Congestion Control Parameter Settings

Congestion control settings are accessed through configfs. Additional DCQCN tunings are available via module parameters can be tuned when using out of tree irdma driver.

To access congestion control settings:

1. After driver load, change to the irdma configfs directory: cd /sys/kernel/config/irdma
2. Create a new directory for each RDMA device you want to configure. Note: Use ibv_​devices for a list of RDMA devices.

   For example, to create configfs entries for the rdmap<interface> device:

   mkdir rdmap<interface>
3. List the new directory to get its dynamic congestion control knobs and values: cd rdmap<interface> for f in *; do echo -n "$f: "; cat "$f"; done;

   If the interface is in iWARP mode, the files have an "iw_​" prefix:

   • iw_​dctcp_​enable
   • iw_​ecn_​enable
   • iw_​timely_​enable

   If the interface is in RoCEv2 mode, the files have a "roce_​" prefix:

   • roce_​dcqcn_​enable
   • roce_​dctcp_​enable
   • roce_​timely_​enable
4. Enable or disable the desired algorithms.
   1. To enable an algorithm: echo 1 > <attribute>

      For example, to add ECN marker processing to the default TCP New Reno iWARP congestion control algorithm:

      echo 1 > /sys/kernel/config/irdma/rdmap<interface>/iw_ecn_enable
   2. To disable an algorithm: echo 0 > <attribute>

      For example: echo 0 > /sys/kernel/config/irdma/rdmap<interface>/iw_ecn_enable

   3. To read the current status: cat <attribute>

      Default values:

      • iwarp_​dctcp_​en: off
      • iwarp_​timely_​en: off
      • iwarp_​ecn_​en: ON
      • roce_​timely_​en: off
      • roce_​dctcp_​en: off
      • roce_​dcqcn_​en: off
5. Remove the configfs directory created above: rmdir /sys/kernel/config/irdma/rdmap<interface> Note:The driver will not unload until you remove the configfs directory.