hwloc-info(1) hwloc hwloc-info(1)
NAME
hwloc-info - Show some information about some objects, a topology or
supported features
SYNOPSIS
hwloc-info [ options ]... <object>...
hwloc-info [ options ] root hwloc-info [ options ] [ topology | levels
| support ]
<object>... may be a space-separated list of target objects to query.
The program reports all information about one object before looking at
the next one:
$ hwloc-info core:2 package:1 pu:all
Core L#2
type = Core
...
Package L#1
...
PU L#0
...
PU L#1
...
The list may also contain special keywords such as:
root for the topology root object.
levels for information about topology levels (default if no target
object is given, identical to --topology).
topology for topology info attributes stored in the root object
(for forward compatibility with topology info attrs in hwloc 3.0).
support for information about supported features (identical to
--support).
Real targets and special keywords may be combined:
$ hwloc-info core:2 topology pu:3 levels
Note that hwloc(7) provides a detailed explanation of the hwloc system
and of valid <object> formats; it should be read before reading this
man page.
OPTIONS
--objects
Report information specific objects. This is the default if
some objects are given on the command-line.
--topology
Report a summary of the topology instead of about some specific
objects. This is equivalent to passing levels as a target
object on the command-line. This is the default if no object is
given on the command-line.
--support
Report the features that are supported by hwloc on the topology.
The features are those available through the
hwloc_topology_get_support() function. This is useful for
verifying which CPU or memory binding options are supported by
the current hwloc installation. This is equivalent to passing
support as a target object on the command-line.
-i <path>, --input <path>
Read the topology from <path> instead of discovering the
topology of the local machine.
If <path> is a file, it may be a XML file exported by a previous
hwloc program. If <path> is "-", the standard input may be used
as a XML file.
On Linux, <path> may be a directory containing the topology
files gathered from another machine topology with hwloc-gather-
topology.
On x86, <path> may be a directory containing a cpuid dump
gathered with hwloc-gather-cpuid.
When the archivemount program is available, <path> may also be a
tarball containing such Linux or x86 topology files.
-i <specification>, --input <specification>
Simulate a fake hierarchy (instead of discovering the topology
on the local machine). If <specification> is "node:2 pu:3", the
topology will contain two NUMA nodes with 3 processing units in
each of them. The <specification> string must end with a number
of PUs.
--if <format>, --input-format <format>
Enforce the input in the given format, among xml, fsroot, cpuid
and synthetic.
-v --verbose
Include additional detail.
-q --quiet -s --silent
Reduce the amount of details to show. A single summary line per
object is displayed.
--get-attr <name>
Only report the attribute of name <name> for each object
(instead of all attributes). The name must exactly match what
is usually reported by the program, for instance "complete
cpuset" in "0.1: complete cpuset = %0x00ffff00".
Only the value is reported, any other prefix or object name is
ignored, so that the output may easily be used by other tools.
This option also works on topology information but it is ignored
for levels and support keywords.
--ancestors
Display information about the object as well as about all its
ancestors up to the root of the topology. This is identical to
--ancestor all
--ancestor <type>
Only display the object ancestors that match the given type.
Some special values matching multiple types may also be given:
kind=normal (CPU objects, including caches), kind=cpu (CPU
objects, excluding caches), kind=cache (all caches, including
memory-side caches), kind=memory (NUMA nodes or memory-side
caches), kind=io (IO objects), kind=all (all objects). See also
Object Kind in Terms and Definitions in the documentation. The
prefix kind= may be omitted if there is no ambiguity.
If multiple ancestors match, they are reported from the deepest
to the highest in the topology. Adding --first will only show
the first one.
--children
Display information about the object children.
--descendants <type>
Display information about the object descendants that match the
given type.
Some special values matching multiple types may also be given:
kind=normal (CPU objects, including caches), kind=cpu (CPU
objects, excluding caches), kind=cache (all caches, including
memory-side caches), kind=memory (NUMA nodes or memory-side
caches), kind=io (IO objects), kind=all (all objects). See also
Object Kind in Terms and Definitions in the documentation. The
prefix kind= may be omitted if there is no ambiguity.
If multiple objects match, they are reported in a depth-first
order (first child, then its children, etc., then second child,
etc.). Adding --first will only show the first one.
--local-memory
Display information about the NUMA nodes that are local to the
given object.
--local-memory-flags
Change the flags used to select local NUMA nodes. Flags may be
given as numeric values or as a comma-separated list of flag
names that are passed to hwloc_get_local_numanode_objs(). Those
names may be substrings of actual flag names as long as a single
one matches. The default is 3 (or smaller,larger) which means
NUMA nodes are displayed if their locality either contains or is
contained in the locality of the given object.
This option enables --local-memory.
--best-memattr <name>
Enable the listing of local memory nodes with --local-memory,
but only display the local nodes that have the best value for
the memory attribute given by <name> (or as an index). If the
memory attribute values depend on the initiator, the object
given to hwloc-info is used as the initiator.
<name> may be suffixed with flags to tune the selection of best
nodes, for instance as bandwidth,strict,default.
default means that default nodes are reported if no best could
be found (see --default-nodes). If neither best nor default
nodes could be found, all local nodes are reported.
strict means that nodes are selected only if their performance
is the best for all the input CPUs. On a dual-socket machine
with HBM in each socket, both HBMs are the best for their local
socket, but not for the remote socket. Hence both HBM are also
considered best for the entire machine by default, but none if
strict.
--default-nodes
Display information about the default NUMA nodes that are local
to the given object. This usually includes DRAM memory nodes
(or nodes of the same memory tier) rather than nodes with
specific characteristics (HBM, NVM, CXL, etc). See
hwloc_topology_get_default_nodeset() for details.
--first
For each input object, only report the first matching output
object (first ancestor, first child, etc.).
-n When outputting object information, prefix each line with the
index of the considered object within the input. For instance,
if three cores were given in input, the output lines will be
prefixed with "0: ", "1: " or "2: ". If --ancestor is also
used, the prefix will be "X.Y: " where X is the index of the
considered object within the input, and Y is the parent index (0
for the object itself, increasing towards the root of the
topology).
--disallowed
Include objects disallowed by administrative limitations.
--restrict <cpuset>
Restrict the topology to the given cpuset. This removes some
PUs and their now-child-less parents.
Beware that restricting the PUs in a topology may change the
logical indexes of many objects, including NUMA nodes.
--restrict nodeset=<nodeset>
Restrict the topology to the given nodeset (unless
--restrict-flags specifies something different). This removes
some NUMA nodes and their now-child-less parents.
Beware that restricting the NUMA nodes in a topology may change
the logical indexes of many objects, including PUs.
--restrict binding
Restrict the topology to the current process binding. This
option requires the use of the actual current machine topology
(or any other topology with --thissystem or with
HWLOC_THISSYSTEM set to 1 in the environment).
Beware that restricting the topology may change the logical
indexes of many objects, including PUs and NUMA nodes.
--restrict-flags <flags>
Enforce flags when restricting the topology. Flags may be given
as numeric values or as a comma-separated list of flag names
that are passed to hwloc_topology_restrict(). Those names may
be substrings of actual flag names as long as a single one
matches, for instance bynodeset,memless. The default is 0 (or
none).
--filter <type>:<kind>, --filter <type>
Filter objects of type <type>, or of any type if <type> is
"all". "io", "cache" and "icache" are also supported.
<kind> specifies the filtering behavior. If "none" or not
specified, all objects of the given type are removed. If "all",
all objects are kept as usual. If "structure", objects are kept
when they bring structure to the topology. If "important" (only
applicable to I/O and Misc), only important objects are kept.
See hwloc_topology_set_type_filter() for more details.
--no-icaches
Do not show Instruction caches, only Data and Unified caches are
considered. This is identical to --filter icache:none.
--no-io
Do not show any I/O device or bridge. This is identical to
--filter io:none. By default, common devices (GPUs, NICs, block
devices, ...) and interesting bridges are shown.
--no-bridges
Do not show any I/O bridge except hostbridges. This is
identical to --filter bridge:none. By default, common devices
(GPUs, NICs, block devices, ...) and interesting bridges are
shown.
--whole-io
Show all I/O devices and bridges. This is identical to --filter
io:all. By default, only common devices (GPUs, NICs, block
devices, ...) and interesting bridges are shown.
--thissystem
Assume that the selected backend provides the topology for the
system on which we are running. This is useful when using
--restrict binding and loading a custom topology such as an XML
file.
--pid <pid>
Detect topology as seen by process <pid>, i.e. as if process
<pid> did the discovery itself. Note that this can for instance
change the set of allowed processors. Also show this process
current CPU binding by marking the corresponding PUs (in Green
in the graphical output, see the COLORS section below, or by
appending (binding) to the verbose text output). If 0 is given
as pid, the current binding for the lstopo process will be
shown.
-p --physical
Use OS/physical indexes instead of logical indexes for input.
-l --logical
Use logical indexes instead of physical/OS indexes for input
(default).
--version
Report version and exit.
-h --help
Display help message and exit.
DESCRIPTION
hwloc-info displays information about the specified objects. It is
intended to be used with tools such as grep for filtering certain
attribute lines. When no object is specified, or when --topology is
passed, hwloc-info prints a summary of the topology. When --support is
passed, hwloc-info lists the supported features for the topology.
Objects may be specified as location tuples, as explained in hwloc(7).
However hexadecimal bitmasks are not accepted since they may correspond
to multiple objects.
NOTE: It is highly recommended that you read the hwloc(7) overview page
before reading this man page. Most of the concepts described in
hwloc(7) directly apply to the hwloc-calc utility.
EXAMPLES
To display information about each package:
$ hwloc-info package:all
Package L#0
logical index = 0
...
To display information about the core whose physical index is 2:
$ hwloc-info -p core:2
Core L#1
logical index = 1
os index = 2
...
To list the OS devices that are of subtype OpenCL:
$ hwloc-info -s "os[OpenCL]:all"
CoProc:6
CoProc:8
To find the PCI bus ID of PCI devices containing OpenCL devices:
$ hwloc-info --ancestor PCI --get-attr "attr PCI bus id"
'os[opencl]:all'
0000:05:00.0
0000:42:00.0
To list the NUMA nodes that are local a PU:
$ hwloc-info --local-memory pu:25
NUMANode L#6 = local memory #0 of PU L#25
type = NUMANode
...
NUMANode L#7 = local memory #1 of PU L#25
type = NUMANode
...
To show the best-bandwidth node(s) among NUMA nodes local to a PU:
$ hwloc-info --local-memory --best-memattr bandwidth pu:25
NUMANode L#7 = local memory #1 of PU L#25
type = NUMANode
...
to find where a NUMA node is attached in the hierarchy of CPU cores:
$ hwloc-info --ancestor kind=normal --first -s numa:1
Package:0
To see levels and topology info attributes stored in the root object:
$ hwloc-info levels topology
depth 0: 1 Machine (type #0)
depth 1: 1 Package (type #1)
depth 2: 2 Core (type #2)
depth 3: 4 PU (type #3)
Special depth -3: 1 NUMANode (type #13)
info Backend = Linux
info LinuxCgroup = /user/622
info Architecture = x86_64
info hwlocVersion = 3.0.0a1-git
SEE ALSO
hwloc(7), lstopo(1), hwloc-calc(1), hwloc-bind(1), hwloc-ps(1)
2.12.1 May 12, 2025 hwloc-info(1)
hwloc 2.12.1 - Generated Sat Jun 14 08:06:37 CDT 2025