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 /*

  * Copyright (c) 1997, 2013, 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/gcTimer.hpp"

 #include "gc_implementation/shared/gcTrace.hpp"

 #include "gc_implementation/shared/spaceDecorator.hpp"

 #include "gc_interface/collectedHeap.inline.hpp"

 #include "memory/allocation.inline.hpp"

 #include "memory/blockOffsetTable.inline.hpp"

 #include "memory/cardTableRS.hpp"

 #include "memory/gcLocker.inline.hpp"

 #include "memory/genCollectedHeap.hpp"

 #include "memory/genMarkSweep.hpp"

 #include "memory/genOopClosures.hpp"

 #include "memory/genOopClosures.inline.hpp"

 #include "memory/generation.hpp"

 #include "memory/generation.inline.hpp"

 #include "memory/space.inline.hpp"

 #include "oops/oop.inline.hpp"

 #include "runtime/java.hpp"

 #include "utilities/copy.hpp"

 #include "utilities/events.hpp"

 Generation::Generation(ReservedSpace rs, size_t initial_size, int level) :

   _level(level),

   _ref_processor(NULL) {

   if (!_virtual_space.initialize(rs, initial_size)) {

     vm_exit_during_initialization("Could not reserve enough space for "

                     "object heap");

   }

   // Mangle all of the the initial generation.

   if (ZapUnusedHeapArea) {

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

       (HeapWord*)_virtual_space.high());

     SpaceMangler::mangle_region(mangle_region);

   }

   _reserved = MemRegion((HeapWord*)_virtual_space.low_boundary(),

           (HeapWord*)_virtual_space.high_boundary());

 }

 GenerationSpec* Generation::spec() {

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   assert(0 <= level() && level() < gch->_n_gens, "Bad gen level");

   return gch->_gen_specs[level()];

 }

 size_t Generation::max_capacity() const {

   return reserved().byte_size();

 }

 void Generation::print_heap_change(size_t prev_used) const {

   if (PrintGCDetails && Verbose) {

     gclog_or_tty->print(" "  SIZE_FORMAT

                         "->" SIZE_FORMAT

                         "("  SIZE_FORMAT ")",

                         prev_used, used(), capacity());

   } else {

     gclog_or_tty->print(" "  SIZE_FORMAT "K"

                         "->" SIZE_FORMAT "K"

                         "("  SIZE_FORMAT "K)",

                         prev_used / K, used() / K, capacity() / K);

   }

 }

 // By default we get a single threaded default reference processor;

 // generations needing multi-threaded refs processing or discovery override this method.

 void Generation::ref_processor_init() {

   assert(_ref_processor == NULL, "a reference processor already exists");

   assert(!_reserved.is_empty(), "empty generation?");

   _ref_processor = new ReferenceProcessor(_reserved);    // a vanilla reference processor

   if (_ref_processor == NULL) {

     vm_exit_during_initialization("Could not allocate ReferenceProcessor object");

   }

 }

 void Generation::print() const { print_on(tty); }

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

   st->print(" %-20s", name());

   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",

              capacity()/K, used()/K);

   st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",

               _virtual_space.low_boundary(),

               _virtual_space.high(),

               _virtual_space.high_boundary());

 }

 void Generation::print_summary_info() { print_summary_info_on(tty); }

 void Generation::print_summary_info_on(outputStream* st) {

   StatRecord* sr = stat_record();

   double time = sr->accumulated_time.seconds();

   st->print_cr("[Accumulated GC generation %d time %3.7f secs, "

                "%d GC's, avg GC time %3.7f]",

                level(), time, sr->invocations,

                sr->invocations > 0 ? time / sr->invocations : 0.0);

 }

 // Utility iterator classes

 class GenerationIsInReservedClosure : public SpaceClosure {

  public:

   const void* _p;

   Space* sp;

   virtual void do_space(Space* s) {

     if (sp == NULL) {

       if (s->is_in_reserved(_p)) sp = s;

     }

   }

   GenerationIsInReservedClosure(const void* p) : _p(p), sp(NULL) {}

 };

 class GenerationIsInClosure : public SpaceClosure {

  public:

   const void* _p;

   Space* sp;

   virtual void do_space(Space* s) {

     if (sp == NULL) {

       if (s->is_in(_p)) sp = s;

     }

   }

   GenerationIsInClosure(const void* p) : _p(p), sp(NULL) {}

 };

 bool Generation::is_in(const void* p) const {

   GenerationIsInClosure blk(p);

   ((Generation*)this)->space_iterate(&blk);

   return blk.sp != NULL;

 }

 DefNewGeneration* Generation::as_DefNewGeneration() {

   assert((kind() == Generation::DefNew) ||

          (kind() == Generation::ParNew) ||

          (kind() == Generation::ASParNew),

     "Wrong youngest generation type");

   return (DefNewGeneration*) this;

 }

 Generation* Generation::next_gen() const {

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   int next = level() + 1;

   if (next < gch->_n_gens) {

     return gch->_gens[next];

   } else {

     return NULL;

   }

 }

 size_t Generation::max_contiguous_available() const {

   // The largest number of contiguous free words in this or any higher generation.

   size_t max = 0;

   for (const Generation* gen = this; gen != NULL; gen = gen->next_gen()) {

     size_t avail = gen->contiguous_available();

     if (avail > max) {

       max = avail;

     }

   }

   return max;

 }

 bool Generation::promotion_attempt_is_safe(size_t max_promotion_in_bytes) const {

   size_t available = max_contiguous_available();

   bool   res = (available >= max_promotion_in_bytes);

   if (PrintGC && Verbose) {

     gclog_or_tty->print_cr(

       "Generation: promo attempt is%s safe: available("SIZE_FORMAT") %s max_promo("SIZE_FORMAT")",

       res? "":" not", available, res? ">=":"<",

       max_promotion_in_bytes);

   }

   return res;

 }

 // Ignores "ref" and calls allocate().

 oop Generation::promote(oop obj, size_t obj_size) {

   assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");

 #ifndef PRODUCT

   if (Universe::heap()->promotion_should_fail()) {

     return NULL;

   }

 #endif  // #ifndef PRODUCT

   HeapWord* result = allocate(obj_size, false);

   if (result != NULL) {

     Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);

     return oop(result);

   } else {

     GenCollectedHeap* gch = GenCollectedHeap::heap();

     return gch->handle_failed_promotion(this, obj, obj_size);

   }

 }

 oop Generation::par_promote(int thread_num,

                             oop obj, markOop m, size_t word_sz) {

   // Could do a bad general impl here that gets a lock.  But no.

   ShouldNotCallThis();

   return NULL;

 }

 void Generation::par_promote_alloc_undo(int thread_num,

                                         HeapWord* obj, size_t word_sz) {

   // Could do a bad general impl here that gets a lock.  But no.

   guarantee(false, "No good general implementation.");

 }

 Space* Generation::space_containing(const void* p) const {

   GenerationIsInReservedClosure blk(p);

   // Cast away const

   ((Generation*)this)->space_iterate(&blk);

   return blk.sp;

 }

 // Some of these are mediocre general implementations.  Should be

 // overridden to get better performance.

 class GenerationBlockStartClosure : public SpaceClosure {

  public:

   const void* _p;

   HeapWord* _start;

   virtual void do_space(Space* s) {

     if (_start == NULL && s->is_in_reserved(_p)) {

       _start = s->block_start(_p);

     }

   }

   GenerationBlockStartClosure(const void* p) { _p = p; _start = NULL; }

 };

 HeapWord* Generation::block_start(const void* p) const {

   GenerationBlockStartClosure blk(p);

   // Cast away const

   ((Generation*)this)->space_iterate(&blk);

   return blk._start;

 }

 class GenerationBlockSizeClosure : public SpaceClosure {

  public:

   const HeapWord* _p;

   size_t size;

   virtual void do_space(Space* s) {

     if (size == 0 && s->is_in_reserved(_p)) {

       size = s->block_size(_p);

     }

   }

   GenerationBlockSizeClosure(const HeapWord* p) { _p = p; size = 0; }

 };

 size_t Generation::block_size(const HeapWord* p) const {

   GenerationBlockSizeClosure blk(p);

   // Cast away const

   ((Generation*)this)->space_iterate(&blk);

   assert(blk.size > 0, "seems reasonable");

   return blk.size;

 }

 class GenerationBlockIsObjClosure : public SpaceClosure {

  public:

   const HeapWord* _p;

   bool is_obj;

   virtual void do_space(Space* s) {

     if (!is_obj && s->is_in_reserved(_p)) {

       is_obj |= s->block_is_obj(_p);

     }

   }

   GenerationBlockIsObjClosure(const HeapWord* p) { _p = p; is_obj = false; }

 };

 bool Generation::block_is_obj(const HeapWord* p) const {

   GenerationBlockIsObjClosure blk(p);

   // Cast away const

   ((Generation*)this)->space_iterate(&blk);

   return blk.is_obj;

 }

 class GenerationOopIterateClosure : public SpaceClosure {

  public:

   ExtendedOopClosure* cl;

   MemRegion mr;

   virtual void do_space(Space* s) {

     s->oop_iterate(mr, cl);

   }

   GenerationOopIterateClosure(ExtendedOopClosure* _cl, MemRegion _mr) :

     cl(_cl), mr(_mr) {}

 };

 void Generation::oop_iterate(ExtendedOopClosure* cl) {

   GenerationOopIterateClosure blk(cl, _reserved);

   space_iterate(&blk);

 }

 void Generation::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {

   GenerationOopIterateClosure blk(cl, mr);

   space_iterate(&blk);

 }

 void Generation::younger_refs_in_space_iterate(Space* sp,

                                                OopsInGenClosure* cl) {

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

   rs->younger_refs_in_space_iterate(sp, cl);

 }

 class GenerationObjIterateClosure : public SpaceClosure {

  private:

   ObjectClosure* _cl;

  public:

   virtual void do_space(Space* s) {

     s->object_iterate(_cl);

   }

   GenerationObjIterateClosure(ObjectClosure* cl) : _cl(cl) {}

 };

 void Generation::object_iterate(ObjectClosure* cl) {

   GenerationObjIterateClosure blk(cl);

   space_iterate(&blk);

 }

 class GenerationSafeObjIterateClosure : public SpaceClosure {

  private:

   ObjectClosure* _cl;

  public:

   virtual void do_space(Space* s) {

     s->safe_object_iterate(_cl);

   }

   GenerationSafeObjIterateClosure(ObjectClosure* cl) : _cl(cl) {}

 };

 void Generation::safe_object_iterate(ObjectClosure* cl) {

   GenerationSafeObjIterateClosure blk(cl);

   space_iterate(&blk);

 }

 void Generation::prepare_for_compaction(CompactPoint* cp) {

   // Generic implementation, can be specialized

   CompactibleSpace* space = first_compaction_space();

   while (space != NULL) {

     space->prepare_for_compaction(cp);

     space = space->next_compaction_space();

   }

 }

 class AdjustPointersClosure: public SpaceClosure {

  public:

   void do_space(Space* sp) {

     sp->adjust_pointers();

   }

 };

 void Generation::adjust_pointers() {

   // Note that this is done over all spaces, not just the compactible

   // ones.

   AdjustPointersClosure blk;

   space_iterate(&blk, true);

 }

 void Generation::compact() {

   CompactibleSpace* sp = first_compaction_space();

   while (sp != NULL) {

     sp->compact();

     sp = sp->next_compaction_space();

   }

 }

 CardGeneration::CardGeneration(ReservedSpace rs, size_t initial_byte_size,

                                int level,

                                GenRemSet* remset) :

   Generation(rs, initial_byte_size, level), _rs(remset),

   _shrink_factor(0), _min_heap_delta_bytes(), _capacity_at_prologue(),

   _used_at_prologue()

 {

   HeapWord* start = (HeapWord*)rs.base();

   size_t reserved_byte_size = rs.size();

   assert((uintptr_t(start) & 3) == 0, "bad alignment");

   assert((reserved_byte_size & 3) == 0, "bad alignment");

   MemRegion reserved_mr(start, heap_word_size(reserved_byte_size));

   _bts = new BlockOffsetSharedArray(reserved_mr,

                                     heap_word_size(initial_byte_size));

   MemRegion committed_mr(start, heap_word_size(initial_byte_size));

   _rs->resize_covered_region(committed_mr);

   if (_bts == NULL)

     vm_exit_during_initialization("Could not allocate a BlockOffsetArray");

   // Verify that the start and end of this generation is the start of a card.

   // If this wasn't true, a single card could span more than on generation,

   // which would cause problems when we commit/uncommit memory, and when we

   // clear and dirty cards.

   guarantee(_rs->is_aligned(reserved_mr.start()), "generation must be card aligned");

   if (reserved_mr.end() != Universe::heap()->reserved_region().end()) {

     // Don't check at the very end of the heap as we'll assert that we're probing off

     // the end if we try.

     guarantee(_rs->is_aligned(reserved_mr.end()), "generation must be card aligned");

   }

   _min_heap_delta_bytes = MinHeapDeltaBytes;

   _capacity_at_prologue = initial_byte_size;

   _used_at_prologue = 0;

 }

 bool CardGeneration::expand(size_t bytes, size_t expand_bytes) {

   assert_locked_or_safepoint(Heap_lock);

   if (bytes == 0) {

     return true;  // That's what grow_by(0) would return

   }

   size_t aligned_bytes  = ReservedSpace::page_align_size_up(bytes);

   if (aligned_bytes == 0){

     // The alignment caused the number of bytes to wrap.  An expand_by(0) will

     // return true with the implication that an expansion was done when it

     // was not.  A call to expand implies a best effort to expand by "bytes"

     // but not a guarantee.  Align down to give a best effort.  This is likely

     // the most that the generation can expand since it has some capacity to

     // start with.

     aligned_bytes = ReservedSpace::page_align_size_down(bytes);

   }

   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);

   bool success = false;

   if (aligned_expand_bytes > aligned_bytes) {

     success = grow_by(aligned_expand_bytes);

   }

   if (!success) {

     success = grow_by(aligned_bytes);

   }

   if (!success) {

     success = grow_to_reserved();

   }

   if (PrintGC && Verbose) {

     if (success && GC_locker::is_active_and_needs_gc()) {

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

     }

   }

   return success;

 }

 // No young generation references, clear this generation's cards.

 void CardGeneration::clear_remembered_set() {

   _rs->clear(reserved());

 }

 // Objects in this generation may have moved, invalidate this

 // generation's cards.

 void CardGeneration::invalidate_remembered_set() {

   _rs->invalidate(used_region());

 }

 void CardGeneration::compute_new_size() {

   assert(_shrink_factor <= 100, "invalid shrink factor");

   size_t current_shrink_factor = _shrink_factor;

   _shrink_factor = 0;

   // We don't have floating point command-line arguments

   // Note:  argument processing ensures that MinHeapFreeRatio < 100.

   const double minimum_free_percentage = MinHeapFreeRatio / 100.0;

   const double maximum_used_percentage = 1.0 - minimum_free_percentage;

   // Compute some numbers about the state of the heap.

   const size_t used_after_gc = used();

   const size_t capacity_after_gc = capacity();

   const double min_tmp = used_after_gc / maximum_used_percentage;

   size_t minimum_desired_capacity = (size_t)MIN2(min_tmp, double(max_uintx));

   // Don't shrink less than the initial generation size

   minimum_desired_capacity = MAX2(minimum_desired_capacity,

                                   spec()->init_size());

   assert(used_after_gc <= minimum_desired_capacity, "sanity check");

   if (PrintGC && Verbose) {

     const size_t free_after_gc = free();

     const double free_percentage = ((double)free_after_gc) / capacity_after_gc;

     gclog_or_tty->print_cr("TenuredGeneration::compute_new_size: ");

     gclog_or_tty->print_cr("  "

                   "  minimum_free_percentage: %6.2f"

                   "  maximum_used_percentage: %6.2f",

                   minimum_free_percentage,

                   maximum_used_percentage);

     gclog_or_tty->print_cr("  "

                   "   free_after_gc   : %6.1fK"

                   "   used_after_gc   : %6.1fK"

                   "   capacity_after_gc   : %6.1fK",

                   free_after_gc / (double) K,

                   used_after_gc / (double) K,

                   capacity_after_gc / (double) K);

     gclog_or_tty->print_cr("  "

                   "   free_percentage: %6.2f",

                   free_percentage);

   }

   if (capacity_after_gc < minimum_desired_capacity) {

     // If we have less free space than we want then expand

     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;

     // Don't expand unless it's significant

     if (expand_bytes >= _min_heap_delta_bytes) {

       expand(expand_bytes, 0); // safe if expansion fails

     }

     if (PrintGC && Verbose) {

       gclog_or_tty->print_cr("    expanding:"

                     "  minimum_desired_capacity: %6.1fK"

                     "  expand_bytes: %6.1fK"

                     "  _min_heap_delta_bytes: %6.1fK",

                     minimum_desired_capacity / (double) K,

                     expand_bytes / (double) K,

                     _min_heap_delta_bytes / (double) K);

     }

     return;

   }

   // No expansion, now see if we want to shrink

   size_t shrink_bytes = 0;

   // We would never want to shrink more than this

   size_t max_shrink_bytes = capacity_after_gc - minimum_desired_capacity;

   if (MaxHeapFreeRatio < 100) {

     const double maximum_free_percentage = MaxHeapFreeRatio / 100.0;

     const double minimum_used_percentage = 1.0 - maximum_free_percentage;

     const double max_tmp = used_after_gc / minimum_used_percentage;

     size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(max_uintx));

     maximum_desired_capacity = MAX2(maximum_desired_capacity,

                                     spec()->init_size());

     if (PrintGC && Verbose) {

       gclog_or_tty->print_cr("  "

                              "  maximum_free_percentage: %6.2f"

                              "  minimum_used_percentage: %6.2f",

                              maximum_free_percentage,

                              minimum_used_percentage);

       gclog_or_tty->print_cr("  "

                              "  _capacity_at_prologue: %6.1fK"

                              "  minimum_desired_capacity: %6.1fK"

                              "  maximum_desired_capacity: %6.1fK",

                              _capacity_at_prologue / (double) K,

                              minimum_desired_capacity / (double) K,

                              maximum_desired_capacity / (double) K);

     }

     assert(minimum_desired_capacity <= maximum_desired_capacity,

            "sanity check");

     if (capacity_after_gc > maximum_desired_capacity) {

       // Capacity too large, compute shrinking size

       shrink_bytes = capacity_after_gc - maximum_desired_capacity;

       // We don't want shrink all the way back to initSize if people call

       // System.gc(), because some programs do that between "phases" and then

       // we'd just have to grow the heap up again for the next phase.  So we

       // damp the shrinking: 0% on the first call, 10% on the second call, 40%

       // on the third call, and 100% by the fourth call.  But if we recompute

       // size without shrinking, it goes back to 0%.

       shrink_bytes = shrink_bytes / 100 * current_shrink_factor;

       assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");

       if (current_shrink_factor == 0) {

         _shrink_factor = 10;

       } else {

         _shrink_factor = MIN2(current_shrink_factor * 4, (size_t) 100);

       }

       if (PrintGC && Verbose) {

         gclog_or_tty->print_cr("  "

                       "  shrinking:"

                       "  initSize: %.1fK"

                       "  maximum_desired_capacity: %.1fK",

                       spec()->init_size() / (double) K,

                       maximum_desired_capacity / (double) K);

         gclog_or_tty->print_cr("  "

                       "  shrink_bytes: %.1fK"

                       "  current_shrink_factor: %d"

                       "  new shrink factor: %d"

                       "  _min_heap_delta_bytes: %.1fK",

                       shrink_bytes / (double) K,

                       current_shrink_factor,

                       _shrink_factor,

                       _min_heap_delta_bytes / (double) K);

       }

     }

   }

   if (capacity_after_gc > _capacity_at_prologue) {

     // We might have expanded for promotions, in which case we might want to

     // take back that expansion if there's room after GC.  That keeps us from

     // stretching the heap with promotions when there's plenty of room.

     size_t expansion_for_promotion = capacity_after_gc - _capacity_at_prologue;

     expansion_for_promotion = MIN2(expansion_for_promotion, max_shrink_bytes);

     // We have two shrinking computations, take the largest

     shrink_bytes = MAX2(shrink_bytes, expansion_for_promotion);

     assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");

     if (PrintGC && Verbose) {

       gclog_or_tty->print_cr("  "

                              "  aggressive shrinking:"

                              "  _capacity_at_prologue: %.1fK"

                              "  capacity_after_gc: %.1fK"

                              "  expansion_for_promotion: %.1fK"

                              "  shrink_bytes: %.1fK",

                              capacity_after_gc / (double) K,

                              _capacity_at_prologue / (double) K,

                              expansion_for_promotion / (double) K,

                              shrink_bytes / (double) K);

     }

   }

   // Don't shrink unless it's significant

   if (shrink_bytes >= _min_heap_delta_bytes) {

     shrink(shrink_bytes);

   }

 }

 // Currently nothing to do.

 void CardGeneration::prepare_for_verify() {}

 void OneContigSpaceCardGeneration::collect(bool   full,

                                            bool   clear_all_soft_refs,

                                            size_t size,

                                            bool   is_tlab) {

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   SpecializationStats::clear();

   // Temporarily expand the span of our ref processor, so

   // refs discovery is over the entire heap, not just this generation

   ReferenceProcessorSpanMutator

     x(ref_processor(), gch->reserved_region());

   STWGCTimer* gc_timer = GenMarkSweep::gc_timer();

   gc_timer->register_gc_start(os::elapsed_counter());

   SerialOldTracer* gc_tracer = GenMarkSweep::gc_tracer();

   gc_tracer->report_gc_start(gch->gc_cause(), gc_timer->gc_start());

   GenMarkSweep::invoke_at_safepoint(_level, ref_processor(), clear_all_soft_refs);

   gc_timer->register_gc_end(os::elapsed_counter());

   gc_tracer->report_gc_end(os::elapsed_counter(), gc_timer->time_partitions());

   SpecializationStats::print();

 }

 HeapWord*

 OneContigSpaceCardGeneration::expand_and_allocate(size_t word_size,

                                                   bool is_tlab,

                                                   bool parallel) {

   assert(!is_tlab, "OneContigSpaceCardGeneration does not support TLAB allocation");

   if (parallel) {

     MutexLocker x(ParGCRareEvent_lock);

     HeapWord* result = NULL;

     size_t byte_size = word_size * HeapWordSize;

     while (true) {

       expand(byte_size, _min_heap_delta_bytes);

       if (GCExpandToAllocateDelayMillis > 0) {

         os::sleep(Thread::current(), GCExpandToAllocateDelayMillis, false);

       }

       result = _the_space->par_allocate(word_size);

       if ( result != NULL) {

         return result;

       } else {

         // If there's not enough expansion space available, give up.

         if (_virtual_space.uncommitted_size() < byte_size) {

           return NULL;

         }

         // else try again

       }

     }

   } else {

     expand(word_size*HeapWordSize, _min_heap_delta_bytes);

     return _the_space->allocate(word_size);

   }

 }

 bool OneContigSpaceCardGeneration::expand(size_t bytes, size_t expand_bytes) {

   GCMutexLocker x(ExpandHeap_lock);

   return CardGeneration::expand(bytes, expand_bytes);

 }

 void OneContigSpaceCardGeneration::shrink(size_t bytes) {

   assert_locked_or_safepoint(ExpandHeap_lock);

   size_t size = ReservedSpace::page_align_size_down(bytes);

   if (size > 0) {

     shrink_by(size);

   }

 }

 size_t OneContigSpaceCardGeneration::capacity() const {

   return _the_space->capacity();

 }

 size_t OneContigSpaceCardGeneration::used() const {

   return _the_space->used();

 }

 size_t OneContigSpaceCardGeneration::free() const {

   return _the_space->free();

 }

 MemRegion OneContigSpaceCardGeneration::used_region() const {

   return the_space()->used_region();

 }

 size_t OneContigSpaceCardGeneration::unsafe_max_alloc_nogc() const {

   return _the_space->free();

 }

 size_t OneContigSpaceCardGeneration::contiguous_available() const {

   return _the_space->free() + _virtual_space.uncommitted_size();

 }

 bool OneContigSpaceCardGeneration::grow_by(size_t bytes) {

   assert_locked_or_safepoint(ExpandHeap_lock);

   bool result = _virtual_space.expand_by(bytes);

   if (result) {

     size_t new_word_size =

        heap_word_size(_virtual_space.committed_size());

     MemRegion mr(_the_space->bottom(), new_word_size);

     // Expand card table

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

     // Expand shared block offset array

     _bts->resize(new_word_size);

     // Fix for bug #4668531

     if (ZapUnusedHeapArea) {

       MemRegion mangle_region(_the_space->end(),

       (HeapWord*)_virtual_space.high());

       SpaceMangler::mangle_region(mangle_region);

     }

     // Expand space -- also expands space's BOT

     // (which uses (part of) shared array above)

     _the_space->set_end((HeapWord*)_virtual_space.high());

     // update the space and generation capacity counters

     update_counters();

     if (Verbose && PrintGC) {

       size_t new_mem_size = _virtual_space.committed_size();

       size_t old_mem_size = new_mem_size - bytes;

       gclog_or_tty->print_cr("Expanding %s from " SIZE_FORMAT "K by "

                       SIZE_FORMAT "K to " SIZE_FORMAT "K",

                       name(), old_mem_size/K, bytes/K, new_mem_size/K);

     }

   }

   return result;

 }

 bool OneContigSpaceCardGeneration::grow_to_reserved() {

   assert_locked_or_safepoint(ExpandHeap_lock);

   bool success = true;

   const size_t remaining_bytes = _virtual_space.uncommitted_size();

   if (remaining_bytes > 0) {

     success = grow_by(remaining_bytes);

     DEBUG_ONLY(if (!success) warning("grow to reserved failed");)

   }

   return success;

 }

 void OneContigSpaceCardGeneration::shrink_by(size_t bytes) {

   assert_locked_or_safepoint(ExpandHeap_lock);

   // Shrink committed space

   _virtual_space.shrink_by(bytes);

   // Shrink space; this also shrinks the space's BOT

   _the_space->set_end((HeapWord*) _virtual_space.high());

   size_t new_word_size = heap_word_size(_the_space->capacity());

   // Shrink the shared block offset array

   _bts->resize(new_word_size);

   MemRegion mr(_the_space->bottom(), new_word_size);

   // Shrink the card table

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

   if (Verbose && PrintGC) {

     size_t new_mem_size = _virtual_space.committed_size();

     size_t old_mem_size = new_mem_size + bytes;

     gclog_or_tty->print_cr("Shrinking %s from " SIZE_FORMAT "K to " SIZE_FORMAT "K",

                   name(), old_mem_size/K, new_mem_size/K);

   }

 }

 // Currently nothing to do.

 void OneContigSpaceCardGeneration::prepare_for_verify() {}

 // Override for a card-table generation with one contiguous

 // space. NOTE: For reasons that are lost in the fog of history,

 // this code is used when you iterate over perm gen objects,

 // even when one uses CDS, where the perm gen has a couple of

 // other spaces; this is because CompactingPermGenGen derives

 // from OneContigSpaceCardGeneration. This should be cleaned up,

 // see CR 6897789..

 void OneContigSpaceCardGeneration::object_iterate(ObjectClosure* blk) {

   _the_space->object_iterate(blk);

 }

 void OneContigSpaceCardGeneration::space_iterate(SpaceClosure* blk,

                                                  bool usedOnly) {

   blk->do_space(_the_space);

 }

 void OneContigSpaceCardGeneration::younger_refs_iterate(OopsInGenClosure* blk) {

   blk->set_generation(this);

   younger_refs_in_space_iterate(_the_space, blk);

   blk->reset_generation();

 }

 void OneContigSpaceCardGeneration::save_marks() {

   _the_space->set_saved_mark();

 }

 void OneContigSpaceCardGeneration::reset_saved_marks() {

   _the_space->reset_saved_mark();

 }

 bool OneContigSpaceCardGeneration::no_allocs_since_save_marks() {

   return _the_space->saved_mark_at_top();

 }

 #define OneContig_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix)      \

                                                                                 \

 void OneContigSpaceCardGeneration::                                             \

 oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk) {                  \

   blk->set_generation(this);                                                    \

   _the_space->oop_since_save_marks_iterate##nv_suffix(blk);                     \

   blk->reset_generation();                                                      \

   save_marks();                                                                 \

 }

 ALL_SINCE_SAVE_MARKS_CLOSURES(OneContig_SINCE_SAVE_MARKS_ITERATE_DEFN)

 #undef OneContig_SINCE_SAVE_MARKS_ITERATE_DEFN

 void OneContigSpaceCardGeneration::gc_epilogue(bool full) {

   _last_gc = WaterMark(the_space(), the_space()->top());

   // update the generation and space performance counters

   update_counters();

   if (ZapUnusedHeapArea) {

     the_space()->check_mangled_unused_area_complete();

   }

 }

 void OneContigSpaceCardGeneration::record_spaces_top() {

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

   the_space()->set_top_for_allocations();

 }

 void OneContigSpaceCardGeneration::verify() {

   the_space()->verify();

 }

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

   Generation::print_on(st);

   st->print("   the");

   the_space()->print_on(st);

 }