1 /* 2 * Copyright (c) 2016, 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 _g1->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()->gcs_are_young()); 51 } 52 53 G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) : 54 _g1(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 _bytes_used_before(0), 61 _recorded_rs_lengths(0), 62 _collection_set_regions(NULL), 63 _collection_set_cur_length(0), 64 _collection_set_max_length(0), 65 // Incremental CSet attributes 66 _inc_build_state(Inactive), 67 _inc_bytes_used_before(0), 68 _inc_recorded_rs_lengths(0), 69 _inc_recorded_rs_lengths_diffs(0), 70 _inc_predicted_elapsed_time_ms(0.0), 71 _inc_predicted_elapsed_time_ms_diffs(0.0) { 72 } 73 74 G1CollectionSet::~G1CollectionSet() { 75 if (_collection_set_regions != NULL) { 76 FREE_C_HEAP_ARRAY(uint, _collection_set_regions); 77 } 78 delete _cset_chooser; 79 } 80 81 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length, 82 uint survivor_cset_region_length) { 83 assert_at_safepoint(true); 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 } 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::set_recorded_rs_lengths(size_t rs_lengths) { 101 _recorded_rs_lengths = rs_lengths; 102 } 103 104 // Add the heap region at the head of the non-incremental collection set 105 void G1CollectionSet::add_old_region(HeapRegion* hr) { 106 assert_at_safepoint(true); 107 108 assert(_inc_build_state == Active, "Precondition"); 109 assert(hr->is_old(), "the region should be old"); 110 111 assert(!hr->in_collection_set(), "should not already be in the CSet"); 112 _g1->register_old_region_with_cset(hr); 113 114 _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index(); 115 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size."); 116 117 _bytes_used_before += hr->used(); 118 size_t rs_length = hr->rem_set()->occupied(); 119 _recorded_rs_lengths += rs_length; 120 _old_region_length += 1; 121 } 122 123 // Initialize the per-collection-set information 124 void G1CollectionSet::start_incremental_building() { 125 assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set."); 126 assert(_inc_build_state == Inactive, "Precondition"); 127 128 _inc_bytes_used_before = 0; 129 130 _inc_recorded_rs_lengths = 0; 131 _inc_recorded_rs_lengths_diffs = 0; 132 _inc_predicted_elapsed_time_ms = 0.0; 133 _inc_predicted_elapsed_time_ms_diffs = 0.0; 134 _inc_build_state = Active; 135 } 136 137 void G1CollectionSet::finalize_incremental_building() { 138 assert(_inc_build_state == Active, "Precondition"); 139 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint"); 140 141 // The two "main" fields, _inc_recorded_rs_lengths and 142 // _inc_predicted_elapsed_time_ms, are updated by the thread 143 // that adds a new region to the CSet. Further updates by the 144 // concurrent refinement thread that samples the young RSet lengths 145 // are accumulated in the *_diffs fields. Here we add the diffs to 146 // the "main" fields. 147 148 if (_inc_recorded_rs_lengths_diffs >= 0) { 149 _inc_recorded_rs_lengths += _inc_recorded_rs_lengths_diffs; 150 } else { 151 // This is defensive. The diff should in theory be always positive 152 // as RSets can only grow between GCs. However, given that we 153 // sample their size concurrently with other threads updating them 154 // it's possible that we might get the wrong size back, which 155 // could make the calculations somewhat inaccurate. 156 size_t diffs = (size_t) (-_inc_recorded_rs_lengths_diffs); 157 if (_inc_recorded_rs_lengths >= diffs) { 158 _inc_recorded_rs_lengths -= diffs; 159 } else { 160 _inc_recorded_rs_lengths = 0; 161 } 162 } 163 _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diffs; 164 165 _inc_recorded_rs_lengths_diffs = 0; 166 _inc_predicted_elapsed_time_ms_diffs = 0.0; 167 } 168 169 void G1CollectionSet::clear() { 170 assert_at_safepoint(true); 171 _collection_set_cur_length = 0; 172 } 173 174 void G1CollectionSet::iterate(HeapRegionClosure* cl) const { 175 iterate_from(cl, 0, 1); 176 } 177 178 void G1CollectionSet::iterate_from(HeapRegionClosure* cl, uint worker_id, uint total_workers) const { 179 size_t len = _collection_set_cur_length; 180 OrderAccess::loadload(); 181 if (len == 0) { 182 return; 183 } 184 size_t start_pos = (worker_id * len) / total_workers; 185 size_t cur_pos = start_pos; 186 187 do { 188 HeapRegion* r = G1CollectedHeap::heap()->region_at(_collection_set_regions[cur_pos]); 189 bool result = cl->doHeapRegion(r); 190 if (result) { 191 cl->incomplete(); 192 return; 193 } 194 cur_pos++; 195 if (cur_pos == len) { 196 cur_pos = 0; 197 } 198 } while (cur_pos != start_pos); 199 } 200 201 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr, 202 size_t new_rs_length) { 203 // Update the CSet information that is dependent on the new RS length 204 assert(hr->is_young(), "Precondition"); 205 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint"); 206 207 // We could have updated _inc_recorded_rs_lengths and 208 // _inc_predicted_elapsed_time_ms directly but we'd need to do 209 // that atomically, as this code is executed by a concurrent 210 // refinement thread, potentially concurrently with a mutator thread 211 // allocating a new region and also updating the same fields. To 212 // avoid the atomic operations we accumulate these updates on two 213 // separate fields (*_diffs) and we'll just add them to the "main" 214 // fields at the start of a GC. 215 216 ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length(); 217 ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length; 218 _inc_recorded_rs_lengths_diffs += rs_lengths_diff; 219 220 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms(); 221 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr); 222 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms; 223 _inc_predicted_elapsed_time_ms_diffs += elapsed_ms_diff; 224 225 hr->set_recorded_rs_length(new_rs_length); 226 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms); 227 } 228 229 void G1CollectionSet::add_young_region_common(HeapRegion* hr) { 230 assert(hr->is_young(), "invariant"); 231 assert(_inc_build_state == Active, "Precondition"); 232 233 size_t collection_set_length = _collection_set_cur_length; 234 assert(collection_set_length <= INT_MAX, "Collection set is too large with %d entries", (int)collection_set_length); 235 hr->set_young_index_in_cset((int)collection_set_length); 236 237 _collection_set_regions[collection_set_length] = hr->hrm_index(); 238 // Concurrent readers must observe the store of the value in the array before an 239 // update to the length field. 240 OrderAccess::storestore(); 241 _collection_set_cur_length++; 242 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed."); 243 244 // This routine is used when: 245 // * adding survivor regions to the incremental cset at the end of an 246 // evacuation pause or 247 // * adding the current allocation region to the incremental cset 248 // when it is retired. 249 // Therefore this routine may be called at a safepoint by the 250 // VM thread, or in-between safepoints by mutator threads (when 251 // retiring the current allocation region) 252 // We need to clear and set the cached recorded/cached collection set 253 // information in the heap region here (before the region gets added 254 // to the collection set). An individual heap region's cached values 255 // are calculated, aggregated with the policy collection set info, 256 // and cached in the heap region here (initially) and (subsequently) 257 // by the Young List sampling code. 258 259 size_t rs_length = hr->rem_set()->occupied(); 260 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr); 261 262 // Cache the values we have added to the aggregated information 263 // in the heap region in case we have to remove this region from 264 // the incremental collection set, or it is updated by the 265 // rset sampling code 266 hr->set_recorded_rs_length(rs_length); 267 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms); 268 269 size_t used_bytes = hr->used(); 270 _inc_recorded_rs_lengths += rs_length; 271 _inc_predicted_elapsed_time_ms += region_elapsed_time_ms; 272 _inc_bytes_used_before += used_bytes; 273 274 assert(!hr->in_collection_set(), "invariant"); 275 _g1->register_young_region_with_cset(hr); 276 } 277 278 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) { 279 assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str()); 280 add_young_region_common(hr); 281 } 282 283 void G1CollectionSet::add_eden_region(HeapRegion* hr) { 284 assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str()); 285 add_young_region_common(hr); 286 } 287 288 #ifndef PRODUCT 289 class G1VerifyYoungAgesClosure : public HeapRegionClosure { 290 public: 291 bool _valid; 292 public: 293 G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { } 294 295 virtual bool doHeapRegion(HeapRegion* r) { 296 guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str()); 297 298 SurvRateGroup* group = r->surv_rate_group(); 299 300 if (group == NULL) { 301 log_error(gc, verify)("## encountered NULL surv_rate_group in young region"); 302 _valid = false; 303 } 304 305 if (r->age_in_surv_rate_group() < 0) { 306 log_error(gc, verify)("## encountered negative age in young region"); 307 _valid = false; 308 } 309 310 return false; 311 } 312 313 bool valid() const { return _valid; } 314 }; 315 316 bool G1CollectionSet::verify_young_ages() { 317 assert_at_safepoint(true); 318 319 G1VerifyYoungAgesClosure cl; 320 iterate(&cl); 321 322 if (!cl.valid()) { 323 LogStreamHandle(Error, gc, verify) log; 324 print(&log); 325 } 326 327 return cl.valid(); 328 } 329 330 class G1PrintCollectionSetClosure : public HeapRegionClosure { 331 outputStream* _st; 332 public: 333 G1PrintCollectionSetClosure(outputStream* st) : HeapRegionClosure(), _st(st) { } 334 335 virtual bool doHeapRegion(HeapRegion* r) { 336 assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index()); 337 _st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d", 338 HR_FORMAT_PARAMS(r), 339 p2i(r->prev_top_at_mark_start()), 340 p2i(r->next_top_at_mark_start()), 341 r->age_in_surv_rate_group_cond()); 342 return false; 343 } 344 }; 345 346 void G1CollectionSet::print(outputStream* st) { 347 st->print_cr("\nCollection_set:"); 348 349 G1PrintCollectionSetClosure cl(st); 350 iterate(&cl); 351 } 352 #endif // !PRODUCT 353 354 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) { 355 double young_start_time_sec = os::elapsedTime(); 356 357 finalize_incremental_building(); 358 359 guarantee(target_pause_time_ms > 0.0, 360 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms); 361 362 size_t pending_cards = _policy->pending_cards(); 363 double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards); 364 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0); 365 366 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", 367 pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms); 368 369 collector_state()->set_last_gc_was_young(collector_state()->gcs_are_young()); 370 371 // The young list is laid with the survivor regions from the previous 372 // pause are appended to the RHS of the young list, i.e. 373 // [Newly Young Regions ++ Survivors from last pause]. 374 375 uint survivor_region_length = survivors->length(); 376 uint eden_region_length = _g1->eden_regions_count(); 377 init_region_lengths(eden_region_length, survivor_region_length); 378 379 verify_young_cset_indices(); 380 381 // Clear the fields that point to the survivor list - they are all young now. 382 survivors->convert_to_eden(); 383 384 _bytes_used_before = _inc_bytes_used_before; 385 time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0); 386 387 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", 388 eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms); 389 390 // The number of recorded young regions is the incremental 391 // collection set's current size 392 set_recorded_rs_lengths(_inc_recorded_rs_lengths); 393 394 double young_end_time_sec = os::elapsedTime(); 395 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0); 396 397 return time_remaining_ms; 398 } 399 400 static int compare_region_idx(const uint a, const uint b) { 401 if (a > b) { 402 return 1; 403 } else if (a == b) { 404 return 0; 405 } else { 406 return -1; 407 } 408 } 409 410 void G1CollectionSet::finalize_old_part(double time_remaining_ms) { 411 double non_young_start_time_sec = os::elapsedTime(); 412 double predicted_old_time_ms = 0.0; 413 414 if (!collector_state()->gcs_are_young()) { 415 cset_chooser()->verify(); 416 const uint min_old_cset_length = _policy->calc_min_old_cset_length(); 417 const uint max_old_cset_length = _policy->calc_max_old_cset_length(); 418 419 uint expensive_region_num = 0; 420 bool check_time_remaining = _policy->adaptive_young_list_length(); 421 422 HeapRegion* hr = cset_chooser()->peek(); 423 while (hr != NULL) { 424 if (old_region_length() >= max_old_cset_length) { 425 // Added maximum number of old regions to the CSet. 426 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). old %u regions, max %u regions", 427 old_region_length(), max_old_cset_length); 428 break; 429 } 430 431 // Stop adding regions if the remaining reclaimable space is 432 // not above G1HeapWastePercent. 433 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes(); 434 double reclaimable_perc = _policy->reclaimable_bytes_perc(reclaimable_bytes); 435 double threshold = (double) G1HeapWastePercent; 436 if (reclaimable_perc <= threshold) { 437 // We've added enough old regions that the amount of uncollected 438 // reclaimable space is at or below the waste threshold. Stop 439 // adding old regions to the CSet. 440 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). " 441 "old %u regions, max %u regions, reclaimable: " SIZE_FORMAT "B (%1.2f%%) threshold: " UINTX_FORMAT "%%", 442 old_region_length(), max_old_cset_length, reclaimable_bytes, reclaimable_perc, G1HeapWastePercent); 443 break; 444 } 445 446 double predicted_time_ms = predict_region_elapsed_time_ms(hr); 447 if (check_time_remaining) { 448 if (predicted_time_ms > time_remaining_ms) { 449 // Too expensive for the current CSet. 450 451 if (old_region_length() >= min_old_cset_length) { 452 // We have added the minimum number of old regions to the CSet, 453 // we are done with this CSet. 454 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high). " 455 "predicted time: %1.2fms, remaining time: %1.2fms old %u regions, min %u regions", 456 predicted_time_ms, time_remaining_ms, old_region_length(), min_old_cset_length); 457 break; 458 } 459 460 // We'll add it anyway given that we haven't reached the 461 // minimum number of old regions. 462 expensive_region_num += 1; 463 } 464 } else { 465 if (old_region_length() >= min_old_cset_length) { 466 // In the non-auto-tuning case, we'll finish adding regions 467 // to the CSet if we reach the minimum. 468 469 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min). old %u regions, min %u regions", 470 old_region_length(), min_old_cset_length); 471 break; 472 } 473 } 474 475 // We will add this region to the CSet. 476 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0); 477 predicted_old_time_ms += predicted_time_ms; 478 cset_chooser()->pop(); // already have region via peek() 479 _g1->old_set_remove(hr); 480 add_old_region(hr); 481 482 hr = cset_chooser()->peek(); 483 } 484 if (hr == NULL) { 485 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)"); 486 } 487 488 if (expensive_region_num > 0) { 489 // We print the information once here at the end, predicated on 490 // whether we added any apparently expensive regions or not, to 491 // avoid generating output per region. 492 log_debug(gc, ergo, cset)("Added expensive regions to CSet (old CSet region num not reached min)." 493 "old: %u regions, expensive: %u regions, min: %u regions, remaining time: %1.2fms", 494 old_region_length(), expensive_region_num, min_old_cset_length, time_remaining_ms); 495 } 496 497 cset_chooser()->verify(); 498 } 499 500 stop_incremental_building(); 501 502 log_debug(gc, ergo, cset)("Finish choosing CSet. old: %u regions, predicted old region time: %1.2fms, time remaining: %1.2f", 503 old_region_length(), predicted_old_time_ms, time_remaining_ms); 504 505 double non_young_end_time_sec = os::elapsedTime(); 506 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0); 507 508 QuickSort::sort<uint>(_collection_set_regions, (int)_collection_set_cur_length, compare_region_idx, true); 509 } 510 511 #ifdef ASSERT 512 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure { 513 private: 514 size_t _young_length; 515 int* _heap_region_indices; 516 public: 517 G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) { 518 _heap_region_indices = NEW_C_HEAP_ARRAY(int, young_length, mtGC); 519 for (size_t i = 0; i < young_length; i++) { 520 _heap_region_indices[i] = -1; 521 } 522 } 523 ~G1VerifyYoungCSetIndicesClosure() { 524 FREE_C_HEAP_ARRAY(int, _heap_region_indices); 525 } 526 527 virtual bool doHeapRegion(HeapRegion* r) { 528 const int idx = r->young_index_in_cset(); 529 530 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()); 531 assert((size_t)idx < _young_length, "Young cset index too large for region %u", r->hrm_index()); 532 533 assert(_heap_region_indices[idx] == -1, 534 "Index %d used by multiple regions, first use by region %u, second by region %u", 535 idx, _heap_region_indices[idx], r->hrm_index()); 536 537 _heap_region_indices[idx] = r->hrm_index(); 538 539 return false; 540 } 541 }; 542 543 void G1CollectionSet::verify_young_cset_indices() const { 544 assert_at_safepoint(true); 545 546 G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length); 547 iterate(&cl); 548 } 549 #endif