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 /*

  * Copyright (c) 2001, 2012, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

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  */

 #include "precompiled.hpp"

 #include "gc_implementation/shared/collectorCounters.hpp"

 #include "gc_implementation/shared/gcPolicyCounters.hpp"

 #include "gc_implementation/shared/spaceDecorator.hpp"

 #include "memory/defNewGeneration.inline.hpp"

 #include "memory/gcLocker.inline.hpp"

 #include "memory/genCollectedHeap.hpp"

 #include "memory/genOopClosures.inline.hpp"

 #include "memory/genRemSet.hpp"

 #include "memory/generationSpec.hpp"

 #include "memory/iterator.hpp"

 #include "memory/referencePolicy.hpp"

 #include "memory/space.inline.hpp"

 #include "oops/instanceRefKlass.hpp"

 #include "oops/oop.inline.hpp"

 #include "runtime/java.hpp"

 #include "runtime/thread.inline.hpp"

 #include "utilities/copy.hpp"

 #include "utilities/stack.inline.hpp"

 //

 // 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)       { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }

 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }

 DefNewGeneration::FastKeepAliveClosure::

 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :

   DefNewGeneration::KeepAliveClosure(cl) {

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

 }

 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p)       { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }

 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(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_is_complete(), "Failed to finish scan");

 }

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

     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)

 {

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

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

 }

 void ScanClosure::do_oop(oop* p)       { ScanClosure::do_oop_work(p); }

 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }

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

     OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)

 {

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

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

 }

 void FastScanClosure::do_oop(oop* p)       { FastScanClosure::do_oop_work(p); }

 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }

 void KlassScanClosure::do_klass(Klass* klass) {

 #ifndef PRODUCT

   if (TraceScavenge) {

     ResourceMark rm;

     gclog_or_tty->print_cr("KlassScanClosure::do_klass %p, %s, dirty: %s",

                            klass,

                            klass->external_name(),

                            klass->has_modified_oops() ? "true" : "false");

   }

 #endif

   // If the klass has not been dirtied we know that there's

   // no references into  the young gen and we can skip it.

   if (klass->has_modified_oops()) {

     if (_accumulate_modified_oops) {

       klass->accumulate_modified_oops();

     }

     // Clear this state since we're going to scavenge all the metadata.

     klass->clear_modified_oops();

     // Tell the closure which Klass is being scanned so that it can be dirtied

     // if oops are left pointing into the young gen.

     _scavenge_closure->set_scanned_klass(klass);

     klass->oops_do(_scavenge_closure);

     _scavenge_closure->set_scanned_klass(NULL);

   }

 }

 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :

   _g(g)

 {

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

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

 }

 void ScanWeakRefClosure::do_oop(oop* p)       { ScanWeakRefClosure::do_oop_work(p); }

 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }

 void FilteringClosure::do_oop(oop* p)       { FilteringClosure::do_oop_work(p); }

 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }

 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,

                                    KlassRemSet* klass_rem_set)

     : _scavenge_closure(scavenge_closure),

       _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}

 DefNewGeneration::DefNewGeneration(ReservedSpace rs,

                                    size_t initial_size,

                                    int level,

                                    const char* policy)

   : Generation(rs, initial_size, level),

     _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, SpaceDecorator::Clear, SpaceDecorator::Mangle);

   update_counters();

   _next_gen = NULL;

   _tenuring_threshold = MaxTenuringThreshold;

   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;

 }

 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,

                                                 bool clear_space,

                                                 bool mangle_space) {

   uintx alignment =

     GenCollectedHeap::heap()->collector_policy()->min_alignment();

   // If the spaces are being cleared (only done at heap initialization

   // currently), the survivor spaces need not be empty.

   // Otherwise, no care is taken for used areas in the survivor spaces

   // so check.

   assert(clear_space || (to()->is_empty() && from()->is_empty()),

     "Initialization of the survivor spaces assumes these are empty");

   // 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);

   // A minimum eden size implies that there is a part of eden that

   // is being used and that affects the initialization of any

   // newly formed eden.

   bool live_in_eden = minimum_eden_size > 0;

   // If not clearing the spaces, do some checking to verify that

   // the space are already mangled.

   if (!clear_space) {

     // Must check mangling before the spaces are reshaped.  Otherwise,

     // the bottom or end of one space may have moved into another

     // a failure of the check may not correctly indicate which space

     // is not properly mangled.

     if (ZapUnusedHeapArea) {

       HeapWord* limit = (HeapWord*) _virtual_space.high();

       eden()->check_mangled_unused_area(limit);

       from()->check_mangled_unused_area(limit);

         to()->check_mangled_unused_area(limit);

     }

   }

   // Reset the spaces for their new regions.

   eden()->initialize(edenMR,

                      clear_space && !live_in_eden,

                      SpaceDecorator::Mangle);

   // If clear_space and live_in_eden, 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 && clear_space && live_in_eden && mangle_space) {

     eden()->mangle_unused_area();

   }

   from()->initialize(fromMR, clear_space, mangle_space);

   to()->initialize(toMR, clear_space, mangle_space);

   // Set next compaction spaces.

   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);

   HeapWord* prev_high = (HeapWord*) _virtual_space.high();

   bool success = _virtual_space.expand_by(bytes);

   if (success && ZapUnusedHeapArea) {

     // Mangle newly committed space immediately because it

     // can be done here more simply that after the new

     // spaces have been computed.

     HeapWord* new_high = (HeapWord*) _virtual_space.high();

     MemRegion mangle_region(prev_high, new_high);

     SpaceMangler::mangle_region(mangle_region);

   }

   // 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) {

     // The spaces have already been mangled at this point but

     // may not have been cleared (set top = bottom) and should be.

     // Mangling was done when the heap was being expanded.

     compute_space_boundaries(eden()->used(),

                              SpaceDecorator::Clear,

                              SpaceDecorator::DontMangle);

     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 (Verbose && PrintGCDetails) {

     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(false /* don't consult_young */) ?

                           "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()) {

     if (Verbose && PrintGCDetails) {

       gclog_or_tty->print(" :: Collection attempt not safe :: ");

     }

     gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one

     return;

   }

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

   init_assuming_no_promotion_failure();

   TraceTime t1(GCCauseString("GC", gch->gc_cause()), 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(SpaceDecorator::Mangle);

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

   assert(gch->no_allocs_since_save_marks(0),

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

   // Not very pretty.

   CollectorPolicy* cp = gch->collector_policy();

   FastScanClosure fsc_with_no_gc_barrier(this, false);

   FastScanClosure fsc_with_gc_barrier(this, true);

   KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,

                                       gch->rem_set()->klass_rem_set());

   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.");

   int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;

   gch->gen_process_strong_roots(_level,

                                 true,  // Process younger gens, if any,

                                        // as strong roots.

                                 true,  // activate StrongRootsScope

                                 true,  // is scavenging

                                 SharedHeap::ScanningOption(so),

                                 &fsc_with_no_gc_barrier,

                                 true,   // walk *all* scavengable nmethods

                                 &fsc_with_gc_barrier,

                                 &klass_scan_closure);

   // "evacuate followers".

   evacuate_followers.do_void();

   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);

   ReferenceProcessor* rp = ref_processor();

   rp->setup_policy(clear_all_soft_refs);

   rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,

                                     NULL);

   if (!promotion_failed()) {

     // Swap the survivor spaces.

     eden()->clear(SpaceDecorator::Mangle);

     from()->clear(SpaceDecorator::Mangle);

     if (ZapUnusedHeapArea) {

       // This is now done here because of the piece-meal mangling which

       // can check for valid mangling at intermediate points in the

       // collection(s).  When a minor collection fails to collect

       // sufficient space resizing of the young generation can occur

       // an redistribute the spaces in the young generation.  Mangle

       // here so that unzapped regions don't get distributed to

       // other spaces.

       to()->mangle_unused_area();

     }

     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);

     // A successful scavenge should restart the GC time limit count which is

     // for full GC's.

     AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();

     size_policy->reset_gc_overhead_limit_count();

     if (PrintGC && !PrintGCDetails) {

       gch->print_heap_change(gch_prev_used);

     }

     assert(!gch->incremental_collection_failed(), "Should be clear");

   } else {

     assert(_promo_failure_scan_stack.is_empty(), "post condition");

     _promo_failure_scan_stack.clear(true); // Clear cached segments.

     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 uniformity wrt ParNewGeneration.

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

     gch->set_incremental_collection_failed();

     // Inform the next generation that a promotion failure occurred.

     _next_gen->promotion_failure_occurred();

     // 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();

   // We need to use a monotonically non-deccreasing time in ms

   // or we will see time-warp warnings and os::javaTimeMillis()

   // does not guarantee monotonicity.

   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;

   update_time_of_last_gc(now);

 }

 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.

   assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),

          "should be the same");

   while (!_objs_with_preserved_marks.is_empty()) {

     oop obj   = _objs_with_preserved_marks.pop();

     markOop m = _preserved_marks_of_objs.pop();

     obj->set_mark(m);

   }

   _objs_with_preserved_marks.clear(true);

   _preserved_marks_of_objs.clear(true);

 }

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

   assert(promotion_failed() && m->must_be_preserved_for_promotion_failure(obj),

          "Oversaving!");

   _objs_with_preserved_marks.push(obj);

   _preserved_marks_of_objs.push(m);

 }

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

   if (m->must_be_preserved_for_promotion_failure(obj)) {

     preserve_mark(obj, m);

   }

 }

 void DefNewGeneration::handle_promotion_failure(oop old) {

   if (PrintPromotionFailure && !_promotion_failed) {

     gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",

                         old->size());

   }

   _promotion_failed = true;

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

   // forward to self

   old->forward_to(old);

   _promo_failure_scan_stack.push(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) {

   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);

     if (obj == NULL) {

       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::drain_promo_failure_scan_stack() {

   while (!_promo_failure_scan_stack.is_empty()) {

      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;

   }

 }

 void DefNewGeneration::reset_scratch() {

   // If contributing scratch in to_space, mangle all of

   // to_space if ZapUnusedHeapArea.  This is needed because

   // top is not maintained while using to-space as scratch.

   if (ZapUnusedHeapArea) {

     to()->mangle_unused_area_complete();

   }

 }

 bool DefNewGeneration::collection_attempt_is_safe() {

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

     if (Verbose && PrintGCDetails) {

       gclog_or_tty->print(" :: to is not 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");

   }

   return _next_gen->promotion_attempt_is_safe(used());

 }

 void DefNewGeneration::gc_epilogue(bool full) {

   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)

   assert(!GC_locker::is_active(), "We should not be executing here");

   // 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();

   if (full) {

     DEBUG_ONLY(seen_incremental_collection_failed = false;)

     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {

       if (Verbose && PrintGCDetails) {

         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",

                             GCCause::to_string(gch->gc_cause()));

       }

       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state

       set_should_allocate_from_space(); // we seem to be running out of space

     } else {

       if (Verbose && PrintGCDetails) {

         gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",

                             GCCause::to_string(gch->gc_cause()));

       }

       gch->clear_incremental_collection_failed(); // We just did a full collection

       clear_should_allocate_from_space(); // if set

     }

   } else {

 #ifdef ASSERT

     // It is possible that incremental_collection_failed() == true

     // here, because an attempted scavenge did not succeed. The policy

     // is normally expected to cause a full collection which should

     // clear that condition, so we should not be here twice in a row

     // with incremental_collection_failed() == true without having done

     // a full collection in between.

     if (!seen_incremental_collection_failed &&

         gch->incremental_collection_failed()) {

       if (Verbose && PrintGCDetails) {

         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",

                             GCCause::to_string(gch->gc_cause()));

       }

       seen_incremental_collection_failed = true;

     } else if (seen_incremental_collection_failed) {

       if (Verbose && PrintGCDetails) {

         gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",

                             GCCause::to_string(gch->gc_cause()));

       }

       assert(gch->gc_cause() == GCCause::_scavenge_alot ||

              (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||

              !gch->incremental_collection_failed(),

              "Twice in a row");

       seen_incremental_collection_failed = false;

     }

 #endif // ASSERT

   }

   if (ZapUnusedHeapArea) {

     eden()->check_mangled_unused_area_complete();

     from()->check_mangled_unused_area_complete();

     to()->check_mangled_unused_area_complete();

   }

   if (!CleanChunkPoolAsync) {

     Chunk::clean_chunk_pool();

   }

   // update the generation and space performance counters

   update_counters();

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

 }

 void DefNewGeneration::record_spaces_top() {

   assert(ZapUnusedHeapArea, "Not mangling unused space");

   eden()->set_top_for_allocations();

   to()->set_top_for_allocations();

   from()->set_top_for_allocations();

 }

 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() {

   eden()->verify();

   from()->verify();

     to()->verify();

 }

 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";

 }

 // Moved from inline file as they are not called inline

 CompactibleSpace* DefNewGeneration::first_compaction_space() const {

   return eden();

 }

 HeapWord* DefNewGeneration::allocate(size_t word_size,

                                      bool is_tlab) {

   // This is the slow-path allocation for the DefNewGeneration.

   // Most allocations are fast-path in compiled code.

   // We try to allocate from the eden.  If that works, we are happy.

   // Note that since DefNewGeneration supports lock-free allocation, we

   // have to use it here, as well.

   HeapWord* result = eden()->par_allocate(word_size);

   if (result != NULL) {

     return result;

   }

   do {

     HeapWord* old_limit = eden()->soft_end();

     if (old_limit < eden()->end()) {

       // Tell the next generation we reached a limit.

       HeapWord* new_limit =

         next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);

       if (new_limit != NULL) {

         Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);

       } else {

         assert(eden()->soft_end() == eden()->end(),

                "invalid state after allocation_limit_reached returned null");

       }

     } else {

       // The allocation failed and the soft limit is equal to the hard limit,

       // there are no reasons to do an attempt to allocate

       assert(old_limit == eden()->end(), "sanity check");

       break;

     }

     // Try to allocate until succeeded or the soft limit can't be adjusted

     result = eden()->par_allocate(word_size);

   } while (result == NULL);

   // If the eden is full and the last collection bailed out, we are running

   // out of heap space, and we try to allocate the from-space, too.

   // allocate_from_space can't be inlined because that would introduce a

   // circular dependency at compile time.

   if (result == NULL) {

     result = allocate_from_space(word_size);

   }

   return result;

 }

 HeapWord* DefNewGeneration::par_allocate(size_t word_size,

                                          bool is_tlab) {

   return eden()->par_allocate(word_size);

 }

 void DefNewGeneration::gc_prologue(bool full) {

   // Ensure that _end and _soft_end are the same in eden space.

   eden()->set_soft_end(eden()->end());

 }

 size_t DefNewGeneration::tlab_capacity() const {

   return eden()->capacity();

 }

 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {

   return unsafe_max_alloc_nogc();

 }