#include <v8-platform.h>

Public Types
typedef void(*	StackTracePrinter) ()

Public Member Functions
virtual	~Platform ()=default

virtual PageAllocator *	GetPageAllocator ()

virtual ZoneBackingAllocator *	GetZoneBackingAllocator ()

virtual void	OnCriticalMemoryPressure ()

virtual bool	OnCriticalMemoryPressure (size_t length)

virtual int	NumberOfWorkerThreads ()=0

virtual std::shared_ptr< v8::TaskRunner >	GetForegroundTaskRunner (Isolate *isolate)=0

virtual void	CallOnWorkerThread (std::unique_ptr< Task > task)=0

virtual void	CallBlockingTaskOnWorkerThread (std::unique_ptr< Task > task)

virtual void	CallLowPriorityTaskOnWorkerThread (std::unique_ptr< Task > task)

virtual void	CallDelayedOnWorkerThread (std::unique_ptr< Task > task, double delay_in_seconds)=0

virtual bool	IdleTasksEnabled (Isolate *isolate)

virtual std::unique_ptr< JobHandle >	PostJob (TaskPriority priority, std::unique_ptr< JobTask > job_task)=0

virtual double	MonotonicallyIncreasingTime ()=0

virtual double	CurrentClockTimeMillis ()=0

virtual StackTracePrinter	GetStackTracePrinter ()

virtual TracingController *	GetTracingController ()=0

virtual void	DumpWithoutCrashing ()

virtual HighAllocationThroughputObserver *	GetHighAllocationThroughputObserver ()

Static Protected Member Functions
static V8_EXPORT double	SystemClockTimeMillis ()

Detailed Description

V8 Platform abstraction layer.

The embedder has to provide an implementation of this interface before initializing the rest of V8.

Definition at line 886 of file v8-platform.h.

Member Typedef Documentation

◆ StackTracePrinter

typedef void(* StackTracePrinter) ()

Definition at line 1052 of file v8-platform.h.

Constructor & Destructor Documentation

◆ ~Platform()

virtual ~Platform ( )

virtualdefault

Member Function Documentation

◆ CallBlockingTaskOnWorkerThread()

virtual void CallBlockingTaskOnWorkerThread ( std::unique_ptr< Task > task )

inlinevirtual

Schedules a task that blocks the main thread to be invoked with high-priority on a worker thread.

Definition at line 955 of file v8-platform.h.

References Platform::CallOnWorkerThread().

◆ CallDelayedOnWorkerThread()

virtual void CallDelayedOnWorkerThread	(	std::unique_ptr< Task >	task,
		double	delay_in_seconds
	)

pure virtual

Schedules a task to be invoked on a worker thread after |delay_in_seconds| expires.

◆ CallLowPriorityTaskOnWorkerThread()

virtual void CallLowPriorityTaskOnWorkerThread ( std::unique_ptr< Task > task )

inlinevirtual

Schedules a task to be invoked with low-priority on a worker thread.

Definition at line 964 of file v8-platform.h.

References Platform::CallOnWorkerThread().

◆ CallOnWorkerThread()

virtual void CallOnWorkerThread ( std::unique_ptr< Task > task )

pure virtual

Schedules a task to be invoked on a worker thread.

Referenced by Platform::CallBlockingTaskOnWorkerThread(), and Platform::CallLowPriorityTaskOnWorkerThread().

◆ CurrentClockTimeMillis()

virtual double CurrentClockTimeMillis ( )

pure virtual

Current wall-clock time in milliseconds since epoch. This function is expected to return at least millisecond-precision values.

◆ DumpWithoutCrashing()

virtual void DumpWithoutCrashing ( )

inlinevirtual

Tells the embedder to generate and upload a crashdump during an unexpected but non-critical scenario.

Definition at line 1069 of file v8-platform.h.

◆ GetForegroundTaskRunner()

virtual std::shared_ptr<v8::TaskRunner> GetForegroundTaskRunner ( Isolate * isolate )

pure virtual

Returns a TaskRunner which can be used to post a task on the foreground. The TaskRunner's NonNestableTasksEnabled() must be true. This function should only be called from a foreground thread.

Referenced by DefaultPlatform::GetForegroundTaskRunner().

◆ GetHighAllocationThroughputObserver()

virtual HighAllocationThroughputObserver* GetHighAllocationThroughputObserver ( )

inlinevirtual

Allows the embedder to observe sections with high throughput allocation operations.

Definition at line 1076 of file v8-platform.h.

◆ GetPageAllocator()

virtual PageAllocator* GetPageAllocator ( )

inlinevirtual

Allows the embedder to manage memory page allocations.

Definition at line 893 of file v8-platform.h.

Referenced by DefaultPlatform::GetPageAllocator().

◆ GetStackTracePrinter()

virtual StackTracePrinter GetStackTracePrinter ( )

inlinevirtual

Returns a function pointer that print a stack trace of the current stack on invocation. Disables printing of the stack trace if nullptr.

Definition at line 1058 of file v8-platform.h.

◆ GetTracingController()

virtual TracingController* GetTracingController ( )

pure virtual

Returns an instance of a v8::TracingController. This must be non-nullptr.

Referenced by DefaultPlatform::GetTracingController().

◆ GetZoneBackingAllocator()

virtual ZoneBackingAllocator* GetZoneBackingAllocator ( )

inlinevirtual

Allows the embedder to specify a custom allocator used for zones.

Definition at line 901 of file v8-platform.h.

◆ IdleTasksEnabled()

virtual bool IdleTasksEnabled ( Isolate * isolate )

inlinevirtual

Returns true if idle tasks are enabled for the given |isolate|.

Definition at line 980 of file v8-platform.h.

◆ MonotonicallyIncreasingTime()

virtual double MonotonicallyIncreasingTime ( )

pure virtual

Monotonically increasing time in seconds from an arbitrary fixed point in the past. This function is expected to return at least millisecond-precision values. For this reason, it is recommended that the fixed point be no further in the past than the epoch.

Referenced by DefaultPlatform::MonotonicallyIncreasingTime().

◆ NumberOfWorkerThreads()

virtual int NumberOfWorkerThreads ( )

pure virtual

Gets the number of worker threads used by Call(BlockingTask)OnWorkerThread(). This can be used to estimate the number of tasks a work package should be split into. A return value of 0 means that there are no worker threads available. Note that a value of 0 won't prohibit V8 from posting tasks using |CallOnWorkerThread|.

◆ OnCriticalMemoryPressure() [1/2]

virtual void OnCriticalMemoryPressure ( )

inlinevirtual

Enables the embedder to respond in cases where V8 can't allocate large blocks of memory. V8 retries the failed allocation once after calling this method. On success, execution continues; otherwise V8 exits with a fatal error. Embedder overrides of this function must NOT call back into V8.

Definition at line 913 of file v8-platform.h.

◆ OnCriticalMemoryPressure() [2/2]

virtual bool OnCriticalMemoryPressure ( size_t length )

inlinevirtual

Enables the embedder to respond in cases where V8 can't allocate large memory regions. The |length| parameter is the amount of memory needed. Returns true if memory is now available. Returns false if no memory could be made available. V8 will retry allocations until this method returns false.

Embedder overrides of this function must NOT call back into V8.

Definition at line 927 of file v8-platform.h.

◆ PostJob()

virtual std::unique_ptr<JobHandle> PostJob	(	TaskPriority	priority,
		std::unique_ptr< JobTask >	job_task
	)

pure virtual

Posts |job_task| to run in parallel. Returns a JobHandle associated with the Job, which can be joined or canceled. This avoids degenerate cases:

Calling CallOnWorkerThread() for each work item, causing significant overhead.
Fixed number of CallOnWorkerThread() calls that split the work and might run for a long time. This is problematic when many components post "num cores" tasks and all expect to use all the cores. In these cases, the scheduler lacks context to be fair to multiple same-priority requests and/or ability to request lower priority work to yield when high priority work comes in. A canonical implementation of |job_task| looks like: class MyJobTask : public JobTask { public: MyJobTask(...) : worker_queue_(...) {} // JobTask: void Run(JobDelegate* delegate) override { while (!delegate->ShouldYield()) { // Smallest unit of work. auto work_item = worker_queue_.TakeWorkItem(); // Thread safe. if (!work_item) return; ProcessWork(work_item); } }

size_t GetMaxConcurrency() const override { return worker_queue_.GetSize(); // Thread safe. } }; auto handle = PostJob(TaskPriority::kUserVisible, std::make_unique<MyJobTask>(...)); handle->Join();

PostJob() and methods of the returned JobHandle/JobDelegate, must never be called while holding a lock that could be acquired by JobTask::Run or JobTask::GetMaxConcurrency – that could result in a deadlock. This is because [1] JobTask::GetMaxConcurrency may be invoked while holding internal lock (A), hence JobTask::GetMaxConcurrency can only use a lock (B) if that lock is never held while calling back into JobHandle from any thread (A=>B/B=>A deadlock) and [2] JobTask::Run or JobTask::GetMaxConcurrency may be invoked synchronously from JobHandle (B=>JobHandle::foo=>B deadlock).

A sufficient PostJob() implementation that uses the default Job provided in libplatform looks like: std::unique_ptr<JobHandle> PostJob( TaskPriority priority, std::unique_ptr<JobTask> job_task) override { return v8::platform::NewDefaultJobHandle( this, priority, std::move(job_task), NumberOfWorkerThreads()); }

Referenced by DefaultPlatform::PostJob().

◆ SystemClockTimeMillis()

static V8_EXPORT double SystemClockTimeMillis ( )

staticprotected

Default implementation of current wall-clock time in milliseconds since epoch. Useful for implementing |CurrentClockTimeMillis| if nothing special needed.

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

include/v8-platform.h

Public Types

Public Member Functions

Static Protected Member Functions

Detailed Description

Member Typedef Documentation

◆ StackTracePrinter

Constructor & Destructor Documentation

◆ ~Platform()

Member Function Documentation

◆ CallBlockingTaskOnWorkerThread()

◆ CallDelayedOnWorkerThread()

◆ CallLowPriorityTaskOnWorkerThread()

◆ CallOnWorkerThread()

◆ CurrentClockTimeMillis()

◆ DumpWithoutCrashing()

◆ GetForegroundTaskRunner()

◆ GetHighAllocationThroughputObserver()

◆ GetPageAllocator()

◆ GetStackTracePrinter()

◆ GetTracingController()

◆ GetZoneBackingAllocator()

◆ IdleTasksEnabled()

◆ MonotonicallyIncreasingTime()

◆ NumberOfWorkerThreads()

◆ OnCriticalMemoryPressure() [1/2]

◆ OnCriticalMemoryPressure() [2/2]

◆ PostJob()

◆ SystemClockTimeMillis()