table of contents
CLENQUEUEMIGRATEMEMO(3clc) | OpenCL Manual | CLENQUEUEMIGRATEMEMO(3clc) |
NAME¶
clEnqueueMigrateMemObjects - Enqueues a command to indicate which device a set of memory objects should be associated with.¶
cl_int
clEnqueueMigrateMemObjects(cl_command_queue command_queue,
cl_uint num_mem_objects,
const cl_mem *mem_objects,
cl_mem_migration_flags flags,
cl_uint num_events_in_wait_list,
const cl_event *event_wait_list,
cl_event *event);
PARAMETERS¶
command_queueA valid command-queue. The specified set of memory
objects in mem_objects will be migrated to the OpenCL device associated
with command_queue or to the host if the
CL_MIGRATE_MEM_OBJECT_HOST has been specified.
num_mem_objects
The number of memory objects specified in
mem_objects.
mem_objects
A pointer to a list of memory objects.
flags
A bit-field that is used to specify migration options.
The table below describes the possible values for flags.
event_wait_list, num_events_in_wait_list
cl_mem_migration flags | Description |
CL_MIGRATE_MEM_OBJECT_HOST | This flag indicates that the specified set of memory objects are to be migrated to the host, regardless of the target command-queue. |
CL_MIGRATE_MEM_OBJECT_- CONTENT_UNDEFINED | This flag indicates that the contents of the set of memory objects are undefined after migration. The specified set of memory objects are migrated to the device associated with command_queue without incurring the overhead of migrating their contents. |
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
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.
NOTES¶
This section describes a mechanism for assigning which device an OpenCL memory object resides. A user may wish to have more explicit control over the location of their memory objects on creation. This could be used to:•Ensure that an object is allocated on a specific
device prior to usage..RE
•Preemptively migrate an object from one device to
another..RE
Typically, memory objects are implicitly migrated to a device for which enqueued
commands, using the memory object, are targeted.
clEnqueueMigrateMemObjects allows this migration to be explicitly
performed ahead of the dependent commands. This allows a user to preemptively
change the association of a memory object, through regular command queue
scheduling, in order to prepare for another upcoming command. This also
permits an application to overlap the placement of memory objects with other
unrelated operations before these memory objects are needed potentially hiding
transfer latencies. Once the event, returned from
clEnqueueMigrateMemObjects, has been marked CL_COMPLETE the
memory objects specified in mem_objects have been successfully migrated
to the device associated with command_queue. The migrated memory object
shall remain resident on the device until another command is enqueued that
either implicitly or explicitly migrates it away.
clEnqueueMigrateMemObjects can also be used to direct the initial
placement of a memory object, after creation, possibly avoiding the initial
overhead of instantiating the object on the first enqueued command to use it.
The user is responsible for managing the event dependencies, associated with
this command, in order to avoid overlapping access to memory objects.
Improperly specified event dependencies passed to
clEnqueueMigrateMemObjects could result in undefined results.
ERRORS¶
clEnqueueMigrateMemObjects 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 command_queue.
•CL_INVALID_CONTEXT if the context associated with
command_queue and memory objects in memobj are not the same or
if the context associated with command_queue and events in
event_wait_list are not the same.
•CL_INVALID_MEM_OBJECT if any of the memory
objects in mem_objs is not a valid memory object.
•CL_INVALID_VALUE if num_mem_objects is
zero or if mem_objects is NULL.
•CL_INVALID_VALUE if flags is not 0 or is
not any of the values described in the table above.
•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_MEM_OBJECT_ALLOCATION_FAILURE if there is a
failure to allocate memory for the specified set of memory objects in
mem_objects.
•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.
SPECIFICATION¶
OpenCL Specification[1]SEE ALSO¶
clEnqueueMapBuffer(3clc), clEnqueueMapImage(3clc)AUTHORS¶
The Khronos GroupCOPYRIGHT¶
Copyright © 2007-2011 The Khronos Group Inc.NOTES¶
- 1.
- OpenCL Specification
page 123, section 5.4.4 - Migrating Memory Objects
06/18/2014 | The Khronos Group |