1 /* 2 * Copyright (c) 2016, 2018, 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.hpp" 27 #include "gc/g1/g1CollectionSet.hpp" 28 #include "gc/g1/g1CollectorState.hpp" 29 #include "gc/g1/g1Policy.hpp" 30 #include "gc/g1/heapRegion.inline.hpp" 31 #include "gc/g1/heapRegionRemSet.hpp" 32 #include "gc/g1/heapRegionSet.hpp" 33 #include "logging/logStream.hpp" 34 #include "utilities/debug.hpp" 35 #include "utilities/quickSort.hpp" 36 37 G1CollectorState* G1CollectionSet::collector_state() { 38 return _g1h->collector_state(); 39 } 40 41 G1GCPhaseTimes* G1CollectionSet::phase_times() { 42 return _policy->phase_times(); 43 } 44 45 CollectionSetChooser* G1CollectionSet::cset_chooser() { 46 return _cset_chooser; 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 _cset_chooser(new CollectionSetChooser()), 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 _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 delete _cset_chooser; 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 } 92 93 void G1CollectionSet::initialize(uint max_region_length) { 94 guarantee(_collection_set_regions == NULL, "Must only initialize once."); 95 _collection_set_max_length = max_region_length; 96 _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC); 97 } 98 99 void G1CollectionSet::set_recorded_rs_lengths(size_t rs_lengths) { 100 _recorded_rs_lengths = rs_lengths; 101 } 102 103 // Add the heap region at the head of the non-incremental collection set 104 void G1CollectionSet::add_old_region(HeapRegion* hr) { 105 assert_at_safepoint_on_vm_thread(); 106 107 assert(_inc_build_state == Active, "Precondition"); 108 assert(hr->is_old(), "the region should be old"); 109 110 assert(!hr->in_collection_set(), "should not already be in the CSet"); 111 _g1h->register_old_region_with_cset(hr); 112 113 _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index(); 114 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size."); 115 116 _bytes_used_before += hr->used(); 117 size_t rs_length = hr->rem_set()->occupied(); 118 _recorded_rs_lengths += rs_length; 119 _old_region_length += 1; 120 } 121 122 // Initialize the per-collection-set information 123 void G1CollectionSet::start_incremental_building() { 124 assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set."); 125 assert(_inc_build_state == Inactive, "Precondition"); 126 127 _inc_bytes_used_before = 0; 128 129 _inc_recorded_rs_lengths = 0; 130 _inc_recorded_rs_lengths_diffs = 0; 131 _inc_predicted_elapsed_time_ms = 0.0; 132 _inc_predicted_elapsed_time_ms_diffs = 0.0; 133 _inc_build_state = Active; 134 } 135 136 void G1CollectionSet::finalize_incremental_building() { 137 assert(_inc_build_state == Active, "Precondition"); 138 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint"); 139 140 // The two "main" fields, _inc_recorded_rs_lengths and 141 // _inc_predicted_elapsed_time_ms, are updated by the thread 142 // that adds a new region to the CSet. Further updates by the 143 // concurrent refinement thread that samples the young RSet lengths 144 // are accumulated in the *_diffs fields. Here we add the diffs to 145 // the "main" fields. 146 147 if (_inc_recorded_rs_lengths_diffs >= 0) { 148 _inc_recorded_rs_lengths += _inc_recorded_rs_lengths_diffs; 149 } else { 150 // This is defensive. The diff should in theory be always positive 151 // as RSets can only grow between GCs. However, given that we 152 // sample their size concurrently with other threads updating them 153 // it's possible that we might get the wrong size back, which 154 // could make the calculations somewhat inaccurate. 155 size_t diffs = (size_t) (-_inc_recorded_rs_lengths_diffs); 156 if (_inc_recorded_rs_lengths >= diffs) { 157 _inc_recorded_rs_lengths -= diffs; 158 } else { 159 _inc_recorded_rs_lengths = 0; 160 } 161 } 162 _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diffs; 163 164 _inc_recorded_rs_lengths_diffs = 0; 165 _inc_predicted_elapsed_time_ms_diffs = 0.0; 166 } 167 168 void G1CollectionSet::clear() { 169 assert_at_safepoint_on_vm_thread(); 170 _collection_set_cur_length = 0; 171 } 172 173 void G1CollectionSet::iterate(HeapRegionClosure* cl) const { 174 iterate_from(cl, 0, 1); 175 } 176 177 void G1CollectionSet::iterate_from(HeapRegionClosure* cl, uint worker_id, uint total_workers) const { 178 size_t len = _collection_set_cur_length; 179 OrderAccess::loadload(); 180 if (len == 0) { 181 return; 182 } 183 size_t start_pos = (worker_id * len) / total_workers; 184 size_t cur_pos = start_pos; 185 186 do { 187 HeapRegion* r = _g1h->region_at(_collection_set_regions[cur_pos]); 188 bool result = cl->do_heap_region(r); 189 if (result) { 190 cl->set_incomplete(); 191 return; 192 } 193 cur_pos++; 194 if (cur_pos == len) { 195 cur_pos = 0; 196 } 197 } while (cur_pos != start_pos); 198 } 199 200 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr, 201 size_t new_rs_length) { 202 // Update the CSet information that is dependent on the new RS length 203 assert(hr->is_young(), "Precondition"); 204 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint"); 205 206 // We could have updated _inc_recorded_rs_lengths and 207 // _inc_predicted_elapsed_time_ms directly but we'd need to do 208 // that atomically, as this code is executed by a concurrent 209 // refinement thread, potentially concurrently with a mutator thread 210 // allocating a new region and also updating the same fields. To 211 // avoid the atomic operations we accumulate these updates on two 212 // separate fields (*_diffs) and we'll just add them to the "main" 213 // fields at the start of a GC. 214 215 ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length(); 216 ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length; 217 _inc_recorded_rs_lengths_diffs += rs_lengths_diff; 218 219 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms(); 220 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr); 221 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms; 222 _inc_predicted_elapsed_time_ms_diffs += elapsed_ms_diff; 223 224 hr->set_recorded_rs_length(new_rs_length); 225 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms); 226 } 227 228 void G1CollectionSet::add_young_region_common(HeapRegion* hr) { 229 assert(hr->is_young(), "invariant"); 230 assert(_inc_build_state == Active, "Precondition"); 231 232 size_t collection_set_length = _collection_set_cur_length; 233 assert(collection_set_length <= INT_MAX, "Collection set is too large with %d entries", (int)collection_set_length); 234 hr->set_young_index_in_cset((int)collection_set_length); 235 236 _collection_set_regions[collection_set_length] = hr->hrm_index(); 237 // Concurrent readers must observe the store of the value in the array before an 238 // update to the length field. 239 OrderAccess::storestore(); 240 _collection_set_cur_length++; 241 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed."); 242 243 // This routine is used when: 244 // * adding survivor regions to the incremental cset at the end of an 245 // evacuation pause or 246 // * adding the current allocation region to the incremental cset 247 // when it is retired. 248 // Therefore this routine may be called at a safepoint by the 249 // VM thread, or in-between safepoints by mutator threads (when 250 // retiring the current allocation region) 251 // We need to clear and set the cached recorded/cached collection set 252 // information in the heap region here (before the region gets added 253 // to the collection set). An individual heap region's cached values 254 // are calculated, aggregated with the policy collection set info, 255 // and cached in the heap region here (initially) and (subsequently) 256 // by the Young List sampling code. 257 // Ignore calls to this due to retirement during full gc. 258 259 if (!_g1h->collector_state()->in_full_gc()) { 260 size_t rs_length = hr->rem_set()->occupied(); 261 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr); 262 263 // Cache the values we have added to the aggregated information 264 // in the heap region in case we have to remove this region from 265 // the incremental collection set, or it is updated by the 266 // rset sampling code 267 hr->set_recorded_rs_length(rs_length); 268 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms); 269 270 _inc_recorded_rs_lengths += rs_length; 271 _inc_predicted_elapsed_time_ms += region_elapsed_time_ms; 272 _inc_bytes_used_before += hr->used(); 273 } 274 275 assert(!hr->in_collection_set(), "invariant"); 276 _g1h->register_young_region_with_cset(hr); 277 } 278 279 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) { 280 assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str()); 281 add_young_region_common(hr); 282 } 283 284 void G1CollectionSet::add_eden_region(HeapRegion* hr) { 285 assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str()); 286 add_young_region_common(hr); 287 } 288 289 #ifndef PRODUCT 290 class G1VerifyYoungAgesClosure : public HeapRegionClosure { 291 public: 292 bool _valid; 293 public: 294 G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { } 295 296 virtual bool do_heap_region(HeapRegion* r) { 297 guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str()); 298 299 SurvRateGroup* group = r->surv_rate_group(); 300 301 if (group == NULL) { 302 log_error(gc, verify)("## encountered NULL surv_rate_group in young region"); 303 _valid = false; 304 } 305 306 if (r->age_in_surv_rate_group() < 0) { 307 log_error(gc, verify)("## encountered negative age in young region"); 308 _valid = false; 309 } 310 311 return false; 312 } 313 314 bool valid() const { return _valid; } 315 }; 316 317 bool G1CollectionSet::verify_young_ages() { 318 assert_at_safepoint_on_vm_thread(); 319 320 G1VerifyYoungAgesClosure cl; 321 iterate(&cl); 322 323 if (!cl.valid()) { 324 LogStreamHandle(Error, gc, verify) log; 325 print(&log); 326 } 327 328 return cl.valid(); 329 } 330 331 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure { 332 outputStream* _st; 333 public: 334 G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { } 335 336 virtual bool do_heap_region(HeapRegion* r) { 337 assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index()); 338 _st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d", 339 HR_FORMAT_PARAMS(r), 340 p2i(r->prev_top_at_mark_start()), 341 p2i(r->next_top_at_mark_start()), 342 r->age_in_surv_rate_group_cond()); 343 return false; 344 } 345 }; 346 347 void G1CollectionSet::print(outputStream* st) { 348 st->print_cr("\nCollection_set:"); 349 350 G1PrintCollectionSetDetailClosure cl(st); 351 iterate(&cl); 352 } 353 #endif // !PRODUCT 354 355 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) { 356 double young_start_time_sec = os::elapsedTime(); 357 358 finalize_incremental_building(); 359 360 guarantee(target_pause_time_ms > 0.0, 361 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms); 362 363 size_t pending_cards = _policy->pending_cards(); 364 double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards); 365 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0); 366 367 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", 368 pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms); 369 370 // The young list is laid with the survivor regions from the previous 371 // pause are appended to the RHS of the young list, i.e. 372 // [Newly Young Regions ++ Survivors from last pause]. 373 374 uint survivor_region_length = survivors->length(); 375 uint eden_region_length = _g1h->eden_regions_count(); 376 init_region_lengths(eden_region_length, survivor_region_length); 377 378 verify_young_cset_indices(); 379 380 // Clear the fields that point to the survivor list - they are all young now. 381 survivors->convert_to_eden(); 382 383 _bytes_used_before = _inc_bytes_used_before; 384 time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0); 385 386 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", 387 eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms); 388 389 // The number of recorded young regions is the incremental 390 // collection set's current size 391 set_recorded_rs_lengths(_inc_recorded_rs_lengths); 392 393 double young_end_time_sec = os::elapsedTime(); 394 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0); 395 396 return time_remaining_ms; 397 } 398 399 static int compare_region_idx(const uint a, const uint b) { 400 if (a > b) { 401 return 1; 402 } else if (a == b) { 403 return 0; 404 } else { 405 return -1; 406 } 407 } 408 409 void G1CollectionSet::finalize_old_part(double time_remaining_ms) { 410 double non_young_start_time_sec = os::elapsedTime(); 411 double predicted_old_time_ms = 0.0; 412 413 if (collector_state()->in_mixed_phase()) { 414 cset_chooser()->verify(); 415 const uint min_old_cset_length = _policy->calc_min_old_cset_length(); 416 const uint max_old_cset_length = _policy->calc_max_old_cset_length(); 417 418 uint expensive_region_num = 0; 419 bool check_time_remaining = _policy->adaptive_young_list_length(); 420 421 HeapRegion* hr = cset_chooser()->peek(); 422 while (hr != NULL) { 423 if (old_region_length() >= max_old_cset_length) { 424 // Added maximum number of old regions to the CSet. 425 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). old %u regions, max %u regions", 426 old_region_length(), max_old_cset_length); 427 break; 428 } 429 430 // Stop adding regions if the remaining reclaimable space is 431 // not above G1HeapWastePercent. 432 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes(); 433 double reclaimable_percent = _policy->reclaimable_bytes_percent(reclaimable_bytes); 434 double threshold = (double) G1HeapWastePercent; 435 if (reclaimable_percent <= threshold) { 436 // We've added enough old regions that the amount of uncollected 437 // reclaimable space is at or below the waste threshold. Stop 438 // adding old regions to the CSet. 439 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). " 440 "old %u regions, max %u regions, reclaimable: " SIZE_FORMAT "B (%1.2f%%) threshold: " UINTX_FORMAT "%%", 441 old_region_length(), max_old_cset_length, reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 442 break; 443 } 444 445 double predicted_time_ms = predict_region_elapsed_time_ms(hr); 446 if (check_time_remaining) { 447 if (predicted_time_ms > time_remaining_ms) { 448 // Too expensive for the current CSet. 449 450 if (old_region_length() >= min_old_cset_length) { 451 // We have added the minimum number of old regions to the CSet, 452 // we are done with this CSet. 453 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high). " 454 "predicted time: %1.2fms, remaining time: %1.2fms old %u regions, min %u regions", 455 predicted_time_ms, time_remaining_ms, old_region_length(), min_old_cset_length); 456 break; 457 } 458 459 // We'll add it anyway given that we haven't reached the 460 // minimum number of old regions. 461 expensive_region_num += 1; 462 } 463 } else { 464 if (old_region_length() >= min_old_cset_length) { 465 // In the non-auto-tuning case, we'll finish adding regions 466 // to the CSet if we reach the minimum. 467 468 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min). old %u regions, min %u regions", 469 old_region_length(), min_old_cset_length); 470 break; 471 } 472 } 473 474 // We will add this region to the CSet. 475 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0); 476 predicted_old_time_ms += predicted_time_ms; 477 cset_chooser()->pop(); // already have region via peek() 478 _g1h->old_set_remove(hr); 479 add_old_region(hr); 480 481 hr = cset_chooser()->peek(); 482 } 483 if (hr == NULL) { 484 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)"); 485 } 486 487 if (expensive_region_num > 0) { 488 // We print the information once here at the end, predicated on 489 // whether we added any apparently expensive regions or not, to 490 // avoid generating output per region. 491 log_debug(gc, ergo, cset)("Added expensive regions to CSet (old CSet region num not reached min)." 492 "old: %u regions, expensive: %u regions, min: %u regions, remaining time: %1.2fms", 493 old_region_length(), expensive_region_num, min_old_cset_length, time_remaining_ms); 494 } 495 496 cset_chooser()->verify(); 497 } 498 499 stop_incremental_building(); 500 501 log_debug(gc, ergo, cset)("Finish choosing CSet. old: %u regions, predicted old region time: %1.2fms, time remaining: %1.2f", 502 old_region_length(), predicted_old_time_ms, time_remaining_ms); 503 504 double non_young_end_time_sec = os::elapsedTime(); 505 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0); 506 507 QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true); 508 } 509 510 #ifdef ASSERT 511 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure { 512 private: 513 size_t _young_length; 514 int* _heap_region_indices; 515 public: 516 G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) { 517 _heap_region_indices = NEW_C_HEAP_ARRAY(int, young_length, mtGC); 518 for (size_t i = 0; i < young_length; i++) { 519 _heap_region_indices[i] = -1; 520 } 521 } 522 ~G1VerifyYoungCSetIndicesClosure() { 523 FREE_C_HEAP_ARRAY(int, _heap_region_indices); 524 } 525 526 virtual bool do_heap_region(HeapRegion* r) { 527 const int idx = r->young_index_in_cset(); 528 529 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()); 530 assert((size_t)idx < _young_length, "Young cset index too large for region %u", r->hrm_index()); 531 532 assert(_heap_region_indices[idx] == -1, 533 "Index %d used by multiple regions, first use by region %u, second by region %u", 534 idx, _heap_region_indices[idx], r->hrm_index()); 535 536 _heap_region_indices[idx] = r->hrm_index(); 537 538 return false; 539 } 540 }; 541 542 void G1CollectionSet::verify_young_cset_indices() const { 543 assert_at_safepoint_on_vm_thread(); 544 545 G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length); 546 iterate(&cl); 547 } 548 #endif