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 GCMemoryManager* mem_mgr, 182 const char* policy) 183 : Generation(rs, initial_size, mem_mgr), 184 _preserved_marks_set(false /* in_c_heap */), 185 _promo_failure_drain_in_progress(false), 186 _should_allocate_from_space(false) 187 { 188 MemRegion cmr((HeapWord*)_virtual_space.low(), 189 (HeapWord*)_virtual_space.high()); 190 GenCollectedHeap* gch = GenCollectedHeap::heap(); 191 192 gch->barrier_set()->resize_covered_region(cmr); 193 194 _eden_space = new ContiguousSpace(); 195 _from_space = new ContiguousSpace(); 196 _to_space = new ContiguousSpace(); 197 198 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) { 199 vm_exit_during_initialization("Could not allocate a new gen space"); 200 } 201 202 // Compute the maximum eden and survivor space sizes. These sizes 203 // are computed assuming the entire reserved space is committed. 204 // These values are exported as performance counters. 205 uintx alignment = gch->collector_policy()->space_alignment(); 206 uintx size = _virtual_space.reserved_size(); 207 _max_survivor_size = compute_survivor_size(size, alignment); 208 _max_eden_size = size - (2*_max_survivor_size); 209 210 // allocate the performance counters 211 GenCollectorPolicy* gcp = gch->gen_policy(); 212 213 // Generation counters -- generation 0, 3 subspaces 214 _gen_counters = new GenerationCounters("new", 0, 3, 215 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space); 216 _gc_counters = new CollectorCounters(policy, 0); 217 218 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space, 219 _gen_counters); 220 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space, 221 _gen_counters); 222 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space, 223 _gen_counters); 224 225 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle); 226 update_counters(); 227 _old_gen = NULL; 228 _tenuring_threshold = MaxTenuringThreshold; 229 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize; 230 231 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer(); 232 } 233 234 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size, 235 bool clear_space, 236 bool mangle_space) { 237 uintx alignment = 238 GenCollectedHeap::heap()->collector_policy()->space_alignment(); 239 240 // If the spaces are being cleared (only done at heap initialization 241 // currently), the survivor spaces need not be empty. 242 // Otherwise, no care is taken for used areas in the survivor spaces 243 // so check. 244 assert(clear_space || (to()->is_empty() && from()->is_empty()), 245 "Initialization of the survivor spaces assumes these are empty"); 246 247 // Compute sizes 248 uintx size = _virtual_space.committed_size(); 249 uintx survivor_size = compute_survivor_size(size, alignment); 250 uintx eden_size = size - (2*survivor_size); 251 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 252 253 if (eden_size < minimum_eden_size) { 254 // May happen due to 64Kb rounding, if so adjust eden size back up 255 minimum_eden_size = align_up(minimum_eden_size, alignment); 256 uintx maximum_survivor_size = (size - minimum_eden_size) / 2; 257 uintx unaligned_survivor_size = 258 align_down(maximum_survivor_size, alignment); 259 survivor_size = MAX2(unaligned_survivor_size, alignment); 260 eden_size = size - (2*survivor_size); 261 assert(eden_size > 0 && survivor_size <= eden_size, "just checking"); 262 assert(eden_size >= minimum_eden_size, "just checking"); 263 } 264 265 char *eden_start = _virtual_space.low(); 266 char *from_start = eden_start + eden_size; 267 char *to_start = from_start + survivor_size; 268 char *to_end = to_start + survivor_size; 269 270 assert(to_end == _virtual_space.high(), "just checking"); 271 assert(Space::is_aligned(eden_start), "checking alignment"); 272 assert(Space::is_aligned(from_start), "checking alignment"); 273 assert(Space::is_aligned(to_start), "checking alignment"); 274 275 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start); 276 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start); 277 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end); 278 279 // A minimum eden size implies that there is a part of eden that 280 // is being used and that affects the initialization of any 281 // newly formed eden. 282 bool live_in_eden = minimum_eden_size > 0; 283 284 // If not clearing the spaces, do some checking to verify that 285 // the space are already mangled. 286 if (!clear_space) { 287 // Must check mangling before the spaces are reshaped. Otherwise, 288 // the bottom or end of one space may have moved into another 289 // a failure of the check may not correctly indicate which space 290 // is not properly mangled. 291 if (ZapUnusedHeapArea) { 292 HeapWord* limit = (HeapWord*) _virtual_space.high(); 293 eden()->check_mangled_unused_area(limit); 294 from()->check_mangled_unused_area(limit); 295 to()->check_mangled_unused_area(limit); 296 } 297 } 298 299 // Reset the spaces for their new regions. 300 eden()->initialize(edenMR, 301 clear_space && !live_in_eden, 302 SpaceDecorator::Mangle); 303 // If clear_space and live_in_eden, we will not have cleared any 304 // portion of eden above its top. This can cause newly 305 // expanded space not to be mangled if using ZapUnusedHeapArea. 306 // We explicitly do such mangling here. 307 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) { 308 eden()->mangle_unused_area(); 309 } 310 from()->initialize(fromMR, clear_space, mangle_space); 311 to()->initialize(toMR, clear_space, mangle_space); 312 313 // Set next compaction spaces. 314 eden()->set_next_compaction_space(from()); 315 // The to-space is normally empty before a compaction so need 316 // not be considered. The exception is during promotion 317 // failure handling when to-space can contain live objects. 318 from()->set_next_compaction_space(NULL); 319 } 320 321 void DefNewGeneration::swap_spaces() { 322 ContiguousSpace* s = from(); 323 _from_space = to(); 324 _to_space = s; 325 eden()->set_next_compaction_space(from()); 326 // The to-space is normally empty before a compaction so need 327 // not be considered. The exception is during promotion 328 // failure handling when to-space can contain live objects. 329 from()->set_next_compaction_space(NULL); 330 331 if (UsePerfData) { 332 CSpaceCounters* c = _from_counters; 333 _from_counters = _to_counters; 334 _to_counters = c; 335 } 336 } 337 338 bool DefNewGeneration::expand(size_t bytes) { 339 MutexLocker x(ExpandHeap_lock); 340 HeapWord* prev_high = (HeapWord*) _virtual_space.high(); 341 bool success = _virtual_space.expand_by(bytes); 342 if (success && ZapUnusedHeapArea) { 343 // Mangle newly committed space immediately because it 344 // can be done here more simply that after the new 345 // spaces have been computed. 346 HeapWord* new_high = (HeapWord*) _virtual_space.high(); 347 MemRegion mangle_region(prev_high, new_high); 348 SpaceMangler::mangle_region(mangle_region); 349 } 350 351 // Do not attempt an expand-to-the reserve size. The 352 // request should properly observe the maximum size of 353 // the generation so an expand-to-reserve should be 354 // unnecessary. Also a second call to expand-to-reserve 355 // value potentially can cause an undue expansion. 356 // For example if the first expand fail for unknown reasons, 357 // but the second succeeds and expands the heap to its maximum 358 // value. 359 if (GCLocker::is_active()) { 360 log_debug(gc)("Garbage collection disabled, expanded heap instead"); 361 } 362 363 return success; 364 } 365 366 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate, 367 size_t new_size_before, 368 size_t alignment) const { 369 size_t desired_new_size = new_size_before; 370 371 if (NewSizeThreadIncrease > 0) { 372 int threads_count; 373 size_t thread_increase_size = 0; 374 375 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'. 376 threads_count = Threads::number_of_non_daemon_threads(); 377 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) { 378 thread_increase_size = threads_count * NewSizeThreadIncrease; 379 380 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'. 381 if (new_size_candidate <= max_uintx - thread_increase_size) { 382 new_size_candidate += thread_increase_size; 383 384 // 3. Check an overflow at 'align_up'. 385 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1)); 386 if (new_size_candidate <= aligned_max) { 387 desired_new_size = align_up(new_size_candidate, alignment); 388 } 389 } 390 } 391 } 392 393 return desired_new_size; 394 } 395 396 void DefNewGeneration::compute_new_size() { 397 // This is called after a GC that includes the old generation, so from-space 398 // will normally be empty. 399 // Note that we check both spaces, since if scavenge failed they revert roles. 400 // If not we bail out (otherwise we would have to relocate the objects). 401 if (!from()->is_empty() || !to()->is_empty()) { 402 return; 403 } 404 405 GenCollectedHeap* gch = GenCollectedHeap::heap(); 406 407 size_t old_size = gch->old_gen()->capacity(); 408 size_t new_size_before = _virtual_space.committed_size(); 409 size_t min_new_size = initial_size(); 410 size_t max_new_size = reserved().byte_size(); 411 assert(min_new_size <= new_size_before && 412 new_size_before <= max_new_size, 413 "just checking"); 414 // All space sizes must be multiples of Generation::GenGrain. 415 size_t alignment = Generation::GenGrain; 416 417 int threads_count = 0; 418 size_t thread_increase_size = 0; 419 420 size_t new_size_candidate = old_size / NewRatio; 421 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease 422 // and reverts to previous value if any overflow happens 423 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment); 424 425 // Adjust new generation size 426 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size); 427 assert(desired_new_size <= max_new_size, "just checking"); 428 429 bool changed = false; 430 if (desired_new_size > new_size_before) { 431 size_t change = desired_new_size - new_size_before; 432 assert(change % alignment == 0, "just checking"); 433 if (expand(change)) { 434 changed = true; 435 } 436 // If the heap failed to expand to the desired size, 437 // "changed" will be false. If the expansion failed 438 // (and at this point it was expected to succeed), 439 // ignore the failure (leaving "changed" as false). 440 } 441 if (desired_new_size < new_size_before && eden()->is_empty()) { 442 // bail out of shrinking if objects in eden 443 size_t change = new_size_before - desired_new_size; 444 assert(change % alignment == 0, "just checking"); 445 _virtual_space.shrink_by(change); 446 changed = true; 447 } 448 if (changed) { 449 // The spaces have already been mangled at this point but 450 // may not have been cleared (set top = bottom) and should be. 451 // Mangling was done when the heap was being expanded. 452 compute_space_boundaries(eden()->used(), 453 SpaceDecorator::Clear, 454 SpaceDecorator::DontMangle); 455 MemRegion cmr((HeapWord*)_virtual_space.low(), 456 (HeapWord*)_virtual_space.high()); 457 gch->barrier_set()->resize_covered_region(cmr); 458 459 log_debug(gc, ergo, heap)( 460 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]", 461 new_size_before/K, _virtual_space.committed_size()/K, 462 eden()->capacity()/K, from()->capacity()/K); 463 log_trace(gc, ergo, heap)( 464 " [allowed " SIZE_FORMAT "K extra for %d threads]", 465 thread_increase_size/K, threads_count); 466 } 467 } 468 469 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) { 470 assert(false, "NYI -- are you sure you want to call this?"); 471 } 472 473 474 size_t DefNewGeneration::capacity() const { 475 return eden()->capacity() 476 + from()->capacity(); // to() is only used during scavenge 477 } 478 479 480 size_t DefNewGeneration::used() const { 481 return eden()->used() 482 + from()->used(); // to() is only used during scavenge 483 } 484 485 486 size_t DefNewGeneration::free() const { 487 return eden()->free() 488 + from()->free(); // to() is only used during scavenge 489 } 490 491 size_t DefNewGeneration::max_capacity() const { 492 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment(); 493 const size_t reserved_bytes = reserved().byte_size(); 494 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment); 495 } 496 497 size_t DefNewGeneration::unsafe_max_alloc_nogc() const { 498 return eden()->free(); 499 } 500 501 size_t DefNewGeneration::capacity_before_gc() const { 502 return eden()->capacity(); 503 } 504 505 size_t DefNewGeneration::contiguous_available() const { 506 return eden()->free(); 507 } 508 509 510 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); } 511 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); } 512 513 void DefNewGeneration::object_iterate(ObjectClosure* blk) { 514 eden()->object_iterate(blk); 515 from()->object_iterate(blk); 516 } 517 518 519 void DefNewGeneration::space_iterate(SpaceClosure* blk, 520 bool usedOnly) { 521 blk->do_space(eden()); 522 blk->do_space(from()); 523 blk->do_space(to()); 524 } 525 526 // The last collection bailed out, we are running out of heap space, 527 // so we try to allocate the from-space, too. 528 HeapWord* DefNewGeneration::allocate_from_space(size_t size) { 529 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc(); 530 531 // If the Heap_lock is not locked by this thread, this will be called 532 // again later with the Heap_lock held. 533 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread())); 534 535 HeapWord* result = NULL; 536 if (do_alloc) { 537 result = from()->allocate(size); 538 } 539 540 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s", 541 size, 542 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ? 543 "true" : "false", 544 Heap_lock->is_locked() ? "locked" : "unlocked", 545 from()->free(), 546 should_try_alloc ? "" : " should_allocate_from_space: NOT", 547 do_alloc ? " Heap_lock is not owned by self" : "", 548 result == NULL ? "NULL" : "object"); 549 550 return result; 551 } 552 553 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, 554 bool is_tlab, 555 bool parallel) { 556 // We don't attempt to expand the young generation (but perhaps we should.) 557 return allocate(size, is_tlab); 558 } 559 560 void DefNewGeneration::adjust_desired_tenuring_threshold() { 561 // Set the desired survivor size to half the real survivor space 562 size_t const survivor_capacity = to()->capacity() / HeapWordSize; 563 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 564 565 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size); 566 567 if (UsePerfData) { 568 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->gen_policy()->counters(); 569 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold); 570 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize); 571 } 572 573 age_table()->print_age_table(_tenuring_threshold); 574 } 575 576 void DefNewGeneration::collect(bool full, 577 bool clear_all_soft_refs, 578 size_t size, 579 bool is_tlab) { 580 assert(full || size > 0, "otherwise we don't want to collect"); 581 582 GenCollectedHeap* gch = GenCollectedHeap::heap(); 583 584 _gc_timer->register_gc_start(); 585 DefNewTracer gc_tracer; 586 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start()); 587 588 _old_gen = gch->old_gen(); 589 590 // If the next generation is too full to accommodate promotion 591 // from this generation, pass on collection; let the next generation 592 // do it. 593 if (!collection_attempt_is_safe()) { 594 log_trace(gc)(":: Collection attempt not safe ::"); 595 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one 596 return; 597 } 598 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); 599 600 init_assuming_no_promotion_failure(); 601 602 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, gch->gc_cause()); 603 604 gch->trace_heap_before_gc(&gc_tracer); 605 606 // These can be shared for all code paths 607 IsAliveClosure is_alive(this); 608 ScanWeakRefClosure scan_weak_ref(this); 609 610 age_table()->clear(); 611 to()->clear(SpaceDecorator::Mangle); 612 // The preserved marks should be empty at the start of the GC. 613 _preserved_marks_set.init(1); 614 615 gch->rem_set()->prepare_for_younger_refs_iterate(false); 616 617 assert(gch->no_allocs_since_save_marks(), 618 "save marks have not been newly set."); 619 620 // Not very pretty. 621 CollectorPolicy* cp = gch->collector_policy(); 622 623 FastScanClosure fsc_with_no_gc_barrier(this, false); 624 FastScanClosure fsc_with_gc_barrier(this, true); 625 626 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier, 627 gch->rem_set()->cld_rem_set()->accumulate_modified_oops()); 628 629 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier); 630 FastEvacuateFollowersClosure evacuate_followers(gch, 631 &fsc_with_no_gc_barrier, 632 &fsc_with_gc_barrier); 633 634 assert(gch->no_allocs_since_save_marks(), 635 "save marks have not been newly set."); 636 637 { 638 // DefNew needs to run with n_threads == 0, to make sure the serial 639 // version of the card table scanning code is used. 640 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel. 641 StrongRootsScope srs(0); 642 643 gch->young_process_roots(&srs, 644 &fsc_with_no_gc_barrier, 645 &fsc_with_gc_barrier, 646 &cld_scan_closure); 647 } 648 649 // "evacuate followers". 650 evacuate_followers.do_void(); 651 652 FastKeepAliveClosure keep_alive(this, &scan_weak_ref); 653 ReferenceProcessor* rp = ref_processor(); 654 rp->setup_policy(clear_all_soft_refs); 655 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->num_q()); 656 const ReferenceProcessorStats& stats = 657 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers, 658 NULL, &pt); 659 gc_tracer.report_gc_reference_stats(stats); 660 gc_tracer.report_tenuring_threshold(tenuring_threshold()); 661 pt.print_all_references(); 662 663 assert(gch->no_allocs_since_save_marks(), "save marks have not been newly set."); 664 665 WeakProcessor::weak_oops_do(&is_alive, &keep_alive); 666 667 // Verify that the usage of keep_alive didn't copy any objects. 668 assert(gch->no_allocs_since_save_marks(), "save marks have not been newly set."); 669 670 if (!_promotion_failed) { 671 // Swap the survivor spaces. 672 eden()->clear(SpaceDecorator::Mangle); 673 from()->clear(SpaceDecorator::Mangle); 674 if (ZapUnusedHeapArea) { 675 // This is now done here because of the piece-meal mangling which 676 // can check for valid mangling at intermediate points in the 677 // collection(s). When a young collection fails to collect 678 // sufficient space resizing of the young generation can occur 679 // an redistribute the spaces in the young generation. Mangle 680 // here so that unzapped regions don't get distributed to 681 // other spaces. 682 to()->mangle_unused_area(); 683 } 684 swap_spaces(); 685 686 assert(to()->is_empty(), "to space should be empty now"); 687 688 adjust_desired_tenuring_threshold(); 689 690 // A successful scavenge should restart the GC time limit count which is 691 // for full GC's. 692 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); 693 size_policy->reset_gc_overhead_limit_count(); 694 assert(!gch->incremental_collection_failed(), "Should be clear"); 695 } else { 696 assert(_promo_failure_scan_stack.is_empty(), "post condition"); 697 _promo_failure_scan_stack.clear(true); // Clear cached segments. 698 699 remove_forwarding_pointers(); 700 log_info(gc, promotion)("Promotion failed"); 701 // Add to-space to the list of space to compact 702 // when a promotion failure has occurred. In that 703 // case there can be live objects in to-space 704 // as a result of a partial evacuation of eden 705 // and from-space. 706 swap_spaces(); // For uniformity wrt ParNewGeneration. 707 from()->set_next_compaction_space(to()); 708 gch->set_incremental_collection_failed(); 709 710 // Inform the next generation that a promotion failure occurred. 711 _old_gen->promotion_failure_occurred(); 712 gc_tracer.report_promotion_failed(_promotion_failed_info); 713 714 // Reset the PromotionFailureALot counters. 715 NOT_PRODUCT(gch->reset_promotion_should_fail();) 716 } 717 // We should have processed and cleared all the preserved marks. 718 _preserved_marks_set.reclaim(); 719 // set new iteration safe limit for the survivor spaces 720 from()->set_concurrent_iteration_safe_limit(from()->top()); 721 to()->set_concurrent_iteration_safe_limit(to()->top()); 722 723 // We need to use a monotonically non-decreasing time in ms 724 // or we will see time-warp warnings and os::javaTimeMillis() 725 // does not guarantee monotonicity. 726 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 727 update_time_of_last_gc(now); 728 729 gch->trace_heap_after_gc(&gc_tracer); 730 731 _gc_timer->register_gc_end(); 732 733 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions()); 734 } 735 736 void DefNewGeneration::init_assuming_no_promotion_failure() { 737 _promotion_failed = false; 738 _promotion_failed_info.reset(); 739 from()->set_next_compaction_space(NULL); 740 } 741 742 void DefNewGeneration::remove_forwarding_pointers() { 743 RemoveForwardedPointerClosure rspc; 744 eden()->object_iterate(&rspc); 745 from()->object_iterate(&rspc); 746 restore_preserved_marks(); 747 } 748 749 void DefNewGeneration::restore_preserved_marks() { 750 SharedRestorePreservedMarksTaskExecutor task_executor(NULL); 751 _preserved_marks_set.restore(&task_executor); 752 } 753 754 void DefNewGeneration::handle_promotion_failure(oop old) { 755 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size()); 756 757 _promotion_failed = true; 758 _promotion_failed_info.register_copy_failure(old->size()); 759 _preserved_marks_set.get()->push_if_necessary(old, old->mark()); 760 // forward to self 761 old->forward_to(old); 762 763 _promo_failure_scan_stack.push(old); 764 765 if (!_promo_failure_drain_in_progress) { 766 // prevent recursion in copy_to_survivor_space() 767 _promo_failure_drain_in_progress = true; 768 drain_promo_failure_scan_stack(); 769 _promo_failure_drain_in_progress = false; 770 } 771 } 772 773 oop DefNewGeneration::copy_to_survivor_space(oop old) { 774 assert(is_in_reserved(old) && !old->is_forwarded(), 775 "shouldn't be scavenging this oop"); 776 size_t s = old->size(); 777 oop obj = NULL; 778 779 // Try allocating obj in to-space (unless too old) 780 if (old->age() < tenuring_threshold()) { 781 obj = (oop) to()->allocate_aligned(s); 782 } 783 784 // Otherwise try allocating obj tenured 785 if (obj == NULL) { 786 obj = _old_gen->promote(old, s); 787 if (obj == NULL) { 788 handle_promotion_failure(old); 789 return old; 790 } 791 } else { 792 // Prefetch beyond obj 793 const intx interval = PrefetchCopyIntervalInBytes; 794 Prefetch::write(obj, interval); 795 796 // Copy obj 797 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s); 798 799 // Increment age if obj still in new generation 800 obj->incr_age(); 801 age_table()->add(obj, s); 802 } 803 804 // Done, insert forward pointer to obj in this header 805 old->forward_to(obj); 806 807 return obj; 808 } 809 810 void DefNewGeneration::drain_promo_failure_scan_stack() { 811 while (!_promo_failure_scan_stack.is_empty()) { 812 oop obj = _promo_failure_scan_stack.pop(); 813 obj->oop_iterate(_promo_failure_scan_stack_closure); 814 } 815 } 816 817 void DefNewGeneration::save_marks() { 818 eden()->set_saved_mark(); 819 to()->set_saved_mark(); 820 from()->set_saved_mark(); 821 } 822 823 824 void DefNewGeneration::reset_saved_marks() { 825 eden()->reset_saved_mark(); 826 to()->reset_saved_mark(); 827 from()->reset_saved_mark(); 828 } 829 830 831 bool DefNewGeneration::no_allocs_since_save_marks() { 832 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden"); 833 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from"); 834 return to()->saved_mark_at_top(); 835 } 836 837 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \ 838 \ 839 void DefNewGeneration:: \ 840 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ 841 cl->set_generation(this); \ 842 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \ 843 to()->oop_since_save_marks_iterate##nv_suffix(cl); \ 844 from()->oop_since_save_marks_iterate##nv_suffix(cl); \ 845 cl->reset_generation(); \ 846 save_marks(); \ 847 } 848 849 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN) 850 851 #undef DefNew_SINCE_SAVE_MARKS_DEFN 852 853 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor, 854 size_t max_alloc_words) { 855 if (requestor == this || _promotion_failed) { 856 return; 857 } 858 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation"); 859 860 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate. 861 if (to_space->top() > to_space->bottom()) { 862 trace("to_space not empty when contribute_scratch called"); 863 } 864 */ 865 866 ContiguousSpace* to_space = to(); 867 assert(to_space->end() >= to_space->top(), "pointers out of order"); 868 size_t free_words = pointer_delta(to_space->end(), to_space->top()); 869 if (free_words >= MinFreeScratchWords) { 870 ScratchBlock* sb = (ScratchBlock*)to_space->top(); 871 sb->num_words = free_words; 872 sb->next = list; 873 list = sb; 874 } 875 } 876 877 void DefNewGeneration::reset_scratch() { 878 // If contributing scratch in to_space, mangle all of 879 // to_space if ZapUnusedHeapArea. This is needed because 880 // top is not maintained while using to-space as scratch. 881 if (ZapUnusedHeapArea) { 882 to()->mangle_unused_area_complete(); 883 } 884 } 885 886 bool DefNewGeneration::collection_attempt_is_safe() { 887 if (!to()->is_empty()) { 888 log_trace(gc)(":: to is not empty ::"); 889 return false; 890 } 891 if (_old_gen == NULL) { 892 GenCollectedHeap* gch = GenCollectedHeap::heap(); 893 _old_gen = gch->old_gen(); 894 } 895 return _old_gen->promotion_attempt_is_safe(used()); 896 } 897 898 void DefNewGeneration::gc_epilogue(bool full) { 899 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;) 900 901 assert(!GCLocker::is_active(), "We should not be executing here"); 902 // Check if the heap is approaching full after a collection has 903 // been done. Generally the young generation is empty at 904 // a minimum at the end of a collection. If it is not, then 905 // the heap is approaching full. 906 GenCollectedHeap* gch = GenCollectedHeap::heap(); 907 if (full) { 908 DEBUG_ONLY(seen_incremental_collection_failed = false;) 909 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) { 910 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen", 911 GCCause::to_string(gch->gc_cause())); 912 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state 913 set_should_allocate_from_space(); // we seem to be running out of space 914 } else { 915 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen", 916 GCCause::to_string(gch->gc_cause())); 917 gch->clear_incremental_collection_failed(); // We just did a full collection 918 clear_should_allocate_from_space(); // if set 919 } 920 } else { 921 #ifdef ASSERT 922 // It is possible that incremental_collection_failed() == true 923 // here, because an attempted scavenge did not succeed. The policy 924 // is normally expected to cause a full collection which should 925 // clear that condition, so we should not be here twice in a row 926 // with incremental_collection_failed() == true without having done 927 // a full collection in between. 928 if (!seen_incremental_collection_failed && 929 gch->incremental_collection_failed()) { 930 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed", 931 GCCause::to_string(gch->gc_cause())); 932 seen_incremental_collection_failed = true; 933 } else if (seen_incremental_collection_failed) { 934 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed", 935 GCCause::to_string(gch->gc_cause())); 936 assert(gch->gc_cause() == GCCause::_scavenge_alot || 937 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) || 938 !gch->incremental_collection_failed(), 939 "Twice in a row"); 940 seen_incremental_collection_failed = false; 941 } 942 #endif // ASSERT 943 } 944 945 if (ZapUnusedHeapArea) { 946 eden()->check_mangled_unused_area_complete(); 947 from()->check_mangled_unused_area_complete(); 948 to()->check_mangled_unused_area_complete(); 949 } 950 951 if (!CleanChunkPoolAsync) { 952 Chunk::clean_chunk_pool(); 953 } 954 955 // update the generation and space performance counters 956 update_counters(); 957 gch->gen_policy()->counters()->update_counters(); 958 } 959 960 void DefNewGeneration::record_spaces_top() { 961 assert(ZapUnusedHeapArea, "Not mangling unused space"); 962 eden()->set_top_for_allocations(); 963 to()->set_top_for_allocations(); 964 from()->set_top_for_allocations(); 965 } 966 967 void DefNewGeneration::ref_processor_init() { 968 Generation::ref_processor_init(); 969 } 970 971 972 void DefNewGeneration::update_counters() { 973 if (UsePerfData) { 974 _eden_counters->update_all(); 975 _from_counters->update_all(); 976 _to_counters->update_all(); 977 _gen_counters->update_all(); 978 } 979 } 980 981 void DefNewGeneration::verify() { 982 eden()->verify(); 983 from()->verify(); 984 to()->verify(); 985 } 986 987 void DefNewGeneration::print_on(outputStream* st) const { 988 Generation::print_on(st); 989 st->print(" eden"); 990 eden()->print_on(st); 991 st->print(" from"); 992 from()->print_on(st); 993 st->print(" to "); 994 to()->print_on(st); 995 } 996 997 998 const char* DefNewGeneration::name() const { 999 return "def new generation"; 1000 } 1001 1002 // Moved from inline file as they are not called inline 1003 CompactibleSpace* DefNewGeneration::first_compaction_space() const { 1004 return eden(); 1005 } 1006 1007 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) { 1008 // This is the slow-path allocation for the DefNewGeneration. 1009 // Most allocations are fast-path in compiled code. 1010 // We try to allocate from the eden. If that works, we are happy. 1011 // Note that since DefNewGeneration supports lock-free allocation, we 1012 // have to use it here, as well. 1013 HeapWord* result = eden()->par_allocate(word_size); 1014 if (result != NULL) { 1015 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1016 _old_gen->sample_eden_chunk(); 1017 } 1018 } else { 1019 // If the eden is full and the last collection bailed out, we are running 1020 // out of heap space, and we try to allocate the from-space, too. 1021 // allocate_from_space can't be inlined because that would introduce a 1022 // circular dependency at compile time. 1023 result = allocate_from_space(word_size); 1024 } 1025 return result; 1026 } 1027 1028 HeapWord* DefNewGeneration::par_allocate(size_t word_size, 1029 bool is_tlab) { 1030 HeapWord* res = eden()->par_allocate(word_size); 1031 if (CMSEdenChunksRecordAlways && _old_gen != NULL) { 1032 _old_gen->sample_eden_chunk(); 1033 } 1034 return res; 1035 } 1036 1037 size_t DefNewGeneration::tlab_capacity() const { 1038 return eden()->capacity(); 1039 } 1040 1041 size_t DefNewGeneration::tlab_used() const { 1042 return eden()->used(); 1043 } 1044 1045 size_t DefNewGeneration::unsafe_max_tlab_alloc() const { 1046 return unsafe_max_alloc_nogc(); 1047 }