High memory usage

We are using BIG IP VE ESX(Z100) and OS is 11.6.0 .We are having problem with High memory . According to log:

 

tmsh show sys memory | head

 

Sys::System Memory Information Memory Used(%) Current Average Max(since 03/08/18 14:57:17)

TMM Memory Used 3 3 3 Other Memory Used 74 74 74 Swap Used 13 13 13

 

TMM is using only < 4%.

 

Queries are:

 

1. As we are getting alert over memory 90% memory is used, how to make it down to normal state? 2.As Linux is using most , is there any way to clear the cache?
2. Is it address to capacity or it is normal behavior?

Pls assist...