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// Copyright 2020 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.
#ifndef V8_METRICS_H_
#define V8_METRICS_H_
#include "v8.h" // NOLINT(build/include_directory)
namespace v8 {
namespace metrics {
struct WasmModuleDecoded {
bool async = false;
bool streamed = false;
bool success = false;
size_t module_size_in_bytes = 0;
size_t function_count = 0;
int64_t wall_clock_time_in_us = 0;
struct WasmModuleCompiled {
bool async = false;
bool streamed = false;
bool cached = false;
bool deserialized = false;
bool lazy = false;
bool success = false;
size_t code_size_in_bytes = 0;
size_t liftoff_bailout_count = 0;
int64_t wall_clock_time_in_us = 0;
struct WasmModuleInstantiated {
bool async = false;
bool success = false;
size_t imported_function_count = 0;
int64_t wall_clock_time_in_us = 0;
struct WasmModuleTieredUp {
bool lazy = false;
size_t code_size_in_bytes = 0;
int64_t wall_clock_time_in_us = 0;
struct WasmModulesPerIsolate {
size_t count = 0;
V(WasmModuleDecoded) \
V(WasmModuleCompiled) \
V(WasmModuleInstantiated) \
#define V8_THREAD_SAFE_METRICS_EVENTS(V) V(WasmModulesPerIsolate)
* This class serves as a base class for recording event-based metrics in V8.
* There a two kinds of metrics, those which are expected to be thread-safe and
* whose implementation is required to fulfill this requirement and those whose
* implementation does not have that requirement and only needs to be
* executable on the main thread. If such an event is triggered from a
* background thread, it will be delayed and executed by the foreground task
* runner.
* The thread-safe events are listed in the V8_THREAD_SAFE_METRICS_EVENTS
* macro above while the main thread event are listed in
* V8_MAIN_THREAD_METRICS_EVENTS above. For the former, a virtual method
* AddMainThreadEvent(const E& event, v8::Context::Token token) will be
* generated and for the latter AddThreadSafeEvent(const E& event).
* Thread-safe events are not allowed to access the context and therefore do
* not carry a context ID with them. These IDs can be generated using
* Recorder::GetContextId() and the ID will be valid throughout the lifetime
* of the isolate. It is not guaranteed that the ID will still resolve to
* a valid context using Recorder::GetContext() at the time the metric is
* recorded. In this case, an empty handle will be returned.
* The embedder is expected to call v8::Isolate::SetMetricsRecorder()
* providing its implementation and have the virtual methods overwritten
* for the events it cares about.
class V8_EXPORT Recorder {
// A unique identifier for a context in this Isolate.
// It is guaranteed to not be reused throughout the lifetime of the Isolate.
class ContextId {
ContextId() : id_(kEmptyId) {}
bool IsEmpty() const { return id_ == kEmptyId; }
static const ContextId Empty() { return ContextId{kEmptyId}; }
bool operator==(const ContextId& other) const { return id_ == other.id_; }
bool operator!=(const ContextId& other) const { return id_ != other.id_; }
friend class ::v8::Context;
friend class ::v8::internal::Isolate;
explicit ContextId(uintptr_t id) : id_(id) {}
static constexpr uintptr_t kEmptyId = 0;
uintptr_t id_;
virtual ~Recorder() = default;
virtual void AddMainThreadEvent(const E& event, ContextId context_id) {}
virtual void AddThreadSafeEvent(const E& event) {}
virtual void NotifyIsolateDisposal() {}
// Return the context with the given id or an empty handle if the context
// was already garbage collected.
static MaybeLocal<Context> GetContext(Isolate* isolate, ContextId id);
// Return the unique id corresponding to the given context.
static ContextId GetContextId(Local<Context> context);
} // namespace metrics
} // namespace v8
#endif // V8_METRICS_H_