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dart-sdk/runtime/vm/object_graph.cc
Ryan Macnak 28c2491f8d [vm, service] Account for weakness in getRetainingPath and getRetainedSize. 
We had been treating all references as strong for these RPCs. Now weak references are skipped, but ephemeron references are still treated as strong.

TEST=ci
Bug: https://github.com/dart-lang/sdk/issues/49155
Change-Id: I6c4f344ce3c0df5bdbeb133a697bb26ff972f372
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/302367
Reviewed-by: Ben Konyi <bkonyi@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>
2023-05-10 16:12:28 +00:00

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// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include "vm/object_graph.h"
#include "vm/dart.h"
#include "vm/dart_api_state.h"
#include "vm/growable_array.h"
#include "vm/isolate.h"
#include "vm/native_symbol.h"
#include "vm/object.h"
#include "vm/object_store.h"
#include "vm/profiler.h"
#include "vm/raw_object.h"
#include "vm/raw_object_fields.h"
#include "vm/reusable_handles.h"
#include "vm/visitor.h"
namespace dart {
#if defined(DART_ENABLE_HEAP_SNAPSHOT_WRITER)
static bool IsUserClass(intptr_t cid) {
if (cid == kContextCid) return true;
if (cid == kTypeArgumentsCid) return false;
return !IsInternalOnlyClassId(cid);
}
// A slot in the fixed-size portion of a heap object.
//
// This may be a regulard dart field, a unboxed dart field or
// a slot of any type in a predefined layout.
struct ObjectSlot {
uint16_t offset;
bool is_compressed_pointer;
const char* name;
ObjectSlot(uint16_t offset, bool is_compressed_pointer, const char* name)
: offset(offset),
is_compressed_pointer(is_compressed_pointer),
name(name) {}
};
class ObjectSlots {
public:
using ObjectSlotsType = ZoneGrowableArray<ObjectSlot>;
explicit ObjectSlots(Thread* thread) {
auto class_table = thread->isolate_group()->class_table();
const intptr_t class_count = class_table->NumCids();
HANDLESCOPE(thread);
auto& cls = Class::Handle(thread->zone());
auto& fields = Array::Handle(thread->zone());
auto& field = Field::Handle(thread->zone());
auto& name = String::Handle(thread->zone());
cid2object_slots_.FillWith(nullptr, 0, class_count);
contains_only_tagged_words_.FillWith(false, 0, class_count);
for (intptr_t cid = 1; cid < class_count; cid++) {
if (!class_table->HasValidClassAt(cid)) continue;
// Non-finalized classes are abstract, so we will not collect any field
// information for them.
cls = class_table->At(cid);
if (!cls.is_finalized()) continue;
auto slots = cid2object_slots_[cid] = new ObjectSlotsType();
for (const auto& entry : OffsetsTable::offsets_table()) {
if (entry.class_id == cid) {
slots->Add(ObjectSlot(entry.offset, entry.is_compressed_pointer,
entry.field_name));
}
}
// The VM doesn't define a layout for the object, so it's a regular Dart
// class.
if (slots->is_empty()) {
// If the class has native fields, the native fields array is the first
// field and therefore starts after the `kWordSize` tagging word.
if (cls.num_native_fields() > 0) {
slots->Add(ObjectSlot(kWordSize, true, "native_fields"));
}
// If the class or any super class is generic, it will have a type
// arguments vector.
const auto tav_offset = cls.host_type_arguments_field_offset();
if (tav_offset != Class::kNoTypeArguments) {
slots->Add(ObjectSlot(tav_offset, true, "type_arguments"));
}
// Add slots for all user-defined instance fields in the hierarchy.
while (!cls.IsNull()) {
fields = cls.fields();
if (!fields.IsNull()) {
for (intptr_t i = 0; i < fields.Length(); ++i) {
field ^= fields.At(i);
if (!field.is_instance()) continue;
name = field.name();
// If the field is unboxed, we don't know the size of it (may be
// multiple words) - but that doesn't matter because
// a) we will process instances using the slots we collect
// (instead of regular GC visitor);
// b) we will not write the value of the field and instead treat
// it like a dummy reference to 0 (like we do with Smis).
slots->Add(ObjectSlot(field.HostOffset(), !field.is_unboxed(),
name.ToCString()));
}
}
cls = cls.SuperClass();
}
}
// We sort the slots, so we'll visit the slots in memory order.
slots->Sort([](const ObjectSlot* a, const ObjectSlot* b) {
return a->offset - b->offset;
});
// As optimization as well as to support variable-length data, we remember
// whether this class has only pure tagged pointers in it, then we can
// safely use regular GC visitors.
bool contains_only_tagged_words = true;
for (auto& slot : *slots) {
if (!slot.is_compressed_pointer) {
contains_only_tagged_words = false;
break;
}
}
#if defined(DEBUG)
// For pure pointer objects, the slots have to start after tagging word
// and be without holes (otherwise, e.g. if a slot was not declared,
// the visitors will visit them but we won't emit the field description in
// the heap snapshot).
if (contains_only_tagged_words) {
intptr_t expected_offset = kWordSize;
for (auto& slot : *slots) {
RELEASE_ASSERT(slot.offset = expected_offset);
expected_offset += kCompressedWordSize;
}
}
ASSERT(contains_only_tagged_words ||
(cid != kArrayCid && cid != kImmutableArrayCid));
#endif // defined(DEBUG)
contains_only_tagged_words_[cid] = contains_only_tagged_words;
}
}
const ObjectSlotsType* ObjectSlotsFor(intptr_t cid) const {
return cid2object_slots_[cid];
}
// Returns `true` if all fields are tagged (i.e. no unboxed fields).
bool ContainsOnlyTaggedPointers(intptr_t cid) {
return contains_only_tagged_words_[cid];
}
private:
GrowableArray<ObjectSlotsType*> cid2object_slots_;
GrowableArray<bool> contains_only_tagged_words_;
};
// The state of a pre-order, depth-first traversal of an object graph.
// When a node is visited, *all* its children are pushed to the stack at once.
// We insert a sentinel between the node and its children on the stack, to
// remember that the node has been visited. The node is kept on the stack while
// its children are processed, to give the visitor a complete chain of parents.
//
// TODO(koda): Potential optimizations:
// - Use tag bits for compact Node and sentinel representations.
class ObjectGraph::Stack : public ObjectPointerVisitor {
public:
explicit Stack(IsolateGroup* isolate_group)
: ObjectPointerVisitor(isolate_group),
include_vm_objects_(true),
data_(kInitialCapacity) {
object_ids_ = new WeakTable();
}
~Stack() {
delete object_ids_;
object_ids_ = nullptr;
}
bool trace_values_through_fields() const override { return true; }
// Marks and pushes. Used to initialize this stack with roots.
// We can use ObjectIdTable normally used by serializers because it
// won't be in use while handling a service request (ObjectGraph's only use).
void VisitPointers(ObjectPtr* first, ObjectPtr* last) override {
for (ObjectPtr* current = first; current <= last; ++current) {
Visit(current, *current);
}
}
#if defined(DART_COMPRESSED_POINTERS)
void VisitCompressedPointers(uword heap_base,
CompressedObjectPtr* first,
CompressedObjectPtr* last) override {
for (CompressedObjectPtr* current = first; current <= last; ++current) {
Visit(current, current->Decompress(heap_base));
}
}
#endif
void Visit(void* ptr, ObjectPtr obj) {
if (obj->IsHeapObject() && !obj->untag()->InVMIsolateHeap() &&
object_ids_->GetValueExclusive(obj) == 0) { // not visited yet
if (!include_vm_objects_ && !IsUserClass(obj->GetClassId())) {
return;
}
object_ids_->SetValueExclusive(obj, 1);
Node node;
node.ptr = ptr;
node.obj = obj;
node.gc_root_type = gc_root_type();
data_.Add(node);
}
}
// Traverses the object graph from the current state.
void TraverseGraph(ObjectGraph::Visitor* visitor) {
while (!data_.is_empty()) {
Node node = data_.Last();
if (node.ptr == kSentinel) {
data_.RemoveLast();
// The node below the sentinel has already been visited.
data_.RemoveLast();
continue;
}
ObjectPtr obj = node.obj;
ASSERT(obj->IsHeapObject());
Node sentinel;
sentinel.ptr = kSentinel;
data_.Add(sentinel);
StackIterator it(this, data_.length() - 2);
visitor->gc_root_type = node.gc_root_type;
Visitor::Direction direction = visitor->VisitObject(&it);
if (direction == ObjectGraph::Visitor::kAbort) {
break;
}
if (direction == ObjectGraph::Visitor::kProceed) {
set_gc_root_type(node.gc_root_type);
ASSERT(obj->IsHeapObject());
switch (obj->GetClassId()) {
case kWeakArrayCid:
VisitWeakArray(static_cast<WeakArrayPtr>(obj));
break;
case kWeakReferenceCid:
VisitWeakReference(static_cast<WeakReferencePtr>(obj));
break;
case kFinalizerEntryCid:
VisitFinalizerEntry(static_cast<FinalizerEntryPtr>(obj));
break;
default:
obj->untag()->VisitPointers(this);
break;
}
clear_gc_root_type();
}
}
}
void VisitWeakArray(WeakArrayPtr array) {}
void VisitWeakReference(WeakReferencePtr ref) {
#if !defined(DART_COMPRESSED_POINTERS)
VisitPointers(&ref->untag()->type_arguments_,
&ref->untag()->type_arguments_);
#else
VisitCompressedPointers(ref->heap_base(), &ref->untag()->type_arguments_,
&ref->untag()->type_arguments_);
#endif
}
void VisitFinalizerEntry(FinalizerEntryPtr entry) {
#if !defined(DART_COMPRESSED_POINTERS)
VisitPointers(&entry->untag()->token_, &entry->untag()->token_);
VisitPointers(&entry->untag()->next_, &entry->untag()->next_);
#else
VisitCompressedPointers(entry->heap_base(), &entry->untag()->token_,
&entry->untag()->token_);
VisitCompressedPointers(entry->heap_base(), &entry->untag()->next_,
&entry->untag()->next_);
#endif
}
bool visit_weak_persistent_handles() const override {
return visit_weak_persistent_handles_;
}
void set_visit_weak_persistent_handles(bool value) {
visit_weak_persistent_handles_ = value;
}
bool include_vm_objects_;
private:
struct Node {
void* ptr; // kSentinel for the sentinel node.
ObjectPtr obj;
const char* gc_root_type;
};
bool visit_weak_persistent_handles_ = false;
static ObjectPtr* const kSentinel;
static constexpr intptr_t kInitialCapacity = 1024;
static constexpr intptr_t kNoParent = -1;
intptr_t Parent(intptr_t index) const {
// The parent is just below the next sentinel.
for (intptr_t i = index; i >= 1; --i) {
if (data_[i].ptr == kSentinel) {
return i - 1;
}
}
return kNoParent;
}
// During the iteration of the heap we are already at a safepoint, so there is
// no need to let the GC know about [object_ids_] (i.e. GC cannot run while we
// use [object_ids]).
WeakTable* object_ids_ = nullptr;
GrowableArray<Node> data_;
friend class StackIterator;
DISALLOW_COPY_AND_ASSIGN(Stack);
};
ObjectPtr* const ObjectGraph::Stack::kSentinel = nullptr;
ObjectPtr ObjectGraph::StackIterator::Get() const {
return stack_->data_[index_].obj;
}
bool ObjectGraph::StackIterator::MoveToParent() {
intptr_t parent = stack_->Parent(index_);
if (parent == Stack::kNoParent) {
return false;
} else {
index_ = parent;
return true;
}
}
intptr_t ObjectGraph::StackIterator::OffsetFromParent() const {
intptr_t parent_index = stack_->Parent(index_);
if (parent_index == Stack::kNoParent) {
return -1;
}
Stack::Node parent = stack_->data_[parent_index];
uword parent_start = UntaggedObject::ToAddr(parent.obj);
Stack::Node child = stack_->data_[index_];
uword child_ptr_addr = reinterpret_cast<uword>(child.ptr);
intptr_t offset = child_ptr_addr - parent_start;
if (offset > 0 && offset < parent.obj->untag()->HeapSize()) {
return offset;
} else {
// Some internal VM objects visit pointers not contained within the parent.
// For instance, UntaggedCode::VisitCodePointers visits pointers in
// instructions.
ASSERT(!parent.obj->IsDartInstance());
return -1;
}
}
static void IterateUserFields(ObjectPointerVisitor* visitor) {
visitor->set_gc_root_type("user global");
Thread* thread = Thread::Current();
// Scope to prevent handles create here from appearing as stack references.
HANDLESCOPE(thread);
Zone* zone = thread->zone();
const GrowableObjectArray& libraries = GrowableObjectArray::Handle(
zone, thread->isolate_group()->object_store()->libraries());
Library& library = Library::Handle(zone);
Object& entry = Object::Handle(zone);
Class& cls = Class::Handle(zone);
Array& fields = Array::Handle(zone);
Field& field = Field::Handle(zone);
for (intptr_t i = 0; i < libraries.Length(); i++) {
library ^= libraries.At(i);
DictionaryIterator entries(library);
while (entries.HasNext()) {
entry = entries.GetNext();
if (entry.IsClass()) {
cls ^= entry.ptr();
fields = cls.fields();
for (intptr_t j = 0; j < fields.Length(); j++) {
field ^= fields.At(j);
ObjectPtr ptr = field.ptr();
visitor->VisitPointer(&ptr);
}
} else if (entry.IsField()) {
field ^= entry.ptr();
ObjectPtr ptr = field.ptr();
visitor->VisitPointer(&ptr);
}
}
}
visitor->clear_gc_root_type();
}
ObjectGraph::ObjectGraph(Thread* thread) : ThreadStackResource(thread) {
// The VM isolate has all its objects pre-marked, so iterating over it
// would be a no-op.
ASSERT(thread->isolate() != Dart::vm_isolate());
}
ObjectGraph::~ObjectGraph() {}
void ObjectGraph::IterateObjects(ObjectGraph::Visitor* visitor) {
Stack stack(isolate_group());
stack.set_visit_weak_persistent_handles(
visitor->visit_weak_persistent_handles());
isolate_group()->VisitObjectPointers(&stack,
ValidationPolicy::kDontValidateFrames);
stack.TraverseGraph(visitor);
}
void ObjectGraph::IterateUserObjects(ObjectGraph::Visitor* visitor) {
Stack stack(isolate_group());
stack.set_visit_weak_persistent_handles(
visitor->visit_weak_persistent_handles());
IterateUserFields(&stack);
stack.include_vm_objects_ = false;
stack.TraverseGraph(visitor);
}
void ObjectGraph::IterateObjectsFrom(const Object& root,
ObjectGraph::Visitor* visitor) {
Stack stack(isolate_group());
stack.set_visit_weak_persistent_handles(
visitor->visit_weak_persistent_handles());
ObjectPtr root_raw = root.ptr();
stack.VisitPointer(&root_raw);
stack.TraverseGraph(visitor);
}
class InstanceAccumulator : public ObjectVisitor {
public:
InstanceAccumulator(ObjectGraph::Stack* stack, intptr_t class_id)
: stack_(stack), class_id_(class_id) {}
void VisitObject(ObjectPtr obj) override {
if (obj->GetClassId() == class_id_) {
ObjectPtr rawobj = obj;
stack_->VisitPointer(&rawobj);
}
}
private:
ObjectGraph::Stack* stack_;
const intptr_t class_id_;
DISALLOW_COPY_AND_ASSIGN(InstanceAccumulator);
};
void ObjectGraph::IterateObjectsFrom(intptr_t class_id,
HeapIterationScope* iteration,
ObjectGraph::Visitor* visitor) {
Stack stack(isolate_group());
InstanceAccumulator accumulator(&stack, class_id);
iteration->IterateObjectsNoImagePages(&accumulator);
stack.TraverseGraph(visitor);
}
class SizeVisitor : public ObjectGraph::Visitor {
public:
SizeVisitor() : size_(0) {}
intptr_t size() const { return size_; }
virtual bool ShouldSkip(ObjectPtr obj) const { return false; }
virtual Direction VisitObject(ObjectGraph::StackIterator* it) {
ObjectPtr obj = it->Get();
if (ShouldSkip(obj)) {
return kBacktrack;
}
size_ += obj->untag()->HeapSize();
return kProceed;
}
private:
intptr_t size_;
};
class SizeExcludingObjectVisitor : public SizeVisitor {
public:
explicit SizeExcludingObjectVisitor(const Object& skip) : skip_(skip) {}
virtual bool ShouldSkip(ObjectPtr obj) const { return obj == skip_.ptr(); }
private:
const Object& skip_;
};
class SizeExcludingClassVisitor : public SizeVisitor {
public:
explicit SizeExcludingClassVisitor(intptr_t skip) : skip_(skip) {}
virtual bool ShouldSkip(ObjectPtr obj) const {
return obj->GetClassId() == skip_;
}
private:
const intptr_t skip_;
};
intptr_t ObjectGraph::SizeRetainedByInstance(const Object& obj) {
HeapIterationScope iteration_scope(Thread::Current(), true);
SizeVisitor total;
IterateObjects(&total);
intptr_t size_total = total.size();
SizeExcludingObjectVisitor excluding_obj(obj);
IterateObjects(&excluding_obj);
intptr_t size_excluding_obj = excluding_obj.size();
return size_total - size_excluding_obj;
}
intptr_t ObjectGraph::SizeReachableByInstance(const Object& obj) {
HeapIterationScope iteration_scope(Thread::Current(), true);
SizeVisitor total;
IterateObjectsFrom(obj, &total);
return total.size();
}
intptr_t ObjectGraph::SizeRetainedByClass(intptr_t class_id) {
HeapIterationScope iteration_scope(Thread::Current(), true);
SizeVisitor total;
IterateObjects(&total);
intptr_t size_total = total.size();
SizeExcludingClassVisitor excluding_class(class_id);
IterateObjects(&excluding_class);
intptr_t size_excluding_class = excluding_class.size();
return size_total - size_excluding_class;
}
intptr_t ObjectGraph::SizeReachableByClass(intptr_t class_id) {
HeapIterationScope iteration_scope(Thread::Current(), true);
SizeVisitor total;
IterateObjectsFrom(class_id, &iteration_scope, &total);
return total.size();
}
class RetainingPathVisitor : public ObjectGraph::Visitor {
public:
// We cannot use a GrowableObjectArray, since we must not trigger GC.
RetainingPathVisitor(ObjectPtr obj, const Array& path)
: thread_(Thread::Current()), obj_(obj), path_(path), length_(0) {}
intptr_t length() const { return length_; }
virtual bool visit_weak_persistent_handles() const { return true; }
bool ShouldSkip(ObjectPtr obj) {
// A retaining path through ICData is never the only retaining path,
// and it is less informative than its alternatives.
intptr_t cid = obj->GetClassId();
switch (cid) {
case kICDataCid:
return true;
default:
return false;
}
}
bool ShouldStop(ObjectPtr obj) {
// A static field is considered a root from a language point of view.
if (obj->IsField()) {
const Field& field = Field::Handle(static_cast<FieldPtr>(obj));
return field.is_static();
}
return false;
}
void StartList() { was_last_array_ = false; }
intptr_t HideNDescendant(ObjectPtr obj) {
// A GrowableObjectArray overwrites its internal storage.
// Keeping both of them in the list is redundant.
if (was_last_array_ && obj->IsGrowableObjectArray()) {
was_last_array_ = false;
return 1;
}
// A LinkedHasMap overwrites its internal storage.
// Keeping both of them in the list is redundant.
if (was_last_array_ && obj->IsMap()) {
was_last_array_ = false;
return 1;
}
was_last_array_ = obj->IsArray();
return 0;
}
virtual Direction VisitObject(ObjectGraph::StackIterator* it) {
if (it->Get() != obj_) {
if (ShouldSkip(it->Get())) {
return kBacktrack;
} else {
return kProceed;
}
} else {
HANDLESCOPE(thread_);
Object& current = Object::Handle();
Smi& offset_from_parent = Smi::Handle();
StartList();
do {
// We collapse the backingstore of some internal objects.
length_ -= HideNDescendant(it->Get());
intptr_t obj_index = length_ * 2;
intptr_t offset_index = obj_index + 1;
if (!path_.IsNull() && offset_index < path_.Length()) {
current = it->Get();
path_.SetAt(obj_index, current);
offset_from_parent = Smi::New(it->OffsetFromParent());
path_.SetAt(offset_index, offset_from_parent);
}
++length_;
} while (!ShouldStop(it->Get()) && it->MoveToParent());
return kAbort;
}
}
private:
Thread* thread_;
ObjectPtr obj_;
const Array& path_;
intptr_t length_;
bool was_last_array_;
};
ObjectGraph::RetainingPathResult ObjectGraph::RetainingPath(Object* obj,
const Array& path) {
HeapIterationScope iteration_scope(Thread::Current(), true);
// To break the trivial path, the handle 'obj' is temporarily cleared during
// the search, but restored before returning.
ObjectPtr raw = obj->ptr();
*obj = Object::null();
RetainingPathVisitor visitor(raw, path);
IterateUserObjects(&visitor);
if (visitor.length() == 0) {
IterateObjects(&visitor);
}
*obj = raw;
return {visitor.length(), visitor.gc_root_type};
}
class InboundReferencesVisitor : public ObjectVisitor,
public ObjectPointerVisitor {
public:
// We cannot use a GrowableObjectArray, since we must not trigger GC.
InboundReferencesVisitor(Isolate* isolate,
ObjectPtr target,
const Array& references,
Object* scratch)
: ObjectPointerVisitor(isolate->group()),
source_(nullptr),
target_(target),
references_(references),
scratch_(scratch),
length_(0) {
ASSERT(Thread::Current()->no_safepoint_scope_depth() != 0);
}
bool trace_values_through_fields() const override { return true; }
intptr_t length() const { return length_; }
void VisitObject(ObjectPtr raw_obj) override {
source_ = raw_obj;
raw_obj->untag()->VisitPointers(this);
}
void VisitPointers(ObjectPtr* first, ObjectPtr* last) override {
for (ObjectPtr* current_ptr = first; current_ptr <= last; current_ptr++) {
ObjectPtr current_obj = *current_ptr;
if (current_obj == target_) {
intptr_t obj_index = length_ * 2;
intptr_t offset_index = obj_index + 1;
if (!references_.IsNull() && offset_index < references_.Length()) {
*scratch_ = source_;
references_.SetAt(obj_index, *scratch_);
*scratch_ = Smi::New(0);
uword source_start = UntaggedObject::ToAddr(source_);
uword current_ptr_addr = reinterpret_cast<uword>(current_ptr);
intptr_t offset = current_ptr_addr - source_start;
if (offset > 0 && offset < source_->untag()->HeapSize()) {
*scratch_ = Smi::New(offset);
} else {
// Some internal VM objects visit pointers not contained within the
// parent. For instance, UntaggedCode::VisitCodePointers visits
// pointers in instructions.
ASSERT(!source_->IsDartInstance());
*scratch_ = Smi::New(-1);
}
references_.SetAt(offset_index, *scratch_);
}
++length_;
}
}
}
#if defined(DART_COMPRESSED_POINTERS)
void VisitCompressedPointers(uword heap_base,
CompressedObjectPtr* first,
CompressedObjectPtr* last) override {
for (CompressedObjectPtr* current_ptr = first; current_ptr <= last;
current_ptr++) {
ObjectPtr current_obj = current_ptr->Decompress(heap_base);
if (current_obj == target_) {
intptr_t obj_index = length_ * 2;
intptr_t offset_index = obj_index + 1;
if (!references_.IsNull() && offset_index < references_.Length()) {
*scratch_ = source_;
references_.SetAt(obj_index, *scratch_);
*scratch_ = Smi::New(0);
uword source_start = UntaggedObject::ToAddr(source_);
uword current_ptr_addr = reinterpret_cast<uword>(current_ptr);
intptr_t offset = current_ptr_addr - source_start;
if (offset > 0 && offset < source_->untag()->HeapSize()) {
*scratch_ = Smi::New(offset);
} else {
// Some internal VM objects visit pointers not contained within the
// parent. For instance, UntaggedCode::VisitCodePointers visits
// pointers in instructions.
ASSERT(!source_->IsDartInstance());
*scratch_ = Smi::New(-1);
}
references_.SetAt(offset_index, *scratch_);
}
++length_;
}
}
}
#endif
private:
ObjectPtr source_;
ObjectPtr target_;
const Array& references_;
Object* scratch_;
intptr_t length_;
};
intptr_t ObjectGraph::InboundReferences(Object* obj, const Array& references) {
Object& scratch = Object::Handle();
HeapIterationScope iteration(Thread::Current());
NoSafepointScope no_safepoint;
InboundReferencesVisitor visitor(isolate(), obj->ptr(), references, &scratch);
iteration.IterateObjects(&visitor);
return visitor.length();
}
// Each Page is divided into blocks of size kBlockSize. Each object belongs
// to the block containing its header word.
// When generating a heap snapshot, we assign objects sequential ids in heap
// iteration order. A bitvector is computed that indicates the number of objects
// in each block, so the id of any object in the block can be found be adding
// the number of bits set before the object to the block's first id.
// Compare ForwardingBlock used for heap compaction.
class CountingBlock {
public:
void Clear() {
base_count_ = 0;
count_bitvector_ = 0;
}
intptr_t Lookup(uword addr) const {
uword block_offset = addr & ~kBlockMask;
intptr_t bitvector_shift = block_offset >> kObjectAlignmentLog2;
ASSERT(bitvector_shift < kBitsPerWord);
uword preceding_bitmask = (static_cast<uword>(1) << bitvector_shift) - 1;
return base_count_ +
Utils::CountOneBitsWord(count_bitvector_ & preceding_bitmask);
}
void Record(uword old_addr, intptr_t id) {
if (base_count_ == 0) {
ASSERT(count_bitvector_ == 0);
base_count_ = id; // First object in the block.
}
uword block_offset = old_addr & ~kBlockMask;
intptr_t bitvector_shift = block_offset >> kObjectAlignmentLog2;
ASSERT(bitvector_shift < kBitsPerWord);
count_bitvector_ |= static_cast<uword>(1) << bitvector_shift;
}
private:
intptr_t base_count_;
uword count_bitvector_;
COMPILE_ASSERT(kBitVectorWordsPerBlock == 1);
DISALLOW_COPY_AND_ASSIGN(CountingBlock);
};
class CountingPage {
public:
void Clear() {
for (intptr_t i = 0; i < kBlocksPerPage; i++) {
blocks_[i].Clear();
}
}
intptr_t Lookup(uword addr) { return BlockFor(addr)->Lookup(addr); }
void Record(uword addr, intptr_t id) {
return BlockFor(addr)->Record(addr, id);
}
CountingBlock* BlockFor(uword addr) {
intptr_t page_offset = addr & ~kPageMask;
intptr_t block_number = page_offset / kBlockSize;
ASSERT(block_number >= 0);
ASSERT(block_number <= kBlocksPerPage);
return &blocks_[block_number];
}
private:
CountingBlock blocks_[kBlocksPerPage];
DISALLOW_ALLOCATION();
DISALLOW_IMPLICIT_CONSTRUCTORS(CountingPage);
};
void HeapSnapshotWriter::EnsureAvailable(intptr_t needed) {
intptr_t available = capacity_ - size_;
if (available >= needed) {
return;
}
if (buffer_ != nullptr) {
Flush();
}
ASSERT(buffer_ == nullptr);
intptr_t chunk_size = kPreferredChunkSize;
const intptr_t reserved_prefix = writer_->ReserveChunkPrefixSize();
if (chunk_size < (reserved_prefix + needed)) {
chunk_size = reserved_prefix + needed;
}
buffer_ = reinterpret_cast<uint8_t*>(malloc(chunk_size));
size_ = reserved_prefix;
capacity_ = chunk_size;
}
void HeapSnapshotWriter::Flush(bool last) {
if (size_ == 0 && !last) {
return;
}
writer_->WriteChunk(buffer_, size_, last);
buffer_ = nullptr;
size_ = 0;
capacity_ = 0;
}
void HeapSnapshotWriter::SetupCountingPages() {
for (intptr_t i = 0; i < kMaxImagePages; i++) {
image_page_ranges_[i].base = 0;
image_page_ranges_[i].size = 0;
}
intptr_t next_offset = 0;
Page* image_page =
Dart::vm_isolate_group()->heap()->old_space()->image_pages_;
while (image_page != nullptr) {
RELEASE_ASSERT(next_offset <= kMaxImagePages);
image_page_ranges_[next_offset].base = image_page->object_start();
image_page_ranges_[next_offset].size =
image_page->object_end() - image_page->object_start();
image_page = image_page->next();
next_offset++;
}
image_page = isolate_group()->heap()->old_space()->image_pages_;
while (image_page != nullptr) {
RELEASE_ASSERT(next_offset <= kMaxImagePages);
image_page_ranges_[next_offset].base = image_page->object_start();
image_page_ranges_[next_offset].size =
image_page->object_end() - image_page->object_start();
image_page = image_page->next();
next_offset++;
}
Page* page = isolate_group()->heap()->old_space()->pages_;
while (page != nullptr) {
page->forwarding_page();
CountingPage* counting_page =
reinterpret_cast<CountingPage*>(page->forwarding_page());
ASSERT(counting_page != nullptr);
counting_page->Clear();
page = page->next();
}
}
bool HeapSnapshotWriter::OnImagePage(ObjectPtr obj) const {
const uword addr = UntaggedObject::ToAddr(obj);
for (intptr_t i = 0; i < kMaxImagePages; i++) {
if ((addr - image_page_ranges_[i].base) < image_page_ranges_[i].size) {
return true;
}
}
return false;
}
CountingPage* HeapSnapshotWriter::FindCountingPage(ObjectPtr obj) const {
if (obj->IsOldObject() && !OnImagePage(obj)) {
// On a regular or large page.
Page* page = Page::Of(obj);
return reinterpret_cast<CountingPage*>(page->forwarding_page());
}
// On an image page or in new space.
return nullptr;
}
void HeapSnapshotWriter::AssignObjectId(ObjectPtr obj) {
if (!obj->IsHeapObject()) {
thread()->heap()->SetObjectId(obj, ++object_count_);
return;
}
CountingPage* counting_page = FindCountingPage(obj);
if (counting_page != nullptr) {
// Likely: object on an ordinary page.
counting_page->Record(UntaggedObject::ToAddr(obj), ++object_count_);
} else {
// Unlikely: new space object, or object on a large or image page.
thread()->heap()->SetObjectId(obj, ++object_count_);
}
}
intptr_t HeapSnapshotWriter::GetObjectId(ObjectPtr obj) const {
if (!obj->IsHeapObject()) {
intptr_t id = thread()->heap()->GetObjectId(obj);
ASSERT(id != 0);
return id;
}
if (FLAG_write_protect_code && obj->IsInstructions() && !OnImagePage(obj)) {
// A non-writable alias mapping may exist for instruction pages.
obj = Page::ToWritable(obj);
}
CountingPage* counting_page = FindCountingPage(obj);
intptr_t id;
if (counting_page != nullptr) {
// Likely: object on an ordinary page.
id = counting_page->Lookup(UntaggedObject::ToAddr(obj));
} else {
// Unlikely: new space object, or object on a large or image page.
id = thread()->heap()->GetObjectId(obj);
}
ASSERT(id != 0);
return id;
}
void HeapSnapshotWriter::ClearObjectIds() {
thread()->heap()->ResetObjectIdTable();
}
void HeapSnapshotWriter::CountReferences(intptr_t count) {
reference_count_ += count;
}
void HeapSnapshotWriter::CountExternalProperty() {
external_property_count_ += 1;
}
void HeapSnapshotWriter::AddSmi(SmiPtr smi) {
if (thread()->heap()->GetObjectId(smi) == WeakTable::kNoValue) {
thread()->heap()->SetObjectId(smi, -1);
smis_.Add(smi);
}
}
class Pass1Visitor : public ObjectVisitor,
public ObjectPointerVisitor,
public HandleVisitor {
public:
explicit Pass1Visitor(HeapSnapshotWriter* writer, ObjectSlots* object_slots)
: ObjectVisitor(),
ObjectPointerVisitor(IsolateGroup::Current()),
HandleVisitor(Thread::Current()),
writer_(writer),
object_slots_(object_slots) {}
void VisitObject(ObjectPtr obj) override {
if (obj->IsPseudoObject()) return;
writer_->AssignObjectId(obj);
const auto cid = obj->GetClassId();
if (object_slots_->ContainsOnlyTaggedPointers(cid)) {
obj->untag()->VisitPointersPrecise(this);
} else {
for (auto& slot : *object_slots_->ObjectSlotsFor(cid)) {
if (slot.is_compressed_pointer) {
auto target = reinterpret_cast<CompressedObjectPtr*>(
UntaggedObject::ToAddr(obj->untag()) + slot.offset);
VisitCompressedPointers(obj->heap_base(), target, target);
} else {
writer_->CountReferences(1);
}
}
}
}
void VisitPointers(ObjectPtr* from, ObjectPtr* to) override {
for (ObjectPtr* ptr = from; ptr <= to; ptr++) {
ObjectPtr obj = *ptr;
if (!obj->IsHeapObject()) {
writer_->AddSmi(static_cast<SmiPtr>(obj));
}
writer_->CountReferences(1);
}
}
#if defined(DART_COMPRESSED_POINTERS)
void VisitCompressedPointers(uword heap_base,
CompressedObjectPtr* from,
CompressedObjectPtr* to) override {
for (CompressedObjectPtr* ptr = from; ptr <= to; ptr++) {
ObjectPtr obj = ptr->Decompress(heap_base);
if (!obj->IsHeapObject()) {
writer_->AddSmi(static_cast<SmiPtr>(obj));
}
writer_->CountReferences(1);
}
}
#endif
void VisitHandle(uword addr) override {
FinalizablePersistentHandle* weak_persistent_handle =
reinterpret_cast<FinalizablePersistentHandle*>(addr);
if (!weak_persistent_handle->ptr()->IsHeapObject()) {
return; // Free handle.
}
writer_->CountExternalProperty();
}
private:
HeapSnapshotWriter* const writer_;
ObjectSlots* object_slots_;
DISALLOW_COPY_AND_ASSIGN(Pass1Visitor);
};
class CountImagePageRefs : public ObjectVisitor {
public:
CountImagePageRefs() : ObjectVisitor() {}
void VisitObject(ObjectPtr obj) override {
if (obj->IsPseudoObject()) return;
count_++;
}
intptr_t count() const { return count_; }
private:
intptr_t count_ = 0;
DISALLOW_COPY_AND_ASSIGN(CountImagePageRefs);
};
class WriteImagePageRefs : public ObjectVisitor {
public:
explicit WriteImagePageRefs(HeapSnapshotWriter* writer)
: ObjectVisitor(), writer_(writer) {}
void VisitObject(ObjectPtr obj) override {
if (obj->IsPseudoObject()) return;
#if defined(DEBUG)
count_++;
#endif
writer_->WriteUnsigned(writer_->GetObjectId(obj));
}
#if defined(DEBUG)
intptr_t count() const { return count_; }
#endif
private:
HeapSnapshotWriter* const writer_;
#if defined(DEBUG)
intptr_t count_ = 0;
#endif
DISALLOW_COPY_AND_ASSIGN(WriteImagePageRefs);
};
enum NonReferenceDataTags {
kNoData = 0,
kNullData,
kBoolData,
kIntData,
kDoubleData,
kLatin1Data,
kUTF16Data,
kLengthData,
kNameData,
};
static constexpr intptr_t kMaxStringElements = 128;
enum ExtraCids {
kRootExtraCid = 1, // 1-origin
kImagePageExtraCid = 2,
kIsolateExtraCid = 3,
kNumExtraCids = 3,
};
class Pass2Visitor : public ObjectVisitor,
public ObjectPointerVisitor,
public HandleVisitor {
public:
explicit Pass2Visitor(HeapSnapshotWriter* writer, ObjectSlots* object_slots)
: ObjectVisitor(),
ObjectPointerVisitor(IsolateGroup::Current()),
HandleVisitor(Thread::Current()),
writer_(writer),
object_slots_(object_slots) {}
void VisitObject(ObjectPtr obj) override {
if (obj->IsPseudoObject()) return;
intptr_t cid = obj->GetClassId();
writer_->WriteUnsigned(cid + kNumExtraCids);
writer_->WriteUnsigned(discount_sizes_ ? 0 : obj->untag()->HeapSize());
if (cid == kNullCid) {
writer_->WriteUnsigned(kNullData);
} else if (cid == kBoolCid) {
writer_->WriteUnsigned(kBoolData);
writer_->WriteUnsigned(
static_cast<uintptr_t>(static_cast<BoolPtr>(obj)->untag()->value_));
} else if (cid == kSentinelCid) {
if (obj == Object::sentinel().ptr()) {
writer_->WriteUnsigned(kNameData);
writer_->WriteUtf8("uninitialized");
} else if (obj == Object::transition_sentinel().ptr()) {
writer_->WriteUnsigned(kNameData);
writer_->WriteUtf8("initializing");
} else {
writer_->WriteUnsigned(kNoData);
}
} else if (cid == kSmiCid) {
UNREACHABLE();
} else if (cid == kMintCid) {
writer_->WriteUnsigned(kIntData);
writer_->WriteSigned(static_cast<MintPtr>(obj)->untag()->value_);
} else if (cid == kDoubleCid) {
writer_->WriteUnsigned(kDoubleData);
writer_->WriteBytes(&(static_cast<DoublePtr>(obj)->untag()->value_),
sizeof(double));
} else if (cid == kOneByteStringCid) {
OneByteStringPtr str = static_cast<OneByteStringPtr>(obj);
intptr_t len = Smi::Value(str->untag()->length());
intptr_t trunc_len = Utils::Minimum(len, kMaxStringElements);
writer_->WriteUnsigned(kLatin1Data);
writer_->WriteUnsigned(len);
writer_->WriteUnsigned(trunc_len);
writer_->WriteBytes(&str->untag()->data()[0], trunc_len);
} else if (cid == kExternalOneByteStringCid) {
ExternalOneByteStringPtr str = static_cast<ExternalOneByteStringPtr>(obj);
intptr_t len = Smi::Value(str->untag()->length());
intptr_t trunc_len = Utils::Minimum(len, kMaxStringElements);
writer_->WriteUnsigned(kLatin1Data);
writer_->WriteUnsigned(len);
writer_->WriteUnsigned(trunc_len);
writer_->WriteBytes(&str->untag()->external_data_[0], trunc_len);
} else if (cid == kTwoByteStringCid) {
TwoByteStringPtr str = static_cast<TwoByteStringPtr>(obj);
intptr_t len = Smi::Value(str->untag()->length());
intptr_t trunc_len = Utils::Minimum(len, kMaxStringElements);
writer_->WriteUnsigned(kUTF16Data);
writer_->WriteUnsigned(len);
writer_->WriteUnsigned(trunc_len);
writer_->WriteBytes(&str->untag()->data()[0], trunc_len * 2);
} else if (cid == kExternalTwoByteStringCid) {
ExternalTwoByteStringPtr str = static_cast<ExternalTwoByteStringPtr>(obj);
intptr_t len = Smi::Value(str->untag()->length());
intptr_t trunc_len = Utils::Minimum(len, kMaxStringElements);
writer_->WriteUnsigned(kUTF16Data);
writer_->WriteUnsigned(len);
writer_->WriteUnsigned(trunc_len);
writer_->WriteBytes(&str->untag()->external_data_[0], trunc_len * 2);
} else if (cid == kArrayCid || cid == kImmutableArrayCid) {
writer_->WriteUnsigned(kLengthData);
writer_->WriteUnsigned(
Smi::Value(static_cast<ArrayPtr>(obj)->untag()->length()));
} else if (cid == kGrowableObjectArrayCid) {
writer_->WriteUnsigned(kLengthData);
writer_->WriteUnsigned(Smi::Value(
static_cast<GrowableObjectArrayPtr>(obj)->untag()->length()));
} else if (cid == kMapCid || cid == kConstMapCid) {
writer_->WriteUnsigned(kLengthData);
writer_->WriteUnsigned(
Smi::Value(static_cast<MapPtr>(obj)->untag()->used_data()));
} else if (cid == kSetCid || cid == kConstSetCid) {
writer_->WriteUnsigned(kLengthData);
writer_->WriteUnsigned(
Smi::Value(static_cast<SetPtr>(obj)->untag()->used_data()));
} else if (cid == kObjectPoolCid) {
writer_->WriteUnsigned(kLengthData);
writer_->WriteUnsigned(static_cast<ObjectPoolPtr>(obj)->untag()->length_);
} else if (IsTypedDataClassId(cid)) {
writer_->WriteUnsigned(kLengthData);
writer_->WriteUnsigned(
Smi::Value(static_cast<TypedDataPtr>(obj)->untag()->length()));
} else if (IsExternalTypedDataClassId(cid)) {
writer_->WriteUnsigned(kLengthData);
writer_->WriteUnsigned(Smi::Value(
static_cast<ExternalTypedDataPtr>(obj)->untag()->length()));
} else if (cid == kFunctionCid) {
writer_->WriteUnsigned(kNameData);
ScrubAndWriteUtf8(static_cast<FunctionPtr>(obj)->untag()->name());
} else if (cid == kCodeCid) {
ObjectPtr owner = static_cast<CodePtr>(obj)->untag()->owner_;
if (!owner->IsHeapObject()) {
// Precompiler removed owner object from the snapshot,
// only leaving Smi classId.
writer_->WriteUnsigned(kNoData);
} else if (owner->IsFunction()) {
writer_->WriteUnsigned(kNameData);
ScrubAndWriteUtf8(static_cast<FunctionPtr>(owner)->untag()->name());
} else if (owner->IsClass()) {
writer_->WriteUnsigned(kNameData);
ScrubAndWriteUtf8(static_cast<ClassPtr>(owner)->untag()->name());
} else {
writer_->WriteUnsigned(kNoData);
}
} else if (cid == kFieldCid) {
writer_->WriteUnsigned(kNameData);
ScrubAndWriteUtf8(static_cast<FieldPtr>(obj)->untag()->name());
} else if (cid == kClassCid) {
writer_->WriteUnsigned(kNameData);
ScrubAndWriteUtf8(static_cast<ClassPtr>(obj)->untag()->name());
} else if (cid == kLibraryCid) {
writer_->WriteUnsigned(kNameData);
ScrubAndWriteUtf8(static_cast<LibraryPtr>(obj)->untag()->url());
} else if (cid == kScriptCid) {
writer_->WriteUnsigned(kNameData);
ScrubAndWriteUtf8(static_cast<ScriptPtr>(obj)->untag()->url());
} else if (cid == kTypeArgumentsCid) {
// Handle scope so we do not change the root set.
// We are assuming that TypeArguments::PrintSubvectorName never allocates
// objects or zone handles.
HANDLESCOPE(thread());
const TypeArguments& args =
TypeArguments::Handle(static_cast<TypeArgumentsPtr>(obj));
TextBuffer buffer(128);
args.PrintSubvectorName(0, args.Length(), TypeArguments::kScrubbedName,
&buffer);
writer_->WriteUnsigned(kNameData);
writer_->WriteUtf8(buffer.buffer());
} else {
writer_->WriteUnsigned(kNoData);
}
if (object_slots_->ContainsOnlyTaggedPointers(cid)) {
DoCount();
obj->untag()->VisitPointersPrecise(this);
DoWrite();
obj->untag()->VisitPointersPrecise(this);
} else {
auto slots = object_slots_->ObjectSlotsFor(cid);
DoCount();
counted_ += slots->length();
DoWrite();
for (auto& slot : *slots) {
if (slot.is_compressed_pointer) {
auto target = reinterpret_cast<CompressedObjectPtr*>(
UntaggedObject::ToAddr(obj->untag()) + slot.offset);
VisitCompressedPointers(obj->heap_base(), target, target);
} else {
writer_->WriteUnsigned(0);
}
written_++;
total_++;
}
}
}
void ScrubAndWriteUtf8(StringPtr str) {
if (str == String::null()) {
writer_->WriteUtf8("null");
} else {
String handle;
handle = str;
char* value = handle.ToMallocCString();
writer_->ScrubAndWriteUtf8(value);
free(value);
}
}
void set_discount_sizes(bool value) { discount_sizes_ = value; }
void DoCount() {
writing_ = false;
counted_ = 0;
written_ = 0;
}
void DoWrite() {
writing_ = true;
writer_->WriteUnsigned(counted_);
}
void VisitPointers(ObjectPtr* from, ObjectPtr* to) override {
if (writing_) {
for (ObjectPtr* ptr = from; ptr <= to; ptr++) {
ObjectPtr target = *ptr;
written_++;
total_++;
writer_->WriteUnsigned(writer_->GetObjectId(target));
}
} else {
intptr_t count = to - from + 1;
ASSERT(count >= 0);
counted_ += count;
}
}
#if defined(DART_COMPRESSED_POINTERS)
void VisitCompressedPointers(uword heap_base,
CompressedObjectPtr* from,
CompressedObjectPtr* to) override {
if (writing_) {
for (CompressedObjectPtr* ptr = from; ptr <= to; ptr++) {
ObjectPtr target = ptr->Decompress(heap_base);
written_++;
total_++;
writer_->WriteUnsigned(writer_->GetObjectId(target));
}
} else {
intptr_t count = to - from + 1;
ASSERT(count >= 0);
counted_ += count;
}
}
#endif
void VisitHandle(uword addr) override {
FinalizablePersistentHandle* weak_persistent_handle =
reinterpret_cast<FinalizablePersistentHandle*>(addr);
if (!weak_persistent_handle->ptr()->IsHeapObject()) {
return; // Free handle.
}
writer_->WriteUnsigned(writer_->GetObjectId(weak_persistent_handle->ptr()));
writer_->WriteUnsigned(weak_persistent_handle->external_size());
// Attempt to include a native symbol name.
auto const name = NativeSymbolResolver::LookupSymbolName(
reinterpret_cast<uword>(weak_persistent_handle->callback()), nullptr);
writer_->WriteUtf8((name == nullptr) ? "Unknown native function" : name);
if (name != nullptr) {
NativeSymbolResolver::FreeSymbolName(name);
}
}
void CountExtraRefs(intptr_t count) {
ASSERT(!writing_);
counted_ += count;
}
void WriteExtraRef(intptr_t oid) {
ASSERT(writing_);
written_++;
writer_->WriteUnsigned(oid);
}
private:
IsolateGroup* isolate_group_;
HeapSnapshotWriter* const writer_;
ObjectSlots* object_slots_;
bool writing_ = false;
intptr_t counted_ = 0;
intptr_t written_ = 0;
intptr_t total_ = 0;
bool discount_sizes_ = false;
DISALLOW_COPY_AND_ASSIGN(Pass2Visitor);
};
class Pass3Visitor : public ObjectVisitor {
public:
explicit Pass3Visitor(HeapSnapshotWriter* writer)
: ObjectVisitor(), thread_(Thread::Current()), writer_(writer) {}
void VisitObject(ObjectPtr obj) override {
if (obj->IsPseudoObject()) {
return;
}
writer_->WriteUnsigned(
HeapSnapshotWriter::GetHeapSnapshotIdentityHash(thread_, obj));
}
private:
Thread* thread_;
HeapSnapshotWriter* const writer_;
DISALLOW_COPY_AND_ASSIGN(Pass3Visitor);
};
class CollectStaticFieldNames : public ObjectVisitor {
public:
CollectStaticFieldNames(intptr_t field_table_size,
const char** field_table_names)
: ObjectVisitor(),
field_table_size_(field_table_size),
field_table_names_(field_table_names),
field_(Field::Handle()) {}
void VisitObject(ObjectPtr obj) override {
if (obj->IsField()) {
field_ ^= obj;
if (field_.is_static()) {
intptr_t id = field_.field_id();
if (id > 0) {
ASSERT(id < field_table_size_);
field_table_names_[id] = field_.UserVisibleNameCString();
}
}
}
}
private:
intptr_t field_table_size_;
const char** field_table_names_;
Field& field_;
DISALLOW_COPY_AND_ASSIGN(CollectStaticFieldNames);
};
void VmServiceHeapSnapshotChunkedWriter::WriteChunk(uint8_t* buffer,
intptr_t size,
bool last) {
JSONStream js;
{
JSONObject jsobj(&js);
jsobj.AddProperty("jsonrpc", "2.0");
jsobj.AddProperty("method", "streamNotify");
{
JSONObject params(&jsobj, "params");
params.AddProperty("streamId", Service::heapsnapshot_stream.id());
{
JSONObject event(&params, "event");
event.AddProperty("type", "Event");
event.AddProperty("kind", "HeapSnapshot");
event.AddProperty("isolate", thread()->isolate());
event.AddPropertyTimeMillis("timestamp", OS::GetCurrentTimeMillis());
event.AddProperty("last", last);
}
}
}
Service::SendEventWithData(Service::heapsnapshot_stream.id(), "HeapSnapshot",
kMetadataReservation, js.buffer()->buffer(),
js.buffer()->length(), buffer, size);
}
FileHeapSnapshotWriter::FileHeapSnapshotWriter(Thread* thread,
const char* filename,
bool* success)
: ChunkedWriter(thread), success_(success) {
auto open = Dart::file_open_callback();
auto write = Dart::file_write_callback();
auto close = Dart::file_close_callback();
if (open != nullptr && write != nullptr && close != nullptr) {
file_ = open(filename, /*write=*/true);
}
// If we have open/write/close callbacks we assume it can be done
// successfully. (Those embedder-provided callbacks currently don't allow
// signaling of failure conditions)
if (success_ != nullptr) *success_ = file_ != nullptr;
}
FileHeapSnapshotWriter::~FileHeapSnapshotWriter() {
if (file_ != nullptr) {
Dart::file_close_callback()(file_);
}
}
void FileHeapSnapshotWriter::WriteChunk(uint8_t* buffer,
intptr_t size,
bool last) {
if (file_ != nullptr) {
Dart::file_write_callback()(buffer, size, file_);
}
free(buffer);
}
CallbackHeapSnapshotWriter::CallbackHeapSnapshotWriter(
Thread* thread,
Dart_HeapSnapshotWriteChunkCallback callback,
void* context)
: ChunkedWriter(thread), callback_(callback), context_(context) {}
CallbackHeapSnapshotWriter::~CallbackHeapSnapshotWriter() {}
void CallbackHeapSnapshotWriter::WriteChunk(uint8_t* buffer,
intptr_t size,
bool last) {
callback_(context_, buffer, size, last);
}
void HeapSnapshotWriter::Write() {
HeapIterationScope iteration(thread());
WriteBytes("dartheap", 8); // Magic value.
WriteUnsigned(0); // Flags.
WriteUtf8(isolate()->name());
Heap* H = thread()->heap();
{
intptr_t used = H->TotalUsedInWords() << kWordSizeLog2;
intptr_t capacity = H->TotalCapacityInWords() << kWordSizeLog2;
intptr_t external = H->TotalExternalInWords() << kWordSizeLog2;
intptr_t image = H->old_space()->ImageInWords() << kWordSizeLog2;
WriteUnsigned(used + image);
WriteUnsigned(capacity + image);
WriteUnsigned(external);
}
ObjectSlots object_slots(thread());
{
HANDLESCOPE(thread());
ClassTable* class_table = isolate_group()->class_table();
class_count_ = class_table->NumCids() - 1;
Class& cls = Class::Handle();
Library& lib = Library::Handle();
String& str = String::Handle();
intptr_t field_table_size = isolate()->field_table()->NumFieldIds();
const char** field_table_names =
thread()->zone()->Alloc<const char*>(field_table_size);
for (intptr_t i = 0; i < field_table_size; i++) {
field_table_names[i] = nullptr;
}
{
CollectStaticFieldNames visitor(field_table_size, field_table_names);
iteration.IterateObjects(&visitor);
}
WriteUnsigned(class_count_ + kNumExtraCids);
{
ASSERT(kRootExtraCid == 1);
WriteUnsigned(0); // Flags
WriteUtf8("Root"); // Name
WriteUtf8(""); // Library name
WriteUtf8(""); // Library uri
WriteUtf8(""); // Reserved
WriteUnsigned(0); // Field count
}
{
ASSERT(kImagePageExtraCid == 2);
WriteUnsigned(0); // Flags
WriteUtf8("Read-Only Pages"); // Name
WriteUtf8(""); // Library name
WriteUtf8(""); // Library uri
WriteUtf8(""); // Reserved
WriteUnsigned(0); // Field count
}
{
ASSERT(kIsolateExtraCid == 3);
WriteUnsigned(0); // Flags
WriteUtf8("Isolate"); // Name
WriteUtf8(""); // Library name
WriteUtf8(""); // Library uri
WriteUtf8(""); // Reserved
WriteUnsigned(field_table_size); // Field count
for (intptr_t i = 0; i < field_table_size; i++) {
intptr_t flags = 1; // Strong.
WriteUnsigned(flags);
WriteUnsigned(i); // Index.
const char* name = field_table_names[i];
WriteUtf8(name == nullptr ? "" : name);
WriteUtf8(""); // Reserved
}
}
ASSERT(kNumExtraCids == 3);
for (intptr_t cid = 1; cid <= class_count_; cid++) {
if (!class_table->HasValidClassAt(cid)) {
WriteUnsigned(0); // Flags
WriteUtf8(""); // Name
WriteUtf8(""); // Library name
WriteUtf8(""); // Library uri
WriteUtf8(""); // Reserved
WriteUnsigned(0); // Field count
} else {
cls = class_table->At(cid);
WriteUnsigned(0); // Flags
str = cls.Name();
ScrubAndWriteUtf8(const_cast<char*>(str.ToCString()));
lib = cls.library();
if (lib.IsNull()) {
WriteUtf8("");
WriteUtf8("");
} else {
str = lib.name();
ScrubAndWriteUtf8(const_cast<char*>(str.ToCString()));
str = lib.url();
ScrubAndWriteUtf8(const_cast<char*>(str.ToCString()));
}
WriteUtf8(""); // Reserved
if (auto slots = object_slots.ObjectSlotsFor(cid)) {
WriteUnsigned(slots->length());
for (intptr_t index = 0; index < slots->length(); ++index) {
const auto& slot = (*slots)[index];
const intptr_t kStrongFlag = 1;
WriteUnsigned(kStrongFlag);
WriteUnsigned(index);
ScrubAndWriteUtf8(const_cast<char*>(slot.name));
WriteUtf8(""); // Reserved
}
} else {
// May be an abstract class.
ASSERT(!cls.is_finalized());
WriteUnsigned(0);
}
}
}
}
SetupCountingPages();
intptr_t num_isolates = 0;
intptr_t num_image_objects = 0;
{
Pass1Visitor visitor(this, &object_slots);
// Root "objects".
{
++object_count_;
isolate_group()->VisitSharedPointers(&visitor);
}
{
++object_count_;
CountImagePageRefs visitor;
H->old_space()->VisitObjectsImagePages(&visitor);
num_image_objects = visitor.count();
CountReferences(num_image_objects);
}
{
isolate_group()->ForEachIsolate(
[&](Isolate* isolate) {
++object_count_;
isolate->VisitObjectPointers(&visitor,
ValidationPolicy::kDontValidateFrames);
isolate->VisitStackPointers(&visitor,
ValidationPolicy::kDontValidateFrames);
++num_isolates;
},
/*at_safepoint=*/true);
}
CountReferences(1); // Root -> Image Pages
CountReferences(num_isolates); // Root -> Isolate
// Heap objects.
iteration.IterateVMIsolateObjects(&visitor);
iteration.IterateObjects(&visitor);
// External properties.
isolate()->group()->VisitWeakPersistentHandles(&visitor);
// Smis.
for (SmiPtr smi : smis_) {
AssignObjectId(smi);
}
}
{
Pass2Visitor visitor(this, &object_slots);
WriteUnsigned(reference_count_);
WriteUnsigned(object_count_);
// Root "objects".
{
WriteUnsigned(kRootExtraCid);
WriteUnsigned(0); // shallowSize
WriteUnsigned(kNoData);
visitor.DoCount();
isolate_group()->VisitSharedPointers(&visitor);
visitor.CountExtraRefs(num_isolates + 1);
visitor.DoWrite();
isolate_group()->VisitSharedPointers(&visitor);
visitor.WriteExtraRef(2); // Root -> Image Pages
for (intptr_t i = 0; i < num_isolates; i++) {
// 0 = sentinel, 1 = root, 2 = image pages, 2+ = isolates
visitor.WriteExtraRef(i + 3);
}
}
{
WriteUnsigned(kImagePageExtraCid);
WriteUnsigned(0); // shallowSize
WriteUnsigned(kNoData);
WriteUnsigned(num_image_objects);
WriteImagePageRefs visitor(this);
H->old_space()->VisitObjectsImagePages(&visitor);
DEBUG_ASSERT(visitor.count() == num_image_objects);
}
isolate_group()->ForEachIsolate(
[&](Isolate* isolate) {
WriteUnsigned(kIsolateExtraCid);
WriteUnsigned(0); // shallowSize
WriteUnsigned(kNameData);
WriteUtf8(
OS::SCreate(thread()->zone(), "%" Pd64, isolate->main_port()));
visitor.DoCount();
isolate->VisitObjectPointers(&visitor,
ValidationPolicy::kDontValidateFrames);
isolate->VisitStackPointers(&visitor,
ValidationPolicy::kDontValidateFrames);
visitor.DoWrite();
isolate->VisitObjectPointers(&visitor,
ValidationPolicy::kDontValidateFrames);
isolate->VisitStackPointers(&visitor,
ValidationPolicy::kDontValidateFrames);
},
/*at_safepoint=*/true);
// Heap objects.
visitor.set_discount_sizes(true);
iteration.IterateVMIsolateObjects(&visitor);
visitor.set_discount_sizes(false);
iteration.IterateObjects(&visitor);
// Smis.
for (SmiPtr smi : smis_) {
WriteUnsigned(kSmiCid + kNumExtraCids);
WriteUnsigned(0); // Heap size.
WriteUnsigned(kIntData);
WriteUnsigned(Smi::Value(smi));
WriteUnsigned(0); // No slots.
}
// External properties.
WriteUnsigned(external_property_count_);
isolate()->group()->VisitWeakPersistentHandles(&visitor);
}
{
// Identity hash codes
Pass3Visitor visitor(this);
WriteUnsigned(0); // Root fake object.
WriteUnsigned(0); // Image pages fake object.
isolate_group()->ForEachIsolate(
[&](Isolate* isolate) {
WriteUnsigned(0); // Isolate fake object.
},
/*at_safepoint=*/true);
// Handle visit rest of the objects.
iteration.IterateVMIsolateObjects(&visitor);
iteration.IterateObjects(&visitor);
for (SmiPtr smi : smis_) {
USE(smi);
WriteUnsigned(0); // No identity hash.
}
}
ClearObjectIds();
Flush(true);
}
uint32_t HeapSnapshotWriter::GetHeapSnapshotIdentityHash(Thread* thread,
ObjectPtr obj) {
if (!obj->IsHeapObject()) return 0;
intptr_t cid = obj->GetClassId();
uint32_t hash = 0;
switch (cid) {
case kForwardingCorpse:
case kFreeListElement:
case kSmiCid:
UNREACHABLE();
case kArrayCid:
case kBoolCid:
case kCodeSourceMapCid:
case kCompressedStackMapsCid:
case kDoubleCid:
case kExternalOneByteStringCid:
case kExternalTwoByteStringCid:
case kGrowableObjectArrayCid:
case kImmutableArrayCid:
case kConstMapCid:
case kConstSetCid:
case kInstructionsCid:
case kInstructionsSectionCid:
case kInstructionsTableCid:
case kMapCid:
case kSetCid:
case kMintCid:
case kNeverCid:
case kSentinelCid:
case kNullCid:
case kObjectPoolCid:
case kOneByteStringCid:
case kPcDescriptorsCid:
case kTwoByteStringCid:
case kVoidCid:
// Don't provide hash codes for objects with the above CIDs in order
// to try and avoid having to initialize identity hash codes for common
// primitives and types that don't have hash codes.
break;
default: {
hash = GetHashHelper(thread, obj);
}
}
return hash;
}
// Generates a random value which can serve as an identity hash.
// It must be a non-zero smi value (see also [Object._objectHashCode]).
static uint32_t GenerateHash(Random* random) {
uint32_t hash;
do {
hash = random->NextUInt32();
} while (hash == 0 || (kSmiBits < 32 && !Smi::IsValid(hash)));
return hash;
}
uint32_t HeapSnapshotWriter::GetHashHelper(Thread* thread, ObjectPtr obj) {
uint32_t hash;
#if defined(HASH_IN_OBJECT_HEADER)
hash = Object::GetCachedHash(obj);
if (hash == 0) {
ASSERT(!thread->heap()->old_space()->IsObjectFromImagePages(obj));
hash = GenerateHash(thread->random());
Object::SetCachedHashIfNotSet(obj, hash);
}
#else
Heap* heap = thread->heap();
hash = heap->GetHash(obj);
if (hash == 0) {
ASSERT(!heap->old_space()->IsObjectFromImagePages(obj));
hash = GenerateHash(thread->random());
heap->SetHashIfNotSet(obj, hash);
}
#endif
return hash;
}
CountObjectsVisitor::CountObjectsVisitor(Thread* thread, intptr_t class_count)
: ObjectVisitor(),
HandleVisitor(thread),
new_count_(new intptr_t[class_count]),
new_size_(new intptr_t[class_count]),
new_external_size_(new intptr_t[class_count]),
old_count_(new intptr_t[class_count]),
old_size_(new intptr_t[class_count]),
old_external_size_(new intptr_t[class_count]) {
memset(new_count_.get(), 0, class_count * sizeof(intptr_t));
memset(new_size_.get(), 0, class_count * sizeof(intptr_t));
memset(new_external_size_.get(), 0, class_count * sizeof(intptr_t));
memset(old_count_.get(), 0, class_count * sizeof(intptr_t));
memset(old_size_.get(), 0, class_count * sizeof(intptr_t));
memset(old_external_size_.get(), 0, class_count * sizeof(intptr_t));
}
void CountObjectsVisitor::VisitObject(ObjectPtr obj) {
intptr_t cid = obj->GetClassId();
intptr_t size = obj->untag()->HeapSize();
if (obj->IsNewObject()) {
new_count_[cid] += 1;
new_size_[cid] += size;
} else {
old_count_[cid] += 1;
old_size_[cid] += size;
}
}
void CountObjectsVisitor::VisitHandle(uword addr) {
FinalizablePersistentHandle* handle =
reinterpret_cast<FinalizablePersistentHandle*>(addr);
ObjectPtr obj = handle->ptr();
if (!obj->IsHeapObject()) {
return;
}
intptr_t cid = obj->GetClassId();
intptr_t size = handle->external_size();
if (obj->IsNewObject()) {
new_external_size_[cid] += size;
} else {
old_external_size_[cid] += size;
}
}
#endif // defined(DART_ENABLE_HEAP_SNAPSHOT_WRITER)
} // namespace dart
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