Diagnosing kernel memory leak issues
Sometimes, despite minimal or very low traffic, the memory utilization of the FortiWeb remains relatively high, for example, reaching around 80%. This situation could indicate the presence of a potential kernel memory leak. Run cat /proc/meminfo in Shell. Check if the slab (memory consumed by the kernel) is exceptionally high (reaching values of 1 GB or even 10 GB).
The following is an example of the output of cat /proc/meminfo.
MemTotal: 16186144 kB
MemFree: 481784 kB
MemAvailable: 13119360 kB
Buffers: 1106296 kB
Cached: 1378200 kB
SwapCached: 0 kB
Active: 3015388 kB
Inactive: 1157396 kB
Active(anon): 1693084 kB
Inactive(anon): 71832 kB
Active(file): 1322304 kB
Inactive(file): 1085564 kB
Unevictable: 47960 kB
Mlocked: 47960 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 128 kB
Writeback: 0 kB
AnonPages: 1735972 kB
Mapped: 170672 kB
Shmem: 81160 kB
KReclaimable: 10399120 kB
Slab: 10623512 kB
SReclaimable: 10399120 kB
SUnreclaim: 224392 kB
KernelStack: 6496 kB
PageTables: 13568 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 8093072 kB
Committed_AS: 5777048 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 11028 kB
VmallocChunk: 0 kB
Percpu: 1984 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
Hugetlb: 0 kB
DirectMap4k: 88204 kB
DirectMap2M: 4022272 kB
DirectMap1G: 12582912 kB
In this case, it's recommended to run the following command to release cache every 45 minutes.
config system settings
set enable-cache-flush enable
end
-
By default,
enable-cache-flushis enabled on FortiWeb-VM and disabled on FortiWeb appliance. -
The system only logs the operations when the feature is enabled or disabled. No event log is recorded for each cache flush that occurs every 45 minutes.
-
Even if the memory usage is not high, when
enable-cache-flushis enabled, the cache is flushed every 45 minutes as per the configuration.