C Specification

To enqueue a command to do a memcpy operation, call the function

cl_int clEnqueueSVMMemcpy(
    cl_command_queue command_queue,
    cl_bool blocking_copy,
    void* dst_ptr,
    const void* src_ptr,
    size_t size,
    cl_uint num_events_in_wait_list,
    const cl_event* event_wait_list,
    cl_event* event);


  • command_queue refers to the host command-queue in which the read / write command will be queued. If either dst_ptr or src_ptr is allocated using clSVMAlloc then the OpenCL context allocated against must match that of command_queue.

  • blocking_copy indicates if the copy operation is blocking or non-blocking.

  • If blocking_copy is CL_​TRUE i.e. the copy command is blocking, clEnqueueSVMMemcpy does not return until the buffer data has been copied into memory pointed to by dst_ptr.

  • size is the size in bytes of data being copied.

  • dst_ptr is the pointer to a host or SVM memory allocation where data is copied to.

  • src_ptr is the pointer to a host or SVM memory allocation where data is copied from.

  • event_wait_list and num_events_in_wait_list specify events that need to complete before this particular command can be executed. If event_wait_list is NULL, then this particular command does not wait on any event to complete. If event_wait_list is NULL, num_events_in_wait_list must be 0. If event_wait_list is not NULL, the list of events pointed to by event_wait_list must be valid and num_events_in_wait_list must be greater than 0. The events specified in event_wait_list act as synchronization points. The context associated with events in event_wait_list and command_queue must be the same. The memory associated with event_wait_list can be reused or freed after the function returns.

  • event returns an event object that identifies this particular read / write command and can be used to query or queue a wait for this particular command to complete. event can be NULL in which case it will not be possible for the application to query the status of this command or queue a wait for this command to complete. If the event_wait_list and the event arguments are not NULL, the event argument should not refer to an element of the event_wait_list array.


If blocking_copy is CL_​FALSE i.e. the copy command is non-blocking, clEnqueueSVMMemcpy queues a non-blocking copy command and returns. The contents of the buffer that dst_ptr points to cannot be used until the copy command has completed. The event argument returns an event object which can be used to query the execution status of the read command. When the copy command has completed, the contents of the buffer that dst_ptr points to can be used by the application.

If the memory allocation(s) containing dst_ptr and/or src_ptr are allocated using clSVMAlloc and either is not allocated from the same context from which command_queue was created the behavior is undefined.

clEnqueueSVMMemcpy returns CL_​SUCCESS if the function is executed successfully. Otherwise, it returns one of the following errors:

  • CL_​INVALID_​COMMAND_​QUEUE if command_queue is not a valid host command-queue.

  • CL_​INVALID_​CONTEXT if the context associated with command_queue and events in event_wait_list are not the same.

  • CL_​INVALID_​EVENT_​WAIT_​LIST if event_wait_list is NULL and num_events_in_wait_list > 0, or event_wait_list is not NULL and num_events_in_wait_list is 0, or if event objects in event_wait_list are not valid events.

  • CL_​EXEC_​STATUS_​ERROR_​FOR_​EVENTS_​IN_​WAIT_​LIST if the copy operation is blocking and the execution status of any of the events in event_wait_list is a negative integer value.

  • CL_​INVALID_​VALUE if dst_ptr or src_ptr are NULL.

  • CL_​MEM_​COPY_​OVERLAP if the values specified for dst_ptr, src_ptr and size result in an overlapping copy.

  • CL_​OUT_​OF_​RESOURCES if there is a failure to allocate resources required by the OpenCL implementation on the device.

  • CL_​OUT_​OF_​HOST_​MEMORY if there is a failure to allocate resources required by the OpenCL implementation on the host.

See Also

Document Notes

For more information, see the OpenCL Specification

This page is extracted from the OpenCL Specification. Fixes and changes should be made to the Specification, not directly.

Copyright (c) 2014-2020 Khronos Group. This work is licensed under a Creative Commons Attribution 4.0 International License.