Find Sum of RSS memory in ps command in linux/unix

Find Sum of RSS memory in ps command in linux/unix

• In KB
• ps aux | awk 'BEGIN {sum=0} {sum +=$6} END {print sum}'
• In MB
• ps aux | awk 'BEGIN {sum=0} {sum +=$6} END {print sum/1024}'
• In GB
• ps aux | awk 'BEGIN {sum=0} {sum +=$6} END {print sum/1024/1024}'

How to find free memory available

• cat /proc/meminfo
• using free command
• In KB
• free
• In MB
• free -m
• In GB
• free -g 

I observed

• Sum of RSS memory in ps less than memory actually used
• Total used memory a lot higher than sum of RSS
• Reason
• The Linux kernel will use available memory for disk caching