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