User Manual

Features Overview and ConfigurationRev 2.3-1.0.1
Mellanox Technologies
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Assuming the y dateline was between y=4 and y=0, this spanning tree has a branch that crosses a
dateline. However, again this cannot contribute to credit loops as it occurs on a 1D ring (the ring
for x=3) that is broken by a failure, as in the above example.
3.2.2.5.6.3 Torus Topology Discovery
The algorithm used by torus-2QoS to construct the torus topology from the undirected graph rep-
resenting the fabric requires that the radix of each dimension be configured via torus-2QoS.conf.
It also requires that the torus topology be "seeded"; for a 3D torus this requires configuring four
switches that define the three coordinate directions of the torus. Given this starting information,
the algorithm is to examine the cube formed by the eight switch locations bounded by the corners
(x,y
,z) and (x+1,y+1,z+1). Based on switches already placed into the torus topology at some of
these locations, the algorithm examines 4-loops of interswitch links to find the one that is consis-
tent with a face of the cube of switch locations, and adds its swiches to the discovered topology
in the correct locations.
Because the algorithm is based on examining the topology of 4-loops of links, a torus with one or
more radix-4 dimensions requires extra initial seed configuration.
See torus-2QoS.conf(5) for
details. Torus-2QoS will detect and report when it has insufficient configuration for a torus with
radix-4 dimensions.
In the event the torus is significantly degraded, i.e., there are many missing switches or links, it
may happen that torus-2QoS is unable to place into the torus some switches and/or links that
were discovered in the fabric, and will generate a warning in that case.
A similar condition
occurs if torus-2QoS is misconfigured, i.e., the radix of a torus dimension as configured does not
match the radix of that torus dimension as wired, and many switches/links in the fabric will not
be placed into the torus.
3.2.2.5.6.4 Quality Of Service Configuration
OpenSM will not program switchs and channel adapters with SL2VL maps or VL arbitration
configuration unless it is invoked with -Q. Since torus-2QoS depends on such functionality for
correct operation, always invoke OpenSM with -Q when torus-2QoS is in the list of routing
engines. Any quality of service configuration method supported by OpenSM will work with
torus-2QoS, subject to the following limitations and considerations. For all routing engines sup-
ported by OpenSM except torus-2QoS, there is a one-to-one correspondence between QoS level