You can execute one of the below command to find allocated physical memory on your Linux operating system.
# free -m
total used free shared buffers cached
Mem: 26505 26195 310 0 0 10244
-/+ buffers/cache: 15950 10555
Swap: 12287 5039 7248
# dmesg | grep Memory
Memory: 27128032k/28835840k available
(2019k kernel code, 658780k reserved, 921k data, 208k init)
# grep MemTotal /proc/meminfo
MemTotal: 27141860 kB
