FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
Article Id 278475

This article describes how to fix an issue where the CPU on a specific core goes high on SoftIRQ and stops processing traffic.

Scope FortiGate-F series.

On the firewall, the CPU on a specific Core might go high on SoftIRQ.

Free memory on the device goes low. A high file system cache consumes a lot of memory.


To observe the issue:


get sys per status

Memory: 49539064k total, 17105140k used (34.5%), 544324k free (1.1%), 31889600k freeable (64.4%) <----- Intermittent traffic issue observed.
Memory: 49539064k total, 16674616k used (33.7%), 2786832k free (5.6%), 30077616k freeable (60.7%)


 'diag hardware sysinfo memory' shows high cache memory usage.


Apply one of the following options as a workaround.

  • Disable disk logging or filter out the forward-traffic log type.
  • Delete FortiGate traffic logs stored in the local disk,
  • Configure the Fortianalyzer/Syslog server.

To delete logs on the disk,


execute log filter category 0
execute log filter device 1
execute log delete


To solve the issue permanently, upgrade to FortiOS v7.2.8, v7.0.14, or v7.4.4.