rev 58017 : [mq]: 8238854-remove-superfluous-alloc-checks

   1 /*
   2  * Copyright (c) 2001, 2020, 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/serial/serialHeap.inline.hpp"
  28 #include "gc/serial/tenuredGeneration.hpp"
  29 #include "gc/shared/adaptiveSizePolicy.hpp"
  30 #include "gc/shared/ageTable.inline.hpp"
  31 #include "gc/shared/cardTableRS.hpp"
  32 #include "gc/shared/collectorCounters.hpp"
  33 #include "gc/shared/gcArguments.hpp"
  34 #include "gc/shared/gcHeapSummary.hpp"
  35 #include "gc/shared/gcLocker.hpp"
  36 #include "gc/shared/gcPolicyCounters.hpp"
  37 #include "gc/shared/gcTimer.hpp"
  38 #include "gc/shared/gcTrace.hpp"
  39 #include "gc/shared/gcTraceTime.inline.hpp"
  40 #include "gc/shared/genOopClosures.inline.hpp"
  41 #include "gc/shared/generationSpec.hpp"
  42 #include "gc/shared/preservedMarks.inline.hpp"
  43 #include "gc/shared/referencePolicy.hpp"
  44 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
  45 #include "gc/shared/space.inline.hpp"
  46 #include "gc/shared/spaceDecorator.inline.hpp"
  47 #include "gc/shared/strongRootsScope.hpp"
  48 #include "gc/shared/weakProcessor.hpp"
  49 #include "logging/log.hpp"
  50 #include "memory/iterator.inline.hpp"
  51 #include "memory/resourceArea.hpp"
  52 #include "oops/instanceRefKlass.hpp"
  53 #include "oops/oop.inline.hpp"
  54 #include "runtime/java.hpp"
  55 #include "runtime/prefetch.inline.hpp"
  56 #include "runtime/thread.inline.hpp"
  57 #include "utilities/align.hpp"
  58 #include "utilities/copy.hpp"
  59 #include "utilities/globalDefinitions.hpp"
  60 #include "utilities/stack.inline.hpp"
  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::DefNew, "Expected the young generation here");
  69 }
  70 
  71 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
  72   return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded();
  73 }
  74 
  75 DefNewGeneration::KeepAliveClosure::
  76 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
  77   _rs = GenCollectedHeap::heap()->rem_set();
  78 }
  79 
  80 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  81 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
  82 
  83 
  84 DefNewGeneration::FastKeepAliveClosure::
  85 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
  86   DefNewGeneration::KeepAliveClosure(cl) {
  87   _boundary = g->reserved().end();
  88 }
  89 
  90 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  91 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
  92 
  93 DefNewGeneration::FastEvacuateFollowersClosure::
  94 FastEvacuateFollowersClosure(SerialHeap* heap,
  95                              FastScanClosure* cur,
  96                              FastScanClosure* older) :
  97   _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
  98 {
  99 }
 100 
 101 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
 102   do {
 103     _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
 104   } while (!_heap->no_allocs_since_save_marks());
 105   guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
 106 }
 107 
 108 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
 109     OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 110 {
 111   _boundary = _g->reserved().end();
 112 }
 113 
 114 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
 115     OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
 116 {
 117   _boundary = _g->reserved().end();
 118 }
 119 
 120 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
 121   NOT_PRODUCT(ResourceMark rm);
 122   log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
 123                                   p2i(cld),
 124                                   cld->loader_name_and_id(),
 125                                   cld->has_modified_oops() ? "true" : "false");
 126 
 127   // If the cld has not been dirtied we know that there's
 128   // no references into  the young gen and we can skip it.
 129   if (cld->has_modified_oops()) {
 130     if (_accumulate_modified_oops) {
 131       cld->accumulate_modified_oops();
 132     }
 133 
 134     // Tell the closure which CLD is being scanned so that it can be dirtied
 135     // if oops are left pointing into the young gen.
 136     _scavenge_closure->set_scanned_cld(cld);
 137 
 138     // Clean the cld since we're going to scavenge all the metadata.
 139     cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
 140 
 141     _scavenge_closure->set_scanned_cld(NULL);
 142   }
 143 }
 144 
 145 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
 146   _g(g)
 147 {
 148   _boundary = _g->reserved().end();
 149 }
 150 
 151 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
 152                                    size_t initial_size,
 153                                    size_t min_size,
 154                                    size_t max_size,
 155                                    const char* policy)
 156   : Generation(rs, initial_size),
 157     _preserved_marks_set(false /* in_c_heap */),
 158     _promo_failure_drain_in_progress(false),
 159     _should_allocate_from_space(false)
 160 {
 161   MemRegion cmr((HeapWord*)_virtual_space.low(),
 162                 (HeapWord*)_virtual_space.high());
 163   GenCollectedHeap* gch = GenCollectedHeap::heap();
 164 
 165   gch->rem_set()->resize_covered_region(cmr);
 166 
 167   _eden_space = new ContiguousSpace();
 168   _from_space = new ContiguousSpace();
 169   _to_space   = new ContiguousSpace();
 170 
 171   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
 172     vm_exit_during_initialization("Could not allocate a new gen space");
 173   }
 174 
 175   // Compute the maximum eden and survivor space sizes. These sizes
 176   // are computed assuming the entire reserved space is committed.
 177   // These values are exported as performance counters.
 178   uintx size = _virtual_space.reserved_size();
 179   _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
 180   _max_eden_size = size - (2*_max_survivor_size);
 181 
 182   // allocate the performance counters
 183 
 184   // Generation counters -- generation 0, 3 subspaces
 185   _gen_counters = new GenerationCounters("new", 0, 3,
 186       min_size, max_size, &_virtual_space);
 187   _gc_counters = new CollectorCounters(policy, 0);
 188 
 189   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
 190                                       _gen_counters);
 191   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
 192                                       _gen_counters);
 193   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
 194                                     _gen_counters);
 195 
 196   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
 197   update_counters();
 198   _old_gen = NULL;
 199   _tenuring_threshold = MaxTenuringThreshold;
 200   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
 201 
 202   _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
 203 }
 204 
 205 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
 206                                                 bool clear_space,
 207                                                 bool mangle_space) {
 208   // If the spaces are being cleared (only done at heap initialization
 209   // currently), the survivor spaces need not be empty.
 210   // Otherwise, no care is taken for used areas in the survivor spaces
 211   // so check.
 212   assert(clear_space || (to()->is_empty() && from()->is_empty()),
 213     "Initialization of the survivor spaces assumes these are empty");
 214 
 215   // Compute sizes
 216   uintx size = _virtual_space.committed_size();
 217   uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
 218   uintx eden_size = size - (2*survivor_size);
 219   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 220 
 221   if (eden_size < minimum_eden_size) {
 222     // May happen due to 64Kb rounding, if so adjust eden size back up
 223     minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
 224     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
 225     uintx unaligned_survivor_size =
 226       align_down(maximum_survivor_size, SpaceAlignment);
 227     survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
 228     eden_size = size - (2*survivor_size);
 229     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
 230     assert(eden_size >= minimum_eden_size, "just checking");
 231   }
 232 
 233   char *eden_start = _virtual_space.low();
 234   char *from_start = eden_start + eden_size;
 235   char *to_start   = from_start + survivor_size;
 236   char *to_end     = to_start   + survivor_size;
 237 
 238   assert(to_end == _virtual_space.high(), "just checking");
 239   assert(Space::is_aligned(eden_start), "checking alignment");
 240   assert(Space::is_aligned(from_start), "checking alignment");
 241   assert(Space::is_aligned(to_start),   "checking alignment");
 242 
 243   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
 244   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
 245   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
 246 
 247   // A minimum eden size implies that there is a part of eden that
 248   // is being used and that affects the initialization of any
 249   // newly formed eden.
 250   bool live_in_eden = minimum_eden_size > 0;
 251 
 252   // If not clearing the spaces, do some checking to verify that
 253   // the space are already mangled.
 254   if (!clear_space) {
 255     // Must check mangling before the spaces are reshaped.  Otherwise,
 256     // the bottom or end of one space may have moved into another
 257     // a failure of the check may not correctly indicate which space
 258     // is not properly mangled.
 259     if (ZapUnusedHeapArea) {
 260       HeapWord* limit = (HeapWord*) _virtual_space.high();
 261       eden()->check_mangled_unused_area(limit);
 262       from()->check_mangled_unused_area(limit);
 263         to()->check_mangled_unused_area(limit);
 264     }
 265   }
 266 
 267   // Reset the spaces for their new regions.
 268   eden()->initialize(edenMR,
 269                      clear_space && !live_in_eden,
 270                      SpaceDecorator::Mangle);
 271   // If clear_space and live_in_eden, we will not have cleared any
 272   // portion of eden above its top. This can cause newly
 273   // expanded space not to be mangled if using ZapUnusedHeapArea.
 274   // We explicitly do such mangling here.
 275   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
 276     eden()->mangle_unused_area();
 277   }
 278   from()->initialize(fromMR, clear_space, mangle_space);
 279   to()->initialize(toMR, clear_space, mangle_space);
 280 
 281   // Set next compaction spaces.
 282   eden()->set_next_compaction_space(from());
 283   // The to-space is normally empty before a compaction so need
 284   // not be considered.  The exception is during promotion
 285   // failure handling when to-space can contain live objects.
 286   from()->set_next_compaction_space(NULL);
 287 }
 288 
 289 void DefNewGeneration::swap_spaces() {
 290   ContiguousSpace* s = from();
 291   _from_space        = to();
 292   _to_space          = s;
 293   eden()->set_next_compaction_space(from());
 294   // The to-space is normally empty before a compaction so need
 295   // not be considered.  The exception is during promotion
 296   // failure handling when to-space can contain live objects.
 297   from()->set_next_compaction_space(NULL);
 298 
 299   if (UsePerfData) {
 300     CSpaceCounters* c = _from_counters;
 301     _from_counters = _to_counters;
 302     _to_counters = c;
 303   }
 304 }
 305 
 306 bool DefNewGeneration::expand(size_t bytes) {
 307   MutexLocker x(ExpandHeap_lock);
 308   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
 309   bool success = _virtual_space.expand_by(bytes);
 310   if (success && ZapUnusedHeapArea) {
 311     // Mangle newly committed space immediately because it
 312     // can be done here more simply that after the new
 313     // spaces have been computed.
 314     HeapWord* new_high = (HeapWord*) _virtual_space.high();
 315     MemRegion mangle_region(prev_high, new_high);
 316     SpaceMangler::mangle_region(mangle_region);
 317   }
 318 
 319   // Do not attempt an expand-to-the reserve size.  The
 320   // request should properly observe the maximum size of
 321   // the generation so an expand-to-reserve should be
 322   // unnecessary.  Also a second call to expand-to-reserve
 323   // value potentially can cause an undue expansion.
 324   // For example if the first expand fail for unknown reasons,
 325   // but the second succeeds and expands the heap to its maximum
 326   // value.
 327   if (GCLocker::is_active()) {
 328     log_debug(gc)("Garbage collection disabled, expanded heap instead");
 329   }
 330 
 331   return success;
 332 }
 333 
 334 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
 335                                                     size_t new_size_before,
 336                                                     size_t alignment) const {
 337   size_t desired_new_size = new_size_before;
 338 
 339   if (NewSizeThreadIncrease > 0) {
 340     int threads_count;
 341     size_t thread_increase_size = 0;
 342 
 343     // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
 344     threads_count = Threads::number_of_non_daemon_threads();
 345     if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
 346       thread_increase_size = threads_count * NewSizeThreadIncrease;
 347 
 348       // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
 349       if (new_size_candidate <= max_uintx - thread_increase_size) {
 350         new_size_candidate += thread_increase_size;
 351 
 352         // 3. Check an overflow at 'align_up'.
 353         size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
 354         if (new_size_candidate <= aligned_max) {
 355           desired_new_size = align_up(new_size_candidate, alignment);
 356         }
 357       }
 358     }
 359   }
 360 
 361   return desired_new_size;
 362 }
 363 
 364 void DefNewGeneration::compute_new_size() {
 365   // This is called after a GC that includes the old generation, so from-space
 366   // will normally be empty.
 367   // Note that we check both spaces, since if scavenge failed they revert roles.
 368   // If not we bail out (otherwise we would have to relocate the objects).
 369   if (!from()->is_empty() || !to()->is_empty()) {
 370     return;
 371   }
 372 
 373   GenCollectedHeap* gch = GenCollectedHeap::heap();
 374 
 375   size_t old_size = gch->old_gen()->capacity();
 376   size_t new_size_before = _virtual_space.committed_size();
 377   size_t min_new_size = initial_size();
 378   size_t max_new_size = reserved().byte_size();
 379   assert(min_new_size <= new_size_before &&
 380          new_size_before <= max_new_size,
 381          "just checking");
 382   // All space sizes must be multiples of Generation::GenGrain.
 383   size_t alignment = Generation::GenGrain;
 384 
 385   int threads_count = 0;
 386   size_t thread_increase_size = 0;
 387 
 388   size_t new_size_candidate = old_size / NewRatio;
 389   // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
 390   // and reverts to previous value if any overflow happens
 391   size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
 392 
 393   // Adjust new generation size
 394   desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
 395   assert(desired_new_size <= max_new_size, "just checking");
 396 
 397   bool changed = false;
 398   if (desired_new_size > new_size_before) {
 399     size_t change = desired_new_size - new_size_before;
 400     assert(change % alignment == 0, "just checking");
 401     if (expand(change)) {
 402        changed = true;
 403     }
 404     // If the heap failed to expand to the desired size,
 405     // "changed" will be false.  If the expansion failed
 406     // (and at this point it was expected to succeed),
 407     // ignore the failure (leaving "changed" as false).
 408   }
 409   if (desired_new_size < new_size_before && eden()->is_empty()) {
 410     // bail out of shrinking if objects in eden
 411     size_t change = new_size_before - desired_new_size;
 412     assert(change % alignment == 0, "just checking");
 413     _virtual_space.shrink_by(change);
 414     changed = true;
 415   }
 416   if (changed) {
 417     // The spaces have already been mangled at this point but
 418     // may not have been cleared (set top = bottom) and should be.
 419     // Mangling was done when the heap was being expanded.
 420     compute_space_boundaries(eden()->used(),
 421                              SpaceDecorator::Clear,
 422                              SpaceDecorator::DontMangle);
 423     MemRegion cmr((HeapWord*)_virtual_space.low(),
 424                   (HeapWord*)_virtual_space.high());
 425     gch->rem_set()->resize_covered_region(cmr);
 426 
 427     log_debug(gc, ergo, heap)(
 428         "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
 429         new_size_before/K, _virtual_space.committed_size()/K,
 430         eden()->capacity()/K, from()->capacity()/K);
 431     log_trace(gc, ergo, heap)(
 432         "  [allowed " SIZE_FORMAT "K extra for %d threads]",
 433           thread_increase_size/K, threads_count);
 434       }
 435 }
 436 
 437 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
 438   assert(false, "NYI -- are you sure you want to call this?");
 439 }
 440 
 441 
 442 size_t DefNewGeneration::capacity() const {
 443   return eden()->capacity()
 444        + from()->capacity();  // to() is only used during scavenge
 445 }
 446 
 447 
 448 size_t DefNewGeneration::used() const {
 449   return eden()->used()
 450        + from()->used();      // to() is only used during scavenge
 451 }
 452 
 453 
 454 size_t DefNewGeneration::free() const {
 455   return eden()->free()
 456        + from()->free();      // to() is only used during scavenge
 457 }
 458 
 459 size_t DefNewGeneration::max_capacity() const {
 460   const size_t reserved_bytes = reserved().byte_size();
 461   return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
 462 }
 463 
 464 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
 465   return eden()->free();
 466 }
 467 
 468 size_t DefNewGeneration::capacity_before_gc() const {
 469   return eden()->capacity();
 470 }
 471 
 472 size_t DefNewGeneration::contiguous_available() const {
 473   return eden()->free();
 474 }
 475 
 476 
 477 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
 478 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
 479 
 480 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
 481   eden()->object_iterate(blk);
 482   from()->object_iterate(blk);
 483 }
 484 
 485 
 486 void DefNewGeneration::space_iterate(SpaceClosure* blk,
 487                                      bool usedOnly) {
 488   blk->do_space(eden());
 489   blk->do_space(from());
 490   blk->do_space(to());
 491 }
 492 
 493 // The last collection bailed out, we are running out of heap space,
 494 // so we try to allocate the from-space, too.
 495 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
 496   bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
 497 
 498   // If the Heap_lock is not locked by this thread, this will be called
 499   // again later with the Heap_lock held.
 500   bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
 501 
 502   HeapWord* result = NULL;
 503   if (do_alloc) {
 504     result = from()->allocate(size);
 505   }
 506 
 507   log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):  will_fail: %s  heap_lock: %s  free: " SIZE_FORMAT "%s%s returns %s",
 508                         size,
 509                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
 510                           "true" : "false",
 511                         Heap_lock->is_locked() ? "locked" : "unlocked",
 512                         from()->free(),
 513                         should_try_alloc ? "" : "  should_allocate_from_space: NOT",
 514                         do_alloc ? "  Heap_lock is not owned by self" : "",
 515                         result == NULL ? "NULL" : "object");
 516 
 517   return result;
 518 }
 519 
 520 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
 521                                                 bool   is_tlab,
 522                                                 bool   parallel) {
 523   // We don't attempt to expand the young generation (but perhaps we should.)
 524   return allocate(size, is_tlab);
 525 }
 526 
 527 void DefNewGeneration::adjust_desired_tenuring_threshold() {
 528   // Set the desired survivor size to half the real survivor space
 529   size_t const survivor_capacity = to()->capacity() / HeapWordSize;
 530   size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 531 
 532   _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
 533 
 534   if (UsePerfData) {
 535     GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
 536     gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
 537     gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
 538   }
 539 
 540   age_table()->print_age_table(_tenuring_threshold);
 541 }
 542 
 543 void DefNewGeneration::collect(bool   full,
 544                                bool   clear_all_soft_refs,
 545                                size_t size,
 546                                bool   is_tlab) {
 547   assert(full || size > 0, "otherwise we don't want to collect");
 548 
 549   SerialHeap* heap = SerialHeap::heap();
 550 
 551   _gc_timer->register_gc_start();
 552   DefNewTracer gc_tracer;
 553   gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
 554 
 555   _old_gen = heap->old_gen();
 556 
 557   // If the next generation is too full to accommodate promotion
 558   // from this generation, pass on collection; let the next generation
 559   // do it.
 560   if (!collection_attempt_is_safe()) {
 561     log_trace(gc)(":: Collection attempt not safe ::");
 562     heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
 563     return;
 564   }
 565   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
 566 
 567   init_assuming_no_promotion_failure();
 568 
 569   GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
 570 
 571   heap->trace_heap_before_gc(&gc_tracer);
 572 
 573   // These can be shared for all code paths
 574   IsAliveClosure is_alive(this);
 575   ScanWeakRefClosure scan_weak_ref(this);
 576 
 577   age_table()->clear();
 578   to()->clear(SpaceDecorator::Mangle);
 579   // The preserved marks should be empty at the start of the GC.
 580   _preserved_marks_set.init(1);
 581 
 582   heap->rem_set()->prepare_for_younger_refs_iterate(false);
 583 
 584   assert(heap->no_allocs_since_save_marks(),
 585          "save marks have not been newly set.");
 586 
 587   FastScanClosure fsc_with_no_gc_barrier(this, false);
 588   FastScanClosure fsc_with_gc_barrier(this, true);
 589 
 590   CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
 591                                   heap->rem_set()->cld_rem_set()->accumulate_modified_oops());
 592 
 593   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
 594   FastEvacuateFollowersClosure evacuate_followers(heap,
 595                                                   &fsc_with_no_gc_barrier,
 596                                                   &fsc_with_gc_barrier);
 597 
 598   assert(heap->no_allocs_since_save_marks(),
 599          "save marks have not been newly set.");
 600 
 601   {
 602     // DefNew needs to run with n_threads == 0, to make sure the serial
 603     // version of the card table scanning code is used.
 604     // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
 605     StrongRootsScope srs(0);
 606 
 607     heap->young_process_roots(&srs,
 608                               &fsc_with_no_gc_barrier,
 609                               &fsc_with_gc_barrier,
 610                               &cld_scan_closure);
 611   }
 612 
 613   // "evacuate followers".
 614   evacuate_followers.do_void();
 615 
 616   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
 617   ReferenceProcessor* rp = ref_processor();
 618   rp->setup_policy(clear_all_soft_refs);
 619   ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
 620   const ReferenceProcessorStats& stats =
 621   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
 622                                     NULL, &pt);
 623   gc_tracer.report_gc_reference_stats(stats);
 624   gc_tracer.report_tenuring_threshold(tenuring_threshold());
 625   pt.print_all_references();
 626 
 627   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
 628 
 629   WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
 630 
 631   // Verify that the usage of keep_alive didn't copy any objects.
 632   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
 633 
 634   if (!_promotion_failed) {
 635     // Swap the survivor spaces.
 636     eden()->clear(SpaceDecorator::Mangle);
 637     from()->clear(SpaceDecorator::Mangle);
 638     if (ZapUnusedHeapArea) {
 639       // This is now done here because of the piece-meal mangling which
 640       // can check for valid mangling at intermediate points in the
 641       // collection(s).  When a young collection fails to collect
 642       // sufficient space resizing of the young generation can occur
 643       // an redistribute the spaces in the young generation.  Mangle
 644       // here so that unzapped regions don't get distributed to
 645       // other spaces.
 646       to()->mangle_unused_area();
 647     }
 648     swap_spaces();
 649 
 650     assert(to()->is_empty(), "to space should be empty now");
 651 
 652     adjust_desired_tenuring_threshold();
 653 
 654     // A successful scavenge should restart the GC time limit count which is
 655     // for full GC's.
 656     AdaptiveSizePolicy* size_policy = heap->size_policy();
 657     size_policy->reset_gc_overhead_limit_count();
 658     assert(!heap->incremental_collection_failed(), "Should be clear");
 659   } else {
 660     assert(_promo_failure_scan_stack.is_empty(), "post condition");
 661     _promo_failure_scan_stack.clear(true); // Clear cached segments.
 662 
 663     remove_forwarding_pointers();
 664     log_info(gc, promotion)("Promotion failed");
 665     // Add to-space to the list of space to compact
 666     // when a promotion failure has occurred.  In that
 667     // case there can be live objects in to-space
 668     // as a result of a partial evacuation of eden
 669     // and from-space.
 670     swap_spaces();   // For uniformity wrt ParNewGeneration.
 671     from()->set_next_compaction_space(to());
 672     heap->set_incremental_collection_failed();
 673 
 674     // Inform the next generation that a promotion failure occurred.
 675     _old_gen->promotion_failure_occurred();
 676     gc_tracer.report_promotion_failed(_promotion_failed_info);
 677 
 678     // Reset the PromotionFailureALot counters.
 679     NOT_PRODUCT(heap->reset_promotion_should_fail();)
 680   }
 681   // We should have processed and cleared all the preserved marks.
 682   _preserved_marks_set.reclaim();
 683   // set new iteration safe limit for the survivor spaces
 684   from()->set_concurrent_iteration_safe_limit(from()->top());
 685   to()->set_concurrent_iteration_safe_limit(to()->top());
 686 
 687   // We need to use a monotonically non-decreasing time in ms
 688   // or we will see time-warp warnings and os::javaTimeMillis()
 689   // does not guarantee monotonicity.
 690   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 691   update_time_of_last_gc(now);
 692 
 693   heap->trace_heap_after_gc(&gc_tracer);
 694 
 695   _gc_timer->register_gc_end();
 696 
 697   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
 698 }
 699 
 700 void DefNewGeneration::init_assuming_no_promotion_failure() {
 701   _promotion_failed = false;
 702   _promotion_failed_info.reset();
 703   from()->set_next_compaction_space(NULL);
 704 }
 705 
 706 void DefNewGeneration::remove_forwarding_pointers() {
 707   RemoveForwardedPointerClosure rspc;
 708   eden()->object_iterate(&rspc);
 709   from()->object_iterate(&rspc);
 710   restore_preserved_marks();
 711 }
 712 
 713 void DefNewGeneration::restore_preserved_marks() {
 714   _preserved_marks_set.restore(NULL);
 715 }
 716 
 717 void DefNewGeneration::handle_promotion_failure(oop old) {
 718   log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
 719 
 720   _promotion_failed = true;
 721   _promotion_failed_info.register_copy_failure(old->size());
 722   _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw());
 723   // forward to self
 724   old->forward_to(old);
 725 
 726   _promo_failure_scan_stack.push(old);
 727 
 728   if (!_promo_failure_drain_in_progress) {
 729     // prevent recursion in copy_to_survivor_space()
 730     _promo_failure_drain_in_progress = true;
 731     drain_promo_failure_scan_stack();
 732     _promo_failure_drain_in_progress = false;
 733   }
 734 }
 735 
 736 oop DefNewGeneration::copy_to_survivor_space(oop old) {
 737   assert(is_in_reserved(old) && !old->is_forwarded(),
 738          "shouldn't be scavenging this oop");
 739   size_t s = old->size();
 740   oop obj = NULL;
 741 
 742   // Try allocating obj in to-space (unless too old)
 743   if (old->age() < tenuring_threshold()) {
 744     obj = (oop) to()->allocate_aligned(s);
 745   }
 746 
 747   // Otherwise try allocating obj tenured
 748   if (obj == NULL) {
 749     obj = _old_gen->promote(old, s);
 750     if (obj == NULL) {
 751       handle_promotion_failure(old);
 752       return old;
 753     }
 754   } else {
 755     // Prefetch beyond obj
 756     const intx interval = PrefetchCopyIntervalInBytes;
 757     Prefetch::write(obj, interval);
 758 
 759     // Copy obj
 760     Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
 761 
 762     // Increment age if obj still in new generation
 763     obj->incr_age();
 764     age_table()->add(obj, s);
 765   }
 766 
 767   // Done, insert forward pointer to obj in this header
 768   old->forward_to(obj);
 769 
 770   return obj;
 771 }
 772 
 773 void DefNewGeneration::drain_promo_failure_scan_stack() {
 774   while (!_promo_failure_scan_stack.is_empty()) {
 775      oop obj = _promo_failure_scan_stack.pop();
 776      obj->oop_iterate(_promo_failure_scan_stack_closure);
 777   }
 778 }
 779 
 780 void DefNewGeneration::save_marks() {
 781   eden()->set_saved_mark();
 782   to()->set_saved_mark();
 783   from()->set_saved_mark();
 784 }
 785 
 786 
 787 void DefNewGeneration::reset_saved_marks() {
 788   eden()->reset_saved_mark();
 789   to()->reset_saved_mark();
 790   from()->reset_saved_mark();
 791 }
 792 
 793 
 794 bool DefNewGeneration::no_allocs_since_save_marks() {
 795   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
 796   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
 797   return to()->saved_mark_at_top();
 798 }
 799 
 800 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
 801                                          size_t max_alloc_words) {
 802   if (requestor == this || _promotion_failed) {
 803     return;
 804   }
 805   assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
 806 
 807   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
 808   if (to_space->top() > to_space->bottom()) {
 809     trace("to_space not empty when contribute_scratch called");
 810   }
 811   */
 812 
 813   ContiguousSpace* to_space = to();
 814   assert(to_space->end() >= to_space->top(), "pointers out of order");
 815   size_t free_words = pointer_delta(to_space->end(), to_space->top());
 816   if (free_words >= MinFreeScratchWords) {
 817     ScratchBlock* sb = (ScratchBlock*)to_space->top();
 818     sb->num_words = free_words;
 819     sb->next = list;
 820     list = sb;
 821   }
 822 }
 823 
 824 void DefNewGeneration::reset_scratch() {
 825   // If contributing scratch in to_space, mangle all of
 826   // to_space if ZapUnusedHeapArea.  This is needed because
 827   // top is not maintained while using to-space as scratch.
 828   if (ZapUnusedHeapArea) {
 829     to()->mangle_unused_area_complete();
 830   }
 831 }
 832 
 833 bool DefNewGeneration::collection_attempt_is_safe() {
 834   if (!to()->is_empty()) {
 835     log_trace(gc)(":: to is not empty ::");
 836     return false;
 837   }
 838   if (_old_gen == NULL) {
 839     GenCollectedHeap* gch = GenCollectedHeap::heap();
 840     _old_gen = gch->old_gen();
 841   }
 842   return _old_gen->promotion_attempt_is_safe(used());
 843 }
 844 
 845 void DefNewGeneration::gc_epilogue(bool full) {
 846   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
 847 
 848   assert(!GCLocker::is_active(), "We should not be executing here");
 849   // Check if the heap is approaching full after a collection has
 850   // been done.  Generally the young generation is empty at
 851   // a minimum at the end of a collection.  If it is not, then
 852   // the heap is approaching full.
 853   GenCollectedHeap* gch = GenCollectedHeap::heap();
 854   if (full) {
 855     DEBUG_ONLY(seen_incremental_collection_failed = false;)
 856     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
 857       log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
 858                             GCCause::to_string(gch->gc_cause()));
 859       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
 860       set_should_allocate_from_space(); // we seem to be running out of space
 861     } else {
 862       log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
 863                             GCCause::to_string(gch->gc_cause()));
 864       gch->clear_incremental_collection_failed(); // We just did a full collection
 865       clear_should_allocate_from_space(); // if set
 866     }
 867   } else {
 868 #ifdef ASSERT
 869     // It is possible that incremental_collection_failed() == true
 870     // here, because an attempted scavenge did not succeed. The policy
 871     // is normally expected to cause a full collection which should
 872     // clear that condition, so we should not be here twice in a row
 873     // with incremental_collection_failed() == true without having done
 874     // a full collection in between.
 875     if (!seen_incremental_collection_failed &&
 876         gch->incremental_collection_failed()) {
 877       log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
 878                             GCCause::to_string(gch->gc_cause()));
 879       seen_incremental_collection_failed = true;
 880     } else if (seen_incremental_collection_failed) {
 881       log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
 882                             GCCause::to_string(gch->gc_cause()));
 883       assert(gch->gc_cause() == GCCause::_scavenge_alot ||
 884              !gch->incremental_collection_failed(),
 885              "Twice in a row");
 886       seen_incremental_collection_failed = false;
 887     }
 888 #endif // ASSERT
 889   }
 890 
 891   if (ZapUnusedHeapArea) {
 892     eden()->check_mangled_unused_area_complete();
 893     from()->check_mangled_unused_area_complete();
 894     to()->check_mangled_unused_area_complete();
 895   }
 896 
 897   if (!CleanChunkPoolAsync) {
 898     Chunk::clean_chunk_pool();
 899   }
 900 
 901   // update the generation and space performance counters
 902   update_counters();
 903   gch->counters()->update_counters();
 904 }
 905 
 906 void DefNewGeneration::record_spaces_top() {
 907   assert(ZapUnusedHeapArea, "Not mangling unused space");
 908   eden()->set_top_for_allocations();
 909   to()->set_top_for_allocations();
 910   from()->set_top_for_allocations();
 911 }
 912 
 913 void DefNewGeneration::ref_processor_init() {
 914   Generation::ref_processor_init();
 915 }
 916 
 917 
 918 void DefNewGeneration::update_counters() {
 919   if (UsePerfData) {
 920     _eden_counters->update_all();
 921     _from_counters->update_all();
 922     _to_counters->update_all();
 923     _gen_counters->update_all();
 924   }
 925 }
 926 
 927 void DefNewGeneration::verify() {
 928   eden()->verify();
 929   from()->verify();
 930     to()->verify();
 931 }
 932 
 933 void DefNewGeneration::print_on(outputStream* st) const {
 934   Generation::print_on(st);
 935   st->print("  eden");
 936   eden()->print_on(st);
 937   st->print("  from");
 938   from()->print_on(st);
 939   st->print("  to  ");
 940   to()->print_on(st);
 941 }
 942 
 943 
 944 const char* DefNewGeneration::name() const {
 945   return "def new generation";
 946 }
 947 
 948 // Moved from inline file as they are not called inline
 949 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
 950   return eden();
 951 }
 952 
 953 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
 954   // This is the slow-path allocation for the DefNewGeneration.
 955   // Most allocations are fast-path in compiled code.
 956   // We try to allocate from the eden.  If that works, we are happy.
 957   // Note that since DefNewGeneration supports lock-free allocation, we
 958   // have to use it here, as well.
 959   HeapWord* result = eden()->par_allocate(word_size);
 960   if (result != NULL) {
 961     if (_old_gen != NULL) {
 962       _old_gen->sample_eden_chunk();
 963     }
 964   } else {
 965     // If the eden is full and the last collection bailed out, we are running
 966     // out of heap space, and we try to allocate the from-space, too.
 967     // allocate_from_space can't be inlined because that would introduce a
 968     // circular dependency at compile time.
 969     result = allocate_from_space(word_size);
 970   }
 971   return result;
 972 }
 973 
 974 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
 975                                          bool is_tlab) {
 976   HeapWord* res = eden()->par_allocate(word_size);
 977   if (_old_gen != NULL) {
 978     _old_gen->sample_eden_chunk();
 979   }
 980   return res;
 981 }
 982 
 983 size_t DefNewGeneration::tlab_capacity() const {
 984   return eden()->capacity();
 985 }
 986 
 987 size_t DefNewGeneration::tlab_used() const {
 988   return eden()->used();
 989 }
 990 
 991 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
 992   return unsafe_max_alloc_nogc();
 993 }
--- EOF ---