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Stress GC less by allocating exponentially growing string chunks in JSON.stringify.

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R=verwaest@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/11232002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12775 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
yangguo@chromium.org 2012-10-19 12:39:43 +00:00
parent f910052543
commit 8148f972e8
2 changed files with 44 additions and 19 deletions
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58
src/json-stringifier.h
View File

@ -42,7 +42,9 @@ class BasicJsonStringifier BASE_EMBEDDED {
MaybeObject* Stringify(Handle<Object> object);
private:
static const int kPartLength = 8 * 1024;
static const int kInitialPartLength = 32;
static const int kMaxPartLength = 16 * 1024;
static const int kPartLengthGrowthFactor = 2;
static const int kStackLimit = 8 * 1024;
enum Result { UNCHANGED, SUCCESS, BAILOUT, CIRCULAR, STACK_OVERFLOW };
@ -130,12 +132,23 @@ class BasicJsonStringifier BASE_EMBEDDED {
INLINE(Result StackPush(Handle<Object> object));
INLINE(void StackPop());
INLINE(Handle<String> accumulator()) {
return Handle<String>(String::cast(accumulator_store_->value()));
}
INLINE(void set_accumulator(Handle<String> string)) {
return accumulator_store_->set_value(*string);
}
Isolate* isolate_;
Handle<String> accumulator_;
// We use a value wrapper for the string accumulator to keep the
// (indirect) handle to it in the outermost handle scope.
Handle<JSValue> accumulator_store_;
Handle<String> current_part_;
Handle<String> tojson_symbol_;
Handle<JSArray> stack_;
int current_index_;
int part_length_;
bool is_ascii_;
static const int kJsonQuotesCharactersPerEntry = 8;
@ -180,9 +193,11 @@ const char* const BasicJsonStringifier::JsonQuotes =
BasicJsonStringifier::BasicJsonStringifier(Isolate* isolate)
: isolate_(isolate), current_index_(0), is_ascii_(true) {
accumulator_ = isolate_->factory()->empty_string();
accumulator_store_ = Handle<JSValue>::cast(
isolate_->factory()->ToObject(isolate_->factory()->empty_string()));
part_length_ = kInitialPartLength;
current_part_ =
isolate_->factory()->NewRawAsciiString(kPartLength);
isolate_->factory()->NewRawAsciiString(kInitialPartLength);
tojson_symbol_ = isolate_->factory()->LookupAsciiSymbol("toJSON");
stack_ = isolate_->factory()->NewJSArray(8);
}
@ -192,7 +207,7 @@ MaybeObject* BasicJsonStringifier::Stringify(Handle<Object> object) {
switch (Serialize(object)) {
case SUCCESS:
ShrinkCurrentPart();
return *isolate_->factory()->NewConsString(accumulator_, current_part_);
return *isolate_->factory()->NewConsString(accumulator(), current_part_);
case UNCHANGED:
return isolate_->heap()->undefined_value();
case CIRCULAR:
@ -215,7 +230,7 @@ void BasicJsonStringifier::Append_(Char c) {
SeqTwoByteString::cast(*current_part_)->SeqTwoByteStringSet(
current_index_++, c);
}
if (current_index_ == kPartLength) Extend<is_ascii>();
if (current_index_ == part_length_) Extend<is_ascii>();
}
@ -228,7 +243,7 @@ void BasicJsonStringifier::AppendUnchecked_(Char c) {
SeqTwoByteString::cast(*current_part_)->SeqTwoByteStringSet(
current_index_++, c);
}
ASSERT(current_index_ < kPartLength);
ASSERT(current_index_ < part_length_);
}
@ -403,6 +418,7 @@ BasicJsonStringifier::Result BasicJsonStringifier::SerializeDouble(
BasicJsonStringifier::Result BasicJsonStringifier::SerializeArray(
Handle<JSArray> object) {
HandleScope handle_scope(isolate_);
if (StackPush(object) == CIRCULAR) return CIRCULAR;
int length = Smi::cast(object->length())->value();
Append('[');
@ -460,12 +476,14 @@ BasicJsonStringifier::Result BasicJsonStringifier::SerializeArray(
}
Append(']');
StackPop();
current_part_ = handle_scope.CloseAndEscape(current_part_);
return SUCCESS;
}
BasicJsonStringifier::Result BasicJsonStringifier::SerializeObject(
Handle<JSObject> object) {
HandleScope handle_scope(isolate_);
Result stack_push = StackPush(object);
if (stack_push != SUCCESS) return stack_push;
if (object->IsJSGlobalProxy()) return BAILOUT;
@ -502,12 +520,13 @@ BasicJsonStringifier::Result BasicJsonStringifier::SerializeObject(
}
Append('}');
StackPop();
current_part_ = handle_scope.CloseAndEscape(current_part_);
return SUCCESS;
}
void BasicJsonStringifier::ShrinkCurrentPart() {
ASSERT(current_index_ < kPartLength);
ASSERT(current_index_ < part_length_);
if (current_index_ == 0) {
current_part_ = isolate_->factory()->empty_string();
return;
@ -515,10 +534,10 @@ void BasicJsonStringifier::ShrinkCurrentPart() {
int string_size, allocated_string_size;
if (is_ascii_) {
allocated_string_size = SeqAsciiString::SizeFor(kPartLength);
allocated_string_size = SeqAsciiString::SizeFor(part_length_);
string_size = SeqAsciiString::SizeFor(current_index_);
} else {
allocated_string_size = SeqTwoByteString::SizeFor(kPartLength);
allocated_string_size = SeqTwoByteString::SizeFor(part_length_);
string_size = SeqTwoByteString::SizeFor(current_index_);
}
@ -538,14 +557,17 @@ void BasicJsonStringifier::ShrinkCurrentPart() {
template <bool is_ascii>
void BasicJsonStringifier::Extend() {
accumulator_ =
isolate_->factory()->NewConsString(accumulator_, current_part_);
set_accumulator(
isolate_->factory()->NewConsString(accumulator(), current_part_));
if (part_length_ <= kMaxPartLength / kPartLengthGrowthFactor) {
part_length_ *= kPartLengthGrowthFactor;
}
if (is_ascii) {
current_part_ =
isolate_->factory()->NewRawAsciiString(kPartLength);
isolate_->factory()->NewRawAsciiString(part_length_);
} else {
current_part_ =
isolate_->factory()->NewRawTwoByteString(kPartLength);
isolate_->factory()->NewRawTwoByteString(part_length_);
}
current_index_ = 0;
}
@ -553,10 +575,10 @@ void BasicJsonStringifier::Extend() {
void BasicJsonStringifier::ChangeEncoding() {
ShrinkCurrentPart();
accumulator_ = isolate_->factory()->NewConsString(accumulator_,
current_part_);
set_accumulator(
isolate_->factory()->NewConsString(accumulator(), current_part_));
current_part_ =
isolate_->factory()->NewRawTwoByteString(kPartLength);
isolate_->factory()->NewRawTwoByteString(part_length_);
current_index_ = 0;
is_ascii_ = false;
}
@ -565,7 +587,7 @@ void BasicJsonStringifier::ChangeEncoding() {
template <bool is_ascii, typename Char>
void BasicJsonStringifier::SerializeString_(Vector<const Char> vector) {
int length = vector.length();
if (current_index_ + (length << 3) < (kPartLength - 2)) {
if (current_index_ + (length << 3) < (part_length_ - 2)) {
AppendUnchecked_<is_ascii, char>('"');
for (int i = 0; i < length; i++) {
Char c = vector[i];

5
test/mjsunit/json.js
View File

@ -268,11 +268,14 @@ assertEquals('"toJSON 123"',
JSON.stringify({ toJSON : function() { return 'toJSON 123'; } }));
assertEquals('{"a":321}',
JSON.stringify({ a : { toJSON : function() { return 321; } } }));
var counter = 0;
assertEquals('{"getter":123}',
JSON.stringify({ get getter() { return 123; } }));
JSON.stringify({ get getter() { counter++; return 123; } }));
assertEquals(1, counter);
assertEquals('{"a":"abc","b":"\u1234bc"}',
JSON.stringify({ a : "abc", b : "\u1234bc" }));
var a = { a : 1, b : 2 };
delete a.a;
assertEquals('{"b":2}', JSON.stringify(a));