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NAME

       hwloc - General information about hwloc ("hardware locality").

DESCRIPTION

       hwloc  provides  command  line  tools  and  a  C API to obtain the hierarchical map of key
       computing elements, such  as:  NUMA  memory  nodes,  shared  caches,  processor  packages,
       processor  cores,  and processor "threads".  hwloc also gathers various attributes such as
       cache and memory information, and is portable across  a  variety  of  different  operating
       systems and platforms.

   Definitions
       hwloc  has  some  specific  definitions for terms that are used in this man page and other
       hwloc documentation.

       hwloc CPU set:
            A set of processors included in an hwloc object, expressed as a  bitmask  indexed  by
            the  physical  numbers of the CPUs (as announced by the OS).  The hwloc definition of
            "CPU set" does not carry any the  same  connotations  as  Linux's  "CPU  set"  (e.g.,
            process affinity, etc.).

       hwloc node set:
            A  set  of  NUMA memory nodes near an hwloc object, expressed as a bitmask indexed by
            the physical numbers of the NUMA nodes (as announced by the OS).

       Linux CPU set:
            See  http://www.mjmwired.net/kernel/Documentation/cpusets.txt  for  a  discussion  of
            Linux  CPU  sets.   A  super-short-ignoring-many-details description (taken from that
            page) is:

             "Cpusets provide a mechanism for assigning a set of CPUs and Memory Nodes to  a  set
            of tasks."

       Linux Cgroup:
            See  http://www.mjmwired.net/kernel/Documentation/cgroups.txt  for  a  discussion  of
            Linux control groups.  A super-short-ignoring-many-details  description  (taken  from
            that page) is:

             "Control  Groups provide a mechanism for aggregating/partitioning sets of tasks, and
            all their future children, into hierarchical groups with specialized behaviour."

       To be clear, hwloc supports all of the above concepts.  It is  simply  worth  noting  that
       they are different things.

   Location Specification
       Locations  refer  to  specific regions within a topology.  Before reading the rest of this
       man page, it may be useful to read lstopo(1) and/or run lstopo on your machine to see  the
       reported  topology tree.  Seeing and understanding a topology tree will definitely help in
       understanding the concepts that are discussed below.

       Locations can be specified in multiple ways:

       Tuples:   Tuples of hwloc "objects" and associated indexes can be specified  in  the  form
                 object:index.   hwloc  objects  represent types of mapped items (e.g., packages,
                 cores, etc.) in a topology tree; indexes are non-negative integers that  specify
                 a  unique  physical  object  in a topology tree.  Both concepts are described in
                 detail, below.

                 Indexes may also be specified as ranges.  x-y enumerates from index x to y.  x:y
                 enumerates y objects starting from index x (wrapping around the end of the index
                 range if needed).  x- enumerates all objects starting from index x.   all,  odd,
                 and  even  are also supported for listing all objects, or only those with odd or
                 even indexes.

                 Chaining   multiple   tuples    together    in    the    more    general    form
                 object1:index[.object2:index2[...]]   is  permissable.   While the first tuple's
                 object may appear anywhere in the topology, the Nth tuple's object must  have  a
                 shallower  topology  depth  than the (N+1)th tuple's object.  Put simply: as you
                 move right in a tuple chain, objects must go deeper in the topology tree.   When
                 using  logical  indexes  (which  is  the  default), indexes specified in chained
                 tuples  are  relative  to  the  scope  of  the  parent  object.   For   example,
                 "package:0.core:1" refers to the second core in the first package.

                 When  using  OS/physical  indexes,  the first object matching the given index is
                 used.

                 PCI and OS devices may also be designed using their  identifier.   For  example,
                 "pci=02:03.1" is the PCI device with bus ID "02:03.1".  "os=eth0" is the network
                 interface whose software name is "eth0".

       Hex:      For tools that manipulate object  as  sets  (e.g.  hwloc-calc  and  hwloc-bind),
                 locations  can  also  be  specified  as hexidecimal bitmasks prefixed with "0x".
                 Commas must be used to separate the  hex  digits  into  blocks  of  8,  such  as
                 "0xffc0140,0x00020110".   Leading  zeros  in  each  block  do  not  need  to  be
                 specified.  For example, "0xffc0140,0x20110" is equivalent to the prior example,
                 and  "0x0000000f"  is  exactly  equivalent  to  "0xf".  Intermediate blocks of 8
                 digits that are all zeoro can be left  empty;  "0xff0,,0x13"  is  equivalent  to
                 "0xff0,0x00000000,0x13".   If  the  location is prefixed with the special string
                 "0xf...f", then all unspecified bits are set (as if the set were infinite).  For
                 example,  "0xf...f,0x1"  sets  both the first bit and all bits starting with the
                 33rd.  The string "0xf...f" -- with no other specified values -- sets all bits.

       "all" and "root" are special locations consisting in the root object in tree. It  contains
       the entire current topology.

       Some  tools  directly operate on these objects (e.g. hwloc-info and hwloc-annotate).  They
       do not support hexadecimal locations because each  location  may  correspond  to  multiple
       objects.  For instance, there can be exactly one L3 cache per package and NUMA node, which
       means it's the same location.  If multiple locations are given on the command-line,  these
       tools will operation on each location individually and consecutively.

       Some  other  tools internally manipulate objects as sets (e.g. hwloc-calc and hwloc-bind).
       They translate each input location into a hexidecimal location.  When I/O or Misc  objects
       are used, they are translated into the set of processors (or NUMA nodes) that are close to
       the given object (because I/O or Misc objects do not contain processors or NUMA nodes).

       If multiple locations are specified on the command-line (delimited  by  whitespace),  they
       are  combined  (the  overall location is wider).  If prefixed with "~", the given location
       will be cleared instead of added to the current list of locations.  If prefixed with  "x",
       the  given location will be and'ed instead of added to the current list.  If prefixed with
       "^", the given location will be xor'ed.

       More complex operations may be performed  by  using  hwloc-calc  to  compute  intermediate
       values.

   hwloc Objects
       Objects  in  tuples  can  be  any  of  the  following  strings  (listed  from "biggest" to
       "smallest"):

       machine   A set of processors and memory.

       numanode  A NUMA node; a set of processors around memory which the processors can directly
                 access.   If  hbm  is  used instead of numanode in locations, command-line tools
                 only consider high-bandwidth memory nodes such as Intel Xeon Phi MCDRAM.

       package   Typically a physical package or chip, that goes into a package, it is a grouping
                 of one or more processors.

       l1cache ... l5cache
                 A data (or unified) cache.

       l1icache ... l3icache
                 An instruction cache.

       core      A  single,  physical  processing  unit  which may still contain multiple logical
                 processors, such as hardware threads.

       pu        Short for processor unit (not process!).  The smallest physical  execution  unit
                 that  hwloc recognizes.  For example, there may be multiple PUs on a core (e.g.,
                 hardware threads).

       osdev, pcidev, bridge, and misc may also be used to specify special devices although  some
       of them have dedicated identification ways as explained in Location Specification.

       Finally, note that an object can be denoted by its numeric "depth" in the topology graph.

   hwloc Indexes
       Indexes  are  integer  values  that  uniquely  specify  a given object of a specific type.
       Indexes can be expressed  either  as  logical  values  or  physical  values.   Most  hwloc
       utilities  accept  logical indexes by default.  Passing --physical switches to physical/OS
       indexes.  Both logical and physical indexes are described on this man page.

       Logical indexes are relative to the object order in the output from  the  lstopo  command.
       They always start with 0 and increment by 1 for each successive object.

       Physical indexes are how the operating system refers to objects.  Note that while physical
       indexes are non-negative integer values, the hardware and/or operating system  may  choose
       arbitrary  values  --  they  may  not  start  with  0, and successive objects may not have
       consecutive values.

       For example, if the first few lines of lstopo -p output are the following:

         Machine (47GB)
           NUMANode P#0 (24GB) + Package P#0 + L3 (12MB)
             L2 (256KB) + L1 (32KB) + Core P#0 + PU P#0
             L2 (256KB) + L1 (32KB) + Core P#1 + PU P#0
             L2 (256KB) + L1 (32KB) + Core P#2 + PU P#0
             L2 (256KB) + L1 (32KB) + Core P#8 + PU P#0
             L2 (256KB) + L1 (32KB) + Core P#9 + PU P#0
             L2 (256KB) + L1 (32KB) + Core P#10 + PU P#0
           NUMANode P#1 (24GB) + Package P#1 + L3 (12MB)
             L2 (256KB) + L1 (32KB) + Core P#0 + PU P#0
             L2 (256KB) + L1 (32KB) + Core P#1 + PU P#0
             L2 (256KB) + L1 (32KB) + Core P#2 + PU P#0
             L2 (256KB) + L1 (32KB) + Core P#8 + PU P#0
             L2 (256KB) + L1 (32KB) + Core P#9 + PU P#0
             L2 (256KB) + L1 (32KB) + Core P#10 + PU P#0

       In this example, the first core on  the  second  package  is  logically  number  6  (i.e.,
       logically  the 7th core, starting from 0).  Its physical index is 0, but note that another
       core also has a physical index of 0.  Hence, physical indexes may only be relevant  within
       the  scope  of  their parent (or set of ancestors).  In this example, to uniquely identify
       logical core 6 with physical indexes, you must specify (at a minimum) both a package and a
       core: package 1, core 0.

       Index  values,  regardless  of  whether  they are logical or physical, can be expressed in
       several different forms (where X, Y, and N are positive integers):

       X         The object with index value X.

       X-Y       All the objects with index values >= X and <= Y.

       X-        All the objects with index values >= X.

       X:N       N objects starting with index X, possibly wrapping around the end of the level.

       all       A special index value indicating all valid index values.

       odd       A special index value indicating all valid odd index values.

       even      A special index value indicating all valid even index values.

       REMEMBER: hwloc's command line  tools  accept  logical  indexes  for  location  values  by
       default.  Use --physical and --logical to switch from one mode to another.

SEE ALSO

       hwloc's  command  line tool documentation: lstopo(1), hwloc-bind(1), hwloc-calc(1), hwloc-
       distrib(1), hwloc-ps(1).

       hwloc has many C API functions, each of which have their own man page.  Some top-level man
       pages  are also provided, grouping similar functions together.  A few good places to start
       might   include:   hwlocality_objects(3),   hwlocality_types(3),   hwlocality_creation(3),
       hwlocality_cpuset(3), hwlocality_information(3), and hwlocality_binding(3).

       For a listing of all available hwloc man pages, look at all "hwloc*" files in the man1 and
       man3 directories.