runtime/reference_table.cc - platform/art - Gitiles

 /*
  * Copyright (C) 2008 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "reference_table.h"

 #include "android-base/stringprintf.h"

 #include "base/mutex.h"
 #include "base/utils.h"
 #include "gc/allocation_record.h"
 #include "gc/heap.h"
 #include "indirect_reference_table.h"
 #include "mirror/array-inl.h"
 #include "mirror/array.h"
 #include "mirror/class-inl.h"
 #include "mirror/class.h"
 #include "mirror/object-inl.h"
 #include "mirror/string-inl.h"
 #include "runtime-inl.h"
 #include "thread.h"

 namespace art {

 using android::base::StringAppendF;
 using android::base::StringPrintf;

 ReferenceTable::ReferenceTable(const char* name, size_t initial_size, size_t max_size)
     : name_(name), max_size_(max_size) {
   CHECK_LE(initial_size, max_size);
   entries_.reserve(initial_size);
 }

 ReferenceTable::~ReferenceTable() {
 }

 void ReferenceTable::Add(ObjPtr<mirror::Object> obj) {
   DCHECK(obj != nullptr);
   VerifyObject(obj);
   if (entries_.size() >= max_size_) {
     LOG(FATAL) << "ReferenceTable '" << name_ << "' "
                << "overflowed (" << max_size_ << " entries)";
   }
   entries_.push_back(GcRoot<mirror::Object>(obj));
 }

 void ReferenceTable::Remove(ObjPtr<mirror::Object> obj) {
   // We iterate backwards on the assumption that references are LIFO.
   for (int i = entries_.size() - 1; i >= 0; --i) {
     ObjPtr<mirror::Object> entry = entries_[i].Read();
     if (entry == obj) {
       entries_.erase(entries_.begin() + i);
       return;
     }
   }
 }

 // If "obj" is an array, return the number of elements in the array.
 // Otherwise, return zero.
 static size_t GetElementCount(ObjPtr<mirror::Object> obj) REQUIRES_SHARED(Locks::mutator_lock_) {
   // We assume the special cleared value isn't an array in the if statement below.
   DCHECK(!Runtime::Current()->GetClearedJniWeakGlobal()->IsArrayInstance());
   if (obj == nullptr || !obj->IsArrayInstance()) {
     return 0;
   }
   return obj->AsArray()->GetLength();
 }

 // Log an object with some additional info.
 //
 // Pass in the number of elements in the array (or 0 if this is not an
 // array object), and the number of additional objects that are identical
 // or equivalent to the original.
 static void DumpSummaryLine(std::ostream& os, ObjPtr<mirror::Object> obj, size_t element_count,
                             int identical, int equiv)
     REQUIRES_SHARED(Locks::mutator_lock_) {
   if (obj == nullptr) {
     os << "    null reference (count=" << equiv << ")\n";
     return;
   }
   if (Runtime::Current()->IsClearedJniWeakGlobal(obj)) {
     os << "    cleared jweak (count=" << equiv << ")\n";
     return;
   }

   std::string className(obj->PrettyTypeOf());
   if (obj->IsClass()) {
     // We're summarizing multiple instances, so using the exemplar
     // Class' type parameter here would be misleading.
     className = "java.lang.Class";
   }
   if (element_count != 0) {
     StringAppendF(&className, " (%zd elements)", element_count);
   }

   size_t total = identical + equiv + 1;
   std::string msg(StringPrintf("%5zd of %s", total, className.c_str()));
   if (identical + equiv != 0) {
     StringAppendF(&msg, " (%d unique instances)", equiv + 1);
   }
   os << "    " << msg << "\n";
 }

 size_t ReferenceTable::Size() const {
   return entries_.size();
 }

 void ReferenceTable::Dump(std::ostream& os) {
   os << name_ << " reference table dump:\n";
   Dump(os, entries_);
 }

 void ReferenceTable::Dump(std::ostream& os, Table& entries) {
   // Compare GC roots, first by class, then size, then address.
   struct GcRootComparator {
     bool operator()(GcRoot<mirror::Object> root1, GcRoot<mirror::Object> root2) const
       // TODO: enable analysis when analysis can work with the STL.
         NO_THREAD_SAFETY_ANALYSIS {
       Locks::mutator_lock_->AssertSharedHeld(Thread::Current());
       // These GC roots are already forwarded in ReferenceTable::Dump. We sort by class since there
       // are no suspend points which can happen during the sorting process. This works since
       // we are guaranteed that the addresses of obj1, obj2, obj1->GetClass, obj2->GetClass wont
       // change during the sorting process. The classes are forwarded by ref->GetClass().
       ObjPtr<mirror::Object> obj1 = root1.Read<kWithoutReadBarrier>();
       ObjPtr<mirror::Object> obj2 = root2.Read<kWithoutReadBarrier>();
       DCHECK(obj1 != nullptr);
       DCHECK(obj2 != nullptr);
       Runtime* runtime = Runtime::Current();
       DCHECK(!runtime->IsClearedJniWeakGlobal(obj1));
       DCHECK(!runtime->IsClearedJniWeakGlobal(obj2));
       // Sort by class...
       if (obj1->GetClass() != obj2->GetClass()) {
         return obj1->GetClass() < obj2->GetClass();
       }
       // ...then by size...
       const size_t size1 = obj1->SizeOf();
       const size_t size2 = obj2->SizeOf();
       if (size1 != size2) {
         return size1 < size2;
       }
       // ...and finally by address.
       return obj1.Ptr() < obj2.Ptr();
     }
   };

   if (entries.empty()) {
     os << "  (empty)\n";
     return;
   }

   // Dump the most recent N entries.
   const size_t kLast = 10;
   size_t count = entries.size();
   int first = count - kLast;
   if (first < 0) {
     first = 0;
   }
   os << "  Last " << (count - first) << " entries (of " << count << "):\n";
   Runtime* runtime = Runtime::Current();
   for (int idx = count - 1; idx >= first; --idx) {
     ObjPtr<mirror::Object> ref = entries[idx].Read();
     if (ref == nullptr) {
       continue;
     }
     if (runtime->IsClearedJniWeakGlobal(ref)) {
       os << StringPrintf("    %5d: cleared jweak\n", idx);
       continue;
     }
     if (ref->GetClass() == nullptr) {
       // should only be possible right after a plain dvmMalloc().
       size_t size = ref->SizeOf();
       os << StringPrintf("    %5d: %p (raw) (%zd bytes)\n", idx, ref.Ptr(), size);
       continue;
     }

     std::string className(ref->PrettyTypeOf());

     std::string extras;
     size_t element_count = GetElementCount(ref);
     if (element_count != 0) {
       StringAppendF(&extras, " (%zd elements)", element_count);
     } else if (ref->GetClass()->IsStringClass()) {
       ObjPtr<mirror::String> s = ref->AsString();
       std::string utf8(s->ToModifiedUtf8());
       if (s->GetLength() <= 16) {
         StringAppendF(&extras, " \"%s\"", utf8.c_str());
       } else {
         StringAppendF(&extras, " \"%.16s... (%d chars)", utf8.c_str(), s->GetLength());
       }
     } else if (ref->IsReferenceInstance()) {
       ObjPtr<mirror::Object> referent = ref->AsReference()->GetReferent();
       if (referent == nullptr) {
         extras = " (referent is null)";
       } else {
         extras = StringPrintf(" (referent is a %s)", referent->PrettyTypeOf().c_str());
       }
     }
     os << StringPrintf("    %5d: ", idx) << ref << " " << className << extras << "\n";
     if (runtime->GetHeap()->IsAllocTrackingEnabled()) {
       MutexLock mu(Thread::Current(), *Locks::alloc_tracker_lock_);

       gc::AllocRecordObjectMap* records = runtime->GetHeap()->GetAllocationRecords();
       DCHECK(records != nullptr);
       // It's annoying that this is a list. But this code should be very uncommon to be executed.

       auto print_stack = [&](ObjPtr<mirror::Object> to_print, const std::string& msg)
           REQUIRES_SHARED(Locks::mutator_lock_)
           REQUIRES(Locks::alloc_tracker_lock_) {
         for (auto it = records->Begin(), end = records->End(); it != end; ++it) {
           GcRoot<mirror::Object>& stack_for_object = it->first;
           gc::AllocRecord& record = it->second;
           if (stack_for_object.Read() == to_print.Ptr()) {
             os << "          " << msg << "\n";
             const gc::AllocRecordStackTrace* trace = record.GetStackTrace();
             size_t depth = trace->GetDepth();
             if (depth == 0) {
               os << "            (No managed frames)\n";
             } else {
               for (size_t i = 0; i < depth; ++i) {
                 const gc::AllocRecordStackTraceElement& frame = trace->GetStackElement(i);
                 os << "            ";
                 if (frame.GetMethod() == nullptr) {
                   os << "(missing method data)\n";
                   continue;
                 }
                 os << frame.GetMethod()->PrettyMethod(true)
                    << ":"
                    << frame.ComputeLineNumber()
                    << "\n";
               }
             }
             break;
           }
         }
       };
       // Print the stack trace of the ref.
       print_stack(ref, "Allocated at:");

       // If it's a reference, see if we have data about the referent.
       if (ref->IsReferenceInstance()) {
         ObjPtr<mirror::Object> referent = ref->AsReference()->GetReferent();
         if (referent != nullptr) {
           print_stack(referent, "Referent allocated at:");
         }
       }
     }
   }

   // Make a copy of the table and sort it, only adding non null and not cleared elements.
   Table sorted_entries;
   for (GcRoot<mirror::Object>& root : entries) {
     if (!root.IsNull() && !runtime->IsClearedJniWeakGlobal(root.Read())) {
       sorted_entries.push_back(root);
     }
   }
   if (sorted_entries.empty()) {
     return;
   }
   std::sort(sorted_entries.begin(), sorted_entries.end(), GcRootComparator());

   class SummaryElement {
    public:
     GcRoot<mirror::Object> root;
     size_t equiv;
     size_t identical;

     SummaryElement() : equiv(0), identical(0) {}
     SummaryElement(SummaryElement&& ref) noexcept {
       root = ref.root;
       equiv = ref.equiv;
       identical = ref.identical;
     }
     SummaryElement(const SummaryElement&) = default;
     SummaryElement& operator=(SummaryElement&&) = default;

     void Reset(GcRoot<mirror::Object>& _root) {
       root = _root;
       equiv = 0;
       identical = 0;
     }
   };
   std::vector<SummaryElement> sorted_summaries;
   {
     SummaryElement prev;

     for (GcRoot<mirror::Object>& root : sorted_entries) {
       ObjPtr<mirror::Object> current = root.Read<kWithoutReadBarrier>();

       if (UNLIKELY(prev.root.IsNull())) {
         prev.Reset(root);
         continue;
       }

       ObjPtr<mirror::Object> prevObj = prev.root.Read<kWithoutReadBarrier>();
       if (current == prevObj) {
         // Same reference, added more than once.
         ++prev.identical;
       } else if (current->GetClass() == prevObj->GetClass() &&
           GetElementCount(current) == GetElementCount(prevObj)) {
         // Same class / element count, different object.
         ++prev.equiv;
       } else {
         sorted_summaries.push_back(prev);
         prev.Reset(root);
       }
       prev.root = root;
     }
     sorted_summaries.push_back(prev);

     // Compare summary elements, first by combined count, then by identical (indicating leaks),
     // then by class (and size and address).
     struct SummaryElementComparator {
       GcRootComparator gc_root_cmp;

       bool operator()(SummaryElement& elem1, SummaryElement& elem2) const
           NO_THREAD_SAFETY_ANALYSIS {
         Locks::mutator_lock_->AssertSharedHeld(Thread::Current());

         size_t count1 = elem1.equiv + elem1.identical;
         size_t count2 = elem2.equiv + elem2.identical;
         if (count1 != count2) {
           return count1 > count2;
         }

         if (elem1.identical != elem2.identical) {
           return elem1.identical > elem2.identical;
         }

         // Otherwise, compare the GC roots as before.
         return gc_root_cmp(elem1.root, elem2.root);
       }
     };
     std::sort(sorted_summaries.begin(), sorted_summaries.end(), SummaryElementComparator());
   }

   // Dump a summary of the whole table.
   os << "  Summary:\n";
   for (SummaryElement& elem : sorted_summaries) {
     ObjPtr<mirror::Object> elemObj = elem.root.Read<kWithoutReadBarrier>();
     DumpSummaryLine(os, elemObj, GetElementCount(elemObj), elem.identical, elem.equiv);
   }
 }

 void ReferenceTable::VisitRoots(RootVisitor* visitor, const RootInfo& root_info) {
   BufferedRootVisitor<kDefaultBufferedRootCount> buffered_visitor(visitor, root_info);
   for (GcRoot<mirror::Object>& root : entries_) {
     buffered_visitor.VisitRoot(root);
   }
 }

 }  // namespace art
	/*
	* Copyright (C) 2008 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "reference_table.h"

	#include "android-base/stringprintf.h"

	#include "base/mutex.h"
	#include "base/utils.h"
	#include "gc/allocation_record.h"
	#include "gc/heap.h"
	#include "indirect_reference_table.h"
	#include "mirror/array-inl.h"
	#include "mirror/array.h"
	#include "mirror/class-inl.h"
	#include "mirror/class.h"
	#include "mirror/object-inl.h"
	#include "mirror/string-inl.h"
	#include "runtime-inl.h"
	#include "thread.h"

	namespace art {

	using android::base::StringAppendF;
	using android::base::StringPrintf;

	ReferenceTable::ReferenceTable(const char* name, size_t initial_size, size_t max_size)
	: name_(name), max_size_(max_size) {
	CHECK_LE(initial_size, max_size);
	entries_.reserve(initial_size);
	}

	ReferenceTable::~ReferenceTable() {
	}

	void ReferenceTable::Add(ObjPtr<mirror::Object> obj) {
	DCHECK(obj != nullptr);
	VerifyObject(obj);
	if (entries_.size() >= max_size_) {
	LOG(FATAL) << "ReferenceTable '" << name_ << "' "
	<< "overflowed (" << max_size_ << " entries)";
	}
	entries_.push_back(GcRoot<mirror::Object>(obj));
	}

	void ReferenceTable::Remove(ObjPtr<mirror::Object> obj) {
	// We iterate backwards on the assumption that references are LIFO.
	for (int i = entries_.size() - 1; i >= 0; --i) {
	ObjPtr<mirror::Object> entry = entries_[i].Read();
	if (entry == obj) {
	entries_.erase(entries_.begin() + i);
	return;
	}
	}
	}

	// If "obj" is an array, return the number of elements in the array.
	// Otherwise, return zero.
	static size_t GetElementCount(ObjPtr<mirror::Object> obj) REQUIRES_SHARED(Locks::mutator_lock_) {
	// We assume the special cleared value isn't an array in the if statement below.
	DCHECK(!Runtime::Current()->GetClearedJniWeakGlobal()->IsArrayInstance());
	if (obj == nullptr \|\| !obj->IsArrayInstance()) {
	return 0;
	}
	return obj->AsArray()->GetLength();
	}

	// Log an object with some additional info.
	//
	// Pass in the number of elements in the array (or 0 if this is not an
	// array object), and the number of additional objects that are identical
	// or equivalent to the original.
	static void DumpSummaryLine(std::ostream& os, ObjPtr<mirror::Object> obj, size_t element_count,
	int identical, int equiv)
	REQUIRES_SHARED(Locks::mutator_lock_) {
	if (obj == nullptr) {
	os << " null reference (count=" << equiv << ")\n";
	return;
	}
	if (Runtime::Current()->IsClearedJniWeakGlobal(obj)) {
	os << " cleared jweak (count=" << equiv << ")\n";
	return;
	}

	std::string className(obj->PrettyTypeOf());
	if (obj->IsClass()) {
	// We're summarizing multiple instances, so using the exemplar
	// Class' type parameter here would be misleading.
	className = "java.lang.Class";
	}
	if (element_count != 0) {
	StringAppendF(&className, " (%zd elements)", element_count);
	}

	size_t total = identical + equiv + 1;
	std::string msg(StringPrintf("%5zd of %s", total, className.c_str()));
	if (identical + equiv != 0) {
	StringAppendF(&msg, " (%d unique instances)", equiv + 1);
	}
	os << " " << msg << "\n";
	}

	size_t ReferenceTable::Size() const {
	return entries_.size();
	}

	void ReferenceTable::Dump(std::ostream& os) {
	os << name_ << " reference table dump:\n";
	Dump(os, entries_);
	}

	void ReferenceTable::Dump(std::ostream& os, Table& entries) {
	// Compare GC roots, first by class, then size, then address.
	struct GcRootComparator {
	bool operator()(GcRoot<mirror::Object> root1, GcRoot<mirror::Object> root2) const
	// TODO: enable analysis when analysis can work with the STL.
	NO_THREAD_SAFETY_ANALYSIS {
	Locks::mutator_lock_->AssertSharedHeld(Thread::Current());
	// These GC roots are already forwarded in ReferenceTable::Dump. We sort by class since there
	// are no suspend points which can happen during the sorting process. This works since
	// we are guaranteed that the addresses of obj1, obj2, obj1->GetClass, obj2->GetClass wont
	// change during the sorting process. The classes are forwarded by ref->GetClass().
	ObjPtr<mirror::Object> obj1 = root1.Read<kWithoutReadBarrier>();
	ObjPtr<mirror::Object> obj2 = root2.Read<kWithoutReadBarrier>();
	DCHECK(obj1 != nullptr);
	DCHECK(obj2 != nullptr);
	Runtime* runtime = Runtime::Current();
	DCHECK(!runtime->IsClearedJniWeakGlobal(obj1));
	DCHECK(!runtime->IsClearedJniWeakGlobal(obj2));
	// Sort by class...
	if (obj1->GetClass() != obj2->GetClass()) {
	return obj1->GetClass() < obj2->GetClass();
	}
	// ...then by size...
	const size_t size1 = obj1->SizeOf();
	const size_t size2 = obj2->SizeOf();
	if (size1 != size2) {
	return size1 < size2;
	}
	// ...and finally by address.
	return obj1.Ptr() < obj2.Ptr();
	}
	};

	if (entries.empty()) {
	os << " (empty)\n";
	return;
	}

	// Dump the most recent N entries.
	const size_t kLast = 10;
	size_t count = entries.size();
	int first = count - kLast;
	if (first < 0) {
	first = 0;
	}
	os << " Last " << (count - first) << " entries (of " << count << "):\n";
	Runtime* runtime = Runtime::Current();
	for (int idx = count - 1; idx >= first; --idx) {
	ObjPtr<mirror::Object> ref = entries[idx].Read();
	if (ref == nullptr) {
	continue;
	}
	if (runtime->IsClearedJniWeakGlobal(ref)) {
	os << StringPrintf(" %5d: cleared jweak\n", idx);
	continue;
	}
	if (ref->GetClass() == nullptr) {
	// should only be possible right after a plain dvmMalloc().
	size_t size = ref->SizeOf();
	os << StringPrintf(" %5d: %p (raw) (%zd bytes)\n", idx, ref.Ptr(), size);
	continue;
	}

	std::string className(ref->PrettyTypeOf());

	std::string extras;
	size_t element_count = GetElementCount(ref);
	if (element_count != 0) {
	StringAppendF(&extras, " (%zd elements)", element_count);
	} else if (ref->GetClass()->IsStringClass()) {
	ObjPtr<mirror::String> s = ref->AsString();
	std::string utf8(s->ToModifiedUtf8());
	if (s->GetLength() <= 16) {
	StringAppendF(&extras, " \"%s\"", utf8.c_str());
	} else {
	StringAppendF(&extras, " \"%.16s... (%d chars)", utf8.c_str(), s->GetLength());
	}
	} else if (ref->IsReferenceInstance()) {
	ObjPtr<mirror::Object> referent = ref->AsReference()->GetReferent();
	if (referent == nullptr) {
	extras = " (referent is null)";
	} else {
	extras = StringPrintf(" (referent is a %s)", referent->PrettyTypeOf().c_str());
	}
	}
	os << StringPrintf(" %5d: ", idx) << ref << " " << className << extras << "\n";
	if (runtime->GetHeap()->IsAllocTrackingEnabled()) {
	MutexLock mu(Thread::Current(), *Locks::alloc_tracker_lock_);

	gc::AllocRecordObjectMap* records = runtime->GetHeap()->GetAllocationRecords();
	DCHECK(records != nullptr);
	// It's annoying that this is a list. But this code should be very uncommon to be executed.

	auto print_stack = [&](ObjPtr<mirror::Object> to_print, const std::string& msg)
	REQUIRES_SHARED(Locks::mutator_lock_)
	REQUIRES(Locks::alloc_tracker_lock_) {
	for (auto it = records->Begin(), end = records->End(); it != end; ++it) {
	GcRoot<mirror::Object>& stack_for_object = it->first;
	gc::AllocRecord& record = it->second;
	if (stack_for_object.Read() == to_print.Ptr()) {
	os << " " << msg << "\n";
	const gc::AllocRecordStackTrace* trace = record.GetStackTrace();
	size_t depth = trace->GetDepth();
	if (depth == 0) {
	os << " (No managed frames)\n";
	} else {
	for (size_t i = 0; i < depth; ++i) {
	const gc::AllocRecordStackTraceElement& frame = trace->GetStackElement(i);
	os << " ";
	if (frame.GetMethod() == nullptr) {
	os << "(missing method data)\n";
	continue;
	}
	os << frame.GetMethod()->PrettyMethod(true)
	<< ":"
	<< frame.ComputeLineNumber()
	<< "\n";
	}
	}
	break;
	}
	}
	};
	// Print the stack trace of the ref.
	print_stack(ref, "Allocated at:");

	// If it's a reference, see if we have data about the referent.
	if (ref->IsReferenceInstance()) {
	ObjPtr<mirror::Object> referent = ref->AsReference()->GetReferent();
	if (referent != nullptr) {
	print_stack(referent, "Referent allocated at:");
	}
	}
	}
	}

	// Make a copy of the table and sort it, only adding non null and not cleared elements.
	Table sorted_entries;
	for (GcRoot<mirror::Object>& root : entries) {
	if (!root.IsNull() && !runtime->IsClearedJniWeakGlobal(root.Read())) {
	sorted_entries.push_back(root);
	}
	}
	if (sorted_entries.empty()) {
	return;
	}
	std::sort(sorted_entries.begin(), sorted_entries.end(), GcRootComparator());

	class SummaryElement {
	public:
	GcRoot<mirror::Object> root;
	size_t equiv;
	size_t identical;

	SummaryElement() : equiv(0), identical(0) {}
	SummaryElement(SummaryElement&& ref) noexcept {
	root = ref.root;
	equiv = ref.equiv;
	identical = ref.identical;
	}
	SummaryElement(const SummaryElement&) = default;
	SummaryElement& operator=(SummaryElement&&) = default;

	void Reset(GcRoot<mirror::Object>& _root) {
	root = _root;
	equiv = 0;
	identical = 0;
	}
	};
	std::vector<SummaryElement> sorted_summaries;
	{
	SummaryElement prev;

	for (GcRoot<mirror::Object>& root : sorted_entries) {
	ObjPtr<mirror::Object> current = root.Read<kWithoutReadBarrier>();

	if (UNLIKELY(prev.root.IsNull())) {
	prev.Reset(root);
	continue;
	}

	ObjPtr<mirror::Object> prevObj = prev.root.Read<kWithoutReadBarrier>();
	if (current == prevObj) {
	// Same reference, added more than once.
	++prev.identical;
	} else if (current->GetClass() == prevObj->GetClass() &&
	GetElementCount(current) == GetElementCount(prevObj)) {
	// Same class / element count, different object.
	++prev.equiv;
	} else {
	sorted_summaries.push_back(prev);
	prev.Reset(root);
	}
	prev.root = root;
	}
	sorted_summaries.push_back(prev);

	// Compare summary elements, first by combined count, then by identical (indicating leaks),
	// then by class (and size and address).
	struct SummaryElementComparator {
	GcRootComparator gc_root_cmp;

	bool operator()(SummaryElement& elem1, SummaryElement& elem2) const
	NO_THREAD_SAFETY_ANALYSIS {
	Locks::mutator_lock_->AssertSharedHeld(Thread::Current());

	size_t count1 = elem1.equiv + elem1.identical;
	size_t count2 = elem2.equiv + elem2.identical;
	if (count1 != count2) {
	return count1 > count2;
	}

	if (elem1.identical != elem2.identical) {
	return elem1.identical > elem2.identical;
	}

	// Otherwise, compare the GC roots as before.
	return gc_root_cmp(elem1.root, elem2.root);
	}
	};
	std::sort(sorted_summaries.begin(), sorted_summaries.end(), SummaryElementComparator());
	}

	// Dump a summary of the whole table.
	os << " Summary:\n";
	for (SummaryElement& elem : sorted_summaries) {
	ObjPtr<mirror::Object> elemObj = elem.root.Read<kWithoutReadBarrier>();
	DumpSummaryLine(os, elemObj, GetElementCount(elemObj), elem.identical, elem.equiv);
	}
	}

	void ReferenceTable::VisitRoots(RootVisitor* visitor, const RootInfo& root_info) {
	BufferedRootVisitor<kDefaultBufferedRootCount> buffered_visitor(visitor, root_info);
	for (GcRoot<mirror::Object>& root : entries_) {
	buffered_visitor.VisitRoot(root);
	}
	}

	} // namespace art