Hi
It could be something to do with your config. I have a vanilla conf but memory is running at about 35% on my box.
But typically for the NS200s, the 5.4 code requires more memory than any of the older codes.
If you do not need as much sessions you can try to reduce the session limit to see if that helps eg:
ns208(M)-> get sess info
alloc 3/max 64000, alloc failed 0, mcast alloc 0, di alloc failed 0
total reserved 0, free sessions in shared pool 63997
ns208(M)->
ns208(M)-> get envar | i max
max-session=32000
ns208(M)->