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joyeecheungRafaelGSS
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src: implement countObjectsWithPrototype
This implements an internal utility for counting objects in the heap with a specified prototype. In addition this adds a checkIfCollectableByCounting() test helper. PR-URL: #50572 Refs: v8/v8@0fd478b Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com> Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
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src/heap_utils.cc

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Original file line numberDiff line numberDiff line change
@@ -474,6 +474,39 @@ void TriggerHeapSnapshot(const FunctionCallbackInfo<Value>& args) {
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return args.GetReturnValue().Set(filename_v);
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}
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class PrototypeChainHas : public v8::QueryObjectPredicate {
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public:
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PrototypeChainHas(Local<Context> context, Local<Object> search)
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: context_(context), search_(search) {}
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// What we can do in the filter can be quite limited, but looking up
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// the prototype chain is something that the inspector console API
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// queryObject() does so it is supported.
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bool Filter(Local<Object> object) override {
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for (Local<Value> proto = object->GetPrototype(); proto->IsObject();
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proto = proto.As<Object>()->GetPrototype()) {
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if (search_ == proto) return true;
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}
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return false;
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}
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private:
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Local<Context> context_;
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Local<Object> search_;
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};
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void CountObjectsWithPrototype(const FunctionCallbackInfo<Value>& args) {
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CHECK_EQ(args.Length(), 1);
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CHECK(args[0]->IsObject());
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Local<Object> proto = args[0].As<Object>();
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Isolate* isolate = args.GetIsolate();
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Local<Context> context = isolate->GetCurrentContext();
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PrototypeChainHas prototype_chain_has(context, proto);
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std::vector<Global<Object>> out;
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isolate->GetHeapProfiler()->QueryObjects(context, &prototype_chain_has, &out);
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args.GetReturnValue().Set(static_cast<uint32_t>(out.size()));
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}
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void Initialize(Local<Object> target,
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Local<Value> unused,
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Local<Context> context,
@@ -482,12 +515,15 @@ void Initialize(Local<Object> target,
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SetMethod(context, target, "triggerHeapSnapshot", TriggerHeapSnapshot);
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SetMethod(
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context, target, "createHeapSnapshotStream", CreateHeapSnapshotStream);
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SetMethod(
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context, target, "countObjectsWithPrototype", CountObjectsWithPrototype);
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}
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void RegisterExternalReferences(ExternalReferenceRegistry* registry) {
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registry->Register(BuildEmbedderGraph);
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registry->Register(TriggerHeapSnapshot);
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registry->Register(CreateHeapSnapshotStream);
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registry->Register(CountObjectsWithPrototype);
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}
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} // namespace heap

test/common/gc.js

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Original file line numberDiff line numberDiff line change
@@ -75,7 +75,54 @@ async function runAndBreathe(fn, repeat, waitTime = 20) {
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}
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}
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/**
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* This requires --expose-internals.
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* This function can be used to check if an object factory leaks or not by
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* iterating over the heap and count objects with the specified class
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* (which is checked by looking up the prototype chain).
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* @param {(i: number) => number} fn The factory receiving iteration count
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* and returning number of objects created. The return value should be
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* precise otherwise false negatives can be produced.
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* @param {Function} klass The class whose object is used to count the objects
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* @param {number} count Number of iterations that this check should be done
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* @param {number} waitTime Optional breathing time for GC.
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*/
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async function checkIfCollectableByCounting(fn, klass, count, waitTime = 20) {
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const { internalBinding } = require('internal/test/binding');
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const { countObjectsWithPrototype } = internalBinding('heap_utils');
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const { prototype, name } = klass;
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const initialCount = countObjectsWithPrototype(prototype);
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console.log(`Initial count of ${name}: ${initialCount}`);
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let totalCreated = 0;
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for (let i = 0; i < count; ++i) {
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const created = await fn(i);
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totalCreated += created;
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console.log(`#${i}: created ${created} ${name}, total ${totalCreated}`);
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await wait(waitTime); // give GC some breathing room.
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const currentCount = countObjectsWithPrototype(prototype);
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const collected = totalCreated - (currentCount - initialCount);
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console.log(`#${i}: counted ${currentCount} ${name}, collected ${collected}`);
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if (collected > 0) {
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console.log(`Detected ${collected} collected ${name}, finish early`);
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return;
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}
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}
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await wait(waitTime); // give GC some breathing room.
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const currentCount = countObjectsWithPrototype(prototype);
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const collected = totalCreated - (currentCount - initialCount);
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console.log(`Last count: counted ${currentCount} ${name}, collected ${collected}`);
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// Some objects with the prototype can be collected.
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if (collected > 0) {
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console.log(`Detected ${collected} collected ${name}`);
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return;
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}
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throw new Error(`${name} cannot be collected`);
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}
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module.exports = {
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checkIfCollectable,
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runAndBreathe,
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checkIfCollectableByCounting,
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};

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