V8 API Reference Guide for node.js v9.10.0 - v9.11.1
Classes | Public Types | Public Member Functions | Static Public Attributes | List of all members
v8::HeapProfiler Class Reference

#include <v8-profiler.h>


class  ObjectNameResolver
struct  RetainerInfos

Public Types

enum  SamplingFlags { kSamplingNoFlags = 0, kSamplingForceGC = 1 << 0 }
typedef std::unordered_set< const v8::PersistentBase< v8::Value > * > RetainerChildren
typedef std::vector< std::pair< v8::RetainedObjectInfo *, RetainerChildren > > RetainerGroups
typedef std::vector< std::pair< const v8::PersistentBase< v8::Value > *, const v8::PersistentBase< v8::Value > * > > RetainerEdges
typedef RetainerInfos(* GetRetainerInfosCallback) (v8::Isolate *isolate)
typedef RetainedObjectInfo *(* WrapperInfoCallback) (uint16_t class_id, Local< Value > wrapper)

Public Member Functions

int GetSnapshotCount ()
const HeapSnapshotGetHeapSnapshot (int index)
SnapshotObjectId GetObjectId (Local< Value > value)
Local< ValueFindObjectById (SnapshotObjectId id)
void ClearObjectIds ()
const HeapSnapshotTakeHeapSnapshot (ActivityControl *control=NULL, ObjectNameResolver *global_object_name_resolver=NULL)
void StartTrackingHeapObjects (bool track_allocations=false)
SnapshotObjectId GetHeapStats (OutputStream *stream, int64_t *timestamp_us=NULL)
void StopTrackingHeapObjects ()
bool StartSamplingHeapProfiler (uint64_t sample_interval=512 *1024, int stack_depth=16, SamplingFlags flags=kSamplingNoFlags)
void StopSamplingHeapProfiler ()
AllocationProfileGetAllocationProfile ()
void DeleteAllHeapSnapshots ()
void SetWrapperClassInfoProvider (uint16_t class_id, WrapperInfoCallback callback)
void SetGetRetainerInfosCallback (GetRetainerInfosCallback callback)

Static Public Attributes

static const SnapshotObjectId kUnknownObjectId = 0
static const uint16_t kPersistentHandleNoClassId = 0

Detailed Description

Interface for controlling heap profiling. Instance of the profiler can be retrieved using v8::Isolate::GetHeapProfiler.

Member Typedef Documentation

typedef RetainerInfos(* v8::HeapProfiler::GetRetainerInfosCallback) (v8::Isolate *isolate)

Callback function invoked to retrieve all RetainerInfos from the embedder.

typedef RetainedObjectInfo*(* v8::HeapProfiler::WrapperInfoCallback) (uint16_t class_id, Local< Value > wrapper)

Callback function invoked for obtaining RetainedObjectInfo for the given JavaScript wrapper object. It is prohibited to enter V8 while the callback is running: only getters on the handle and GetPointerFromInternalField on the objects are allowed.

Member Function Documentation

void v8::HeapProfiler::ClearObjectIds ( )

Clears internal map from SnapshotObjectId to heap object. The new objects will not be added into it unless a heap snapshot is taken or heap object tracking is kicked off.

void v8::HeapProfiler::DeleteAllHeapSnapshots ( )

Deletes all snapshots taken. All previously returned pointers to snapshots and their contents become invalid after this call.

Local<Value> v8::HeapProfiler::FindObjectById ( SnapshotObjectId  id)

Returns heap object with given SnapshotObjectId if the object is alive, otherwise empty handle is returned.

AllocationProfile* v8::HeapProfiler::GetAllocationProfile ( )

Returns the sampled profile of allocations allocated (and still live) since StartSamplingHeapProfiler was called. The ownership of the pointer is transferred to the caller. Returns nullptr if sampling heap profiler is not active.

const HeapSnapshot* v8::HeapProfiler::GetHeapSnapshot ( int  index)

Returns a snapshot by index.

SnapshotObjectId v8::HeapProfiler::GetHeapStats ( OutputStream stream,
int64_t *  timestamp_us = NULL 

Adds a new time interval entry to the aggregated statistics array. The time interval entry contains information on the current heap objects population size. The method also updates aggregated statistics and reports updates for all previous time intervals via the OutputStream object. Updates on each time interval are provided as a stream of the HeapStatsUpdate structure instances. If |timestamp_us| is supplied, timestamp of the new entry will be written into it. The return value of the function is the last seen heap object Id.

StartTrackingHeapObjects must be called before the first call to this method.

SnapshotObjectId v8::HeapProfiler::GetObjectId ( Local< Value value)

Returns SnapshotObjectId for a heap object referenced by |value| if it has been seen by the heap profiler, kUnknownObjectId otherwise.

int v8::HeapProfiler::GetSnapshotCount ( )

Returns the number of snapshots taken.

void v8::HeapProfiler::SetWrapperClassInfoProvider ( uint16_t  class_id,
WrapperInfoCallback  callback 

Binds a callback to embedder's class ID.

bool v8::HeapProfiler::StartSamplingHeapProfiler ( uint64_t  sample_interval = 512 *1024,
int  stack_depth = 16,
SamplingFlags  flags = kSamplingNoFlags 

Starts gathering a sampling heap profile. A sampling heap profile is similar to tcmalloc's heap profiler and Go's mprof. It samples object allocations and builds an online 'sampling' heap profile. At any point in time, this profile is expected to be a representative sample of objects currently live in the system. Each sampled allocation includes the stack trace at the time of allocation, which makes this really useful for memory leak detection.

This mechanism is intended to be cheap enough that it can be used in production with minimal performance overhead.

Allocations are sampled using a randomized Poisson process. On average, one allocation will be sampled every |sample_interval| bytes allocated. The |stack_depth| parameter controls the maximum number of stack frames to be captured on each allocation.

NOTE: This is a proof-of-concept at this point. Right now we only sample newspace allocations. Support for paged space allocation (e.g. pre-tenured objects, large objects, code objects, etc.) and native allocations doesn't exist yet, but is anticipated in the future.

Objects allocated before the sampling is started will not be included in the profile.

Returns false if a sampling heap profiler is already running.

void v8::HeapProfiler::StartTrackingHeapObjects ( bool  track_allocations = false)

Starts tracking of heap objects population statistics. After calling this method, all heap objects relocations done by the garbage collector are being registered.

|track_allocations| parameter controls whether stack trace of each allocation in the heap will be recorded and reported as part of HeapSnapshot.

void v8::HeapProfiler::StopSamplingHeapProfiler ( )

Stops the sampling heap profile and discards the current profile.

void v8::HeapProfiler::StopTrackingHeapObjects ( )

Stops tracking of heap objects population statistics, cleans up all collected data. StartHeapObjectsTracking must be called again prior to calling GetHeapStats next time.

const HeapSnapshot* v8::HeapProfiler::TakeHeapSnapshot ( ActivityControl control = NULL,
ObjectNameResolver global_object_name_resolver = NULL 

Takes a heap snapshot and returns it.

Member Data Documentation

const uint16_t v8::HeapProfiler::kPersistentHandleNoClassId = 0

Default value of persistent handle class ID. Must not be used to define a class. Can be used to reset a class of a persistent handle.

const SnapshotObjectId v8::HeapProfiler::kUnknownObjectId = 0

A constant for invalid SnapshotObjectId. GetSnapshotObjectId will return it in case heap profiler cannot find id for the object passed as parameter. HeapSnapshot::GetNodeById will always return NULL for such id.

The documentation for this class was generated from the following file: