v8/src/handles.cc
jochen cb7aa79b12 Expose a lower bound of malloc'd memory via heap statistics
We expect that the majority of malloc'd memory held by V8 is allocated
in Zone objects. Introduce an Allocator class that is used by Zones to
manage memory, and allows for querying the current usage.

BUG=none
R=titzer@chromium.org,bmeurer@chromium.org,jarin@chromium.org
LOG=n
TBR=rossberg@chromium.org

Review URL: https://codereview.chromium.org/1847543002

Cr-Commit-Position: refs/heads/master@{#35196}
2016-04-01 10:01:56 +00:00

203 lines
6.5 KiB
C++

// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/handles.h"
#include "src/address-map.h"
#include "src/base/logging.h"
#include "src/identity-map.h"
#include "src/objects-inl.h"
namespace v8 {
namespace internal {
#ifdef DEBUG
bool HandleBase::IsDereferenceAllowed(DereferenceCheckMode mode) const {
DCHECK_NOT_NULL(location_);
Object* object = *location_;
if (object->IsSmi()) return true;
HeapObject* heap_object = HeapObject::cast(object);
Heap* heap = heap_object->GetHeap();
Object** roots_array_start = heap->roots_array_start();
if (roots_array_start <= location_ &&
location_ < roots_array_start + Heap::kStrongRootListLength &&
heap->RootCanBeTreatedAsConstant(
static_cast<Heap::RootListIndex>(location_ - roots_array_start))) {
return true;
}
if (!AllowHandleDereference::IsAllowed()) return false;
if (mode == INCLUDE_DEFERRED_CHECK &&
!AllowDeferredHandleDereference::IsAllowed()) {
// Accessing cells, maps and internalized strings is safe.
if (heap_object->IsCell()) return true;
if (heap_object->IsMap()) return true;
if (heap_object->IsInternalizedString()) return true;
return !heap->isolate()->IsDeferredHandle(location_);
}
return true;
}
#endif
int HandleScope::NumberOfHandles(Isolate* isolate) {
HandleScopeImplementer* impl = isolate->handle_scope_implementer();
int n = impl->blocks()->length();
if (n == 0) return 0;
return ((n - 1) * kHandleBlockSize) + static_cast<int>(
(isolate->handle_scope_data()->next - impl->blocks()->last()));
}
Object** HandleScope::Extend(Isolate* isolate) {
HandleScopeData* current = isolate->handle_scope_data();
Object** result = current->next;
DCHECK(result == current->limit);
// Make sure there's at least one scope on the stack and that the
// top of the scope stack isn't a barrier.
if (!Utils::ApiCheck(current->level != current->sealed_level,
"v8::HandleScope::CreateHandle()",
"Cannot create a handle without a HandleScope")) {
return NULL;
}
HandleScopeImplementer* impl = isolate->handle_scope_implementer();
// If there's more room in the last block, we use that. This is used
// for fast creation of scopes after scope barriers.
if (!impl->blocks()->is_empty()) {
Object** limit = &impl->blocks()->last()[kHandleBlockSize];
if (current->limit != limit) {
current->limit = limit;
DCHECK(limit - current->next < kHandleBlockSize);
}
}
// If we still haven't found a slot for the handle, we extend the
// current handle scope by allocating a new handle block.
if (result == current->limit) {
// If there's a spare block, use it for growing the current scope.
result = impl->GetSpareOrNewBlock();
// Add the extension to the global list of blocks, but count the
// extension as part of the current scope.
impl->blocks()->Add(result);
current->limit = &result[kHandleBlockSize];
}
return result;
}
void HandleScope::DeleteExtensions(Isolate* isolate) {
HandleScopeData* current = isolate->handle_scope_data();
isolate->handle_scope_implementer()->DeleteExtensions(current->limit);
}
#ifdef ENABLE_HANDLE_ZAPPING
void HandleScope::ZapRange(Object** start, Object** end) {
DCHECK(end - start <= kHandleBlockSize);
for (Object** p = start; p != end; p++) {
*reinterpret_cast<Address*>(p) = kHandleZapValue;
}
}
#endif
Address HandleScope::current_level_address(Isolate* isolate) {
return reinterpret_cast<Address>(&isolate->handle_scope_data()->level);
}
Address HandleScope::current_next_address(Isolate* isolate) {
return reinterpret_cast<Address>(&isolate->handle_scope_data()->next);
}
Address HandleScope::current_limit_address(Isolate* isolate) {
return reinterpret_cast<Address>(&isolate->handle_scope_data()->limit);
}
CanonicalHandleScope::CanonicalHandleScope(Isolate* isolate)
: isolate_(isolate), zone_(isolate->allocator()) {
HandleScopeData* handle_scope_data = isolate_->handle_scope_data();
prev_canonical_scope_ = handle_scope_data->canonical_scope;
handle_scope_data->canonical_scope = this;
root_index_map_ = new RootIndexMap(isolate);
identity_map_ = new IdentityMap<Object**>(isolate->heap(), &zone_);
canonical_level_ = handle_scope_data->level;
}
CanonicalHandleScope::~CanonicalHandleScope() {
delete root_index_map_;
delete identity_map_;
isolate_->handle_scope_data()->canonical_scope = prev_canonical_scope_;
}
Object** CanonicalHandleScope::Lookup(Object* object) {
DCHECK_LE(canonical_level_, isolate_->handle_scope_data()->level);
if (isolate_->handle_scope_data()->level != canonical_level_) {
// We are in an inner handle scope. Do not canonicalize since we will leave
// this handle scope while still being in the canonical scope.
return HandleScope::CreateHandle(isolate_, object);
}
if (object->IsHeapObject()) {
int index = root_index_map_->Lookup(HeapObject::cast(object));
if (index != RootIndexMap::kInvalidRootIndex) {
return isolate_->heap()
->root_handle(static_cast<Heap::RootListIndex>(index))
.location();
}
}
Object*** entry = identity_map_->Get(object);
if (*entry == nullptr) {
// Allocate new handle location.
*entry = HandleScope::CreateHandle(isolate_, object);
}
return reinterpret_cast<Object**>(*entry);
}
DeferredHandleScope::DeferredHandleScope(Isolate* isolate)
: impl_(isolate->handle_scope_implementer()) {
impl_->BeginDeferredScope();
HandleScopeData* data = impl_->isolate()->handle_scope_data();
Object** new_next = impl_->GetSpareOrNewBlock();
Object** new_limit = &new_next[kHandleBlockSize];
DCHECK(data->limit == &impl_->blocks()->last()[kHandleBlockSize]);
impl_->blocks()->Add(new_next);
#ifdef DEBUG
prev_level_ = data->level;
#endif
data->level++;
prev_limit_ = data->limit;
prev_next_ = data->next;
data->next = new_next;
data->limit = new_limit;
}
DeferredHandleScope::~DeferredHandleScope() {
impl_->isolate()->handle_scope_data()->level--;
DCHECK(handles_detached_);
DCHECK(impl_->isolate()->handle_scope_data()->level == prev_level_);
}
DeferredHandles* DeferredHandleScope::Detach() {
DeferredHandles* deferred = impl_->Detach(prev_limit_);
HandleScopeData* data = impl_->isolate()->handle_scope_data();
data->next = prev_next_;
data->limit = prev_limit_;
#ifdef DEBUG
handles_detached_ = true;
#endif
return deferred;
}
} // namespace internal
} // namespace v8