Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 2001-2007 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 # include "incls/_precompiled.incl"

 # include "incls/_defNewGeneration.cpp.incl"

 //

 // DefNewGeneration functions.

 // Methods of protected closure types.

 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {

   assert(g->level() == 0, "Optimized for youngest gen.");

 }

 void DefNewGeneration::IsAliveClosure::do_object(oop p) {

   assert(false, "Do not call.");

 }

 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {

   return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();

 }

 DefNewGeneration::KeepAliveClosure::

 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {

   GenRemSet* rs = GenCollectedHeap::heap()->rem_set();

   assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");

   _rs = (CardTableRS*)rs;

 }

 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) {

   // We never expect to see a null reference being processed

   // as a weak reference.

   assert (*p != NULL, "expected non-null ref");

   assert ((*p)->is_oop(), "expected an oop while scanning weak refs");

   _cl->do_oop_nv(p);

   // Card marking is trickier for weak refs.

   // This oop is a 'next' field which was filled in while we

   // were discovering weak references. While we might not need

   // to take a special action to keep this reference alive, we

   // will need to dirty a card as the field was modified.

   //

   // Alternatively, we could create a method which iterates through

   // each generation, allowing them in turn to examine the modified

   // field.

   //

   // We could check that p is also in an older generation, but

   // dirty cards in the youngest gen are never scanned, so the

   // extra check probably isn't worthwhile.

   if (Universe::heap()->is_in_reserved(p)) {

     _rs->inline_write_ref_field_gc(p, *p);

   }

 }

 DefNewGeneration::FastKeepAliveClosure::

 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :

   DefNewGeneration::KeepAliveClosure(cl) {

   _boundary = g->reserved().end();

 }

 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) {

   assert (*p != NULL, "expected non-null ref");

   assert ((*p)->is_oop(), "expected an oop while scanning weak refs");

   _cl->do_oop_nv(p);

   // Optimized for Defnew generation if it's the youngest generation:

   // we set a younger_gen card if we have an older->youngest

   // generation pointer.

   if (((HeapWord*)(*p) < _boundary) && Universe::heap()->is_in_reserved(p)) {

     _rs->inline_write_ref_field_gc(p, *p);

   }

 }

 DefNewGeneration::EvacuateFollowersClosure::

 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,

                          ScanClosure* cur, ScanClosure* older) :

   _gch(gch), _level(level),

   _scan_cur_or_nonheap(cur), _scan_older(older)

 {}

 void DefNewGeneration::EvacuateFollowersClosure::do_void() {

   do {

     _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,

                                        _scan_older);

   } while (!_gch->no_allocs_since_save_marks(_level));

 }

 DefNewGeneration::FastEvacuateFollowersClosure::

 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,

                              DefNewGeneration* gen,

                              FastScanClosure* cur, FastScanClosure* older) :

   _gch(gch), _level(level), _gen(gen),

   _scan_cur_or_nonheap(cur), _scan_older(older)

 {}

 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {

   do {

     _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,

                                        _scan_older);

   } while (!_gch->no_allocs_since_save_marks(_level));

   guarantee(_gen->promo_failure_scan_stack() == NULL

             || _gen->promo_failure_scan_stack()->length() == 0,

             "Failed to finish scan");

 }

 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :

   OopsInGenClosure(g), _g(g), _gc_barrier(gc_barrier)

 {

   assert(_g->level() == 0, "Optimized for youngest generation");

   _boundary = _g->reserved().end();

 }

 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :

   OopsInGenClosure(g), _g(g), _gc_barrier(gc_barrier)

 {

   assert(_g->level() == 0, "Optimized for youngest generation");

   _boundary = _g->reserved().end();

 }

 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :

   OopClosure(g->ref_processor()), _g(g)

 {

   assert(_g->level() == 0, "Optimized for youngest generation");

   _boundary = _g->reserved().end();

 }

 DefNewGeneration::DefNewGeneration(ReservedSpace rs,

                                    size_t initial_size,

                                    int level,

                                    const char* policy)

   : Generation(rs, initial_size, level),

     _objs_with_preserved_marks(NULL),

     _preserved_marks_of_objs(NULL),

     _promo_failure_scan_stack(NULL),

     _promo_failure_drain_in_progress(false),

     _should_allocate_from_space(false)

 {

   MemRegion cmr((HeapWord*)_virtual_space.low(),

                 (HeapWord*)_virtual_space.high());

   Universe::heap()->barrier_set()->resize_covered_region(cmr);

   if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {

     _eden_space = new ConcEdenSpace(this);

   } else {

     _eden_space = new EdenSpace(this);

   }

   _from_space = new ContiguousSpace();

   _to_space   = new ContiguousSpace();

   if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)

     vm_exit_during_initialization("Could not allocate a new gen space");

   // Compute the maximum eden and survivor space sizes. These sizes

   // are computed assuming the entire reserved space is committed.

   // These values are exported as performance counters.

   uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();

   uintx size = _virtual_space.reserved_size();

   _max_survivor_size = compute_survivor_size(size, alignment);

   _max_eden_size = size - (2*_max_survivor_size);

   // allocate the performance counters

   // Generation counters -- generation 0, 3 subspaces

   _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);

   _gc_counters = new CollectorCounters(policy, 0);

   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,

                                       _gen_counters);

   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,

                                       _gen_counters);

   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,

                                     _gen_counters);

   compute_space_boundaries(0);

   update_counters();

   _next_gen = NULL;

   _tenuring_threshold = MaxTenuringThreshold;

   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;

 }

 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size) {

   uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();

   // Compute sizes

   uintx size = _virtual_space.committed_size();

   uintx survivor_size = compute_survivor_size(size, alignment);

   uintx eden_size = size - (2*survivor_size);

   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");

   if (eden_size < minimum_eden_size) {

     // May happen due to 64Kb rounding, if so adjust eden size back up

     minimum_eden_size = align_size_up(minimum_eden_size, alignment);

     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;

     uintx unaligned_survivor_size =

       align_size_down(maximum_survivor_size, alignment);

     survivor_size = MAX2(unaligned_survivor_size, alignment);

     eden_size = size - (2*survivor_size);

     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");

     assert(eden_size >= minimum_eden_size, "just checking");

   }

   char *eden_start = _virtual_space.low();

   char *from_start = eden_start + eden_size;

   char *to_start   = from_start + survivor_size;

   char *to_end     = to_start   + survivor_size;

   assert(to_end == _virtual_space.high(), "just checking");

   assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");

   assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");

   assert(Space::is_aligned((HeapWord*)to_start),   "checking alignment");

   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);

   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);

   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);

   eden()->initialize(edenMR, (minimum_eden_size == 0));

   // If minumum_eden_size != 0, we will not have cleared any

   // portion of eden above its top. This can cause newly

   // expanded space not to be mangled if using ZapUnusedHeapArea.

   // We explicitly do such mangling here.

   if (ZapUnusedHeapArea && (minimum_eden_size != 0)) {

     eden()->mangle_unused_area();

   }

   from()->initialize(fromMR, true);

     to()->initialize(toMR  , true);

   eden()->set_next_compaction_space(from());

   // The to-space is normally empty before a compaction so need

   // not be considered.  The exception is during promotion

   // failure handling when to-space can contain live objects.

   from()->set_next_compaction_space(NULL);

 }

 void DefNewGeneration::swap_spaces() {

   ContiguousSpace* s = from();

   _from_space        = to();

   _to_space          = s;

   eden()->set_next_compaction_space(from());

   // The to-space is normally empty before a compaction so need

   // not be considered.  The exception is during promotion

   // failure handling when to-space can contain live objects.

   from()->set_next_compaction_space(NULL);

   if (UsePerfData) {

     CSpaceCounters* c = _from_counters;

     _from_counters = _to_counters;

     _to_counters = c;

   }

 }

 bool DefNewGeneration::expand(size_t bytes) {

   MutexLocker x(ExpandHeap_lock);

   bool success = _virtual_space.expand_by(bytes);

   // Do not attempt an expand-to-the reserve size.  The

   // request should properly observe the maximum size of

   // the generation so an expand-to-reserve should be

   // unnecessary.  Also a second call to expand-to-reserve

   // value potentially can cause an undue expansion.

   // For example if the first expand fail for unknown reasons,

   // but the second succeeds and expands the heap to its maximum

   // value.

   if (GC_locker::is_active()) {

     if (PrintGC && Verbose) {

       gclog_or_tty->print_cr("Garbage collection disabled, expanded heap instead");

     }

   }

   return success;

 }

 void DefNewGeneration::compute_new_size() {

   // This is called after a gc that includes the following generation

   // (which is required to exist.)  So from-space will normally be empty.

   // Note that we check both spaces, since if scavenge failed they revert roles.

   // If not we bail out (otherwise we would have to relocate the objects)

   if (!from()->is_empty() || !to()->is_empty()) {

     return;

   }

   int next_level = level() + 1;

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   assert(next_level < gch->_n_gens,

          "DefNewGeneration cannot be an oldest gen");

   Generation* next_gen = gch->_gens[next_level];

   size_t old_size = next_gen->capacity();

   size_t new_size_before = _virtual_space.committed_size();

   size_t min_new_size = spec()->init_size();

   size_t max_new_size = reserved().byte_size();

   assert(min_new_size <= new_size_before &&

          new_size_before <= max_new_size,

          "just checking");

   // All space sizes must be multiples of Generation::GenGrain.

   size_t alignment = Generation::GenGrain;

   // Compute desired new generation size based on NewRatio and

   // NewSizeThreadIncrease

   size_t desired_new_size = old_size/NewRatio;

   int threads_count = Threads::number_of_non_daemon_threads();

   size_t thread_increase_size = threads_count * NewSizeThreadIncrease;

   desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);

   // Adjust new generation size

   desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);

   assert(desired_new_size <= max_new_size, "just checking");

   bool changed = false;

   if (desired_new_size > new_size_before) {

     size_t change = desired_new_size - new_size_before;

     assert(change % alignment == 0, "just checking");

     if (expand(change)) {

        changed = true;

     }

     // If the heap failed to expand to the desired size,

     // "changed" will be false.  If the expansion failed

     // (and at this point it was expected to succeed),

     // ignore the failure (leaving "changed" as false).

   }

   if (desired_new_size < new_size_before && eden()->is_empty()) {

     // bail out of shrinking if objects in eden

     size_t change = new_size_before - desired_new_size;

     assert(change % alignment == 0, "just checking");

     _virtual_space.shrink_by(change);

     changed = true;

   }

   if (changed) {

     compute_space_boundaries(eden()->used());

     MemRegion cmr((HeapWord*)_virtual_space.low(), (HeapWord*)_virtual_space.high());

     Universe::heap()->barrier_set()->resize_covered_region(cmr);

     if (Verbose && PrintGC) {

       size_t new_size_after  = _virtual_space.committed_size();

       size_t eden_size_after = eden()->capacity();

       size_t survivor_size_after = from()->capacity();

       gclog_or_tty->print("New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden="

         SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",

         new_size_before/K, new_size_after/K, eden_size_after/K, survivor_size_after/K);

       if (WizardMode) {

         gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",

           thread_increase_size/K, threads_count);

       }

       gclog_or_tty->cr();

     }

   }

 }

 void DefNewGeneration::object_iterate_since_last_GC(ObjectClosure* cl) {

   // $$$ This may be wrong in case of "scavenge failure"?

   eden()->object_iterate(cl);

 }

 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {

   assert(false, "NYI -- are you sure you want to call this?");

 }

 size_t DefNewGeneration::capacity() const {

   return eden()->capacity()

        + from()->capacity();  // to() is only used during scavenge

 }

 size_t DefNewGeneration::used() const {

   return eden()->used()

        + from()->used();      // to() is only used during scavenge

 }

 size_t DefNewGeneration::free() const {

   return eden()->free()

        + from()->free();      // to() is only used during scavenge

 }

 size_t DefNewGeneration::max_capacity() const {

   const size_t alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();

   const size_t reserved_bytes = reserved().byte_size();

   return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);

 }

 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {

   return eden()->free();

 }

 size_t DefNewGeneration::capacity_before_gc() const {

   return eden()->capacity();

 }

 size_t DefNewGeneration::contiguous_available() const {

   return eden()->free();

 }

 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }

 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }

 void DefNewGeneration::object_iterate(ObjectClosure* blk) {

   eden()->object_iterate(blk);

   from()->object_iterate(blk);

 }

 void DefNewGeneration::space_iterate(SpaceClosure* blk,

                                      bool usedOnly) {

   blk->do_space(eden());

   blk->do_space(from());

   blk->do_space(to());

 }

 // The last collection bailed out, we are running out of heap space,

 // so we try to allocate the from-space, too.

 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {

   HeapWord* result = NULL;

   if (PrintGC && Verbose) {

     gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"

                   "  will_fail: %s"

                   "  heap_lock: %s"

                   "  free: " SIZE_FORMAT,

                   size,

                GenCollectedHeap::heap()->incremental_collection_will_fail() ? "true" : "false",

                Heap_lock->is_locked() ? "locked" : "unlocked",

                from()->free());

     }

   if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {

     if (Heap_lock->owned_by_self() ||

         (SafepointSynchronize::is_at_safepoint() &&

          Thread::current()->is_VM_thread())) {

       // If the Heap_lock is not locked by this thread, this will be called

       // again later with the Heap_lock held.

       result = from()->allocate(size);

     } else if (PrintGC && Verbose) {

       gclog_or_tty->print_cr("  Heap_lock is not owned by self");

     }

   } else if (PrintGC && Verbose) {

     gclog_or_tty->print_cr("  should_allocate_from_space: NOT");

   }

   if (PrintGC && Verbose) {

     gclog_or_tty->print_cr("  returns %s", result == NULL ? "NULL" : "object");

   }

   return result;

 }

 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,

                                                 bool   is_tlab,

                                                 bool   parallel) {

   // We don't attempt to expand the young generation (but perhaps we should.)

   return allocate(size, is_tlab);

 }

 void DefNewGeneration::collect(bool   full,

                                bool   clear_all_soft_refs,

                                size_t size,

                                bool   is_tlab) {

   assert(full || size > 0, "otherwise we don't want to collect");

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   _next_gen = gch->next_gen(this);

   assert(_next_gen != NULL,

     "This must be the youngest gen, and not the only gen");

   // If the next generation is too full to accomodate promotion

   // from this generation, pass on collection; let the next generation

   // do it.

   if (!collection_attempt_is_safe()) {

     gch->set_incremental_collection_will_fail();

     return;

   }

   assert(to()->is_empty(), "Else not collection_attempt_is_safe");

   init_assuming_no_promotion_failure();

   TraceTime t1("GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);

   // Capture heap used before collection (for printing).

   size_t gch_prev_used = gch->used();

   SpecializationStats::clear();

   // These can be shared for all code paths

   IsAliveClosure is_alive(this);

   ScanWeakRefClosure scan_weak_ref(this);

   age_table()->clear();

   to()->clear();

   gch->rem_set()->prepare_for_younger_refs_iterate(false);

   assert(gch->no_allocs_since_save_marks(0),

          "save marks have not been newly set.");

   // Weak refs.

   // FIXME: Are these storage leaks, or are they resource objects?

 #ifdef COMPILER2

   ReferencePolicy *soft_ref_policy = new LRUMaxHeapPolicy();

 #else

   ReferencePolicy *soft_ref_policy = new LRUCurrentHeapPolicy();

 #endif // COMPILER2

   // Not very pretty.

   CollectorPolicy* cp = gch->collector_policy();

   FastScanClosure fsc_with_no_gc_barrier(this, false);

   FastScanClosure fsc_with_gc_barrier(this, true);

   set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);

   FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,

                                                   &fsc_with_no_gc_barrier,

                                                   &fsc_with_gc_barrier);

   assert(gch->no_allocs_since_save_marks(0),

          "save marks have not been newly set.");

   gch->gen_process_strong_roots(_level,

                                 true, // Process younger gens, if any, as

                                       // strong roots.

                                 false,// not collecting permanent generation.

                                 SharedHeap::SO_AllClasses,

                                 &fsc_with_gc_barrier,

                                 &fsc_with_no_gc_barrier);

   // "evacuate followers".

   evacuate_followers.do_void();

   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);

   ref_processor()->process_discovered_references(

     soft_ref_policy, &is_alive, &keep_alive, &evacuate_followers, NULL);

   if (!promotion_failed()) {

     // Swap the survivor spaces.

     eden()->clear();

     from()->clear();

     swap_spaces();

     assert(to()->is_empty(), "to space should be empty now");

     // Set the desired survivor size to half the real survivor space

     _tenuring_threshold =

       age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);

     if (PrintGC && !PrintGCDetails) {

       gch->print_heap_change(gch_prev_used);

     }

   } else {

     assert(HandlePromotionFailure,

       "Should not be here unless promotion failure handling is on");

     assert(_promo_failure_scan_stack != NULL &&

       _promo_failure_scan_stack->length() == 0, "post condition");

     // deallocate stack and it's elements

     delete _promo_failure_scan_stack;

     _promo_failure_scan_stack = NULL;

     remove_forwarding_pointers();

     if (PrintGCDetails) {

       gclog_or_tty->print(" (promotion failed)");

     }

     // Add to-space to the list of space to compact

     // when a promotion failure has occurred.  In that

     // case there can be live objects in to-space

     // as a result of a partial evacuation of eden

     // and from-space.

     swap_spaces();   // For the sake of uniformity wrt ParNewGeneration::collect().

     from()->set_next_compaction_space(to());

     gch->set_incremental_collection_will_fail();

     // Reset the PromotionFailureALot counters.

     NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)

   }

   // set new iteration safe limit for the survivor spaces

   from()->set_concurrent_iteration_safe_limit(from()->top());

   to()->set_concurrent_iteration_safe_limit(to()->top());

   SpecializationStats::print();

   update_time_of_last_gc(os::javaTimeMillis());

 }

 class RemoveForwardPointerClosure: public ObjectClosure {

 public:

   void do_object(oop obj) {

     obj->init_mark();

   }

 };

 void DefNewGeneration::init_assuming_no_promotion_failure() {

   _promotion_failed = false;

   from()->set_next_compaction_space(NULL);

 }

 void DefNewGeneration::remove_forwarding_pointers() {

   RemoveForwardPointerClosure rspc;

   eden()->object_iterate(&rspc);

   from()->object_iterate(&rspc);

   // Now restore saved marks, if any.

   if (_objs_with_preserved_marks != NULL) {

     assert(_preserved_marks_of_objs != NULL, "Both or none.");

     assert(_objs_with_preserved_marks->length() ==

            _preserved_marks_of_objs->length(), "Both or none.");

     for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {

       oop obj   = _objs_with_preserved_marks->at(i);

       markOop m = _preserved_marks_of_objs->at(i);

       obj->set_mark(m);

     }

     delete _objs_with_preserved_marks;

     delete _preserved_marks_of_objs;

     _objs_with_preserved_marks = NULL;

     _preserved_marks_of_objs = NULL;

   }

 }

 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {

   if (m->must_be_preserved_for_promotion_failure(obj)) {

     if (_objs_with_preserved_marks == NULL) {

       assert(_preserved_marks_of_objs == NULL, "Both or none.");

       _objs_with_preserved_marks = new (ResourceObj::C_HEAP)

         GrowableArray<oop>(PreserveMarkStackSize, true);

       _preserved_marks_of_objs = new (ResourceObj::C_HEAP)

         GrowableArray<markOop>(PreserveMarkStackSize, true);

     }

     _objs_with_preserved_marks->push(obj);

     _preserved_marks_of_objs->push(m);

   }

 }

 void DefNewGeneration::handle_promotion_failure(oop old) {

   preserve_mark_if_necessary(old, old->mark());

   // forward to self

   old->forward_to(old);

   _promotion_failed = true;

   push_on_promo_failure_scan_stack(old);

   if (!_promo_failure_drain_in_progress) {

     // prevent recursion in copy_to_survivor_space()

     _promo_failure_drain_in_progress = true;

     drain_promo_failure_scan_stack();

     _promo_failure_drain_in_progress = false;

   }

 }

 oop DefNewGeneration::copy_to_survivor_space(oop old, oop* from) {

   assert(is_in_reserved(old) && !old->is_forwarded(),

          "shouldn't be scavenging this oop");

   size_t s = old->size();

   oop obj = NULL;

   // Try allocating obj in to-space (unless too old)

   if (old->age() < tenuring_threshold()) {

     obj = (oop) to()->allocate(s);

   }

   // Otherwise try allocating obj tenured

   if (obj == NULL) {

     obj = _next_gen->promote(old, s, from);

     if (obj == NULL) {

       if (!HandlePromotionFailure) {

         // A failed promotion likely means the MaxLiveObjectEvacuationRatio flag

         // is incorrectly set. In any case, its seriously wrong to be here!

         vm_exit_out_of_memory(s*wordSize, "promotion");

       }

       handle_promotion_failure(old);

       return old;

     }

   } else {

     // Prefetch beyond obj

     const intx interval = PrefetchCopyIntervalInBytes;

     Prefetch::write(obj, interval);

     // Copy obj

     Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);

     // Increment age if obj still in new generation

     obj->incr_age();

     age_table()->add(obj, s);

   }

   // Done, insert forward pointer to obj in this header

   old->forward_to(obj);

   return obj;

 }

 void DefNewGeneration::push_on_promo_failure_scan_stack(oop obj) {

   if (_promo_failure_scan_stack == NULL) {

     _promo_failure_scan_stack = new (ResourceObj::C_HEAP)

                                     GrowableArray<oop>(40, true);

   }

   _promo_failure_scan_stack->push(obj);

 }

 void DefNewGeneration::drain_promo_failure_scan_stack() {

   assert(_promo_failure_scan_stack != NULL, "precondition");

   while (_promo_failure_scan_stack->length() > 0) {

      oop obj = _promo_failure_scan_stack->pop();

      obj->oop_iterate(_promo_failure_scan_stack_closure);

   }

 }

 void DefNewGeneration::save_marks() {

   eden()->set_saved_mark();

   to()->set_saved_mark();

   from()->set_saved_mark();

 }

 void DefNewGeneration::reset_saved_marks() {

   eden()->reset_saved_mark();

   to()->reset_saved_mark();

   from()->reset_saved_mark();

 }

 bool DefNewGeneration::no_allocs_since_save_marks() {

   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");

   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");

   return to()->saved_mark_at_top();

 }

 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \

                                                                 \

 void DefNewGeneration::                                         \

 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) {   \

   cl->set_generation(this);                                     \

   eden()->oop_since_save_marks_iterate##nv_suffix(cl);          \

   to()->oop_since_save_marks_iterate##nv_suffix(cl);            \

   from()->oop_since_save_marks_iterate##nv_suffix(cl);          \

   cl->reset_generation();                                       \

   save_marks();                                                 \

 }

 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)

 #undef DefNew_SINCE_SAVE_MARKS_DEFN

 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,

                                          size_t max_alloc_words) {

   if (requestor == this || _promotion_failed) return;

   assert(requestor->level() > level(), "DefNewGeneration must be youngest");

   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.

   if (to_space->top() > to_space->bottom()) {

     trace("to_space not empty when contribute_scratch called");

   }

   */

   ContiguousSpace* to_space = to();

   assert(to_space->end() >= to_space->top(), "pointers out of order");

   size_t free_words = pointer_delta(to_space->end(), to_space->top());

   if (free_words >= MinFreeScratchWords) {

     ScratchBlock* sb = (ScratchBlock*)to_space->top();

     sb->num_words = free_words;

     sb->next = list;

     list = sb;

   }

 }

 bool DefNewGeneration::collection_attempt_is_safe() {

   if (!to()->is_empty()) {

     return false;

   }

   if (_next_gen == NULL) {

     GenCollectedHeap* gch = GenCollectedHeap::heap();

     _next_gen = gch->next_gen(this);

     assert(_next_gen != NULL,

            "This must be the youngest gen, and not the only gen");

   }

   // Decide if there's enough room for a full promotion

   // When using extremely large edens, we effectively lose a

   // large amount of old space.  Use the "MaxLiveObjectEvacuationRatio"

   // flag to reduce the minimum evacuation space requirements. If

   // there is not enough space to evacuate eden during a scavenge,

   // the VM will immediately exit with an out of memory error.

   // This flag has not been tested

   // with collectors other than simple mark & sweep.

   //

   // Note that with the addition of promotion failure handling, the

   // VM will not immediately exit but will undo the young generation

   // collection.  The parameter is left here for compatibility.

   const double evacuation_ratio = MaxLiveObjectEvacuationRatio / 100.0;

   // worst_case_evacuation is based on "used()".  For the case where this

   // method is called after a collection, this is still appropriate because

   // the case that needs to be detected is one in which a full collection

   // has been done and has overflowed into the young generation.  In that

   // case a minor collection will fail (the overflow of the full collection

   // means there is no space in the old generation for any promotion).

   size_t worst_case_evacuation = (size_t)(used() * evacuation_ratio);

   return _next_gen->promotion_attempt_is_safe(worst_case_evacuation,

                                               HandlePromotionFailure);

 }

 void DefNewGeneration::gc_epilogue(bool full) {

   // Check if the heap is approaching full after a collection has

   // been done.  Generally the young generation is empty at

   // a minimum at the end of a collection.  If it is not, then

   // the heap is approaching full.

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   clear_should_allocate_from_space();

   if (collection_attempt_is_safe()) {

     gch->clear_incremental_collection_will_fail();

   } else {

     gch->set_incremental_collection_will_fail();

     if (full) { // we seem to be running out of space

       set_should_allocate_from_space();

     }

   }

   // update the generation and space performance counters

   update_counters();

   gch->collector_policy()->counters()->update_counters();

 }

 void DefNewGeneration::update_counters() {

   if (UsePerfData) {

     _eden_counters->update_all();

     _from_counters->update_all();

     _to_counters->update_all();

     _gen_counters->update_all();

   }

 }

 void DefNewGeneration::verify(bool allow_dirty) {

   eden()->verify(allow_dirty);

   from()->verify(allow_dirty);

     to()->verify(allow_dirty);

 }

 void DefNewGeneration::print_on(outputStream* st) const {

   Generation::print_on(st);

   st->print("  eden");

   eden()->print_on(st);

   st->print("  from");

   from()->print_on(st);

   st->print("  to  ");

   to()->print_on(st);

 }

 const char* DefNewGeneration::name() const {

   return "def new generation";

 }