ISPConfig & Memory usage

[catalyst]

I have just setup my server with Fedora 6 and ISPConfig 2.2.11 and find the memory is drop from 17xxxxx KB to 461992 KB within 1 day.
Why it can't release the memory? I am afraid that it will be halt after running a few days longer if the LowFree memory is running out.
Do you have an idea on this issues?
Thank you!

Cached: 861368 kB
SwapCached: 0 kB
Active: 1168824 kB
Inactive: 210220 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 2029112 kB
LowFree: 461992 kB
SwapTotal: 2031608 kB
SwapFree: 2031608 kB
Dirty: 3752 kB
Writeback: 0 kB
AnonPages: 384704 kB
Mapped: 31100 kB
Slab: 147236 kB
PageTables: 19732 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
CommitLimit: 3046164 kB
Committed_AS: 792020 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 2916 kB
VmallocChunk: 34359735187 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
Hugepagesize: 2048 kB

[falko]

Linux always uses all available memory, even if there are very few applications running. It caches lots of data to be faster.

[catalyst]

Thank you!
I saw that the LowFree droped to 20000 Kb and rebound to more free memory now!