oracular (3) clEnqueueMigrateMemObjects.3clc.gz
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_queue
A 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.
┌───────────────────────────┬───────────────────────────────────────┐
│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_- │ This flag indicates that the contents │
│CONTENT_UNDEFINED │ 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. │
└───────────────────────────┴───────────────────────────────────────┘
event_wait_list, 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 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 Group
COPYRIGHT
Copyright © 2007-2011 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or
associated documentation files (the "Materials"), to deal in the Materials without restriction, including
without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to
the condition that this copyright notice and permission notice shall be included in all copies or
substantial portions of the Materials.
NOTES
1. OpenCL Specification
page 123, section 5.4.4 - Migrating Memory Objects