NetQ Agent CPU Utilization on Cumulus Linux Switches

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Overview

NetQ Agent is an application running on switches. It monitors and collects telemetry data on the switch, and streams it to the NetQ Platform either in the cloud or on premises. NetQ Agents, like other applications running on the switch, may cause high CPU utilization when the CPU is available. This does not interfere with normal switch traffic, but can be manually limited.

Issue Presentation

High CPU utilization by the NetQ Agent may be seen on switches running Cumulus Linux. You might see this high utilization when monitoring the CPU through SNMP or Grafana or other monitoring tools in the form of an alarm or event based on your threshold settings for CPU usage.

Manage the NetQ Agent Behavior

One way you can monitor CPU usage by the NetQ Agent and other services is to run the following command on the Cumulus Linux switch:

root@hostname:/var/log# ps %mem | head

PID PPID CMD %MEM %CPU
889 1 /usr/sbin/switchd 6.5 18.8
1246 1 /usr/share/venvs/netq-apps/ 2.9 0.0
10866 10773 /usr/share/venvs/netq-agent 2.2 11.9
10773 1 /usr/share/venvs/netq-agent 2.0 1.3
10957 10866 /usr/share/venvs/netq-agent 1.9 1.6
1243 1 /usr/bin/python -O /usr/sbi 1.1 0.0
1020 1 /usr/bin/python /usr/sbin/p 0.6 0.2
1245 1 /usr/bin/python /usr/bin/ne 0.5 0.9
1021 1 /usr/bin/python /usr/sbin/s 0.5 0.4

Cumulus Linux has a built-in load balancing algorithm that regulates CPU usage, allowing the NetQ Agent to only use the CPU when it is available. The NetQ Agent is a low priority Linux process, running at priority level 5. When there is no scheduling contention, the NetQ Agent can use as much bandwidth as the CPU has available. When there is contention, it yields to higher priority processes, such as protocol daemons and the switch ASIC driver and kernel tasks.

You have an additional option to set a limit on how much CPU bandwidth the NetQ Agent can use in the NetQ 2.4.1 and Cumulus Linux 3.7.12 or 4.1 and later releases. Run the following NetQ CLI command on the Cumulus Linux switch to cap the CPU utilization by the NetQ Agent:

netq config add agent cpu-limit <limit>

The recommended limit is 60% to start. If you find this is too high or too low, you can adjust it.

For example, we can check the value of the current setting, modify it, and then verify it has been changed.

  1. Check what the limit is set to now.
    root@hostname:/var/log# netq config show agent cpu-limit
    CPU Quota
    -----------
    100%
  2. Modify the limit to CPU usage by the NetQ Agent to a maximum of 60%.
    root@hostname:/var/log# netq config add agent cpu-limit 60
    Successfully set agent CPU limit to 60
    Please restart agent(netq config restart agent)

    root@hostname:/var/log# netq config restart agent
    Restarting netq-agent... Success!
  3. Verify the setting.
    root@hostname:/var/log# netq config show agent cpu-limit
    CPU Quota
    -----------
    60
    You can also view the setting in JSON format:
    root@hostname:/var/log# netq config show agent cpu-limit json
    {
    "cpu-limit":60
    }

Conclusion

While the NetQ Agent may cause high CPU usage on switches, it does not interfere with normal operations. The NetQ Agent is designated as a low priority service and thus only uses CPU when it is available. If you prefer, you can control the amount of available CPU bandwidth that the NetQ Agent uses by setting a limit with the NetQ CLI netq config add agent cpu-limit command.

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