hwloc-distances (1) Linux Manual Page
NAME
hwloc-distances – Displays distance matrices
SYNOPSIS
hwloc-distances [options]
OPTIONS
-l–logical- Display hwloc logical indexes (default) instead of physical/OS indexes.
-p–physical- Display OS/physical indexes instead of hwloc logical indexes.
-i<file>,–input<file>- Read topology from XML file <file> (instead of discovering the topology on the local machine). If <file> is "-", the standard input is used. XML support must have been compiled in to hwloc for this option to be usable.
-i<directory>,–input<directory>- Read topology from the chroot specified by <directory> (instead of discovering the topology on the local machine). This option is generally only available on Linux. The chroot was usually created by gathering another machine topology with hwloc-gather-topology.
-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,fsrootandsynthetic. –restrict<cpuset>- Restrict the topology to the given cpuset.
–whole-system- Do not consider administration limitations.
-v–verbose- Verbose messages.
–version- Report version and exit.
DESCRIPTION
hwloc-distances displays also distance matrices attached to the topology. The value in the i-th row and j-th column is the distance from object #i to object #j.
Unless defined by the user, matrices currently always contain relative latencies between NUMA nodes (which may or may not be accurate). See the definition of struct hwloc_distances_s in include/hwloc.h or the documentation for details.
These latencies are normalized to the latency of a local (non-NUMA) access. Hence 3.5 in row #i column #j means that the latency from cores in NUMA node #i to memory in NUMA node #j is 3.5 higher than the latency from cores to their local memory. A breadth-first traversal of the topology is performed starting from the root to find all distance matrices.
NOTE: lstopo may also display distance matrices in its verbose textual output. However lstopo only prints matrices that cover the entire topology while hwloc-distances also displays matrices that ignore part of the topology.
EXAMPLES
On a quad-package opteron machine:
index
RETURN VALUE
Upon successful execution, hwloc-distances returns 0.
hwloc-distances will return nonzero if any kind of error occurs, such as (but not limited to) failure to parse the command line.