Troubleshooting Tip: FortiGate-F Series: Firewall stops processing traffic when Free memory was low on device

[imathew]

Description	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.
Solution	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.