idx > -1, "Young index must be set for all regions in the incremental collection set but is not for region %u.", r->hrm_index()); 557 assert((size_t)idx < _young_length, "Young cset index too large for region %u", r->hrm_index()); 558 559 assert(_heap_region_indices[idx] == -1, 560 "Index %d used by multiple regions, first use by region %u, second by region %u", 561 idx, _heap_region_indices[idx], r->hrm_index()); 562 563 _heap_region_indices[idx] = r->hrm_index(); 564 565 return false; 566 } 567 }; 568 569 void G1CollectionSet::verify_young_cset_indices() const { 570 assert_at_safepoint_on_vm_thread(); 571 572 G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length); 573 iterate(&cl); 574 } 575 #endif