I don’t know what could be the problem (if any, at this point).
I have a pretty little physical machine that has a system uptime of about 29 day 14 hours (Asterisk itself was restarted/reloaded many times due to updates) and its memory details are (just as an example to you):
top - 07:55:19 up 29 days, 14:04, 1 user, load average: 0.22, 0.14, 0.05
Tasks: 137 total, 1 running, 136 sleeping, 0 stopped, 0 zombie
Cpu0 : 4.0%us, 1.0%sy, 0.0%ni, 94.9%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu1 : 4.7%us, 1.0%sy, 0.0%ni, 94.3%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu2 : 1.7%us, 0.3%sy, 0.0%ni, 98.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu3 : 0.3%us, 0.7%sy, 0.0%ni, 99.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 1905232k total, 1655060k used, 250172k free, 301676k buffers
Swap: 785400k total, 47840k used, 737560k free, 734908k cached
As you can see the used RAM size has a value near the physical RAM size but I didn’t noticed nothing abnormal on the system (note that the “App” memory size reported by FreePBX GUI is 34% so there isn’t a clear relationship, or maybe I’m not able to see one, between what is reported by top/htop and what is reported on “App” memory size FreePBX GUI, at least to my eyes).
After a reboot the “App” memory size dropped to 14% (21% if I enter the GUI) and the used RAM size dropped to about 407 MBytes (about 570 MBytes once entered into the GUI) which is a value, compared to the one reported above before reboot, quite reasonable to me.
I only noticed that (htop, MEM% sorted) reports a lot of processes related to iSymphonyServer.jar on top.