v8  5.1.281(node6.10.3)
V8 is Google's open source JavaScript engine
HeapProfiler Class Reference

#include <v8-profiler.h>

Data Structures

class  ObjectNameResolver
 

Public Types

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)
 
void StopSamplingHeapProfiler ()
 
AllocationProfileGetAllocationProfile ()
 
void DeleteAllHeapSnapshots ()
 
void SetWrapperClassInfoProvider (uint16_t class_id, WrapperInfoCallback callback)
 
size_t GetProfilerMemorySize ()
 
void SetRetainedObjectInfo (UniqueId id, RetainedObjectInfo *info)
 

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.

Definition at line 516 of file v8-profiler.h.

Member Typedef Documentation

typedef RetainedObjectInfo*(* 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.

Definition at line 524 of file v8-profiler.h.

Member Function Documentation

void 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 DeleteAllHeapSnapshots ( )

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

Local<Value> FindObjectById ( SnapshotObjectId  id)

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

AllocationProfile* GetAllocationProfile ( )

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

const HeapSnapshot* GetHeapSnapshot ( int  index)

Returns a snapshot by index.

SnapshotObjectId 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 GetObjectId ( Local< Value value)

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

size_t GetProfilerMemorySize ( )

Returns memory used for profiler internal data and snapshots.

int GetSnapshotCount ( )

Returns the number of snapshots taken.

void SetRetainedObjectInfo ( UniqueId  id,
RetainedObjectInfo info 
)

Sets a RetainedObjectInfo for an object group (see V8::SetObjectGroupId).

void SetWrapperClassInfoProvider ( uint16_t  class_id,
WrapperInfoCallback  callback 
)

Binds a callback to embedder's class ID.

bool StartSamplingHeapProfiler ( uint64_t  sample_interval = 512 *1024,
int  stack_depth = 16 
)

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 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 StopSamplingHeapProfiler ( )

Stops the sampling heap profile and discards the current profile.

void 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* TakeHeapSnapshot ( ActivityControl control = NULL,
ObjectNameResolver global_object_name_resolver = NULL 
)

Takes a heap snapshot and returns it.

Field Documentation

const uint16_t kPersistentHandleNoClassId = 0
static

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.

Definition at line 674 of file v8-profiler.h.

const SnapshotObjectId kUnknownObjectId = 0
static

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.

Definition at line 557 of file v8-profiler.h.


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