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

 /*

  * Copyright (c) 2001, 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

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  */

 #include "precompiled.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "gc_implementation/shared/gcHeapSummary.hpp"

 #include "gc_implementation/shared/gcTrace.hpp"

 #include "gc_implementation/shared/gcTraceTime.hpp"

 #include "gc_implementation/shared/gcWhen.hpp"

 #include "gc_implementation/shared/vmGCOperations.hpp"

 #include "gc_interface/allocTracer.hpp"

 #include "gc_interface/collectedHeap.hpp"

 #include "gc_interface/collectedHeap.inline.hpp"

 #include "memory/metaspace.hpp"

 #include "oops/oop.inline.hpp"

 #include "oops/instanceMirrorKlass.hpp"

 #include "runtime/init.hpp"

 #include "runtime/thread.inline.hpp"

 #include "services/heapDumper.hpp"

 #ifdef ASSERT

 int CollectedHeap::_fire_out_of_memory_count = 0;

 #endif

 size_t CollectedHeap::_filler_array_max_size = 0;

 template <>

 void EventLogBase<GCMessage>::print(outputStream* st, GCMessage& m) {

   st->print_cr("GC heap %s", m.is_before ? "before" : "after");

   st->print_raw(m);

 }

 void GCHeapLog::log_heap(bool before) {

   if (!should_log()) {

     return;

   }

   double timestamp = fetch_timestamp();

   MutexLockerEx ml(&_mutex, Mutex::_no_safepoint_check_flag);

   int index = compute_log_index();

   _records[index].thread = NULL; // Its the GC thread so it's not that interesting.

   _records[index].timestamp = timestamp;

   _records[index].data.is_before = before;

   stringStream st(_records[index].data.buffer(), _records[index].data.size());

   if (before) {

     Universe::print_heap_before_gc(&st, true);

   } else {

     Universe::print_heap_after_gc(&st, true);

   }

 }

 VirtualSpaceSummary CollectedHeap::create_heap_space_summary() {

   size_t capacity_in_words = capacity() / HeapWordSize;

   return VirtualSpaceSummary(

     reserved_region().start(), reserved_region().start() + capacity_in_words, reserved_region().end());

 }

 GCHeapSummary CollectedHeap::create_heap_summary() {

   VirtualSpaceSummary heap_space = create_heap_space_summary();

   return GCHeapSummary(heap_space, used());

 }

 MetaspaceSummary CollectedHeap::create_metaspace_summary() {

   const MetaspaceSizes meta_space(

       MetaspaceAux::committed_bytes(),

       MetaspaceAux::allocated_used_bytes(),

       MetaspaceAux::reserved_bytes());

   const MetaspaceSizes data_space(

       MetaspaceAux::committed_bytes(Metaspace::NonClassType),

       MetaspaceAux::allocated_used_bytes(Metaspace::NonClassType),

       MetaspaceAux::reserved_bytes(Metaspace::NonClassType));

   const MetaspaceSizes class_space(

       MetaspaceAux::committed_bytes(Metaspace::ClassType),

       MetaspaceAux::allocated_used_bytes(Metaspace::ClassType),

       MetaspaceAux::reserved_bytes(Metaspace::ClassType));

   const MetaspaceChunkFreeListSummary& ms_chunk_free_list_summary =

     MetaspaceAux::chunk_free_list_summary(Metaspace::NonClassType);

   const MetaspaceChunkFreeListSummary& class_chunk_free_list_summary =

     MetaspaceAux::chunk_free_list_summary(Metaspace::ClassType);

   return MetaspaceSummary(MetaspaceGC::capacity_until_GC(), meta_space, data_space, class_space,

                           ms_chunk_free_list_summary, class_chunk_free_list_summary);

 }

 void CollectedHeap::print_heap_before_gc() {

   if (PrintHeapAtGC) {

     Universe::print_heap_before_gc();

   }

   if (_gc_heap_log != NULL) {

     _gc_heap_log->log_heap_before();

   }

 }

 void CollectedHeap::print_heap_after_gc() {

   if (PrintHeapAtGC) {

     Universe::print_heap_after_gc();

   }

   if (_gc_heap_log != NULL) {

     _gc_heap_log->log_heap_after();

   }

 }

 void CollectedHeap::register_nmethod(nmethod* nm) {

   assert_locked_or_safepoint(CodeCache_lock);

 }

 void CollectedHeap::unregister_nmethod(nmethod* nm) {

   assert_locked_or_safepoint(CodeCache_lock);

 }

 void CollectedHeap::trace_heap(GCWhen::Type when, GCTracer* gc_tracer) {

   const GCHeapSummary& heap_summary = create_heap_summary();

   gc_tracer->report_gc_heap_summary(when, heap_summary);

   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();

   gc_tracer->report_metaspace_summary(when, metaspace_summary);

 }

 void CollectedHeap::trace_heap_before_gc(GCTracer* gc_tracer) {

   trace_heap(GCWhen::BeforeGC, gc_tracer);

 }

 void CollectedHeap::trace_heap_after_gc(GCTracer* gc_tracer) {

   trace_heap(GCWhen::AfterGC, gc_tracer);

 }

 // Memory state functions.

 CollectedHeap::CollectedHeap() : _n_par_threads(0)

 {

   const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));

   const size_t elements_per_word = HeapWordSize / sizeof(jint);

   _filler_array_max_size = align_object_size(filler_array_hdr_size() +

                                              max_len / elements_per_word);

   _barrier_set = NULL;

   _is_gc_active = false;

   _total_collections = _total_full_collections = 0;

   _gc_cause = _gc_lastcause = GCCause::_no_gc;

   NOT_PRODUCT(_promotion_failure_alot_count = 0;)

   NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)

   if (UsePerfData) {

     EXCEPTION_MARK;

     // create the gc cause jvmstat counters

     _perf_gc_cause = PerfDataManager::create_string_variable(SUN_GC, "cause",

                              80, GCCause::to_string(_gc_cause), CHECK);

     _perf_gc_lastcause =

                 PerfDataManager::create_string_variable(SUN_GC, "lastCause",

                              80, GCCause::to_string(_gc_lastcause), CHECK);

   }

   _defer_initial_card_mark = false; // strengthened by subclass in pre_initialize() below.

   // Create the ring log

   if (LogEvents) {

     _gc_heap_log = new GCHeapLog();

   } else {

     _gc_heap_log = NULL;

   }

 }

 // This interface assumes that it's being called by the

 // vm thread. It collects the heap assuming that the

 // heap lock is already held and that we are executing in

 // the context of the vm thread.

 void CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {

   assert(Thread::current()->is_VM_thread(), "Precondition#1");

   assert(Heap_lock->is_locked(), "Precondition#2");

   GCCauseSetter gcs(this, cause);

   switch (cause) {

     case GCCause::_heap_inspection:

     case GCCause::_heap_dump:

     case GCCause::_metadata_GC_threshold : {

       HandleMark hm;

       do_full_collection(false);        // don't clear all soft refs

       break;

     }

     case GCCause::_last_ditch_collection: {

       HandleMark hm;

       do_full_collection(true);         // do clear all soft refs

       break;

     }

     default:

       ShouldNotReachHere(); // Unexpected use of this function

   }

 }

 void CollectedHeap::pre_initialize() {

   // Used for ReduceInitialCardMarks (when COMPILER2 is used);

   // otherwise remains unused.

 #ifdef COMPILER2

   _defer_initial_card_mark =    ReduceInitialCardMarks && can_elide_tlab_store_barriers()

                              && (DeferInitialCardMark || card_mark_must_follow_store());

 #else

   assert(_defer_initial_card_mark == false, "Who would set it?");

 #endif

 }

 #ifndef PRODUCT

 void CollectedHeap::check_for_bad_heap_word_value(HeapWord* addr, size_t size) {

   if (CheckMemoryInitialization && ZapUnusedHeapArea) {

     for (size_t slot = 0; slot < size; slot += 1) {

       assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal),

              "Found badHeapWordValue in post-allocation check");

     }

   }

 }

 void CollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) {

   if (CheckMemoryInitialization && ZapUnusedHeapArea) {

     for (size_t slot = 0; slot < size; slot += 1) {

       assert((*(intptr_t*) (addr + slot)) == ((intptr_t) badHeapWordVal),

              "Found non badHeapWordValue in pre-allocation check");

     }

   }

 }

 #endif // PRODUCT

 #ifdef ASSERT

 void CollectedHeap::check_for_valid_allocation_state() {

   Thread *thread = Thread::current();

   // How to choose between a pending exception and a potential

   // OutOfMemoryError?  Don't allow pending exceptions.

   // This is a VM policy failure, so how do we exhaustively test it?

   assert(!thread->has_pending_exception(),

          "shouldn't be allocating with pending exception");

   if (StrictSafepointChecks) {

     assert(thread->allow_allocation(),

            "Allocation done by thread for which allocation is blocked "

            "by No_Allocation_Verifier!");

     // Allocation of an oop can always invoke a safepoint,

     // hence, the true argument

     thread->check_for_valid_safepoint_state(true);

   }

 }

 #endif

 HeapWord* CollectedHeap::allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size) {

   // Retain tlab and allocate object in shared space if

   // the amount free in the tlab is too large to discard.

   if (thread->tlab().free() > thread->tlab().refill_waste_limit()) {

     thread->tlab().record_slow_allocation(size);

     return NULL;

   }

   // Discard tlab and allocate a new one.

   // To minimize fragmentation, the last TLAB may be smaller than the rest.

   size_t new_tlab_size = thread->tlab().compute_size(size);

   thread->tlab().clear_before_allocation();

   if (new_tlab_size == 0) {

     return NULL;

   }

   // Allocate a new TLAB...

   HeapWord* obj = Universe::heap()->allocate_new_tlab(new_tlab_size);

   if (obj == NULL) {

     return NULL;

   }

   AllocTracer::send_allocation_in_new_tlab_event(klass, new_tlab_size * HeapWordSize, size * HeapWordSize);

   if (ZeroTLAB) {

     // ..and clear it.

     Copy::zero_to_words(obj, new_tlab_size);

   } else {

     // ...and zap just allocated object.

 #ifdef ASSERT

     // Skip mangling the space corresponding to the object header to

     // ensure that the returned space is not considered parsable by

     // any concurrent GC thread.

     size_t hdr_size = oopDesc::header_size();

     Copy::fill_to_words(obj + hdr_size, new_tlab_size - hdr_size, badHeapWordVal);

 #endif // ASSERT

   }

   thread->tlab().fill(obj, obj + size, new_tlab_size);

   return obj;

 }

 void CollectedHeap::flush_deferred_store_barrier(JavaThread* thread) {

   MemRegion deferred = thread->deferred_card_mark();

   if (!deferred.is_empty()) {

     assert(_defer_initial_card_mark, "Otherwise should be empty");

     {

       // Verify that the storage points to a parsable object in heap

       DEBUG_ONLY(oop old_obj = oop(deferred.start());)

       assert(is_in(old_obj), "Not in allocated heap");

       assert(!can_elide_initializing_store_barrier(old_obj),

              "Else should have been filtered in new_store_pre_barrier()");

       assert(old_obj->is_oop(true), "Not an oop");

       assert(deferred.word_size() == (size_t)(old_obj->size()),

              "Mismatch: multiple objects?");

     }

     BarrierSet* bs = barrier_set();

     assert(bs->has_write_region_opt(), "No write_region() on BarrierSet");

     bs->write_region(deferred);

     // "Clear" the deferred_card_mark field

     thread->set_deferred_card_mark(MemRegion());

   }

   assert(thread->deferred_card_mark().is_empty(), "invariant");

 }

 size_t CollectedHeap::max_tlab_size() const {

   // TLABs can't be bigger than we can fill with a int[Integer.MAX_VALUE].

   // This restriction could be removed by enabling filling with multiple arrays.

   // If we compute that the reasonable way as

   //    header_size + ((sizeof(jint) * max_jint) / HeapWordSize)

   // we'll overflow on the multiply, so we do the divide first.

   // We actually lose a little by dividing first,

   // but that just makes the TLAB  somewhat smaller than the biggest array,

   // which is fine, since we'll be able to fill that.

   size_t max_int_size = typeArrayOopDesc::header_size(T_INT) +

               sizeof(jint) *

               ((juint) max_jint / (size_t) HeapWordSize);

   return align_size_down(max_int_size, MinObjAlignment);

 }

 // Helper for ReduceInitialCardMarks. For performance,

 // compiled code may elide card-marks for initializing stores

 // to a newly allocated object along the fast-path. We

 // compensate for such elided card-marks as follows:

 // (a) Generational, non-concurrent collectors, such as

 //     GenCollectedHeap(ParNew,DefNew,Tenured) and

 //     ParallelScavengeHeap(ParallelGC, ParallelOldGC)

 //     need the card-mark if and only if the region is

 //     in the old gen, and do not care if the card-mark

 //     succeeds or precedes the initializing stores themselves,

 //     so long as the card-mark is completed before the next

 //     scavenge. For all these cases, we can do a card mark

 //     at the point at which we do a slow path allocation

 //     in the old gen, i.e. in this call.

 // (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires

 //     in addition that the card-mark for an old gen allocated

 //     object strictly follow any associated initializing stores.

 //     In these cases, the memRegion remembered below is

 //     used to card-mark the entire region either just before the next

 //     slow-path allocation by this thread or just before the next scavenge or

 //     CMS-associated safepoint, whichever of these events happens first.

 //     (The implicit assumption is that the object has been fully

 //     initialized by this point, a fact that we assert when doing the

 //     card-mark.)

 // (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a

 //     G1 concurrent marking is in progress an SATB (pre-write-)barrier is

 //     is used to remember the pre-value of any store. Initializing

 //     stores will not need this barrier, so we need not worry about

 //     compensating for the missing pre-barrier here. Turning now

 //     to the post-barrier, we note that G1 needs a RS update barrier

 //     which simply enqueues a (sequence of) dirty cards which may

 //     optionally be refined by the concurrent update threads. Note

 //     that this barrier need only be applied to a non-young write,

 //     but, like in CMS, because of the presence of concurrent refinement

 //     (much like CMS' precleaning), must strictly follow the oop-store.

 //     Thus, using the same protocol for maintaining the intended

 //     invariants turns out, serendepitously, to be the same for both

 //     G1 and CMS.

 //

 // For any future collector, this code should be reexamined with

 // that specific collector in mind, and the documentation above suitably

 // extended and updated.

 oop CollectedHeap::new_store_pre_barrier(JavaThread* thread, oop new_obj) {

   // If a previous card-mark was deferred, flush it now.

   flush_deferred_store_barrier(thread);

   if (can_elide_initializing_store_barrier(new_obj)) {

     // The deferred_card_mark region should be empty

     // following the flush above.

     assert(thread->deferred_card_mark().is_empty(), "Error");

   } else {

     MemRegion mr((HeapWord*)new_obj, new_obj->size());

     assert(!mr.is_empty(), "Error");

     if (_defer_initial_card_mark) {

       // Defer the card mark

       thread->set_deferred_card_mark(mr);

     } else {

       // Do the card mark

       BarrierSet* bs = barrier_set();

       assert(bs->has_write_region_opt(), "No write_region() on BarrierSet");

       bs->write_region(mr);

     }

   }

   return new_obj;

 }

 size_t CollectedHeap::filler_array_hdr_size() {

   return size_t(align_object_offset(arrayOopDesc::header_size(T_INT))); // align to Long

 }

 size_t CollectedHeap::filler_array_min_size() {

   return align_object_size(filler_array_hdr_size()); // align to MinObjAlignment

 }

 #ifdef ASSERT

 void CollectedHeap::fill_args_check(HeapWord* start, size_t words)

 {

   assert(words >= min_fill_size(), "too small to fill");

   assert(words % MinObjAlignment == 0, "unaligned size");

   assert(Universe::heap()->is_in_reserved(start), "not in heap");

   assert(Universe::heap()->is_in_reserved(start + words - 1), "not in heap");

 }

 void CollectedHeap::zap_filler_array(HeapWord* start, size_t words, bool zap)

 {

   if (ZapFillerObjects && zap) {

     Copy::fill_to_words(start + filler_array_hdr_size(),

                         words - filler_array_hdr_size(), 0XDEAFBABE);

   }

 }

 #endif // ASSERT

 void

 CollectedHeap::fill_with_array(HeapWord* start, size_t words, bool zap)

 {

   assert(words >= filler_array_min_size(), "too small for an array");

   assert(words <= filler_array_max_size(), "too big for a single object");

   const size_t payload_size = words - filler_array_hdr_size();

   const size_t len = payload_size * HeapWordSize / sizeof(jint);

   assert((int)len >= 0, err_msg("size too large " SIZE_FORMAT " becomes %d", words, (int)len));

   // Set the length first for concurrent GC.

   ((arrayOop)start)->set_length((int)len);

   post_allocation_setup_common(Universe::intArrayKlassObj(), start);

   DEBUG_ONLY(zap_filler_array(start, words, zap);)

 }

 void

 CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)

 {

   assert(words <= filler_array_max_size(), "too big for a single object");

   if (words >= filler_array_min_size()) {

     fill_with_array(start, words, zap);

   } else if (words > 0) {

     assert(words == min_fill_size(), "unaligned size");

     post_allocation_setup_common(SystemDictionary::Object_klass(), start);

   }

 }

 void CollectedHeap::fill_with_object(HeapWord* start, size_t words, bool zap)

 {

   DEBUG_ONLY(fill_args_check(start, words);)

   HandleMark hm;  // Free handles before leaving.

   fill_with_object_impl(start, words, zap);

 }

 void CollectedHeap::fill_with_objects(HeapWord* start, size_t words, bool zap)

 {

   DEBUG_ONLY(fill_args_check(start, words);)

   HandleMark hm;  // Free handles before leaving.

 #ifdef _LP64

   // A single array can fill ~8G, so multiple objects are needed only in 64-bit.

   // First fill with arrays, ensuring that any remaining space is big enough to

   // fill.  The remainder is filled with a single object.

   const size_t min = min_fill_size();

   const size_t max = filler_array_max_size();

   while (words > max) {

     const size_t cur = words - max >= min ? max : max - min;

     fill_with_array(start, cur, zap);

     start += cur;

     words -= cur;

   }

 #endif

   fill_with_object_impl(start, words, zap);

 }

 void CollectedHeap::post_initialize() {

   collector_policy()->post_heap_initialize();

 }

 HeapWord* CollectedHeap::allocate_new_tlab(size_t size) {

   guarantee(false, "thread-local allocation buffers not supported");

   return NULL;

 }

 void CollectedHeap::ensure_parsability(bool retire_tlabs) {

   // The second disjunct in the assertion below makes a concession

   // for the start-up verification done while the VM is being

   // created. Callers be careful that you know that mutators

   // aren't going to interfere -- for instance, this is permissible

   // if we are still single-threaded and have either not yet

   // started allocating (nothing much to verify) or we have

   // started allocating but are now a full-fledged JavaThread

   // (and have thus made our TLAB's) available for filling.

   assert(SafepointSynchronize::is_at_safepoint() ||

          !is_init_completed(),

          "Should only be called at a safepoint or at start-up"

          " otherwise concurrent mutator activity may make heap "

          " unparsable again");

   const bool use_tlab = UseTLAB;

   const bool deferred = _defer_initial_card_mark;

   // The main thread starts allocating via a TLAB even before it

   // has added itself to the threads list at vm boot-up.

   assert(!use_tlab || Threads::first() != NULL,

          "Attempt to fill tlabs before main thread has been added"

          " to threads list is doomed to failure!");

   for (JavaThread *thread = Threads::first(); thread; thread = thread->next()) {

      if (use_tlab) thread->tlab().make_parsable(retire_tlabs);

 #ifdef COMPILER2

      // The deferred store barriers must all have been flushed to the

      // card-table (or other remembered set structure) before GC starts

      // processing the card-table (or other remembered set).

      if (deferred) flush_deferred_store_barrier(thread);

 #else

      assert(!deferred, "Should be false");

      assert(thread->deferred_card_mark().is_empty(), "Should be empty");

 #endif

   }

 }

 void CollectedHeap::accumulate_statistics_all_tlabs() {

   if (UseTLAB) {

     assert(SafepointSynchronize::is_at_safepoint() ||

          !is_init_completed(),

          "should only accumulate statistics on tlabs at safepoint");

     ThreadLocalAllocBuffer::accumulate_statistics_before_gc();

   }

 }

 void CollectedHeap::resize_all_tlabs() {

   if (UseTLAB) {

     assert(SafepointSynchronize::is_at_safepoint() ||

          !is_init_completed(),

          "should only resize tlabs at safepoint");

     ThreadLocalAllocBuffer::resize_all_tlabs();

   }

 }

 void CollectedHeap::pre_full_gc_dump(GCTimer* timer) {

   if (HeapDumpBeforeFullGC) {

     GCTraceTime tt("Heap Dump (before full gc): ", PrintGCDetails, false, timer);

     // We are doing a "major" collection and a heap dump before

     // major collection has been requested.

     HeapDumper::dump_heap();

   }

   if (PrintClassHistogramBeforeFullGC) {

     GCTraceTime tt("Class Histogram (before full gc): ", PrintGCDetails, true, timer);

     VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */);

     inspector.doit();

   }

 }

 void CollectedHeap::post_full_gc_dump(GCTimer* timer) {

   if (HeapDumpAfterFullGC) {

     GCTraceTime tt("Heap Dump (after full gc): ", PrintGCDetails, false, timer);

     HeapDumper::dump_heap();

   }

   if (PrintClassHistogramAfterFullGC) {

     GCTraceTime tt("Class Histogram (after full gc): ", PrintGCDetails, true, timer);

     VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */);

     inspector.doit();

   }

 }

 oop CollectedHeap::Class_obj_allocate(KlassHandle klass, int size, KlassHandle real_klass, TRAPS) {

   debug_only(check_for_valid_allocation_state());

   assert(!Universe::heap()->is_gc_active(), "Allocation during gc not allowed");

   assert(size >= 0, "int won't convert to size_t");

   HeapWord* obj;

     assert(ScavengeRootsInCode > 0, "must be");

     obj = common_mem_allocate_init(real_klass, size, CHECK_NULL);

   post_allocation_setup_common(klass, obj);

   assert(Universe::is_bootstrapping() ||

          !((oop)obj)->is_array(), "must not be an array");

   NOT_PRODUCT(Universe::heap()->check_for_bad_heap_word_value(obj, size));

   oop mirror = (oop)obj;

   java_lang_Class::set_oop_size(mirror, size);

   // Setup indirections

   if (!real_klass.is_null()) {

     java_lang_Class::set_klass(mirror, real_klass());

     real_klass->set_java_mirror(mirror);

   }

   InstanceMirrorKlass* mk = InstanceMirrorKlass::cast(mirror->klass());

   assert(size == mk->instance_size(real_klass), "should have been set");

   // notify jvmti and dtrace

   post_allocation_notify(klass, (oop)obj);

   return mirror;

 }

 /////////////// Unit tests ///////////////

 #ifndef PRODUCT

 void CollectedHeap::test_is_in() {

   CollectedHeap* heap = Universe::heap();

   uintptr_t epsilon    = (uintptr_t) MinObjAlignment;

   uintptr_t heap_start = (uintptr_t) heap->_reserved.start();

   uintptr_t heap_end   = (uintptr_t) heap->_reserved.end();

   // Test that NULL is not in the heap.

   assert(!heap->is_in(NULL), "NULL is unexpectedly in the heap");

   // Test that a pointer to before the heap start is reported as outside the heap.

   assert(heap_start >= ((uintptr_t)NULL + epsilon), "sanity");

   void* before_heap = (void*)(heap_start - epsilon);

   assert(!heap->is_in(before_heap),

       err_msg("before_heap: " PTR_FORMAT " is unexpectedly in the heap", before_heap));

   // Test that a pointer to after the heap end is reported as outside the heap.

   assert(heap_end <= ((uintptr_t)-1 - epsilon), "sanity");

   void* after_heap = (void*)(heap_end + epsilon);

   assert(!heap->is_in(after_heap),

       err_msg("after_heap: " PTR_FORMAT " is unexpectedly in the heap", after_heap));

 }

 #endif