Managing memory attributes

## Enumerations

enum | hwloc_memattr_flag_e { HWLOC_MEMATTR_FLAG_HIGHER_FIRST = (1UL<<0) , HWLOC_MEMATTR_FLAG_LOWER_FIRST = (1UL<<1) , HWLOC_MEMATTR_FLAG_NEED_INITIATOR = (1UL<<2) }

## Functions

int | hwloc_memattr_get_name (hwloc_topology_t topology, hwloc_memattr_id_t attribute, const char **name)
int | hwloc_memattr_get_flags (hwloc_topology_t topology, hwloc_memattr_id_t attribute, unsigned long *flags)
int | hwloc_memattr_register (hwloc_topology_t topology, const char *name, unsigned long flags, hwloc_memattr_id_t *id)
int | hwloc_memattr_set_value (hwloc_topology_t topology, hwloc_memattr_id_t attribute, hwloc_obj_t target_node, struct hwloc_location *initiator, unsigned long flags, hwloc_uint64_t value)
int | hwloc_memattr_get_targets (hwloc_topology_t topology, hwloc_memattr_id_t attribute, struct hwloc_location *initiator, unsigned long flags, unsigned *nrp, hwloc_obj_t *targets, hwloc_uint64_t *values)
int | hwloc_memattr_get_initiators (hwloc_topology_t topology, hwloc_memattr_id_t attribute, hwloc_obj_t target_node, unsigned long flags, unsigned *nr, struct hwloc_location *initiators, hwloc_uint64_t *values)

## Detailed Description

## Enumeration Type Documentation

## hwloc_memattr_flag_e

enum hwloc_memattr_flag_e

Memory attribute flags. Given to hwloc_memattr_register() and returned by hwloc_memattr_get_flags().

Enumerator
HWLOC_MEMATTR_FLAG_HIGHER_FIRST | The best nodes for this memory attribute are those with the higher values. For instance Bandwidth.
HWLOC_MEMATTR_FLAG_LOWER_FIRST | The best nodes for this memory attribute are those with the lower values. For instance Latency.
HWLOC_MEMATTR_FLAG_NEED_INITIATOR | The value returned for this memory attribute depends on the given initiator. For instance Bandwidth and Latency, but not Capacity.

## Function Documentation

## hwloc_memattr_get_flags()

int hwloc_memattr_get_flags | ( | hwloc_topology_t | topology,
|  | hwloc_memattr_id_t | attribute,
|  | unsigned long * | flags
| ) |  |

Return the flags of the given attribute.

Flags are a OR'ed set of hwloc_memattr_flag_e.

## hwloc_memattr_get_initiators()

int hwloc_memattr_get_initiators | ( | hwloc_topology_t | topology,
|  | hwloc_memattr_id_t | attribute,
|  | hwloc_obj_t | target_node,
|  | unsigned long | flags,
|  | unsigned * | nr,
|  | struct hwloc_location * | initiators,
|  | hwloc_uint64_t * | values
| ) |  |

Return the initiators that have values for a given attribute for a specific target NUMA node.

Return initiators for the given attribute and target node in the `initiators` array. If `values` is not `NULL`, the corresponding attribute values are stored in the array it points to.

On input, `nr` points to the number of initiators that may be stored in the array `initiators` (and `values`). On output, `nr` points to the number of initiators (and values) that were actually found, even if some of them couldn't be stored in the array. Initiators that couldn't be stored are ignored, but the function still returns success (`0`). The caller may find out by comparing the value pointed by `nr` before and after the function call.

The returned initiators should not be modified or freed, they belong to the topology.

`flags` must be `0` for now.

If the attribute does not relate to a specific initiator (it does not have the flag HWLOC_MEMATTR_FLAG_NEED_INITIATOR), no initiator is returned.

Note
  This function is meant for tools and debugging (listing internal information) rather than for application queries. Applications should rather select useful NUMA nodes with hwloc_get_local_numanode_objs() and then look at their attribute values for some relevant initiators.

## hwloc_memattr_get_name()

int hwloc_memattr_get_name | ( | hwloc_topology_t | topology,
|  | hwloc_memattr_id_t | attribute,
|  | const char ** | name
| ) |  |

Return the name of a memory attribute.

## hwloc_memattr_get_targets()

int hwloc_memattr_get_targets | ( | hwloc_topology_t | topology,
|  | hwloc_memattr_id_t | attribute,
|  | struct hwloc_location * | initiator,
|  | unsigned long | flags,
|  | unsigned * | nrp,
|  | hwloc_obj_t * | targets,
|  | hwloc_uint64_t * | values
| ) |  |

Return the target NUMA nodes that have some values for a given attribute.

Return targets for the given attribute in the `targets` array (for the given initiator if any). If `values` is not `NULL`, the corresponding attribute values are stored in the array it points to.

On input, `nr` points to the number of targets that may be stored in the array `targets` (and `values`). On output, `nr` points to the number of targets (and values) that were actually found, even if some of them couldn't be stored in the array. Targets that couldn't be stored are ignored, but the function still returns success (`0`). The caller may find out by comparing the value pointed by `nr` before and after the function call.

The returned targets should not be modified or freed, they belong to the topology.

Argument `initiator` is ignored if the attribute does not relate to a specific initiator (it does not have the flag HWLOC_MEMATTR_FLAG_NEED_INITIATOR). Otherwise `initiator` may be non `NULL` to report only targets that have a value for that initiator.

`flags` must be `0` for now.

Note
  This function is meant for tools and debugging (listing internal information) rather than for application queries. Applications should rather select useful NUMA nodes with hwloc_get_local_numanode_objs() and then look at their attribute values.
  The initiator `initiator` should be of type HWLOC_LOCATION_TYPE_CPUSET when refering to accesses performed by CPU cores. HWLOC_LOCATION_TYPE_OBJECT is currently unused internally by hwloc, but users may for instance use it to provide custom information about host memory accesses performed by GPUs.

## hwloc_memattr_register()

int hwloc_memattr_register | ( | hwloc_topology_t | topology,
|  | const char * | name,
|  | unsigned long | flags,
|  | hwloc_memattr_id_t * | id
| ) |  |

Register a new memory attribute.

Add a specific memory attribute that is not defined in hwloc_memattr_id_e. Flags are a OR'ed set of hwloc_memattr_flag_e. It must contain at least one of HWLOC_MEMATTR_FLAG_HIGHER_FIRST or HWLOC_MEMATTR_FLAG_LOWER_FIRST.

## hwloc_memattr_set_value()

int hwloc_memattr_set_value | ( | hwloc_topology_t | topology,
|  | hwloc_memattr_id_t | attribute,
|  | hwloc_obj_t | target_node,
|  | struct hwloc_location * | initiator,
|  | unsigned long | flags,
|  | hwloc_uint64_t | value
| ) |  |

Set an attribute value for a specific target NUMA node.

If the attribute does not relate to a specific initiator (it does not have the flag HWLOC_MEMATTR_FLAG_NEED_INITIATOR), location `initiator` is ignored and may be `NULL`.

The initiator will be copied into the topology, the caller should free anything allocated to store the initiator, for instance the cpuset.

`flags` must be `0` for now.

Note
  The initiator `initiator` should be of type HWLOC_LOCATION_TYPE_CPUSET when refering to accesses performed by CPU cores. HWLOC_LOCATION_TYPE_OBJECT is currently unused internally by hwloc, but users may for instance use it to provide custom information about host memory accesses performed by GPUs.