1 /* 2 * Copyright (c) 2001, 2017, 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/serial/defNewGeneration.inline.hpp" 27 #include "gc/shared/ageTable.inline.hpp" 28 #include "gc/shared/cardTableRS.hpp" 29 #include "gc/shared/collectorCounters.hpp" 30 #include "gc/shared/gcHeapSummary.hpp" 31 #include "gc/shared/gcLocker.inline.hpp" 32 #include "gc/shared/gcPolicyCounters.hpp" 33 #include "gc/shared/gcTimer.hpp" 34 #include "gc/shared/gcTrace.hpp" 35 #include "gc/shared/gcTraceTime.inline.hpp" 36 #include "gc/shared/genCollectedHeap.hpp" 37 #include "gc/shared/genOopClosures.inline.hpp" 38 #include "gc/shared/generationSpec.hpp" 39 #include "gc/shared/preservedMarks.inline.hpp" 40 #include "gc/shared/referencePolicy.hpp" 41 #include "gc/shared/space.inline.hpp" 42 #include "gc/shared/spaceDecorator.hpp" 43 #include "gc/shared/strongRootsScope.hpp" 44 #include "gc/shared/weakProcessor.hpp" 45 #include "logging/log.hpp" 46 #include "memory/iterator.hpp" 47 #include "memory/resourceArea.hpp" 48 #include "oops/instanceRefKlass.hpp" 49 #include "oops/oop.inline.hpp" 50 #include "runtime/atomic.hpp" 51 #include "runtime/java.hpp" 52 #include "runtime/prefetch.inline.hpp" 53 #include "runtime/thread.inline.hpp" 54 #include "utilities/align.hpp" 55 #include "utilities/copy.hpp" 56 #include "utilities/globalDefinitions.hpp" 57 #include "utilities/stack.inline.hpp" 58 #if INCLUDE_ALL_GCS 59 #include "gc/cms/parOopClosures.hpp" 60 #endif 61 62 // 63 // DefNewGeneration functions. 64 65 // Methods of protected closure types. 66 67 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) { 68 assert(_young_gen->kind() == Generation::ParNew || 69 _young_gen->kind() == Generation::DefNew, "Expected the young generation here"); 70 } 71 72 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) { 73 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded(); 74 } 75 76 DefNewGeneration::KeepAliveClosure:: 77 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) { 78 _rs = GenCollectedHeap::heap()->rem_set(); 79 } 80 81 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 82 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); } 83 84 85 DefNewGeneration::FastKeepAliveClosure:: 86 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) : 87 DefNewGeneration::KeepAliveClosure(cl) { 88 _boundary = g->reserved().end(); 89 } 90 91 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 92 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); } 93 94 DefNewGeneration::EvacuateFollowersClosure:: 95 EvacuateFollowersClosure(GenCollectedHeap* gch, 96 ScanClosure* cur, 97 ScanClosure* older) : 98 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older) 99 {} 100 101 void DefNewGeneration::EvacuateFollowersClosure::do_void() { 102 do { 103 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older); 104 } while (!_gch->no_allocs_since_save_marks()); 105 } 106 107 DefNewGeneration::FastEvacuateFollowersClosure:: 108 FastEvacuateFollowersClosure(GenCollectedHeap* gch, 109 FastScanClosure* cur, 110 FastScanClosure* older) : 111 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older) 112 { 113 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew"); 114 _young_gen = (DefNewGeneration*)_gch->young_gen(); 115 } 116 117 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() { 118 do { 119 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older); 120 } while (!_gch->no_allocs_since_save_marks()); 121 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan"); 122 } 123 124 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) : 125 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 126 { 127 _boundary = _g->reserved().end(); 128 } 129 130 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); } 131 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); } 132 133 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) : 134 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier) 135 { 136 _boundary = _g->reserved().end(); 137 } 138 139 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); } 140 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); } 141 142 void CLDScanClosure::do_cld(ClassLoaderData* cld) { 143 NOT_PRODUCT(ResourceMark rm); 144 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s", 145 p2i(cld), 146 cld->loader_name(), 147 cld->has_modified_oops() ? "true" : "false"); 148 149 // If the cld has not been dirtied we know that there's 150 // no references into the young gen and we can skip it. 151 if (cld->has_modified_oops()) { 152 if (_accumulate_modified_oops) { 153 cld->accumulate_modified_oops(); 154 } 155 156 // Tell the closure which CLD is being scanned so that it can be dirtied 157 // if oops are left pointing into the young gen. 158 _scavenge_closure->set_scanned_cld(cld); 159 160 // Clean the cld since we're going to scavenge all the metadata. 161 cld->oops_do(_scavenge_closure, false, /*clear_modified_oops*/true); 162 163 _scavenge_closure->set_scanned_cld(NULL); 164 } 165 } 166 167 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) : 168 _g(g) 169 { 170 _boundary = _g->reserved().end(); 171 } 172 173 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); } 174 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); } 175 176 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); } 177 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); } 178 179 DefNewGeneration::DefNewGeneration(ReservedSpace rs, 180 size_t initial_size, 181 const char* policy) 182 : Generation(rs, initial_size), 183 _preserved_marks_set(false /* in_c_heap */), 184 _promo_failure_drain_in_progress(false), 185 _should_allocate_from_space(false) 186 { 187 MemRegion cmr((HeapWord*)_virtual_space.low(), 188 (HeapWord*)_virtual_space.high()); 189 GenCollectedHeap* gch = GenCollectedHeap::heap(); 190 191 gch->barrier_set()->resize_covered_region(cmr); 192 193 _eden_space = new ContiguousSpace(); 194 _from_space = new ContiguousSpace(); 195 _to_space = new ContiguousSpace(); 196 197 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) { 198 vm_exit_during_initialization("Could not allocate a new gen space"); 199 } 200 201 // Compute the maximum eden and survivor space sizes. These sizes 202 // are computed assuming the entire reserved space is committed. 203 // These values are exported as performance counters. 204 uintx alignment = gch->collector_policy()->space_alignment(); 205 uintx size = _virtual_space.reserved_size(); 206 _max_survivor_size = compute_survivor_size(size, alignment); 207 _max_eden_size = size - (2*_max_survivor_size); 208 209 // allocate the performance counters 210 GenCollectorPolicy* gcp = gch->gen_policy(); 211 212 // Generation counters -- generation 0, 3 subspaces 213 _gen_counters = new GenerationCounters("new", 0, 3, 214 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space); 215 _gc_counters = new CollectorCounters(policy, 0); 216 217 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 218 _gen_counters); 219 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 220 _gen_counters); 221 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 222 _gen_counters); 223 224 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 225 update_counters(); 226 _old_gen = NULL; 227 _tenuring_threshold = MaxTenuringThreshold; 228 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 229 230 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 231 } 232 233 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 234 bool clear_space, 235 bool mangle_space) { 236 uintx alignment = 237 GenCollectedHeap::heap()->collector_policy()->space_alignment(); 238 239 // If the spaces are being cleared (only done at heap initialization 240 // currently), the survivor spaces need not be empty. 241 // Otherwise, no care is taken for used areas in the survivor spaces 242 // so check. 243 assert(clear_space || (to()->is_empty() && from()->is_empty()), 244 "Initialization of the survivor spaces assumes these are empty"); 245 246 // Compute sizes 247 uintx size = _virtual_space.committed_size(); 248 uintx survivor_size = compute_survivor_size(size, alignment); 249 uintx eden_size = size - (2*survivor_size); 250 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 251 252 if (eden_size < minimum_eden_size) { 253 // May happen due to 64Kb rounding, if so adjust eden size back up 254 minimum_eden_size = align_up(minimum_eden_size, alignment); 255 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 256 uintx unaligned_survivor_size = 257 align_down(maximum_survivor_size, alignment); 258 survivor_size = MAX2(unaligned_survivor_size, alignment); 259 eden_size = size - (2*survivor_size); 260 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 261 assert(eden_size >= minimum_eden_size, "just checking"); 262 } 263 264 char *eden_start = _virtual_space.low(); 265 char *from_start = eden_start + eden_size; 266 char *to_start = from_start + survivor_size; 267 char *to_end = to_start + survivor_size; 268 269 assert(to_end == _virtual_space.high(), "just checking"); 270 assert(Space::is_aligned(eden_start), "checking alignment"); 271 assert(Space::is_aligned(from_start), "checking alignment"); 272 assert(Space::is_aligned(to_start), "checking alignment"); 273 274 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 275 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 276 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 277 278 // A minimum eden size implies that there is a part of eden that 279 // is being used and that affects the initialization of any 280 // newly formed eden. 281 bool live_in_eden = minimum_eden_size > 0; 282 283 // If not clearing the spaces, do some checking to verify that 284 // the space are already mangled. 285 if (!clear_space) { 286 // Must check mangling before the spaces are reshaped. Otherwise, 287 // the bottom or end of one space may have moved into another 288 // a failure of the check may not correctly indicate which space 289 // is not properly mangled. 290 if (ZapUnusedHeapArea) { 291 HeapWord* limit = (HeapWord*) _virtual_space.high(); 292 eden()->check_mangled_unused_area(limit); 293 from()->check_mangled_unused_area(limit); 294 to()->check_mangled_unused_area(limit); 295 } 296 } 297 298 // Reset the spaces for their new regions. 299 eden()->initialize(edenMR, 300 clear_space && !live_in_eden, 301 SpaceDecorator::Mangle); 302 // If clear_space and live_in_eden, we will not have cleared any 303 // portion of eden above its top. This can cause newly 304 // expanded space not to be mangled if using ZapUnusedHeapArea. 305 // We explicitly do such mangling here. 306 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 307 eden()->mangle_unused_area(); 308 } 309 from()->initialize(fromMR, clear_space, mangle_space); 310 to()->initialize(toMR, clear_space, mangle_space); 311 312 // Set next compaction spaces. 313 eden()->set_next_compaction_space(from()); 314 // The to-space is normally empty before a compaction so need 315 // not be considered. The exception is during promotion 316 // failure handling when to-space can contain live objects. 317 from()->set_next_compaction_space(NULL); 318 } 319 320 void DefNewGeneration::swap_spaces() { 321 ContiguousSpace* s = from(); 322 _from_space = to(); 323 _to_space = s; 324 eden()->set_next_compaction_space(from()); 325 // The to-space is normally empty before a compaction so need 326 // not be considered. The exception is during promotion 327 // failure handling when to-space can contain live objects. 328 from()->set_next_compaction_space(NULL); 329 330 if (UsePerfData) { 331 CSpaceCounters* c = _from_counters; 332 _from_counters = _to_counters; 333 _to_counters = c; 334 } 335 } 336 337 bool DefNewGeneration::expand(size_t bytes) { 338 MutexLocker x(ExpandHeap_lock); 339 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 340 bool success = _virtual_space.expand_by(bytes); 341 if (success && ZapUnusedHeapArea) { 342 // Mangle newly committed space immediately because it 343 // can be done here more simply that after the new 344 // spaces have been computed. 345 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 346 MemRegion mangle_region(prev_high, new_high); 347 SpaceMangler::mangle_region(mangle_region); 348 } 349 350 // Do not attempt an expand-to-the reserve size. The 351 // request should properly observe the maximum size of 352 // the generation so an expand-to-reserve should be 353 // unnecessary. Also a second call to expand-to-reserve 354 // value potentially can cause an undue expansion. 355 // For example if the first expand fail for unknown reasons, 356 // but the second succeeds and expands the heap to its maximum 357 // value. 358 if (GCLocker::is_active()) { 359 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 360 } 361 362 return success; 363 } 364 365 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 366 size_t new_size_before, 367 size_t alignment) const { 368 size_t desired_new_size = new_size_before; 369 370 if (NewSizeThreadIncrease > 0) { 371 int threads_count; 372 size_t thread_increase_size = 0; 373 374 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'. 375 threads_count = Threads::number_of_non_daemon_threads(); 376 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 377 thread_increase_size = threads_count * NewSizeThreadIncrease; 378 379 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'. 380 if (new_size_candidate <= max_uintx - thread_increase_size) { 381 new_size_candidate += thread_increase_size; 382 383 // 3. Check an overflow at 'align_up'. 384 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 385 if (new_size_candidate <= aligned_max) { 386 desired_new_size = align_up(new_size_candidate, alignment); 387 } 388 } 389 } 390 } 391 392 return desired_new_size; 393 } 394 395 void DefNewGeneration::compute_new_size() { 396 // This is called after a GC that includes the old generation, so from-space 397 // will normally be empty. 398 // Note that we check both spaces, since if scavenge failed they revert roles. 399 // If not we bail out (otherwise we would have to relocate the objects). 400 if (!from()->is_empty() || !to()->is_empty()) { 401 return; 402 } 403 404 GenCollectedHeap* gch = GenCollectedHeap::heap(); 405 406 size_t old_size = gch->old_gen()->capacity(); 407 size_t new_size_before = _virtual_space.committed_size(); 408 size_t min_new_size = initial_size(); 409 size_t max_new_size = reserved().byte_size(); 410 assert(min_new_size <= new_size_before && 411 new_size_before <= max_new_size, 412 "just checking"); 413 // All space sizes must be multiples of Generation::GenGrain. 414 size_t alignment = Generation::GenGrain; 415 416 int threads_count = 0; 417 size_t thread_increase_size = 0; 418 419 size_t new_size_candidate = old_size / NewRatio; 420 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 421 // and reverts to previous value if any overflow happens 422 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment); 423 424 // Adjust new generation size 425 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 426 assert(desired_new_size <= max_new_size, "just checking"); 427 428 bool changed = false; 429 if (desired_new_size > new_size_before) { 430 size_t change = desired_new_size - new_size_before; 431 assert(change % alignment == 0, "just checking"); 432 if (expand(change)) { 433 changed = true; 434 } 435 // If the heap failed to expand to the desired size, 436 // "changed" will be false. If the expansion failed 437 // (and at this point it was expected to succeed), 438 // ignore the failure (leaving "changed" as false). 439 } 440 if (desired_new_size < new_size_before && eden()->is_empty()) { 441 // bail out of shrinking if objects in eden 442 size_t change = new_size_before - desired_new_size; 443 assert(change % alignment == 0, "just checking"); 444 _virtual_space.shrink_by(change); 445 changed = true; 446 } 447 if (changed) { 448 // The spaces have already been mangled at this point but 449 // may not have been cleared (set top = bottom) and should be. 450 // Mangling was done when the heap was being expanded. 451 compute_space_boundaries(eden()->used(), 452 SpaceDecorator::Clear, 453 SpaceDecorator::DontMangle); 454 MemRegion cmr((HeapWord*)_virtual_space.low(), 455 (HeapWord*)_virtual_space.high()); 456 gch->barrier_set()->resize_covered_region(cmr); 457 458 log_debug(gc, ergo, heap)( 459 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 460 new_size_before/K, _virtual_space.committed_size()/K, 461 eden()->capacity()/K, from()->capacity()/K); 462 log_trace(gc, ergo, heap)( 463 " [allowed " SIZE_FORMAT "K extra for %d threads]", 464 thread_increase_size/K, threads_count); 465 } 466 } 467 468 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 469 assert(false, "NYI -- are you sure you want to call this?"); 470 } 471 472 473 size_t DefNewGeneration::capacity() const { 474 return eden()->capacity() 475 + from()->capacity(); // to() is only used during scavenge 476 } 477 478 479 size_t DefNewGeneration::used() const { 480 return eden()->used() 481 + from()->used(); // to() is only used during scavenge 482 } 483 484 485 size_t DefNewGeneration::free() const { 486 return eden()->free() 487 + from()->free(); // to() is only used during scavenge 488 } 489 490 size_t DefNewGeneration::max_capacity() const { 491 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 492 const size_t reserved_bytes = reserved().byte_size(); 493 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 494 } 495 496 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 497 return eden()->free(); 498 } 499 500 size_t DefNewGeneration::capacity_before_gc() const { 501 return eden()->capacity(); 502 } 503 504 size_t DefNewGeneration::contiguous_available() const { 505 return eden()->free(); 506 } 507 508 509 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); } 510 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 511 512 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 513 eden()->object_iterate(blk); 514 from()->object_iterate(blk); 515 } 516 517 518 void DefNewGeneration::space_iterate(SpaceClosure* blk, 519 bool usedOnly) { 520 blk->do_space(eden()); 521 blk->do_space(from()); 522 blk->do_space(to()); 523 } 524 525 // The last collection bailed out, we are running out of heap space, 526 // so we try to allocate the from-space, too. 527 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 528 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc(); 529 530 // If the Heap_lock is not locked by this thread, this will be called 531 // again later with the Heap_lock held. 532 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 533 534 HeapWord* result = NULL; 535 if (do_alloc) { 536 result = from()->allocate(size); 537 } 538 539 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 540 size, 541 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 542 "true" : "false", 543 Heap_lock->is_locked() ? "locked" : "unlocked", 544 from()->free(), 545 should_try_alloc ? "" : " should_allocate_from_space: NOT", 546 do_alloc ? " Heap_lock is not owned by self" : "", 547 result == NULL ? "NULL" : "object"); 548 549 return result; 550 } 551 552 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 553 bool is_tlab, 554 bool parallel) { 555 // We don't attempt to expand the young generation (but perhaps we should.) 556 return allocate(size, is_tlab); 557 } 558 559 void DefNewGeneration::adjust_desired_tenuring_threshold() { 560 // Set the desired survivor size to half the real survivor space 561 size_t const survivor_capacity = to()->capacity() / HeapWordSize; 562 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 563 564 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size); 565 566 if (UsePerfData) { 567 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->gen_policy()->counters(); 568 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold); 569 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize); 570 } 571 572 age_table()->print_age_table(_tenuring_threshold); 573 } 574 575 void DefNewGeneration::collect(bool full, 576 bool clear_all_soft_refs, 577 size_t size, 578 bool is_tlab) { 579 assert(full || size > 0, "otherwise we don't want to collect"); 580 581 GenCollectedHeap* gch = GenCollectedHeap::heap(); 582 583 _gc_timer->register_gc_start(); 584 DefNewTracer gc_tracer; 585 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 586 587 _old_gen = gch->old_gen(); 588 589 // If the next generation is too full to accommodate promotion 590 // from this generation, pass on collection; let the next generation 591 // do it. 592 if (!collection_attempt_is_safe()) { 593 log_trace(gc)(":: Collection attempt not safe ::"); 594 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 595 return; 596 } 597 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 598 599 init_assuming_no_promotion_failure(); 600 601 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, gch->gc_cause()); 602 603 gch->trace_heap_before_gc(&gc_tracer); 604 605 // These can be shared for all code paths 606 IsAliveClosure is_alive(this); 607 ScanWeakRefClosure scan_weak_ref(this); 608 609 age_table()->clear(); 610 to()->clear(SpaceDecorator::Mangle); 611 // The preserved marks should be empty at the start of the GC. 612 _preserved_marks_set.init(1); 613 614 gch->rem_set()->prepare_for_younger_refs_iterate(false); 615 616 assert(gch->no_allocs_since_save_marks(), 617 "save marks have not been newly set."); 618 619 // Not very pretty. 620 CollectorPolicy* cp = gch->collector_policy(); 621 622 FastScanClosure fsc_with_no_gc_barrier(this, false); 623 FastScanClosure fsc_with_gc_barrier(this, true); 624 625 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier, 626 gch->rem_set()->cld_rem_set()->accumulate_modified_oops()); 627 628 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 629 FastEvacuateFollowersClosure evacuate_followers(gch, 630 &fsc_with_no_gc_barrier, 631 &fsc_with_gc_barrier); 632 633 assert(gch->no_allocs_since_save_marks(), 634 "save marks have not been newly set."); 635 636 { 637 // DefNew needs to run with n_threads == 0, to make sure the serial 638 // version of the card table scanning code is used. 639 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel. 640 StrongRootsScope srs(0); 641 642 gch->young_process_roots(&srs, 643 &fsc_with_no_gc_barrier, 644 &fsc_with_gc_barrier, 645 &cld_scan_closure); 646 } 647 648 // "evacuate followers". 649 evacuate_followers.do_void(); 650 651 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 652 ReferenceProcessor* rp = ref_processor(); 653 rp->setup_policy(clear_all_soft_refs); 654 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->num_q()); 655 const ReferenceProcessorStats& stats = 656 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 657 NULL, &pt); 658 gc_tracer.report_gc_reference_stats(stats); 659 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 660 pt.print_all_references(); 661 662 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 663 664 if (!_promotion_failed) { 665 // Swap the survivor spaces. 666 eden()->clear(SpaceDecorator::Mangle); 667 from()->clear(SpaceDecorator::Mangle); 668 if (ZapUnusedHeapArea) { 669 // This is now done here because of the piece-meal mangling which 670 // can check for valid mangling at intermediate points in the 671 // collection(s). When a young collection fails to collect 672 // sufficient space resizing of the young generation can occur 673 // an redistribute the spaces in the young generation. Mangle 674 // here so that unzapped regions don't get distributed to 675 // other spaces. 676 to()->mangle_unused_area(); 677 } 678 swap_spaces(); 679 680 assert(to()->is_empty(), "to space should be empty now"); 681 682 adjust_desired_tenuring_threshold(); 683 684 // A successful scavenge should restart the GC time limit count which is 685 // for full GC's. 686 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 687 size_policy->reset_gc_overhead_limit_count(); 688 assert(!gch->incremental_collection_failed(), "Should be clear"); 689 } else { 690 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 691 _promo_failure_scan_stack.clear(true); // Clear cached segments. 692 693 remove_forwarding_pointers(); 694 log_info(gc, promotion)("Promotion failed"); 695 // Add to-space to the list of space to compact 696 // when a promotion failure has occurred. In that 697 // case there can be live objects in to-space 698 // as a result of a partial evacuation of eden 699 // and from-space. 700 swap_spaces(); // For uniformity wrt ParNewGeneration. 701 from()->set_next_compaction_space(to()); 702 gch->set_incremental_collection_failed(); 703 704 // Inform the next generation that a promotion failure occurred. 705 _old_gen->promotion_failure_occurred(); 706 gc_tracer.report_promotion_failed(_promotion_failed_info); 707 708 // Reset the PromotionFailureALot counters. 709 NOT_PRODUCT(gch->reset_promotion_should_fail();) 710 } 711 // We should have processed and cleared all the preserved marks. 712 _preserved_marks_set.reclaim(); 713 // set new iteration safe limit for the survivor spaces 714 from()->set_concurrent_iteration_safe_limit(from()->top()); 715 to()->set_concurrent_iteration_safe_limit(to()->top()); 716 717 // We need to use a monotonically non-decreasing time in ms 718 // or we will see time-warp warnings and os::javaTimeMillis() 719 // does not guarantee monotonicity. 720 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 721 update_time_of_last_gc(now); 722 723 gch->trace_heap_after_gc(&gc_tracer); 724 725 _gc_timer->register_gc_end(); 726 727 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 728 } 729 730 void DefNewGeneration::init_assuming_no_promotion_failure() { 731 _promotion_failed = false; 732 _promotion_failed_info.reset(); 733 from()->set_next_compaction_space(NULL); 734 } 735 736 void DefNewGeneration::remove_forwarding_pointers() { 737 RemoveForwardedPointerClosure rspc; 738 eden()->object_iterate(&rspc); 739 from()->object_iterate(&rspc); 740 741 SharedRestorePreservedMarksTaskExecutor task_executor(GenCollectedHeap::heap()->workers()); 742 _preserved_marks_set.restore(&task_executor); 743 } 744 745 void DefNewGeneration::handle_promotion_failure(oop old) { 746 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size()); 747 748 _promotion_failed = true; 749 _promotion_failed_info.register_copy_failure(old->size()); 750 _preserved_marks_set.get()->push_if_necessary(old, old->mark()); 751 // forward to self 752 old->forward_to(old); 753 754 _promo_failure_scan_stack.push(old); 755 756 if (!_promo_failure_drain_in_progress) { 757 // prevent recursion in copy_to_survivor_space() 758 _promo_failure_drain_in_progress = true; 759 drain_promo_failure_scan_stack(); 760 _promo_failure_drain_in_progress = false; 761 } 762 } 763 764 oop DefNewGeneration::copy_to_survivor_space(oop old) { 765 assert(is_in_reserved(old) && !old->is_forwarded(), 766 "shouldn't be scavenging this oop"); 767 size_t s = old->size(); 768 oop obj = NULL; 769 770 // Try allocating obj in to-space (unless too old) 771 if (old->age() < tenuring_threshold()) { 772 obj = (oop) to()->allocate_aligned(s); 773 } 774 775 // Otherwise try allocating obj tenured 776 if (obj == NULL) { 777 obj = _old_gen->promote(old, s); 778 if (obj == NULL) { 779 handle_promotion_failure(old); 780 return old; 781 } 782 } else { 783 // Prefetch beyond obj 784 const intx interval = PrefetchCopyIntervalInBytes; 785 Prefetch::write(obj, interval); 786 787 // Copy obj 788 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 789 790 // Increment age if obj still in new generation 791 obj->incr_age(); 792 age_table()->add(obj, s); 793 } 794 795 // Done, insert forward pointer to obj in this header 796 old->forward_to(obj); 797 798 return obj; 799 } 800 801 void DefNewGeneration::drain_promo_failure_scan_stack() { 802 while (!_promo_failure_scan_stack.is_empty()) { 803 oop obj = _promo_failure_scan_stack.pop(); 804 obj->oop_iterate(_promo_failure_scan_stack_closure); 805 } 806 } 807 808 void DefNewGeneration::save_marks() { 809 eden()->set_saved_mark(); 810 to()->set_saved_mark(); 811 from()->set_saved_mark(); 812 } 813 814 815 void DefNewGeneration::reset_saved_marks() { 816 eden()->reset_saved_mark(); 817 to()->reset_saved_mark(); 818 from()->reset_saved_mark(); 819 } 820 821 822 bool DefNewGeneration::no_allocs_since_save_marks() { 823 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 824 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 825 return to()->saved_mark_at_top(); 826 } 827 828 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 829 \ 830 void DefNewGeneration:: \ 831 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 832 cl->set_generation(this); \ 833 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 834 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 835 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 836 cl->reset_generation(); \ 837 save_marks(); \ 838 } 839 840 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 841 842 #undef DefNew_SINCE_SAVE_MARKS_DEFN 843 844 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 845 size_t max_alloc_words) { 846 if (requestor == this || _promotion_failed) { 847 return; 848 } 849 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 850 851 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 852 if (to_space->top() > to_space->bottom()) { 853 trace("to_space not empty when contribute_scratch called"); 854 } 855 */ 856 857 ContiguousSpace* to_space = to(); 858 assert(to_space->end() >= to_space->top(), "pointers out of order"); 859 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 860 if (free_words >= MinFreeScratchWords) { 861 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 862 sb->num_words = free_words; 863 sb->next = list; 864 list = sb; 865 } 866 } 867 868 void DefNewGeneration::reset_scratch() { 869 // If contributing scratch in to_space, mangle all of 870 // to_space if ZapUnusedHeapArea. This is needed because 871 // top is not maintained while using to-space as scratch. 872 if (ZapUnusedHeapArea) { 873 to()->mangle_unused_area_complete(); 874 } 875 } 876 877 bool DefNewGeneration::collection_attempt_is_safe() { 878 if (!to()->is_empty()) { 879 log_trace(gc)(":: to is not empty ::"); 880 return false; 881 } 882 if (_old_gen == NULL) { 883 GenCollectedHeap* gch = GenCollectedHeap::heap(); 884 _old_gen = gch->old_gen(); 885 } 886 return _old_gen->promotion_attempt_is_safe(used()); 887 } 888 889 void DefNewGeneration::gc_epilogue(bool full) { 890 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 891 892 assert(!GCLocker::is_active(), "We should not be executing here"); 893 // Check if the heap is approaching full after a collection has 894 // been done. Generally the young generation is empty at 895 // a minimum at the end of a collection. If it is not, then 896 // the heap is approaching full. 897 GenCollectedHeap* gch = GenCollectedHeap::heap(); 898 if (full) { 899 DEBUG_ONLY(seen_incremental_collection_failed = false;) 900 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 901 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 902 GCCause::to_string(gch->gc_cause())); 903 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 904 set_should_allocate_from_space(); // we seem to be running out of space 905 } else { 906 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 907 GCCause::to_string(gch->gc_cause())); 908 gch->clear_incremental_collection_failed(); // We just did a full collection 909 clear_should_allocate_from_space(); // if set 910 } 911 } else { 912 #ifdef ASSERT 913 // It is possible that incremental_collection_failed() == true 914 // here, because an attempted scavenge did not succeed. The policy 915 // is normally expected to cause a full collection which should 916 // clear that condition, so we should not be here twice in a row 917 // with incremental_collection_failed() == true without having done 918 // a full collection in between. 919 if (!seen_incremental_collection_failed && 920 gch->incremental_collection_failed()) { 921 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 922 GCCause::to_string(gch->gc_cause())); 923 seen_incremental_collection_failed = true; 924 } else if (seen_incremental_collection_failed) { 925 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 926 GCCause::to_string(gch->gc_cause())); 927 assert(gch->gc_cause() == GCCause::_scavenge_alot || 928 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 929 !gch->incremental_collection_failed(), 930 "Twice in a row"); 931 seen_incremental_collection_failed = false; 932 } 933 #endif // ASSERT 934 } 935 936 if (ZapUnusedHeapArea) { 937 eden()->check_mangled_unused_area_complete(); 938 from()->check_mangled_unused_area_complete(); 939 to()->check_mangled_unused_area_complete(); 940 } 941 942 if (!CleanChunkPoolAsync) { 943 Chunk::clean_chunk_pool(); 944 } 945 946 // update the generation and space performance counters 947 update_counters(); 948 gch->gen_policy()->counters()->update_counters(); 949 } 950 951 void DefNewGeneration::record_spaces_top() { 952 assert(ZapUnusedHeapArea, "Not mangling unused space"); 953 eden()->set_top_for_allocations(); 954 to()->set_top_for_allocations(); 955 from()->set_top_for_allocations(); 956 } 957 958 void DefNewGeneration::ref_processor_init() { 959 Generation::ref_processor_init(); 960 } 961 962 963 void DefNewGeneration::update_counters() { 964 if (UsePerfData) { 965 _eden_counters->update_all(); 966 _from_counters->update_all(); 967 _to_counters->update_all(); 968 _gen_counters->update_all(); 969 } 970 } 971 972 void DefNewGeneration::verify() { 973 eden()->verify(); 974 from()->verify(); 975 to()->verify(); 976 } 977 978 void DefNewGeneration::print_on(outputStream* st) const { 979 Generation::print_on(st); 980 st->print(" eden"); 981 eden()->print_on(st); 982 st->print(" from"); 983 from()->print_on(st); 984 st->print(" to "); 985 to()->print_on(st); 986 } 987 988 989 const char* DefNewGeneration::name() const { 990 return "def new generation"; 991 } 992 993 // Moved from inline file as they are not called inline 994 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 995 return eden(); 996 } 997 998 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 999 // This is the slow-path allocation for the DefNewGeneration. 1000 // Most allocations are fast-path in compiled code. 1001 // We try to allocate from the eden. If that works, we are happy. 1002 // Note that since DefNewGeneration supports lock-free allocation, we 1003 // have to use it here, as well. 1004 HeapWord* result = eden()->par_allocate(word_size); 1005 if (result != NULL) { 1006 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1007 _old_gen->sample_eden_chunk(); 1008 } 1009 } else { 1010 // If the eden is full and the last collection bailed out, we are running 1011 // out of heap space, and we try to allocate the from-space, too. 1012 // allocate_from_space can't be inlined because that would introduce a 1013 // circular dependency at compile time. 1014 result = allocate_from_space(word_size); 1015 } 1016 return result; 1017 } 1018 1019 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1020 bool is_tlab) { 1021 HeapWord* res = eden()->par_allocate(word_size); 1022 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1023 _old_gen->sample_eden_chunk(); 1024 } 1025 return res; 1026 } 1027 1028 size_t DefNewGeneration::tlab_capacity() const { 1029 return eden()->capacity(); 1030 } 1031 1032 size_t DefNewGeneration::tlab_used() const { 1033 return eden()->used(); 1034 } 1035 1036 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1037 return unsafe_max_alloc_nogc(); 1038 }