User Manual

Rev 2.1-1.0.6
Mellanox Technologies
185
8.9 Congestion Control
8.9.1 Congestion Control Overview
Congestion Control Manager is a Subnet Manager (SM) plug-in, i.e. it is a shared library (libcc-
mgr.so) that is dynamically loaded by the Subnet Manager. Congestion Control Manager is
installed as part of Mellanox OFED installation.
The Congestion Control mechanism controls traffic entry into a network and attempts to avoid
oversubscription of any of the processing or link capabilities of the intermediate nodes and net-
works. Additionally, is takes resource reducing steps by reducing the rate of sending packets.
Congestion Control Manager enables and configures Congestion Control mechanism on fabric
nodes (HCAs and switches).
8.9.2 Running OpenSM with Congestion Control Manager
Congestion Control (CC) Manager can be enabled/disabled through SM options file. To do so,
perform the following:
1. Create the file. Run:
opensm -c <options-file-name>'
2. Find the 'event_plugin_name' option in the file, and add 'ccmgr' to it.
# Event plugin name(s)
event_plugin_name ccmgr
3. Run the SM with the new options file: 'opensm -F <options-file-name>'
For further information on how to turn OFF CC, please refer to Section 8.9.3,
“Configuring Con-
gestion Control Manager”, on page 185
8.9.3 Configuring Congestion Control Manager
Congestion Control (CC) Manager comes with a predefined set of setting. However, you can
fine-tune the CC mechanism and CC Manager behavior by modifying some of the options. To do
so, perform the following:
1. Find the '
event_plugin_options' option in the SM options file, and add the following:
conf_file <cc-mgr-options-file-name>':
# Options string that would be passed to the plugin(s)
event_plugin_options ccmgr --conf_file <cc-mgr-options-file-name>
2. Run the SM with the new options file: 'opensm -F <options-file-name>'
Once the Congestion Control is enabled on the fabric nodes, to completely disable
Congestion Control, you will need to actively turn it off. Running the SM w/o the CC
Manager is not sufficient, as the hardware still continues to function in accordance to
the previous CC configuration.