Troubleshooting Tip: High CPU usage of linkmtd daemon when link-monitor or fail-detect is enabled

[epinheiro]

Description	This article describes an issue where the 'linkmtd' daemon consumes high CPU when FortiGate devices process large amounts of traffic with link-monitor or fail-detect enabled.
Scope	Platforms: FortiGate 3000F, FortiGate 3001F, FortiGate 80F, FortiGate 4801F FortiOS versions: 7.2.9 GA, 7.4.5, 7.4.8 GA, 7.4.9, 7.6.4, 7.6.5, 8.0.0
Solution	Symptoms: High CPU utilization of the 'linkmtd' daemon. Cause: Under high traffic conditions, the 'linkmtd' daemon performs unnecessary session dumps and system calls during link-monitor or fail-detect operations, resulting in excessive CPU usage. Workarounds: Remove the link-monitor configuration. Remove the fail-detect configuration. Fixed versions: FortiOS 7.4.9 build 2813 FortiOS 7.6.4 build 3592 FortiOS 8.0.0 build 0045 Resolution: A validation check was introduced to determine whether a session dump is required before executing CPU-intensive system calls, reducing CPU consumption of the 'linkmtd' daemon. Recommendation: Always confirm the recommended FortiOS build by referring to the article Technical Tip: Recommended Release for FortiOS.