hwlocality_configuration(3) Library Functions Manualhwlocality_configuration(3)
NAME
hwlocality_configuration - Topology Detection Configuration and Query
SYNOPSIS
Data Structures
struct hwloc_topology_discovery_support
struct hwloc_topology_cpubind_support
struct hwloc_topology_membind_support
struct hwloc_topology_misc_support
struct hwloc_topology_support
Enumerations
enum hwloc_topology_flags_e { HWLOC_TOPOLOGY_FLAG_INCLUDE_DISALLOWED,
HWLOC_TOPOLOGY_FLAG_IS_THISSYSTEM,
HWLOC_TOPOLOGY_FLAG_THISSYSTEM_ALLOWED_RESOURCES,
HWLOC_TOPOLOGY_FLAG_IMPORT_SUPPORT = (1UL<<3),
HWLOC_TOPOLOGY_FLAG_RESTRICT_TO_CPUBINDING = (1UL<<4),
HWLOC_TOPOLOGY_FLAG_RESTRICT_TO_MEMBINDING = (1UL<<5),
HWLOC_TOPOLOGY_FLAG_DONT_CHANGE_BINDING = (1UL<<6),
HWLOC_TOPOLOGY_FLAG_NO_DISTANCES = (1UL<<7),
HWLOC_TOPOLOGY_FLAG_NO_MEMATTRS = (1UL<<8),
HWLOC_TOPOLOGY_FLAG_NO_CPUKINDS = (1UL<<9) }
enum hwloc_type_filter_e { HWLOC_TYPE_FILTER_KEEP_ALL,
HWLOC_TYPE_FILTER_KEEP_NONE, HWLOC_TYPE_FILTER_KEEP_STRUCTURE,
HWLOC_TYPE_FILTER_KEEP_IMPORTANT }
Functions
int hwloc_topology_set_flags (hwloc_topology_t topology, unsigned long
flags)
unsigned long hwloc_topology_get_flags (hwloc_topology_t topology)
int hwloc_topology_is_thissystem (hwloc_topology_t restrict topology)
const struct hwloc_topology_support * hwloc_topology_get_support
(hwloc_topology_t restrict topology)
int hwloc_topology_set_type_filter (hwloc_topology_t topology,
hwloc_obj_type_t type, enum hwloc_type_filter_e filter)
int hwloc_topology_get_type_filter (hwloc_topology_t topology,
hwloc_obj_type_t type, enum hwloc_type_filter_e *filter)
int hwloc_topology_set_all_types_filter (hwloc_topology_t topology, enum
hwloc_type_filter_e filter)
int hwloc_topology_set_cache_types_filter (hwloc_topology_t topology,
enum hwloc_type_filter_e filter)
int hwloc_topology_set_icache_types_filter (hwloc_topology_t topology,
enum hwloc_type_filter_e filter)
int hwloc_topology_set_io_types_filter (hwloc_topology_t topology, enum
hwloc_type_filter_e filter)
void hwloc_topology_set_userdata (hwloc_topology_t topology, const void
*userdata)
void * hwloc_topology_get_userdata (hwloc_topology_t topology)
Detailed Description
Several functions can optionally be called between hwloc_topology_init()
and hwloc_topology_load() to configure how the detection should be
performed, e.g. to ignore some objects types, define a synthetic
topology, etc.
Enumeration Type Documentation
enum hwloc_topology_flags_e
Flags to be set onto a topology context before load. Flags should be
given to hwloc_topology_set_flags(). They may also be returned by
hwloc_topology_get_flags().
Enumerator
HWLOC_TOPOLOGY_FLAG_INCLUDE_DISALLOWED
Detect the whole system, ignore reservations, include disallowed
objects. Gather all online resources, even if some were disabled
by the administrator. For instance, ignore Linux Cgroup/Cpusets
and gather all processors and memory nodes. However offline PUs
and NUMA nodes are still ignored.
When this flag is not set, PUs and NUMA nodes that are disallowed are
not added to the topology. Parent objects (package, core, cache, etc.)
are added only if some of their children are allowed. All existing PUs
and NUMA nodes in the topology are allowed.
hwloc_topology_get_allowed_cpuset() and
hwloc_topology_get_allowed_nodeset() are equal to the root object cpuset
and nodeset.
When this flag is set, the actual sets of allowed PUs and NUMA nodes are
given by hwloc_topology_get_allowed_cpuset() and
hwloc_topology_get_allowed_nodeset(). They may be smaller than the root
object cpuset and nodeset.
If the current topology is exported to XML and reimported later, this
flag should be set again in the reimported topology so that disallowed
resources are reimported as well.
HWLOC_TOPOLOGY_FLAG_IS_THISSYSTEM
Assume that the selected backend provides the topology for the
system on which we are running. This forces
hwloc_topology_is_thissystem() to return 1, i.e. makes hwloc
assume that the selected backend provides the topology for the
system on which we are running, even if it is not the OS-specific
backend but the XML backend for instance. This means making the
binding functions actually call the OS-specific system calls and
really do binding, while the XML backend would otherwise provide
empty hooks just returning success.
Setting the environment variable HWLOC_THISSYSTEM may also result in the
same behavior.
This can be used for efficiency reasons to first detect the topology
once, save it to an XML file, and quickly reload it later through the
XML backend, but still having binding functions actually do bind.
HWLOC_TOPOLOGY_FLAG_THISSYSTEM_ALLOWED_RESOURCES
Get the set of allowed resources from the local operating system
even if the topology was loaded from XML or synthetic
description. If the topology was loaded from XML or from a
synthetic string, restrict it by applying the current process
restrictions such as Linux Cgroup/Cpuset.
This is useful when the topology is not loaded directly from the local
machine (e.g. for performance reason) and it comes with all resources,
while the running process is restricted to only parts of the machine.
This flag is ignored unless HWLOC_TOPOLOGY_FLAG_IS_THISSYSTEM is also
set since the loaded topology must match the underlying machine where
restrictions will be gathered from.
Setting the environment variable HWLOC_THISSYSTEM_ALLOWED_RESOURCES
would result in the same behavior.
HWLOC_TOPOLOGY_FLAG_IMPORT_SUPPORT
Import support from the imported topology. When importing a XML
topology from a remote machine, binding is disabled by default
(see HWLOC_TOPOLOGY_FLAG_IS_THISSYSTEM). This disabling is also
marked by putting zeroes in the corresponding supported feature
bits reported by hwloc_topology_get_support().
The flag HWLOC_TOPOLOGY_FLAG_IMPORT_SUPPORT actually imports support
bits from the remote machine. It also sets the flag imported_support in
the struct hwloc_topology_misc_support array. If the imported XML did
not contain any support information (exporter hwloc is too old), this
flag is not set.
Note that these supported features are only relevant for the hwloc
installation that actually exported the XML topology (it may vary with
the operating system, or with how hwloc was compiled).
Note that setting this flag however does not enable binding for the
locally imported hwloc topology, it only reports what the remote hwloc
and machine support.
HWLOC_TOPOLOGY_FLAG_RESTRICT_TO_CPUBINDING
Do not consider resources outside of the process CPU binding. If
the binding of the process is limited to a subset of cores,
ignore the other cores during discovery.
The resulting topology is identical to what a call to
hwloc_topology_restrict() would generate, but this flag also prevents
hwloc from ever touching other resources during the discovery.
This flag especially tells the x86 backend to never temporarily rebind a
thread on any excluded core. This is useful on Windows because such
temporary rebinding can change the process binding. Another use-case is
to avoid cores that would not be able to perform the hwloc discovery
anytime soon because they are busy executing some high-priority real-
time tasks.
If process CPU binding is not supported, the thread CPU binding is
considered instead if supported, or the flag is ignored.
This flag requires HWLOC_TOPOLOGY_FLAG_IS_THISSYSTEM as well since
binding support is required.
HWLOC_TOPOLOGY_FLAG_RESTRICT_TO_MEMBINDING
Do not consider resources outside of the process memory binding.
If the binding of the process is limited to a subset of NUMA
nodes, ignore the other NUMA nodes during discovery.
The resulting topology is identical to what a call to
hwloc_topology_restrict() would generate, but this flag also prevents
hwloc from ever touching other resources during the discovery.
This flag is meant to be used together with
HWLOC_TOPOLOGY_FLAG_RESTRICT_TO_CPUBINDING when both cores and NUMA
nodes should be ignored outside of the process binding.
If process memory binding is not supported, the thread memory binding is
considered instead if supported, or the flag is ignored.
This flag requires HWLOC_TOPOLOGY_FLAG_IS_THISSYSTEM as well since
binding support is required.
HWLOC_TOPOLOGY_FLAG_DONT_CHANGE_BINDING
Do not ever modify the process or thread binding during
discovery. This flag disables all hwloc discovery steps that
require a change of the process or thread binding. This currently
only affects the x86 backend which gets entirely disabled.
This is useful when hwloc_topology_load() is called while the
application also creates additional threads or modifies the binding.
This flag is also a strict way to make sure the process binding will not
change to due thread binding changes on Windows (see
HWLOC_TOPOLOGY_FLAG_RESTRICT_TO_CPUBINDING).
HWLOC_TOPOLOGY_FLAG_NO_DISTANCES
Ignore distances. Ignore distance information from the operating
systems (and from XML) and hence do not use distances for
grouping.
HWLOC_TOPOLOGY_FLAG_NO_MEMATTRS
Ignore memory attributes and tiers. Ignore memory attribues from
the operating systems (and from XML) Hence also do not try to
build memory tiers.
HWLOC_TOPOLOGY_FLAG_NO_CPUKINDS
Ignore CPU Kinds. Ignore CPU kind information from the operating
systems (and from XML).
enum hwloc_type_filter_e
Type filtering flags. By default, most objects are kept
(HWLOC_TYPE_FILTER_KEEP_ALL). Instruction caches, memory-side caches,
I/O and Misc objects are ignored by default
(HWLOC_TYPE_FILTER_KEEP_NONE). Group levels are ignored unless they
bring structure (HWLOC_TYPE_FILTER_KEEP_STRUCTURE).
Note that group objects are also ignored individually (without the
entire level) when they do not bring structure.
Enumerator
HWLOC_TYPE_FILTER_KEEP_ALL
Keep all objects of this type. Cannot be set for HWLOC_OBJ_GROUP
(groups are designed only to add more structure to the topology).
HWLOC_TYPE_FILTER_KEEP_NONE
Ignore all objects of this type. The bottom-level type
HWLOC_OBJ_PU, the HWLOC_OBJ_NUMANODE type, and the top-level type
HWLOC_OBJ_MACHINE may not be ignored.
HWLOC_TYPE_FILTER_KEEP_STRUCTURE
Only ignore objects if their entire level does not bring any
structure. Keep the entire level of objects if at least one of
these objects adds structure to the topology. An object brings
structure when it has multiple children and it is not the only
child of its parent.
If all objects in the level are the only child of their parent, and if
none of them has multiple children, the entire level is removed.
Cannot be set for I/O and Misc objects since the topology structure does
not matter there.
HWLOC_TYPE_FILTER_KEEP_IMPORTANT
Only keep likely-important objects of the given type. It is only
useful for I/O object types. For HWLOC_OBJ_PCI_DEVICE and
HWLOC_OBJ_OS_DEVICE, it means that only objects of major/common
kinds are kept (storage, network, OpenFabrics, CUDA, OpenCL,
RSMI, NVML, and displays). Also, only OS devices directly
attached on PCI (e.g. no USB) are reported. For HWLOC_OBJ_BRIDGE,
it means that bridges are kept only if they have children.
This flag equivalent to HWLOC_TYPE_FILTER_KEEP_ALL for Normal, Memory
and Misc types since they are likely important.
Function Documentation
unsigned long hwloc_topology_get_flags (hwloc_topology_t topology)
Get OR'ed flags of a topology. Get the OR'ed set of
hwloc_topology_flags_e of a topology.
If hwloc_topology_set_flags() was not called earlier, no flags are set
(0 is returned).
Returns
the flags previously set with hwloc_topology_set_flags().
Note
This function may also be called after hwloc_topology_load().
const struct hwloc_topology_support * hwloc_topology_get_support
(hwloc_topology_t restrict topology)
Retrieve the topology support. Each flag indicates whether a feature is
supported. If set to 0, the feature is not supported. If set to 1, the
feature is supported, but the corresponding call may still fail in some
corner cases.
These features are also listed by hwloc-info --support
The reported features are what the current topology supports on the
current machine. If the topology was exported to XML from another
machine and later imported here, support still describes what is
supported for this imported topology after import. By default, binding
will be reported as unsupported in this case (see
HWLOC_TOPOLOGY_FLAG_IS_THISSYSTEM).
Topology flag HWLOC_TOPOLOGY_FLAG_IMPORT_SUPPORT may be used to report
the supported features of the original remote machine instead. If it was
successfully imported, imported_support will be set in the struct
hwloc_topology_misc_support array.
Returns
A pointer to a support structure.
Note
The function cannot return NULL.
The returned pointer should not be freed, it belongs to the hwloc
library.
This function may be called before or after hwloc_topology_load()
but the support structure only contains valid information after.
int hwloc_topology_get_type_filter (hwloc_topology_t topology,
hwloc_obj_type_t type, enum hwloc_type_filter_e * filter)
Get the current filtering for the given object type.
Returns
0 on success, -1 on error.
void * hwloc_topology_get_userdata (hwloc_topology_t topology)
Retrieve the topology-specific userdata pointer. Retrieve the
application-given private data pointer that was previously set with
hwloc_topology_set_userdata().
Returns
A pointer to the private-data if any.
NULL if no private-data was previoulsy set.
int hwloc_topology_is_thissystem (hwloc_topology_t restrict topology)
Does the topology context come from this system?
Returns
1 if this topology context was built using the system running this
program.
0 instead (for instance if using another file-system root, a XML
topology file, or a synthetic topology).
Note
This function may also be called after hwloc_topology_load().
int hwloc_topology_set_all_types_filter (hwloc_topology_t topology, enum
hwloc_type_filter_e filter)
Set the filtering for all object types. If some types do not support
this filtering, they are silently ignored.
Returns
0 on success, -1 on error.
int hwloc_topology_set_cache_types_filter (hwloc_topology_t topology, enum
hwloc_type_filter_e filter)
Set the filtering for all CPU cache object types. Memory-side caches are
not involved since they are not CPU caches.
Returns
0 on success, -1 on error.
int hwloc_topology_set_flags (hwloc_topology_t topology, unsigned long
flags)
Set OR'ed flags to non-yet-loaded topology. Set a OR'ed set of
hwloc_topology_flags_e onto a topology that was not yet loaded.
If this function is called multiple times, the last invocation will
erase and replace the set of flags that was previously set.
By default, no flags are set (0).
The flags set in a topology may be retrieved with
hwloc_topology_get_flags().
Returns
0 on success.
-1 on error, for instance if flags are invalid.
int hwloc_topology_set_icache_types_filter (hwloc_topology_t topology, enum
hwloc_type_filter_e filter)
Set the filtering for all CPU instruction cache object types. Memory-
side caches are not involved since they are not CPU caches.
Returns
0 on success, -1 on error.
int hwloc_topology_set_io_types_filter (hwloc_topology_t topology, enum
hwloc_type_filter_e filter)
Set the filtering for all I/O object types.
Returns
0 on success, -1 on error.
int hwloc_topology_set_type_filter (hwloc_topology_t topology,
hwloc_obj_type_t type, enum hwloc_type_filter_e filter)
Set the filtering for the given object type.
Returns
0 on success, -1 on error.
void hwloc_topology_set_userdata (hwloc_topology_t topology, const void *
userdata)
Set the topology-specific userdata pointer. Each topology may store one
application-given private data pointer. It is initialized to NULL. hwloc
will never modify it.
Use it as you wish, after hwloc_topology_init() and until
hwloc_topolog_destroy().
This pointer is not exported to XML.
Author
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