Class DriverAPINativeMethods.Streams

Groups all stream API calls

Inheritance

System.Object

DriverAPINativeMethods.Streams

Inherited Members

System.Object.Equals(System.Object)

System.Object.Equals(System.Object, System.Object)

System.Object.GetHashCode()

System.Object.GetType()

System.Object.MemberwiseClone()

System.Object.ReferenceEquals(System.Object, System.Object)

System.Object.ToString()

Namespace: ManagedCuda

Assembly: ManagedCuda.dll

Syntax

public static class Streams

Methods

cuStreamAddCallback(CUstream, CUstreamCallback, IntPtr, CUStreamAddCallbackFlags)

Adds a callback to be called on the host after all currently enqueued items in the stream have completed. For each cuStreamAddCallback call, the callback will be executed exactly once. The callback will block later work in the stream until it is finished.

The callback may be passed Success or an error code. In the event of a device error, all subsequently executed callbacks will receive an appropriate CUResult.

Callbacks must not make any CUDA API calls. Attempting to use a CUDA API will result in ErrorNotPermitted. Callbacks must not perform any synchronization that may depend on outstanding device work or other callbacks that are not mandated to run earlier. Callbacks without a mandated order (in independent streams) execute in undefined order and may be serialized.

This API requires compute capability 1.1 or greater. See cuDeviceGetAttribute or ::cuDeviceGetProperties to query compute capability. Attempting to use this API with earlier compute versions will return ErrorNotSupported.

Declaration

public static CUResult cuStreamAddCallback(CUstream hStream, CUstreamCallback callback, IntPtr userData, CUStreamAddCallbackFlags flags)

Parameters

Type	Name	Description
CUstream	hStream	Stream to add callback to
CUstreamCallback	callback	The function to call once preceding stream operations are complete
System.IntPtr	userData	User specified data to be passed to the callback function
CUStreamAddCallbackFlags	flags	Reserved for future use; must be 0.

Returns

Type	Description
CUResult	CUDA Error Codes: Success, ErrorDeinitialized, ErrorNotInitialized, ErrorInvalidContext, ErrorInvalidHandle.

cuStreamAttachMemAsync(CUstream, CUdeviceptr, SizeT, CUmemAttach_flags)

Attach memory to a stream asynchronously

Enqueues an operation in hStream to specify stream association of length bytes of memory starting from dptr. This function is a stream-ordered operation, meaning that it is dependent on, and will only take effect when, previous work in stream has completed. Any previous association is automatically replaced.

dptr must point to an address within managed memory space declared using the __managed__ keyword or allocated with cuMemAllocManaged.

length must be zero, to indicate that the entire allocation's stream association is being changed. Currently, it's not possible to change stream association for a portion of an allocation.

The stream association is specified using flags which must be one of CUmemAttach_flags. If the Global flag is specified, the memory can be accessed by any stream on any device. If the Host flag is specified, the program makes a guarantee that it won't access the memory on the device from any stream. If the Single flag is specified, the program makes a guarantee that it will only access the memory on the device from hStream. It is illegal to attach singly to the NULL stream, because the NULL stream is a virtual global stream and not a specific stream. An error will be returned in this case.

When memory is associated with a single stream, the Unified Memory system will allow CPU access to this memory region so long as all operations in hStream have completed, regardless of whether other streams are active. In effect, this constrains exclusive ownership of the managed memory region by an active GPU to per-stream activity instead of whole-GPU activity.

Accessing memory on the device from streams that are not associated with it will produce undefined results. No error checking is performed by the Unified Memory system to ensure that kernels launched into other streams do not access this region.

It is a program's responsibility to order calls to cuStreamAttachMemAsync(CUstream, CUdeviceptr, SizeT, CUmemAttach_flags) via events, synchronization or other means to ensure legal access to memory at all times. Data visibility and coherency will be changed appropriately for all kernels which follow a stream-association change.

If hStream is destroyed while data is associated with it, the association is removed and the association reverts to the default visibility of the allocation as specified at cuMemAllocManaged. For __managed__ variables, the default association is always Global. Note that destroying a stream is an asynchronous operation, and as a result, the change to default association won't happen until all work in the stream has completed.

Declaration

public static CUResult cuStreamAttachMemAsync(CUstream hStream, CUdeviceptr dptr, SizeT length, CUmemAttach_flags flags)

Parameters

Type	Name	Description
CUstream	hStream	Stream in which to enqueue the attach operation
CUdeviceptr	dptr	Pointer to memory (must be a pointer to managed memory)
SizeT	length	Length of memory (must be zero)
CUmemAttach_flags	flags	Must be one of CUmemAttach_flags

Returns

Type	Description
CUResult

cuStreamCreate(ref CUstream, CUStreamFlags)

Creates a stream and returns a handle in phStream. The Flags argument determines behaviors of the stream. Valid values for Flags are:

Default: Default stream creation flag.
NonBlocking: Specifies that work running in the created stream may run concurrently with work in stream 0 (the NULL stream), and that the created stream should perform no implicit synchronization with stream 0.

Declaration

public static CUResult cuStreamCreate(ref CUstream phStream, CUStreamFlags Flags)

Parameters

Type	Name	Description
CUstream	phStream	Returned newly created stream
CUStreamFlags	Flags	Parameters for stream creation

Returns

Type	Description
CUResult	CUDA Error Codes: Success, ErrorDeinitialized, ErrorNotInitialized, ErrorInvalidContext, ErrorInvalidValue, ErrorOutOfMemory. Note that this function may also return error codes from previous, asynchronous launches.

cuStreamCreateWithPriority(ref CUstream, CUStreamFlags, Int32)

Create a stream with the given priority

Creates a stream with the specified priority and returns a handle in phStream.

This API alters the scheduler priority of work in the stream. Work in a higher priority stream may preempt work already executing in a low priority stream.

priority follows a convention where lower numbers represent higher priorities.

'0' represents default priority. The range of meaningful numerical priorities can be queried using cuCtxGetStreamPriorityRange(ref Int32, ref Int32). If the specified priority is outside the numerical range returned by cuCtxGetStreamPriorityRange(ref Int32, ref Int32), it will automatically be clamped to the lowest or the highest number in the range.

Declaration

public static CUResult cuStreamCreateWithPriority(ref CUstream phStream, CUStreamFlags flags, int priority)

Parameters

Type	Name	Description
CUstream	phStream	Returned newly created stream
CUStreamFlags	flags	Flags for stream creation. See ::cuStreamCreate for a list of valid flags
System.Int32	priority	Stream priority. Lower numbers represent higher priorities. See cuCtxGetStreamPriorityRange(ref Int32, ref Int32) for more information about meaningful stream priorities that can be passed.

Returns

Type	Description
CUResult

Remarks

Stream priorities are supported only on Quadro and Tesla GPUs with compute capability 3.5 or higher.

In the current implementation, only compute kernels launched in priority streams are affected by the stream's priority.

Stream priorities have no effect on host-to-device and device-to-host memory operations.

cuStreamDestroy(CUstream)

Destroys the stream specified by hStream.

Declaration

[Obsolete("Don't use this CUDA API call with CUDA version >= 4.0.")]
public static CUResult cuStreamDestroy(CUstream hStream)

Parameters

Type	Name	Description
CUstream	hStream	Stream to destroy

Returns

Type	Description
CUResult	CUDA Error Codes: Success, ErrorDeinitialized, ErrorNotInitialized, ErrorInvalidContext, ErrorInvalidValue. Note that this function may also return error codes from previous, asynchronous launches.

cuStreamDestroy_v2(CUstream)

Destroys the stream specified by hStream.

In the case that the device is still doing work in the stream hStream when cuStreamDestroy(CUstream) is called, the function will return immediately and the resources associated with hStream will be released automatically once the device has completed all work in hStream.

Declaration

public static CUResult cuStreamDestroy_v2(CUstream hStream)

Parameters

Type	Name	Description
CUstream	hStream	Stream to destroy

Returns

Type	Description
CUResult	CUDA Error Codes: Success, ErrorDeinitialized, ErrorNotInitialized, ErrorInvalidContext, ErrorInvalidValue. Note that this function may also return error codes from previous, asynchronous launches.

cuStreamGetFlags(CUstream, ref CUStreamFlags)

Query the flags of a given stream

Query the flags of a stream created using cuStreamCreate(ref CUstream, CUStreamFlags) or cuStreamCreateWithPriority(ref CUstream, CUStreamFlags, Int32) and return the flags in flags.

Declaration

public static CUResult cuStreamGetFlags(CUstream hStream, ref CUStreamFlags flags)

Parameters

Type	Name	Description
CUstream	hStream	Handle to the stream to be queried
CUStreamFlags	flags	Pointer to an unsigned integer in which the stream's flags are returned. The value returned in `flags` is a logical 'OR' of all flags that were used while creating this stream. See cuStreamCreate(ref CUstream, CUStreamFlags) for the list of valid flags

Returns

Type	Description
CUResult

cuStreamGetPriority(CUstream, ref Int32)

Query the priority of a given stream

Query the priority of a stream created using cuStreamCreate(ref CUstream, CUStreamFlags) or cuStreamCreateWithPriority(ref CUstream, CUStreamFlags, Int32) and return the priority in priority. Note that if the stream was created with a priority outside the numerical range returned by cuCtxGetStreamPriorityRange(ref Int32, ref Int32), this function returns the clamped priority. See cuStreamCreateWithPriority(ref CUstream, CUStreamFlags, Int32) for details about priority clamping.

Declaration

public static CUResult cuStreamGetPriority(CUstream hStream, ref int priority)

Parameters

Type	Name	Description
CUstream	hStream	Handle to the stream to be queried
System.Int32	priority	Pointer to a signed integer in which the stream's priority is returned

Returns

Type	Description
CUResult

cuStreamQuery(CUstream)

Returns Success if all operations in the stream specified by hStream have completed, or ErrorNotReady if not.

Declaration

public static CUResult cuStreamQuery(CUstream hStream)

Parameters

Type	Name	Description
CUstream	hStream	Stream to query status of

Returns

Type	Description
CUResult	CUDA Error Codes: Success, ErrorDeinitialized, ErrorNotInitialized, ErrorInvalidContext, ErrorInvalidHandle, ErrorNotReady. Note that this function may also return error codes from previous, asynchronous launches.

cuStreamSynchronize(CUstream)

Waits until the device has completed all operations in the stream specified by hStream. If the context was created with the BlockingSync flag, the CPU thread will block until the stream is finished with all of its tasks.

Declaration

public static CUResult cuStreamSynchronize(CUstream hStream)

Parameters

Type	Name	Description
CUstream	hStream	Stream to wait for

Returns

Type	Description
CUResult	CUDA Error Codes: Success, ErrorDeinitialized, ErrorNotInitialized, ErrorInvalidContext, ErrorInvalidHandle. Note that this function may also return error codes from previous, asynchronous launches.

cuStreamWaitEvent(CUstream, CUevent, UInt32)

Make a compute stream wait on an event

Makes all future work submitted to hStream wait until hEvent reports completion before beginning execution. This synchronization will be performed efficiently on the device.

The stream hStream will wait only for the completion of the most recent host call to cuEventRecord(CUevent, CUstream) on hEvent. Once this call has returned, any functions (including cuEventRecord(CUevent, CUstream) and cuEventDestroy(CUevent) may be called on hEvent again, and the subsequent calls will not have any effect on hStream.

If hStream is 0 (the NULL stream) any future work submitted in any stream will wait for hEvent to complete before beginning execution. This effectively creates a barrier for all future work submitted to the context.

If cuEventRecord(CUevent, CUstream) has not been called on hEvent, this call acts as if the record has already completed, and so is a functional no-op.

Flags argument must be 0.

Declaration

public static CUResult cuStreamWaitEvent(CUstream hStream, CUevent hEvent, uint Flags)

Parameters

Type	Name	Description
CUstream	hStream	Stream to destroy
CUevent	hEvent	Event
System.UInt32	Flags	Flags argument must be set 0.

Returns

Type	Description
CUResult	CUDA Error Codes: Success, ErrorDeinitialized, ErrorNotInitialized, ErrorInvalidContext, ErrorInvalidValue. Note that this function may also return error codes from previous, asynchronous launches.