Provided by: nvidia-cuda-dev_7.5.18-0ubuntu1_amd64 
NAME
Stream Management -
Typedefs
typedef void(CUDART_CB * cudaStreamCallback_t )(cudaStream_t stream, cudaError_t status, void *userData)
Functions
cudaError_t cudaStreamAddCallback (cudaStream_t stream, cudaStreamCallback_t callback, void *userData,
unsigned int flags)
Add a callback to a compute stream.
__cudart_builtin__ cudaError_t cudaStreamAttachMemAsync (cudaStream_t stream, void *devPtr, size_t
length, unsigned int flags)
Attach memory to a stream asynchronously.
cudaError_t cudaStreamCreate (cudaStream_t *pStream)
Create an asynchronous stream.
__cudart_builtin__ cudaError_t cudaStreamCreateWithFlags (cudaStream_t *pStream, unsigned int flags)
Create an asynchronous stream.
__cudart_builtin__ cudaError_t cudaStreamCreateWithPriority (cudaStream_t *pStream, unsigned int flags,
int priority)
Create an asynchronous stream with the specified priority.
__cudart_builtin__ cudaError_t cudaStreamDestroy (cudaStream_t stream)
Destroys and cleans up an asynchronous stream.
__cudart_builtin__ cudaError_t cudaStreamGetFlags (cudaStream_t hStream, unsigned int *flags)
Query the flags of a stream.
__cudart_builtin__ cudaError_t cudaStreamGetPriority (cudaStream_t hStream, int *priority)
Query the priority of a stream.
cudaError_t cudaStreamQuery (cudaStream_t stream)
Queries an asynchronous stream for completion status.
cudaError_t cudaStreamSynchronize (cudaStream_t stream)
Waits for stream tasks to complete.
__cudart_builtin__ cudaError_t cudaStreamWaitEvent (cudaStream_t stream, cudaEvent_t event, unsigned int
flags)
Make a compute stream wait on an event.
Detailed Description
\brief stream management functions of the CUDA runtime API (cuda_runtime_api.h)
This section describes the stream management functions of the CUDA runtime application programming
interface.
Typedef Documentation
typedef void(CUDART_CB * cudaStreamCallback_t)(cudaStream_t stream, cudaError_t status, void *userData)
Type of stream callback functions.
Parameters:
stream The stream as passed to cudaStreamAddCallback, may be NULL.
status cudaSuccess or any persistent error on the stream.
userData User parameter provided at registration.
Function Documentation
cudaError_t cudaStreamAddCallback (cudaStream_t stream, cudaStreamCallback_t callback, void * userData,
unsigned int flags)
Adds a callback to be called on the host after all currently enqueued items in the stream have completed.
For each cudaStreamAddCallback call, a callback will be executed exactly once. The callback will block
later work in the stream until it is finished.
The callback may be passed cudaSuccess or an error code. In the event of a device error, all subsequently
executed callbacks will receive an appropriate cudaError_t.
Callbacks must not make any CUDA API calls. Attempting to use CUDA APIs will result in
cudaErrorNotPermitted. 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.
For the purposes of Unified Memory, callback execution makes a number of guarantees:
• The callback stream is considered idle for the duration of the callback. Thus, for example, a callback
may always use memory attached to the callback stream.
• The start of execution of a callback has the same effect as synchronizing an event recorded in the same
stream immediately prior to the callback. It thus synchronizes streams which have been 'joined' prior
to the callback.
• Adding device work to any stream does not have the effect of making the stream active until all
preceding callbacks have executed. Thus, for example, a callback might use global attached memory even
if work has been added to another stream, if it has been properly ordered with an event.
• Completion of a callback does not cause a stream to become active except as described above. The
callback stream will remain idle if no device work follows the callback, and will remain idle across
consecutive callbacks without device work in between. Thus, for example, stream synchronization can be
done by signaling from a callback at the end of the stream.
Parameters:
stream - Stream to add callback to
callback - The function to call once preceding stream operations are complete
userData - User specified data to be passed to the callback function
flags - Reserved for future use, must be 0
Returns:
cudaSuccess, cudaErrorInvalidResourceHandle, cudaErrorNotSupported
Note:
This function uses standard semantics.
Note that this function may also return error codes from previous, asynchronous launches.
See also:
cudaStreamCreate, cudaStreamCreateWithFlags, cudaStreamQuery, cudaStreamSynchronize,
cudaStreamWaitEvent, cudaStreamDestroy, cudaMallocManaged, cudaStreamAttachMemAsync
__cudart_builtin__ cudaError_t cudaStreamAttachMemAsync (cudaStream_t stream, void * devPtr, size_t length,
unsigned int flags)
Enqueues an operation in stream to specify stream association of length bytes of memory starting from
devPtr. 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.
devPtr must point to an address within managed memory space declared using the __managed__ keyword or
allocated with cudaMallocManaged.
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 cudaMemAttachGlobal,
cudaMemAttachHost or cudaMemAttachSingle. If the cudaMemAttachGlobal flag is specified, the memory can be
accessed by any stream on any device. If the cudaMemAttachHost flag is specified, the program makes a
guarantee that it won't access the memory on the device from any stream. If the cudaMemAttachSingle flag
is specified, the program makes a guarantee that it will only access the memory on the device from
stream. 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 stream 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 cudaStreamAttachMemAsync 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 stream 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 cudaMallocManaged. For __managed__
variables, the default association is always cudaMemAttachGlobal. 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.
Parameters:
stream - Stream in which to enqueue the attach operation
devPtr - Pointer to memory (must be a pointer to managed memory)
length - Length of memory (must be zero)
flags - Must be one of cudaMemAttachGlobal, cudaMemAttachHost or cudaMemAttachSingle
Returns:
cudaSuccess, cudaErrorNotReady, cudaErrorInvalidValue cudaErrorInvalidResourceHandle
Note:
Note that this function may also return error codes from previous, asynchronous launches.
See also:
cudaStreamCreate, cudaStreamCreateWithFlags, cudaStreamWaitEvent, cudaStreamSynchronize,
cudaStreamAddCallback, cudaStreamDestroy, cudaMallocManaged
cudaError_t cudaStreamCreate (cudaStream_t * pStream)
Creates a new asynchronous stream.
Parameters:
pStream - Pointer to new stream identifier
Returns:
cudaSuccess, cudaErrorInvalidValue
Note:
Note that this function may also return error codes from previous, asynchronous launches.
See also:
cudaStreamCreateWithPriority, cudaStreamCreateWithFlags, cudaStreamGetPriority, cudaStreamGetFlags,
cudaStreamQuery, cudaStreamSynchronize, cudaStreamWaitEvent, cudaStreamAddCallback, cudaStreamDestroy
__cudart_builtin__ cudaError_t cudaStreamCreateWithFlags (cudaStream_t * pStream, unsigned int flags)
Creates a new asynchronous stream. The flags argument determines the behaviors of the stream. Valid
values for flags are
• cudaStreamDefault: Default stream creation flag.
• cudaStreamNonBlocking: 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.
Parameters:
pStream - Pointer to new stream identifier
flags - Parameters for stream creation
Returns:
cudaSuccess, cudaErrorInvalidValue
Note:
Note that this function may also return error codes from previous, asynchronous launches.
See also:
cudaStreamCreate, cudaStreamCreateWithPriority, cudaStreamGetFlags, cudaStreamQuery,
cudaStreamSynchronize, cudaStreamWaitEvent, cudaStreamAddCallback, cudaStreamDestroy
__cudart_builtin__ cudaError_t cudaStreamCreateWithPriority (cudaStream_t * pStream, unsigned int flags, int
priority)
Creates a stream with the specified priority and returns a handle in pStream. 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
cudaDeviceGetStreamPriorityRange. If the specified priority is outside the numerical range returned by
cudaDeviceGetStreamPriorityRange, it will automatically be clamped to the lowest or the highest number in
the range.
Parameters:
pStream - Pointer to new stream identifier
flags - Flags for stream creation. See cudaStreamCreateWithFlags for a list of valid flags that can
be passed
priority - Priority of the stream. Lower numbers represent higher priorities. See
cudaDeviceGetStreamPriorityRange for more information about the meaningful stream priorities that can
be passed.
Returns:
cudaSuccess, cudaErrorInvalidValue
Note:
Note that this function may also return error codes from previous, asynchronous launches.
Stream priorities are supported only on 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.
See also:
cudaStreamCreate, cudaStreamCreateWithFlags, cudaDeviceGetStreamPriorityRange, cudaStreamGetPriority,
cudaStreamQuery, cudaStreamWaitEvent, cudaStreamAddCallback, cudaStreamSynchronize, cudaStreamDestroy
__cudart_builtin__ cudaError_t cudaStreamDestroy (cudaStream_t stream)
Destroys and cleans up the asynchronous stream specified by stream.
In case the device is still doing work in the stream stream when cudaStreamDestroy() is called, the
function will return immediately and the resources associated with stream will be released automatically
once the device has completed all work in stream.
Parameters:
stream - Stream identifier
Returns:
cudaSuccess, cudaErrorInvalidResourceHandle
Note:
Note that this function may also return error codes from previous, asynchronous launches.
See also:
cudaStreamCreate, cudaStreamCreateWithFlags, cudaStreamQuery, cudaStreamWaitEvent,
cudaStreamSynchronize, cudaStreamAddCallback
__cudart_builtin__ cudaError_t cudaStreamGetFlags (cudaStream_t hStream, unsigned int * flags)
Query the flags of a stream. The flags are returned in flags. See cudaStreamCreateWithFlags for a list of
valid flags.
Parameters:
hStream - Handle to the stream to be queried
flags - Pointer to an unsigned integer in which the stream's flags are returned
Returns:
cudaSuccess, cudaErrorInvalidValue, cudaErrorInvalidResourceHandle
Note:
Note that this function may also return error codes from previous, asynchronous launches.
See also:
cudaStreamCreateWithPriority, cudaStreamCreateWithFlags, cudaStreamGetPriority
__cudart_builtin__ cudaError_t cudaStreamGetPriority (cudaStream_t hStream, int * priority)
Query the priority of a stream. The priority is returned in in priority. Note that if the stream was
created with a priority outside the meaningful numerical range returned by
cudaDeviceGetStreamPriorityRange, this function returns the clamped priority. See
cudaStreamCreateWithPriority for details about priority clamping.
Parameters:
hStream - Handle to the stream to be queried
priority - Pointer to a signed integer in which the stream's priority is returned
Returns:
cudaSuccess, cudaErrorInvalidValue, cudaErrorInvalidResourceHandle
Note:
Note that this function may also return error codes from previous, asynchronous launches.
See also:
cudaStreamCreateWithPriority, cudaDeviceGetStreamPriorityRange, cudaStreamGetFlags
cudaError_t cudaStreamQuery (cudaStream_t stream)
Returns cudaSuccess if all operations in stream have completed, or cudaErrorNotReady if not.
For the purposes of Unified Memory, a return value of cudaSuccess is equivalent to having called
cudaStreamSynchronize().
Parameters:
stream - Stream identifier
Returns:
cudaSuccess, cudaErrorNotReady, cudaErrorInvalidResourceHandle
Note:
Note that this function may also return error codes from previous, asynchronous launches.
See also:
cudaStreamCreate, cudaStreamCreateWithFlags, cudaStreamWaitEvent, cudaStreamSynchronize,
cudaStreamAddCallback, cudaStreamDestroy
cudaError_t cudaStreamSynchronize (cudaStream_t stream)
Blocks until stream has completed all operations. If the cudaDeviceScheduleBlockingSync flag was set for
this device, the host thread will block until the stream is finished with all of its tasks.
Parameters:
stream - Stream identifier
Returns:
cudaSuccess, cudaErrorInvalidResourceHandle
Note:
Note that this function may also return error codes from previous, asynchronous launches.
See also:
cudaStreamCreate, cudaStreamCreateWithFlags, cudaStreamQuery, cudaStreamWaitEvent,
cudaStreamAddCallback, cudaStreamDestroy
__cudart_builtin__ cudaError_t cudaStreamWaitEvent (cudaStream_t stream, cudaEvent_t event, unsigned int
flags)
Makes all future work submitted to stream wait until event reports completion before beginning execution.
This synchronization will be performed efficiently on the device. The event event may be from a different
context than stream, in which case this function will perform cross-device synchronization.
The stream stream will wait only for the completion of the most recent host call to cudaEventRecord() on
event. Once this call has returned, any functions (including cudaEventRecord() and cudaEventDestroy())
may be called on event again, and the subsequent calls will not have any effect on stream.
If cudaEventRecord() has not been called on event, this call acts as if the record has already completed,
and so is a functional no-op.
Parameters:
stream - Stream to wait
event - Event to wait on
flags - Parameters for the operation (must be 0)
Returns:
cudaSuccess, cudaErrorInvalidResourceHandle
Note:
This function uses standard semantics.
Note that this function may also return error codes from previous, asynchronous launches.
See also:
cudaStreamCreate, cudaStreamCreateWithFlags, cudaStreamQuery, cudaStreamSynchronize,
cudaStreamAddCallback, cudaStreamDestroy
Author
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Version 6.0 15 Aug 2015 Stream Management(3)