Provided by: opensm_3.3.23-2_amd64 
NAME
opensm - InfiniBand subnet manager and administration (SM/SA)
SYNOPSIS
opensm [--version]] [-F | --config <file_name>] [-c(reate-config) <file_name>] [-g(uid)
<GUID in hex>] [-l(mc) <LMC>] [-p(riority) <PRIORITY>] [--subnet_prefix <PREFIX in hex>]
[--smkey <SM_Key>] [--sm_sl <SL number>] [-r(eassign_lids)] [-R <engine name(s)> |
--routing_engine <engine name(s)>] [--do_mesh_analysis] [--lash_start_vl <vl number>]
[--nue_max_num_vls <vl number>] [-A | --ucast_cache] [-z | --connect_roots] [-M <file
name> | --lid_matrix_file <file name>] [-U <file name> | --lfts_file <file name>] [-S |
--sadb_file <file name>] [-a | --root_guid_file <path to file>] [-u | --cn_guid_file <path
to file>] [-G | --io_guid_file <path to file>] [--port-shifting] [--scatter-ports <random
seed>] [-H | --max_reverse_hops <max reverse hops allowed>] [-X |
--guid_routing_order_file <path to file>] [-m | --ids_guid_file <path to file>] [-o(nce)]
[-s(weep) <interval>] [-t(imeout) <milliseconds>] [--retries <number>] [--maxsmps
<number>] [--console [off | local | socket | loopback]] [--console-port <port>] [-i |
--ignore_guids <equalize-ignore-guids-file>] [-w | --hop_weights_file <path to file>] [-O
| --port_search_ordering_file <path to file>] [-O | --dimn_ports_file <path to file>]
(DEPRECATED) [--dump_files_dir <directory-name>] [-f <log file path> | --log_file <log
file path> ] [-L | --log_limit <size in MB>] [-e(rase_log_file)] [-P(config) <partition
config file> ] [-N | --no_part_enforce] (DEPRECATED) [-Z | --part_enforce [both | in | out
| off]] [-W | --allow_both_pkeys] [-Q | --qos [-Y | --qos_policy_file <file name>]]
[--congestion-control] [--cckey <key>] [-y | --stay_on_fatal] [-B | --daemon] [-J |
--pidfile <file_name>] [-I | --inactive] [--perfmgr] [--perfmgr_sweep_time_s <seconds>]
[--prefix_routes_file <path>] [--consolidate_ipv6_snm_req] [--log_prefix <prefix text>]
[--torus_config <path to file>] [-v(erbose)] [-V] [-D <flags>] [-d(ebug) <number>]
[-h(elp)] [-?]
DESCRIPTION
opensm is an InfiniBand compliant Subnet Manager and Administration, and runs on top of
OpenIB.
opensm provides an implementation of an InfiniBand Subnet Manager and Administration. Such
a software entity is required to run for in order to initialize the InfiniBand hardware
(at least one per each InfiniBand subnet).
opensm also now contains an experimental version of a performance manager as well.
opensm defaults were designed to meet the common case usage on clusters with up to a few
hundred nodes. Thus, in this default mode, opensm will scan the IB fabric, initialize it,
and sweep occasionally for changes.
opensm attaches to a specific IB port on the local machine and configures only the fabric
connected to it. (If the local machine has other IB ports, opensm will ignore the fabrics
connected to those other ports). If no port is specified, it will select the first "best"
available port.
opensm can present the available ports and prompt for a port number to attach to.
By default, the run is logged to two files: /var/log/messages and /var/log/opensm.log.
The first file will register only general major events, whereas the second will include
details of reported errors. All errors reported in this second file should be treated as
indicators of IB fabric health issues. (Note that when a fatal and non-recoverable error
occurs, opensm will exit.) Both log files should include the message "SUBNET UP" if
opensm was able to setup the subnet correctly.
OPTIONS
--version
Prints OpenSM version and exits.
-F, --config <config file>
The name of the OpenSM config file. When not specified /etc/opensm/opensm.conf
will be used (if exists).
-c, --create-config <file name>
OpenSM will dump its configuration to the specified file and exit. This is a way
to generate OpenSM configuration file template.
-g, --guid <GUID in hex>
This option specifies the local port GUID value with which OpenSM should bind.
OpenSM may be bound to 1 port at a time. If GUID given is 0, OpenSM displays a
list of possible port GUIDs and waits for user input. Without -g, OpenSM tries to
use the default port.
-l, --lmc <LMC value>
This option specifies the subnet's LMC value. The number of LIDs assigned to each
port is 2^LMC. The LMC value must be in the range 0-7. LMC values > 0 allow
multiple paths between ports. LMC values > 0 should only be used if the subnet
topology actually provides multiple paths between ports, i.e. multiple
interconnects between switches. Without -l, OpenSM defaults to LMC = 0, which
allows one path between any two ports.
-p, --priority <Priority value>
This option specifies the SM´s PRIORITY. This will effect the handover cases,
where master is chosen by priority and GUID. Range goes from 0 (default and lowest
priority) to 15 (highest).
--subnet_prefix <PREFIX in hex>
This option specifies the subnet prefix to use in on the fabric. The default
prefix is 0xfe80000000000000.
--smkey <SM_Key value>
This option specifies the SM´s SM_Key (64 bits). This will effect SM
authentication. Note that OpenSM version 3.2.1 and below used the default value
'1' in a host byte order, it is fixed now but you may need this option to
interoperate with old OpenSM running on a little endian machine.
--sm_sl <SL number>
This option sets the SL to use for communication with the SM/SA. Defaults to 0.
-r, --reassign_lids
This option causes OpenSM to reassign LIDs to all end nodes. Specifying -r on a
running subnet may disrupt subnet traffic. Without -r, OpenSM attempts to preserve
existing LID assignments resolving multiple use of same LID.
-R, --routing_engine <Routing engine names>
This option chooses routing engine(s) to use instead of Min Hop algorithm
(default). Multiple routing engines can be specified separated by commas so that
specific ordering of routing algorithms will be tried if earlier routing engines
fail. If all configured routing engines fail, OpenSM will always attempt to route
with Min Hop unless 'no_fallback' is included in the list of routing engines.
Supported engines: minhop, updn, dnup, file, ftree, lash, dor, torus-2QoS, nue,
dfsssp, sssp.
--do_mesh_analysis
This option enables additional analysis for the lash routing engine to precondition
switch port assignments in regular cartesian meshes which may reduce the number of
SLs required to give a deadlock free routing.
--lash_start_vl <vl number>
This option sets the starting VL to use for the lash routing algorithm. Defaults
to 0.
--nue_max_num_vls <vl number>
This option sets the maximum number of VLs to use for the Nue routing engine.
Every number greater or equal to 0 is allowed, and the default is 1 to enforce
deadlock-freedom even if QoS is not enabled. If set to 0, then Nue routing will
automatically determine and choose maximum supported by the fabric. And if set to
any integer >= 1, then Nue uses min(max_supported,nue_max_num_vls). Rule of thumb
is: higher nue_max_num_vls results in better path balancing.
-A, --ucast_cache
This option enables unicast routing cache and prevents routing recalculation (which
is a heavy task in a large cluster) when there was no topology change detected
during the heavy sweep, or when the topology change does not require new routing
calculation, e.g. when one or more CAs/RTRs/leaf switches going down, or one or
more of these nodes coming back after being down. A very common case that is
handled by the unicast routing cache is host reboot, which otherwise would cause
two full routing recalculations: one when the host goes down, and the other when
the host comes back online.
-z, --connect_roots
This option enforces routing engines (up/down and fat-tree) to make connectivity
between root switches and in this way to be fully IBA compliant. In many cases this
can violate "pure" deadlock free algorithm, so use it carefully.
-M, --lid_matrix_file <file name>
This option specifies the name of the lid matrix dump file from where switch lid
matrices (min hops tables) will be loaded.
-U, --lfts_file <file name>
This option specifies the name of the LFTs file from where switch forwarding tables
will be loaded when using "file" routing engine.
-S, --sadb_file <file name>
This option specifies the name of the SA DB dump file from where SA database will
be loaded.
-a, --root_guid_file <file name>
Set the root nodes for the Up/Down or Fat-Tree routing algorithm to the guids
provided in the given file (one to a line).
-u, --cn_guid_file <file name>
Set the compute nodes for the Fat-Tree or DFSSSP/SSSP routing algorithms to the
port GUIDs provided in the given file (one to a line).
-G, --io_guid_file <file name>
Set the I/O nodes for the Fat-Tree or DFSSSP/SSSP routing algorithms to the port
GUIDs provided in the given file (one to a line).
In the case of Fat-Tree routing:
I/O nodes are non-CN nodes allowed to use up to max_reverse_hops switches the wrong
way around to improve connectivity.
In the case of (DF)SSSP routing:
Providing guids of compute and/or I/O nodes will ensure that paths towards those
nodes are as much separated as possible within their node category, i.e., I/O
traffic will not share the same link if multiple links are available.
--port-shifting
This option enables a feature called port shifting. In some fabrics, particularly
cluster environments, routes commonly align and congest with other routes due to
algorithmically unchanging traffic patterns. This routing option will "shift"
routing around in an attempt to alleviate this problem.
--scatter-ports <random seed>
This option is used to randomize port selection in routing rather than using a
round-robin algorithm (which is the default). Value supplied with option is used as
a random seed. If value is 0, which is the default, the scatter ports option is
disabled.
-H, --max_reverse_hops <max reverse hops allowed>
Set the maximum number of reverse hops an I/O node is allowed to make. A reverse
hop is the use of a switch the wrong way around.
-m, --ids_guid_file <file name>
Name of the map file with set of the IDs which will be used by Up/Down routing
algorithm instead of node GUIDs (format: <guid> <id> per line).
-X, --guid_routing_order_file <file name>
Set the order port guids will be routed for the MinHop and Up/Down routing
algorithms to the guids provided in the given file (one to a line).
-o, --once
This option causes OpenSM to configure the subnet once, then exit. Ports remain in
the ACTIVE state.
-s, --sweep <interval value>
This option specifies the number of seconds between subnet sweeps. Specifying -s 0
disables sweeping. Without -s, OpenSM defaults to a sweep interval of 10 seconds.
-t, --timeout <value>
This option specifies the time in milliseconds used for transaction timeouts.
Timeout values should be > 0. Without -t, OpenSM defaults to a timeout value of
200 milliseconds.
--retries <number>
This option specifies the number of retries used for transactions. Without
--retries, OpenSM defaults to 3 retries for transactions.
--maxsmps <number>
This option specifies the number of VL15 SMP MADs allowed on the wire at any one
time. Specifying --maxsmps 0 allows unlimited outstanding SMPs. Without
--maxsmps, OpenSM defaults to a maximum of 4 outstanding SMPs.
--console [off | local | loopback | socket]
This option brings up the OpenSM console (default off). Note, loopback and socket
open a socket which can be connected to WITHOUT CREDENTIALS. Loopback is safer if
access to your SM host is controlled. tcp_wrappers (hosts.[allow|deny]) is used
with loopback and socket. loopback and socket will only be available if OpenSM was
built with --enable-console-loopback (default yes) and --enable-console-socket
(default no) respectively.
--console-port <port>
Specify an alternate telnet port for the socket console (default 10000). Note that
this option only appears if OpenSM was built with --enable-console-socket.
-i, --ignore_guids <equalize-ignore-guids-file>
This option provides the means to define a set of ports (by node guid and port
number) that will be ignored by the link load equalization algorithm.
-w, --hop_weights_file <path to file>
This option provides weighting factors per port representing a hop cost in
computing the lid matrix. The file consists of lines containing a switch port GUID
(specified as a 64 bit hex number, with leading 0x), output port number, and
weighting factor. Any port not listed in the file defaults to a weighting factor
of 1. Lines starting with # are comments. Weights affect only the output route
from the port, so many useful configurations will require weights to be specified
in pairs.
-O, --port_search_ordering_file <path to file>
This option tweaks the routing. It suitable for two cases: 1. While using DOR
routing algorithm. This option provides a mapping between hypercube dimensions and
ports on a per switch basis for the DOR routing engine. The file consists of lines
containing a switch node GUID (specified as a 64 bit hex number, with leading 0x)
followed by a list of non-zero port numbers, separated by spaces, one switch per
line. The order for the port numbers is in one to one correspondence to the
dimensions. Ports not listed on a line are assigned to the remaining dimensions,
in port order. Anything after a # is a comment. 2. While using general routing
algorithm. This option provides the order of the ports that would be chosen for
routing, from each switch rather than searching for an appropriate port from port 1
to N. The file consists of lines containing a switch node GUID (specified as a 64
bit hex number, with leading 0x) followed by a list of non-zero port numbers,
separated by spaces, one switch per line. In case of DOR, the order for the port
numbers is in one to one correspondence to the dimensions. Ports not listed on a
line are assigned to the remaining dimensions, in port order. Anything after a #
is a comment.
-O, --dimn_ports_file <path to file> (DEPRECATED)
This is a deprecated flag. Please use --port_search_ordering_file instead. This
option provides a mapping between hypercube dimensions and ports on a per switch
basis for the DOR routing engine. The file consists of lines containing a switch
node GUID (specified as a 64 bit hex number, with leading 0x) followed by a list of
non-zero port numbers, separated by spaces, one switch per line. The order for the
port numbers is in one to one correspondence to the dimensions. Ports not listed
on a line are assigned to the remaining dimensions, in port order. Anything after
a # is a comment.
-x, --honor_guid2lid
This option forces OpenSM to honor the guid2lid file, when it comes out of Standby
state, if such file exists under OSM_CACHE_DIR, and is valid. By default, this is
FALSE.
--dump_files_dir <directory name>
This option will set the directory to hold the file dumps.
-f, --log_file <file name>
This option defines the log to be the given file. By default, the log goes to
/var/log/opensm.log. For the log to go to standard output use -f stdout.
-L, --log_limit <size in MB>
This option defines maximal log file size in MB. When specified the log file will
be truncated upon reaching this limit.
-e, --erase_log_file
This option will cause deletion of the log file (if it previously exists). By
default, the log file is accumulative.
-P, --Pconfig <partition config file>
This option defines the optional partition configuration file. The default name is
/etc/opensm/partitions.conf.
--prefix_routes_file <file name>
Prefix routes control how the SA responds to path record queries for off-subnet
DGIDs. By default, the SA fails such queries. The PREFIX ROUTES section below
describes the format of the configuration file. The default path is
/etc/opensm/prefix-routes.conf.
-Q, --qos
This option enables QoS setup. It is disabled by default.
-Y, --qos_policy_file <file name>
This option defines the optional QoS policy file. The default name is
/etc/opensm/qos-policy.conf. See QoS_management_in_OpenSM.txt in opensm doc for
more information on configuring QoS policy via this file.
--congestion_control
(EXPERIMENTAL) This option enables congestion control configuration. It is
disabled by default. See config file for congestion control configuration options.
--cc_key <key> (EXPERIMENTAL) This option configures the CCkey to use when
configuring congestion control. Note that this option does not configure a new
CCkey into switches and CAs. Defaults to 0.
-N, --no_part_enforce (DEPRECATED)
This is a deprecated flag. Please use --part_enforce instead. This option disables
partition enforcement on switch external ports.
-Z, --part_enforce [both | in | out | off]
This option indicates the partition enforcement type (for switches). Enforcement
type can be inbound only (in), outbound only (out), both or disabled (off). Default
is both.
-W, --allow_both_pkeys
This option indicates whether both full and limited membership on the same
partition can be configured in the PKeyTable. Default is not to allow both pkeys.
-y, --stay_on_fatal
This option will cause SM not to exit on fatal initialization issues: if SM
discovers duplicated guids or a 12x link with lane reversal badly configured. By
default, the SM will exit on these errors.
-B, --daemon
Run in daemon mode - OpenSM will run in the background.
-J, --pidfile <file_name>
Makes the SM write its own PID to the specified file when started in daemon mode.
-I, --inactive
Start SM in inactive rather than init SM state. This option can be used in
conjunction with the perfmgr so as to run a standalone performance manager without
SM/SA. However, this is NOT currently implemented in the performance manager.
--perfmgr
Enable the perfmgr. Only takes effect if --enable-perfmgr was specified at
configure time. See performance-manager-HOWTO.txt in opensm doc for more
information on running perfmgr.
--perfmgr_sweep_time_s <seconds>
Specify the sweep time for the performance manager in seconds (default is 180
seconds). Only takes effect if --enable-perfmgr was specified at configure time.
--consolidate_ipv6_snm_req
Use shared MLID for IPv6 Solicited Node Multicast groups per MGID scope and P_Key.
--log_prefix <prefix text>
This option specifies the prefix to the syslog messages from OpenSM. A suitable
prefix can be used to identify the IB subnet in syslog messages when two or more
instances of OpenSM run in a single node to manage multiple fabrics. For example,
in a dual-fabric (or dual-rail) IB cluster, the prefix for the first fabric could
be "mpi" and the other fabric could be "storage".
--torus_config <path to torus-2QoS config file>
This option defines the file name for the extra configuration information needed
for the torus-2QoS routing engine. The default name is
/etc/opensm/torus-2QoS.conf
-v, --verbose
This option increases the log verbosity level. The -v option may be specified
multiple times to further increase the verbosity level. See the -D option for more
information about log verbosity.
-V This option sets the maximum verbosity level and forces log flushing. The -V
option is equivalent to ´-D 0xFF -d 2´. See the -D option for more information
about log verbosity.
-D <value>
This option sets the log verbosity level. A flags field must follow the -D option.
A bit set/clear in the flags enables/disables a specific log level as follows:
BIT LOG LEVEL ENABLED
---- -----------------
0x01 - ERROR (error messages)
0x02 - INFO (basic messages, low volume)
0x04 - VERBOSE (interesting stuff, moderate volume)
0x08 - DEBUG (diagnostic, high volume)
0x10 - FUNCS (function entry/exit, very high volume)
0x20 - FRAMES (dumps all SMP and GMP frames)
0x40 - ROUTING (dump FDB routing information)
0x80 - SYS (syslog at LOG_INFO level in addition to OpenSM logging)
Without -D, OpenSM defaults to ERROR + INFO (0x3). Specifying -D 0 disables all
messages. Specifying -D 0xFF enables all messages (see -V). High verbosity levels
may require increasing the transaction timeout with the -t option.
-d, --debug <value>
This option specifies a debug option. These options are not normally needed. The
number following -d selects the debug option to enable as follows:
OPT Description
--- -----------------
-d0 - Ignore other SM nodes
-d1 - Force single threaded dispatching
-d2 - Force log flushing after each log message
-d3 - Disable multicast support
-h, --help
Display this usage info then exit.
-? Display this usage info then exit.
ENVIRONMENT VARIABLES
The following environment variables control opensm behavior:
OSM_TMP_DIR - controls the directory in which the temporary files generated by opensm are
created. These files are: opensm-subnet.lst, opensm.fdbs, and opensm.mcfdbs. By default,
this directory is /var/log. Note that --dump_files_dir command line option or
dump_file_dir option in option/config file takes precedence over this environment
variable.
OSM_CACHE_DIR - opensm stores certain data to the disk such that subsequent runs are
consistent. The default directory used is /var/cache/opensm. The following files are
included in it:
guid2lid - stores the LID range assigned to each GUID
guid2mkey - stores the MKey previously assigned to each GUID
neighbors - stores a map of the GUIDs at either end of each link
in the fabric
NOTES
When opensm receives a HUP signal, it starts a new heavy sweep as if a trap was received
or a topology change was found.
Also, SIGUSR1 can be used to trigger a reopen of /var/log/opensm.log for logrotate
purposes.
PARTITION CONFIGURATION
The default name of OpenSM partitions configuration file is /etc/opensm/partitions.conf.
The default may be changed by using the --Pconfig (-P) option with OpenSM.
The default partition will be created by OpenSM unconditionally even when partition
configuration file does not exist or cannot be accessed.
The default partition has P_Key value 0x7fff. OpenSM´s port will always have full
membership in default partition. All other end ports will have full membership if the
partition configuration file is not found or cannot be accessed, or limited membership if
the file exists and can be accessed but there is no rule for the Default partition.
Effectively, this amounts to the same as if one of the following rules below appear in the
partition configuration file.
In the case of no rule for the Default partition:
Default=0x7fff : ALL=limited, SELF=full ;
In the case of no partition configuration file or file cannot be accessed:
Default=0x7fff : ALL=full ;
File Format
Comments:
Line content followed after ´#´ character is comment and ignored by parser.
General file format:
<Partition Definition>:[<newline>]<Partition Properties>;
Partition Definition:
[PartitionName][=PKey][,indx0][,ipoib_bc_flags][,defmember=full|limited]
PartitionName - string, will be used with logging. When
omitted, empty string will be used.
PKey - P_Key value for this partition. Only low 15
bits will be used. When omitted will be
autogenerated.
indx0 - indicates that this pkey should be inserted in
block 0 index 0.
ipoib_bc_flags - used to indicate/specify IPoIB capability of
this partition.
defmember=full|limited|both - specifies default membership for
port guid list. Default is limited.
ipoib_bc_flags:
ipoib_flag|[mgroup_flag]*
ipoib_flag:
ipoib - indicates that this partition may be used for
IPoIB, as a result the IPoIB broadcast group will
be created with the mgroup_flag flags given,
if any.
Partition Properties:
[<Port list>|<MCast Group>]* | <Port list>
Port list:
<Port Specifier>[,<Port Specifier>]
Port Specifier:
<PortGUID>[=[full|limited|both]]
PortGUID - GUID of partition member EndPort.
Hexadecimal numbers should start from
0x, decimal numbers are accepted too.
full, limited, - indicates full and/or limited membership for
both this port. When omitted (or unrecognized)
limited membership is assumed. Both
indicates both full and limited membership
for this port.
MCast Group:
mgid=gid[,mgroup_flag]*<newline>
- gid specified is verified to be a Multicast
address. IP groups are verified to match
the rate and mtu of the broadcast group.
The P_Key bits of the mgid for IP groups are
verified to either match the P_Key specified
in by "Partition Definition" or if they are
0x0000 the P_Key will be copied into those
bits.
mgroup_flag:
rate=<val> - specifies rate for this MC group
(default is 3 (10GBps))
mtu=<val> - specifies MTU for this MC group
(default is 4 (2048))
sl=<val> - specifies SL for this MC group
(default is 0)
scope=<val> - specifies scope for this MC group
(default is 2 (link local)). Multiple scope
settings are permitted for a partition.
NOTE: This overwrites the scope nibble of the
specified mgid. Furthermore specifying
multiple scope settings will result in
multiple MC groups being created.
Q_Key=<val> - specifies the Q_Key for this MC group
(default: 0x0b1b for IP groups, 0 for other
groups)
WARNING: changing this for the broadcast
group may break IPoIB on client
nodes!!
TClass=<val> - specifies tclass for this MC group
(default is 0)
FlowLabel=<val> - specifies FlowLabel for this MC group
(default is 0) NOTE: All mgroup_flag flags MUST be
separated by comma (,).
Note that values for rate, mtu, and scope, for both partitions and multicast groups,
should be specified as defined in the IBTA specification (for example, mtu=4 for 2048).
There are several useful keywords for PortGUID definition:
- 'ALL' means all end ports in this subnet.
- 'ALL_CAS' means all Channel Adapter end ports in this subnet.
- 'ALL_SWITCHES' means all Switch end ports in this subnet.
- 'ALL_ROUTERS' means all Router end ports in this subnet.
- 'SELF' means subnet manager's port.
Empty list means no ports in this partition.
Notes:
White space is permitted between delimiters ('=', ',',':',';').
PartitionName does not need to be unique, PKey does need to be unique. If PKey is
repeated then those partition configurations will be merged and first PartitionName will
be used (see also next note).
It is possible to split partition configuration in more than one definition, but then PKey
should be explicitly specified (otherwise different PKey values will be generated for
those definitions).
Examples:
Default=0x7fff : ALL, SELF=full ;
Default=0x7fff : ALL, ALL_SWITCHES=full, SELF=full ;
NewPartition , ipoib : 0x123456=full, 0x3456789034=limi, 0x2134af2306 ;
YetAnotherOne = 0x300 : SELF=full ;
YetAnotherOne = 0x300 : ALL=limited ;
ShareIO = 0x80 , defmember=full : 0x123451, 0x123452;
# 0x123453, 0x123454 will be limited
ShareIO = 0x80 : 0x123453, 0x123454, 0x123455=full;
# 0x123456, 0x123457 will be limited
ShareIO = 0x80 : defmember=limited : 0x123456, 0x123457, 0x123458=full;
ShareIO = 0x80 , defmember=full : 0x123459, 0x12345a;
ShareIO = 0x80 , defmember=full : 0x12345b, 0x12345c=limited, 0x12345d;
# multicast groups added to default
Default=0x7fff,ipoib:
mgid=ff12:401b::0707,sl=1 # random IPv4 group
mgid=ff12:601b::16 # MLDv2-capable routers
mgid=ff12:401b::16 # IGMP
mgid=ff12:601b::2 # All routers
mgid=ff12::1,sl=1,Q_Key=0xDEADBEEF,rate=3,mtu=2 # random group
ALL=full;
Note:
The following rule is equivalent to how OpenSM used to run prior to the partition manager:
Default=0x7fff,ipoib:ALL=full;
QOS CONFIGURATION
There are a set of QoS related low-level configuration parameters. All these parameter
names are prefixed by "qos_" string. Here is a full list of these parameters:
qos_max_vls - The maximum number of VLs that will be on the subnet
qos_high_limit - The limit of High Priority component of VL
Arbitration table (IBA 7.6.9)
qos_vlarb_low - Low priority VL Arbitration table (IBA 7.6.9)
template
qos_vlarb_high - High priority VL Arbitration table (IBA 7.6.9)
template
Both VL arbitration templates are pairs of
VL and weight
qos_sl2vl - SL2VL Mapping table (IBA 7.6.6) template. It is
a list of VLs corresponding to SLs 0-15 (Note
that VL15 used here means drop this SL)
Typical default values (hard-coded in OpenSM initialization) are:
qos_max_vls 15
qos_high_limit 0
qos_vlarb_low 0:0,1:4,2:4,3:4,4:4,5:4,6:4,7:4,8:4,9:4,10:4,11:4,12:4,13:4,14:4
qos_vlarb_high 0:4,1:0,2:0,3:0,4:0,5:0,6:0,7:0,8:0,9:0,10:0,11:0,12:0,13:0,14:0
qos_sl2vl 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,7
The syntax is compatible with rest of OpenSM configuration options and values may be
stored in OpenSM config file (cached options file).
In addition to the above, we may define separate QoS configuration parameters sets for
various target types. As targets, we currently support CAs, routers, switch external
ports, and switch's enhanced port 0. The names of such specialized parameters are prefixed
by "qos_<type>_" string. Here is a full list of the currently supported sets:
qos_ca_ - QoS configuration parameters set for CAs.
qos_rtr_ - parameters set for routers.
qos_sw0_ - parameters set for switches' port 0.
qos_swe_ - parameters set for switches' external ports.
Examples:
qos_sw0_max_vls=2
qos_ca_sl2vl=0,1,2,3,5,5,5,12,12,0,
qos_swe_high_limit=0
PREFIX ROUTES
Prefix routes control how the SA responds to path record queries for off-subnet DGIDs. By
default, the SA fails such queries. Note that IBA does not specify how the SA should
obtain off-subnet path record information. The prefix routes configuration is meant as a
stop-gap until the specification is completed.
Each line in the configuration file is a 64-bit prefix followed by a 64-bit GUID,
separated by white space. The GUID specifies the router port on the local subnet that
will handle the prefix. Blank lines are ignored, as is anything between a # character and
the end of the line. The prefix and GUID are both in hex, the leading 0x is optional.
Either, or both, can be wild-carded by specifying an asterisk instead of an explicit
prefix or GUID.
When responding to a path record query for an off-subnet DGID, opensm searches for the
first prefix match in the configuration file. Therefore, the order of the lines in the
configuration file is important: a wild-carded prefix at the beginning of the
configuration file renders all subsequent lines useless. If there is no match, then
opensm fails the query. It is legal to repeat prefixes in the configuration file, opensm
will return the path to the first available matching router. A configuration file with a
single line where both prefix and GUID are wild-carded means that a path record query
specifying any off-subnet DGID should return a path to the first available router. This
configuration yields the same behavior formerly achieved by compiling opensm with
-DROUTER_EXP which has been obsoleted.
MKEY CONFIGURATION
OpenSM supports configuring a single management key (MKey) for use across the subnet.
The following configuration options are available:
m_key - the 64-bit MKey to be used on the subnet
(IBA 14.2.4)
m_key_protection_level - the numeric value of the MKey ProtectBits
(IBA 14.2.4.1)
m_key_lease_period - the number of seconds a CA will wait for a
response from the SM before resetting the
protection level to 0 (IBA 14.2.4.2).
OpenSM will configure all ports with the MKey specified by m_key, defaulting to a value of
0. A m_key value of 0 disables MKey protection on the subnet. Switches and HCAs with a
non-zero MKey will not accept requests to change their configuration unless the request
includes the proper MKey.
MKey Protection Levels
MKey protection levels modify how switches and CAs respond to SMPs lacking a valid MKey.
OpenSM will configure each port's ProtectBits to support the level defined by the
m_key_protection_level parameter. If no parameter is specified, OpenSM defaults to
operating at protection level 0.
There are currently 4 protection levels defined by the IBA:
0 - Queries return valid data, including MKey. Configuration changes
are not allowed unless the request contains a valid MKey.
1 - Like level 0, but the MKey is set to 0 (0x00000000) in queries,
unless the request contains a valid MKey.
2 - Neither queries nor configuration changes are allowed, unless the
request contains a valid MKey.
3 - Identical to 2. Maintained for backwards compatibility.
MKey Lease Period
InfiniBand supports a MKey lease timeout, which is intended to allow administrators or a
new SM to recover/reset lost MKeys on a fabric.
If MKeys are enabled on the subnet and a switch or CA receives a request that requires a
valid MKey but does not contain one, it warns the SM by sending a trap (Bad M_Key, Trap
256). If the MKey lease period is non-zero, it also starts a countdown timer for the time
specified by the lease period. If a SM (or other agent) responds with the correct MKey,
the timer is stopped and reset. Should the timer reach zero, the switch or CA will reset
its MKey protection level to 0, exposing the MKey and allowing recovery.
OpenSM will initialize all ports to use a mkey lease period of the number of seconds
specified in the config file. If no mkey_lease_period is specified, a default of 0 will
be used.
OpenSM normally quickly responds to all Bad_M_Key traps, resetting the lease timers.
Additionally, OpenSM's subnet sweeps will also cancel any running timers. For maximum
protection against accidentally-exposed MKeys, the MKey lease time should be a few
multiples of the subnet sweep time. If OpenSM detects at startup that your sweep interval
is greater than your MKey lease period, it will reset the lease period to be greater than
the sweep interval. Similarly, if sweeping is disabled at startup, it will be re-enabled
with an interval less than the Mkey lease period.
If OpenSM is required to recover a subnet for which it is missing mkeys, it must do so one
switch level at a time. As such, the total time to recover the subnet may be as long as
the mkey lease period multiplied by the maximum number of hops between the SM and an
endpoint, plus one.
MKey Effects on Diagnostic Utilities
Setting a MKey may have a detrimental effect on diagnostic software run on the subnet,
unless your diagnostic software is able to retrieve MKeys from the SA or can be explicitly
configured with the proper MKey. This is particularly true at protection level 2, where
CAs will ignore queries for management information that do not contain the proper MKey.
ROUTING
OpenSM now offers ten routing engines:
1. Min Hop Algorithm - based on the minimum hops to each node where the path length is
optimized.
2. UPDN Unicast routing algorithm - also based on the minimum hops to each node, but it
is constrained to ranking rules. This algorithm should be chosen if the subnet is not a
pure Fat Tree, and deadlock may occur due to a loop in the subnet.
3. DNUP Unicast routing algorithm - similar to UPDN but allows routing in fabrics which
have some CA nodes attached closer to the roots than some switch nodes.
4. Fat Tree Unicast routing algorithm - this algorithm optimizes routing for congestion-
free "shift" communication pattern. It should be chosen if a subnet is a symmetrical or
almost symmetrical fat-tree of various types, not just K-ary-N-Trees: non-constant K, not
fully staffed, any Constant Bisectional Bandwidth (CBB) ratio. Similar to UPDN, Fat Tree
routing is constrained to ranking rules.
5. LASH unicast routing algorithm - uses InfiniBand virtual layers (SL) to provide
deadlock-free shortest-path routing while also distributing the paths between layers. LASH
is an alternative deadlock-free topology-agnostic routing algorithm to the non-minimal
UPDN algorithm avoiding the use of a potentially congested root node.
6. DOR Unicast routing algorithm - based on the Min Hop algorithm, but avoids port
equalization except for redundant links between the same two switches. This provides
deadlock free routes for hypercubes when the fabric is cabled as a hypercube and for
meshes when cabled as a mesh (see details below).
7. Torus-2QoS unicast routing algorithm - a DOR-based routing algorithm specialized for
2D/3D torus topologies. Torus-2QoS provides deadlock-free routing while supporting two
quality of service (QoS) levels. In addition it is able to route around multiple failed
fabric links or a single failed fabric switch without introducing deadlocks, and without
changing path SL values granted before the failure.
8. DFSSSP unicast routing algorithm - a deadlock-free single-source-shortest-path routing,
which uses the SSSP algorithm (see algorithm 9.) as the base to optimize link utilization
and uses InfiniBand virtual lanes (SL) to provide deadlock-freedom.
9. SSSP unicast routing algorithm - a single-source-shortest-path routing algorithm, which
globally balances the number of routes per link to optimize link utilization. This routing
algorithm has no restrictions in terms of the underlying topology.
10. Nue unicast routing algorithm - a 100%-applicable and deadlock-free routing which can
be used for any arbitrary or faulty network topology and any number of virtual lanes (this
includes the absence of VLs as well). Paths are globally balanced w.r.t the number of
routes per link, and are kept as short as possible while enforcing deadlock-freedom within
the VL constraint.
OpenSM also supports a file method which can load routes from a table. See ´Modular
Routing Engine´ for more information on this.
The basic routing algorithm is comprised of two stages:
1. MinHop matrix calculation
How many hops are required to get from each port to each LID ?
The algorithm to fill these tables is different if you run standard (min hop) or
Up/Down.
For standard routing, a "relaxation" algorithm is used to propagate min hop from every
destination LID through neighbor switches
For Up/Down routing, a BFS from every target is used. The BFS tracks link direction (up
or down) and avoid steps that will perform up after a down step was used.
2. Once MinHop matrices exist, each switch is visited and for each target LID a decision
is made as to what port should be used to get to that LID.
This step is common to standard and Up/Down routing. Each port has a counter counting
the number of target LIDs going through it.
When there are multiple alternative ports with same MinHop to a LID, the one with less
previously assigned LIDs is selected.
If LMC > 0, more checks are added: Within each group of LIDs assigned to same target
port,
a. use only ports which have same MinHop
b. first prefer the ones that go to different systemImageGuid (then the previous LID of
the same LMC group)
c. if none - prefer those which go through another NodeGuid
d. fall back to the number of paths method (if all go to same node).
Effect of Topology Changes
OpenSM will preserve existing routing in any case where there is no change in the fabric
switches unless the -r (--reassign_lids) option is specified.
-r
--reassign_lids
This option causes OpenSM to reassign LIDs to all
end nodes. Specifying -r on a running subnet
may disrupt subnet traffic.
Without -r, OpenSM attempts to preserve existing
LID assignments resolving multiple use of same LID.
If a link is added or removed, OpenSM does not recalculate the routes that do not have to
change. A route has to change if the port is no longer UP or no longer the MinHop. When
routing changes are performed, the same algorithm for balancing the routes is invoked.
In the case of using the file based routing, any topology changes are currently ignored
The 'file' routing engine just loads the LFTs from the file specified, with no reaction to
real topology. Obviously, this will not be able to recheck LIDs (by GUID) for disconnected
nodes, and LFTs for non-existent switches will be skipped. Multicast is not affected by
'file' routing engine (this uses min hop tables).
Min Hop Algorithm
The Min Hop algorithm is invoked by default if no routing algorithm is specified. It can
also be invoked by specifying '-R minhop'.
The Min Hop algorithm is divided into two stages: computation of min-hop tables on every
switch and LFT output port assignment. Link subscription is also equalized with the
ability to override based on port GUID. The latter is supplied by:
-i <equalize-ignore-guids-file>
--ignore_guids <equalize-ignore-guids-file>
This option provides the means to define a set of ports
(by guid) that will be ignored by the link load
equalization algorithm. Note that only endports (CA,
switch port 0, and router ports) and not switch external
ports are supported.
LMC awareness routes based on (remote) system or switch basis.
Purpose of UPDN Algorithm
The UPDN algorithm is designed to prevent deadlocks from occurring in loops of the subnet.
A loop-deadlock is a situation in which it is no longer possible to send data between any
two hosts connected through the loop. As such, the UPDN routing algorithm should be used
if the subnet is not a pure Fat Tree, and one of its loops may experience a deadlock (due,
for example, to high pressure).
The UPDN algorithm is based on the following main stages:
1. Auto-detect root nodes - based on the CA hop length from any switch in the subnet, a
statistical histogram is built for each switch (hop num vs number of occurrences). If the
histogram reflects a specific column (higher than others) for a certain node, then it is
marked as a root node. Since the algorithm is statistical, it may not find any root nodes.
The list of the root nodes found by this auto-detect stage is used by the ranking process
stage.
Note 1: The user can override the node list manually.
Note 2: If this stage cannot find any root nodes, and the user did
not specify a guid list file, OpenSM defaults back to the
Min Hop routing algorithm.
2. Ranking process - All root switch nodes (found in stage 1) are assigned a rank of 0.
Using the BFS algorithm, the rest of the switch nodes in the subnet are ranked
incrementally. This ranking aids in the process of enforcing rules that ensure loop-free
paths.
3. Min Hop Table setting - after ranking is done, a BFS algorithm is run from each (CA or
switch) node in the subnet. During the BFS process, the FDB table of each switch node
traversed by BFS is updated, in reference to the starting node, based on the ranking rules
and guid values.
At the end of the process, the updated FDB tables ensure loop-free paths through the
subnet.
Note: Up/Down routing does not allow LID routing communication between switches that are
located inside spine "switch systems". The reason is that there is no way to allow a LID
route between them that does not break the Up/Down rule. One ramification of this is that
you cannot run SM on switches other than the leaf switches of the fabric.
UPDN Algorithm Usage
Activation through OpenSM
Use '-R updn' option (instead of old '-u') to activate the UPDN algorithm. Use '-a
<root_guid_file>' for adding an UPDN guid file that contains the root nodes for ranking.
If the `-a' option is not used, OpenSM uses its auto-detect root nodes algorithm.
Notes on the guid list file:
1. A valid guid file specifies one guid in each line. Lines with an invalid format will
be discarded.
2. The user should specify the root switch guids. However, it is also possible to
specify CA guids; OpenSM will use the guid of the switch (if it exists) that connects the
CA to the subnet as a root node.
Purpose of DNUP Algorithm
The DNUP algorithm is designed to serve a similar purpose to UPDN. However it is intended
to work in network topologies which are unsuited to UPDN due to nodes being connected
closer to the roots than some of the switches. An example would be a fabric which
contains nodes and uplinks connected to the same switch. The operation of DNUP is the same
as UPDN with the exception of the ranking process. In DNUP all switch nodes are ranked
based solely on their distance from CA Nodes, all switch nodes directly connected to at
least one CA are assigned a value of 1 all other switch nodes are assigned a value of one
more than the minimum rank of all neighbor switch nodes.
Fat-tree Routing Algorithm
The fat-tree algorithm optimizes routing for "shift" communication pattern. It should be
chosen if a subnet is a symmetrical or almost symmetrical fat-tree of various types. It
supports not just K-ary-N-Trees, by handling for non-constant K, cases where not all leafs
(CAs) are present, any CBB ratio. As in UPDN, fat-tree also prevents credit-loop-
deadlocks.
If the root guid file is not provided ('-a' or '--root_guid_file' options), the topology
has to be pure fat-tree that complies with the following rules:
- Tree rank should be between two and eight (inclusively)
- Switches of the same rank should have the same number
of UP-going port groups*, unless they are root switches,
in which case the shouldn't have UP-going ports at all.
- Switches of the same rank should have the same number
of DOWN-going port groups, unless they are leaf switches.
- Switches of the same rank should have the same number
of ports in each UP-going port group.
- Switches of the same rank should have the same number
of ports in each DOWN-going port group.
- All the CAs have to be at the same tree level (rank).
If the root guid file is provided, the topology doesn't have to be pure fat-tree, and it
should only comply with the following rules:
- Tree rank should be between two and eight (inclusively)
- All the Compute Nodes** have to be at the same tree level (rank).
Note that non-compute node CAs are allowed here to be at different
tree ranks.
* ports that are connected to the same remote switch are referenced as ´port group´.
** list of compute nodes (CNs) can be specified by ´-u´ or ´--cn_guid_file´ OpenSM
options.
Topologies that do not comply cause a fallback to min hop routing. Note that this can
also occur on link failures which cause the topology to no longer be "pure" fat-tree.
Note that although fat-tree algorithm supports trees with non-integer CBB ratio, the
routing will not be as balanced as in case of integer CBB ratio. In addition to this,
although the algorithm allows leaf switches to have any number of CAs, the closer the tree
is to be fully populated, the more effective the "shift" communication pattern will be.
In general, even if the root list is provided, the closer the topology to a pure and
symmetrical fat-tree, the more optimal the routing will be.
The algorithm also dumps compute node ordering file (opensm-ftree-ca-order.dump) in the
same directory where the OpenSM log resides. This ordering file provides the CN order that
may be used to create efficient communication pattern, that will match the routing tables.
Routing between non-CN nodes
The use of the cn_guid_file option allows non-CN nodes to be located on different levels
in the fat tree. In such case, it is not guaranteed that the Fat Tree algorithm will
route between two non-CN nodes. To solve this problem, a list of non-CN nodes can be
specified by ´-G´ or ´--io_guid_file´ option. Theses nodes will be allowed to use
switches the wrong way round a specific number of times (specified by ´-H´ or
´--max_reverse_hops´. With the proper max_reverse_hops and io_guid_file values, you can
ensure full connectivity in the Fat Tree.
Please note that using max_reverse_hops creates routes that use the switch in a counter-
stream way. This option should never be used to connect nodes with high bandwidth traffic
between them ! It should only be used to allow connectivity for HA purposes or similar.
Also having routes the other way around can in theory cause credit loops.
Use these options with extreme care !
Activation through OpenSM
Use '-R ftree' option to activate the fat-tree algorithm. Use '-a <root_guid_file>' to
provide root nodes for ranking. If the `-a' option is not used, routing algorithm will
detect roots automatically. Use '-u <root_cn_file>' to provide the list of compute nodes.
If the `-u' option is not used, all the CAs are considered as compute nodes.
Note: LMC > 0 is not supported by fat-tree routing. If this is specified, the default
routing algorithm is invoked instead.
LASH Routing Algorithm
LASH is an acronym for LAyered SHortest Path Routing. It is a deterministic shortest path
routing algorithm that enables topology agnostic deadlock-free routing within
communication networks.
When computing the routing function, LASH analyzes the network topology for the shortest-
path routes between all pairs of sources / destinations and groups these paths into
virtual layers in such a way as to avoid deadlock.
Note LASH analyzes routes and ensures deadlock freedom between switch pairs. The link from
HCA between and switch does not need virtual layers as deadlock will not arise between
switch and HCA.
In more detail, the algorithm works as follows:
1) LASH determines the shortest-path between all pairs of source / destination switches.
Note, LASH ensures the same SL is used for all SRC/DST - DST/SRC pairs and there is no
guarantee that the return path for a given DST/SRC will be the reverse of the route
SRC/DST.
2) LASH then begins an SL assignment process where a route is assigned to a layer (SL) if
the addition of that route does not cause deadlock within that layer. This is achieved by
maintaining and analysing a channel dependency graph for each layer. Once the potential
addition of a path could lead to deadlock, LASH opens a new layer and continues the
process.
3) Once this stage has been completed, it is highly likely that the first layers processed
will contain more paths than the latter ones. To better balance the use of layers, LASH
moves paths from one layer to another so that the number of paths in each layer averages
out.
Note, the implementation of LASH in opensm attempts to use as few layers as possible. This
number can be less than the number of actual layers available.
In general LASH is a very flexible algorithm. It can, for example, reduce to Dimension
Order Routing in certain topologies, it is topology agnostic and fares well in the face of
faults.
It has been shown that for both regular and irregular topologies, LASH outperforms
Up/Down. The reason for this is that LASH distributes the traffic more evenly through a
network, avoiding the bottleneck issues related to a root node and always routes shortest-
path.
The algorithm was developed by Simula Research Laboratory.
Use '-R lash -Q ' option to activate the LASH algorithm.
Note: QoS support has to be turned on in order that SL/VL mappings are used.
Note: LMC > 0 is not supported by the LASH routing. If this is specified, the default
routing algorithm is invoked instead.
For open regular cartesian meshes the DOR algorithm is the ideal routing algorithm. For
toroidal meshes on the other hand there are routing loops that can cause deadlocks. LASH
can be used to route these cases. The performance of LASH can be improved by
preconditioning the mesh in cases where there are multiple links connecting switches and
also in cases where the switches are not cabled consistently. An option exists for LASH to
do this. To invoke this use '-R lash -Q --do_mesh_analysis'. This will add an additional
phase that analyses the mesh to try to determine the dimension and size of a mesh. If it
determines that the mesh looks like an open or closed cartesian mesh it reorders the ports
in dimension order before the rest of the LASH algorithm runs.
DOR Routing Algorithm
The Dimension Order Routing algorithm is based on the Min Hop algorithm and so uses
shortest paths. Instead of spreading traffic out across different paths with the same
shortest distance, it chooses among the available shortest paths based on an ordering of
dimensions. Each port must be consistently cabled to represent a hypercube dimension or a
mesh dimension. Alternatively, the -O option can be used to assign a custom mapping
between the ports on a given switch, and the associated dimension. Paths are grown from a
destination back to a source using the lowest dimension (port) of available paths at each
step. This provides the ordering necessary to avoid deadlock. When there are multiple
links between any two switches, they still represent only one dimension and traffic is
balanced across them unless port equalization is turned off. In the case of hypercubes,
the same port must be used throughout the fabric to represent the hypercube dimension and
match on both ends of the cable, or the -O option used to accomplish the alignment. In
the case of meshes, the dimension should consistently use the same pair of ports, one port
on one end of the cable, and the other port on the other end, continuing along the mesh
dimension, or the -O option used as an override.
Use '-R dor' option to activate the DOR algorithm.
DFSSSP and SSSP Routing Algorithm
The (Deadlock-Free) Single-Source-Shortest-Path routing algorithm is designed to optimize
link utilization thru global balancing of routes, while supporting arbitrary topologies.
The DFSSSP routing algorithm uses InfiniBand virtual lanes (SL) to provide deadlock-
freedom.
The DFSSSP algorithm consists of five major steps:
1) It discovers the subnet and models the subnet as a directed multigraph in which each
node represents a node of the physical network and each edge represents one direction of
the full-duplex links used to connect the nodes.
2) A loop, which iterates over all CA and switches of the subnet, will perform three steps
to generate the linear forwarding tables for each switch:
2.1) use Dijkstra's algorithm to find the shortest path from all nodes to the current
selected destination;
2.2) update the edge weights in the graph, i.e. add the number of routes, which use a link
to reach the destination, to the link/edge;
2.3) update the LFT of each switch with the outgoing port which was used in the current
step to route the traffic to the destination node.
3) After the number of available virtual lanes or layers in the subnet is detected and a
channel dependency graph is initialized for each layer, the algorithm will put each
possible route of the subnet into the first layer.
4) A loop iterates over all channel dependency graphs (CDG) and performs the following
substeps:
4.1) search for a cycle in the current CDG;
4.2) when a cycle is found, i.e. a possible deadlock is present, one edge is selected and
all routes, which induced this edge, are moved to the "next higher" virtual layer
(CDG[i+1]);
4.3) the cycle search is continued until all cycles are broken and routes are moved "up".
5) When the number of needed layers does not exceeds the number of available SL/VL to
remove all cycles in all CDGs, the routing is deadlock-free and an relation table is
generated, which contains the assignment of routes from source to destination to a SL
Note on SSSP:
This algorithm does not perform the steps 3)-5) and can not be considered to be deadlock-
free for all topologies. But on the one hand, you can choose this algorithm for really
large networks (5,000+ CAs and deadlock-free by design) to reduce the runtime of the
algorithm. On the other hand, you might use the SSSP routing algorithm as an alternative,
when all deadlock-free routing algorithms fail to route the network for whatever reason.
In the last case, SSSP was designed to deliver an equal or higher bandwidth due to better
congestion avoidance than the Min Hop routing algorithm.
Notes for usage:
a) running DFSSSP: '-R dfsssp -Q'
a.1) QoS has to be configured to equally spread the load on the available SL or virtual
lanes
a.2) applications must perform a path record query to get path SL for each route, which
the application will use to transmit packages
b) running SSSP: '-R sssp'
c) both algorithms support LMC > 0
Hints for optimizing I/O traffic:
Having more nodes (I/O and compute) connected to a switch than incoming links can result
in a 'bad' routing of the I/O traffic as long as (DF)SSSP routing is not aware of the
dedicated I/O nodes, i.e., in the following network configuration CN1-CN3 might send all
I/O traffic via Link2 to IO1,IO2:
CN1 Link1 IO1
\ /----\ /
CN2 -- Switch1 Switch2 -- CN4
/ \----/ \
CN3 Link2 IO2
To prevent this from happening (DF)SSSP can use both the compute node guid file and the
I/O guid file specified by the ´-u´ or ´--cn_guid_file´ and ´-G´ or ´--io_guid_file´
options (similar to the Fat-Tree routing). This ensures that traffic towards compute
nodes and I/O nodes is balanced separately and therefore distributed as much as possible
across the available links. Port GUIDs, as listed by ibstat, must be specified (not Node
GUIDs).
The priority for the optimization is as follows:
compute nodes -> I/O nodes -> other nodes
Possible use case scenarios:
a) neither ´-u´ nor ´-G´ are specified: all nodes a treated as ´other nodes´ and therefore
balanced equally;
b) ´-G´ is specified: traffic towards I/O nodes will be balanced optimally;
c) the system has three node types, such as login/admin, compute and I/O, but the
balancing focus should be I/O, then one has to use ´-u´ and ´-G´ with I/O guids listed in
cn_guid_file and compute node guids listed in io_guid_file;
d) ...
Torus-2QoS Routing Algorithm
Torus-2QoS is routing algorithm designed for large-scale 2D/3D torus fabrics; see
torus-2QoS(8) for full documentation.
Use '-R torus-2QoS -Q' or '-R torus-2QoS,no_fallback -Q' to activate the torus-2QoS
algorithm.
Nue Routing Algorithm
Use either `-R nue' or `-R nue -Q --nue_max_num_vls <int>' to activate Nue.
Note: if `--nue_max_num_vls' is specified and unequal to 1, then QoS support must be
turned on, so that SL2VL mappings are valid and applications comply with suggested SLs to
avoid credit-loops. For more details on QoS and Nue see below.
The implementation of Nue routing for OpenSM is a 100%-applicable, balanced, and deadlock-
free unicast routing engine (which also configures multicast tables, see 'Note on
multicast' below). The key points of this algorithm are the following:
- 100% fault-tolerant, oblivious routing strategy
- topology-agnostic, i.e., applicable to every topology (no matter if topology
is regular, irregular after faults, or random)
- 100% deadlock-free routing within the resource limits (i.e., it never
exceeds the given number of available virtual lanes, and it does not
necessarily require virtual lanes) for every topology
- very good path balancing and therefore high throughput (even better when
using METIS, see notes below)
- QoS (via SLs/VLs) + deadlock-freedom can be combined (since both rely on
VLs), e.g., using VL0-3 for Nue's deadlock-freedom (and 1. QoS level) and
VL4-7 as second QoS level
- forwarding tables are fast to calculate: O(n^2 * log n), however slightly
slower compared to topology-aware routings (for obvious reasons), and
- the path-to-VL mapping only depends on the destination, which may be useful
for scalable, efficient path resolution and caching mechanisms.
From a very high level perspective, Nue routing is similar to DFSSSP (see above) in the
sense that both use Dijkstra and edge weight updates for path balancing, and paths are
mapped to virtual layers assuming a 1:1 mapping of SL2VL tables. However, the fundamental
difference is that Nue routing doesn't perform the path calculation on the graph
representing the real fabric, and instead routes directly within the channel dependency
graph. This approach allows Nue routing to place routing restrictions (to avoid any
credit-loops) in an on-demand manner, which overcomes the problem of all other good VL-
based algorithms. Meaning, the competitors cannot control or limit the use of VLs, and
might run out of them and have to give up. On the flip side, Nue may have to use detours
for a few routes, and hence cannot really be considered "shortest-path" routing, because
it is impossible to accomplish deadlock-free, shortest-path routing with an limited number
of available virtual lanes for arbitrary network topologies.
Note on the use of METIS library with Nue:
Nue routing may has to separate the LIDs into multiple subsets, one for every virtual
layer, if multiple layers are used. Nue has two options to perform this partitioning (not
to be confused with IB partitions); the first is a fairly simple semi-random assignment of
LIDs to layers/subsets, and the second partitioning uses the METIS library to partition
the network graph into k approximately equal sized parts. The latter approach has shown
better results in terms of path balancing and avoidance of using fallback paths, and hence
it is HIGHLY advised to install/use the METIS library with OpenSM (enforced via `--enable-
metis' configure flag when building OpenSM). For the rare case, that METIS isn't packaged
with the Linux distro, here is a link to the official website to download and install
METIS 5.1.0 manually:
http://glaros.dtc.umn.edu/gkhome/metis/metis/overview
OpenSM's configure script also provides options in case METIS header and library aren't
found in the default path.
Runtime options for Nue:
The behavior of Nue routing can be directly influenced by the osm.conf parameter (which is
also available as command line option):
- nue_max_num_vls: controls/limits the number of virtual lanes/layers which
Nue is allowed to use (detailed explanation in osm.conf file).
Furthermore, Nue supports TRUE and FALSE settings of avoid_throttled_links,
use_ucast_cache, and qos (more on this hereafter); and lmc > 0.
Notes on Quality of Service (QoS):
The advantage of Nue is that it works with AND without QoS being enabled, i.e., the usage
of SLs/VLs for deadlock-freedom can be avoided. Here are the three possible usage
scenarios:
- neither setting `--nue_max_num_vls <int>' nor `-Q': Nue assumes that only 1
virtual layer (identical to physical network; or OperVLs equal to VL0) is
usable and all paths are to be calculated within this one layer. Hence,
there is no need for special SL2VL mappings in the network and the use of
specific SLs by applications.
- setting `-Q' but not `--nue_max_num_vls <int>': This combination works like
the previous one, meaning the SL returned for path record requests is not
defined by Nue, since all paths are deadlock-free without using VLs.
However, any separate QoS settings may influence the SL returned to
applications.
- setting `-Q --nue_max_num_vls <int>' with int != 1: In this configuration,
applications have to query and obey the SL for path records as returned
by Nue because otherwise the deadlock-freedom cannot be guaranteed
anymore. Furthermore, errors in the fabric may require applications to
repath to avoid message deadlocks. Since Nue operates on virtual layer,
admins should configure the SL2VL mapping tables in an homogeneous 1:1
manner across the entire subnet to separate the layers.
As an additional note, using more VLs for Nue usually improves the overall network
throughput, so there are trade offs admins may have to consider when configuring the
subnet manager with Nue routing.
Note on multicast:
The Nue routing engine configures multicast forwarding tables by utilizing a spanning tree
calculation routed at a subnet switch suggested by OpenSM. This spanning tree for a mcast
group will try to use the least overloaded links (w.r.t the ucast paths-per-link
metric/weight) in the fabric. However, Nue routing currently does not guarantee deadlock-
freedom for the set of multicast routes on all topologies, nor for the combination of
deadlock-free unicast routes with additional multicast routes. Assuming, for a given
topology the calculated mcast routes are dl-free, then an admin may fix the latter problem
by separating the VLs, e.g., using VL0-6 for unicast routing by specifying
`--nue_max_num_vls 7' and utilizing VL7 for multicast.
Routing References
To learn more about deadlock-free routing, see the article "Deadlock Free Message Routing
in Multiprocessor Interconnection Networks" by William J Dally and Charles L Seitz (1985).
To learn more about the up/down algorithm, see the article "Effective Strategy to Compute
Forwarding Tables for InfiniBand Networks" by Jose Carlos Sancho, Antonio Robles, and Jose
Duato at the Universidad Politecnica de Valencia.
To learn more about LASH and the flexibility behind it, the requirement for layers,
performance comparisons to other algorithms, see the following articles:
"Layered Routing in Irregular Networks", Lysne et al, IEEE Transactions on Parallel and
Distributed Systems, VOL.16, No12, December 2005.
"Routing for the ASI Fabric Manager", Solheim et al. IEEE Communications Magazine, Vol.44,
No.7, July 2006.
"Layered Shortest Path (LASH) Routing in Irregular System Area Networks", Skeie et al.
IEEE Computer Society Communication Architecture for Clusters 2002.
To learn more about the DFSSSP and SSSP routing algorithm, see the articles:
J. Domke, T. Hoefler and W. Nagel: Deadlock-Free Oblivious Routing for Arbitrary
Topologies, In Proceedings of the 25th IEEE International Parallel & Distributed
Processing Symposium (IPDPS 2011)
T. Hoefler, T. Schneider and A. Lumsdaine: Optimized Routing for Large-Scale InfiniBand
Networks, In 17th Annual IEEE Symposium on High Performance Interconnects (HOTI 2009)
To learn more about the Nue routing algorithm, see the article "Routing on the Dependency
Graph: A New Approach to Deadlock-Free High-Performance Routing" by J. Domke, T. Hoefler
and S. Matsuoka (published in HPDC'16).
Modular Routing Engine
Modular routing engine structure allows for the ease of "plugging" new routing modules.
Currently, only unicast callbacks are supported. Multicast can be added later.
One existing routing module is up-down "updn", which may be activated with '-R updn'
option (instead of old '-u').
General usage is: $ opensm -R 'module-name'
There is also a trivial routing module which is able to load LFT tables from a file.
Main features:
- this will load switch LFTs and/or LID matrices (min hops tables)
- this will load switch LFTs according to the path entries introduced
in the file
- no additional checks will be performed (such as "is port connected",
etc.)
- in case when fabric LIDs were changed this will try to reconstruct
LFTs correctly if endport GUIDs are represented in the file
(in order to disable this, GUIDs may be removed from the file
or zeroed)
The file format is compatible with output of 'ibroute' util and for whole fabric can be
generated with dump_lfts.sh script.
To activate file based routing module, use:
opensm -R file -U /path/to/lfts_file
If the lfts_file is not found or is in error, the default routing algorithm is utilized.
The ability to dump switch lid matrices (aka min hops tables) to file and later to load
these is also supported.
The usage is similar to unicast forwarding tables loading from a lfts file (introduced by
'file' routing engine), but new lid matrix file name should be specified by -M or
--lid_matrix_file option. For example:
opensm -R file -M ./opensm-lid-matrix.dump
The dump file is named ´opensm-lid-matrix.dump´ and will be generated in standard opensm
dump directory (/var/log by default) when OSM_LOG_ROUTING logging flag is set.
When routing engine 'file' is activated, but the lfts file is not specified or not cannot
be open default lid matrix algorithm will be used.
There is also a switch forwarding tables dumper which generates a file compatible with
dump_lfts.sh output. This file can be used as input for forwarding tables loading by
'file' routing engine. Both or one of options -U and -M can be specified together with
´-R file´.
PER MODULE LOGGING CONFIGURATION
To enable per module logging, configure per_module_logging_file to the per module logging
config file name in the opensm options file. To disable, configure per_module_logging_file
to (null) there.
The per module logging config file format is a set of lines with module name and logging
level as follows:
<module name><separator><logging level>
<module name> is the file name including .c
<separator> is either = , space, or tab
<logging level> is the same levels as used in the coarse/overall
logging as follows:
BIT LOG LEVEL ENABLED
---- -----------------
0x01 - ERROR (error messages)
0x02 - INFO (basic messages, low volume)
0x04 - VERBOSE (interesting stuff, moderate volume)
0x08 - DEBUG (diagnostic, high volume)
0x10 - FUNCS (function entry/exit, very high volume)
0x20 - FRAMES (dumps all SMP and GMP frames)
0x40 - ROUTING (dump FDB routing information)
0x80 - SYS (syslog at LOG_INFO level in addition to OpenSM logging)
FILES
/etc/opensm/opensm.conf
default OpenSM config file.
/etc/opensm/ib-node-name-map
default node name map file. See ibnetdiscover for more information on format.
/etc/opensm/partitions.conf
default partition config file
/etc/opensm/qos-policy.conf
default QOS policy config file
/etc/opensm/prefix-routes.conf
default prefix routes file
/etc/opensm/per-module-logging.conf
default per module logging config file
/etc/opensm/torus-2QoS.conf
default torus-2QoS config file
AUTHORS
Hal Rosenstock
<hal@mellanox.com>
Sasha Khapyorsky
<sashak@voltaire.com>
Eitan Zahavi
<eitan@mellanox.co.il>
Yevgeny Kliteynik
<kliteyn@mellanox.co.il>
Thomas Sodring
<tsodring@simula.no>
Ira Weiny
<weiny2@llnl.gov>
Dale Purdy
<purdy@sgi.com>
SEE ALSO
torus-2QoS(8), torus-2QoS.conf(5).