Free (command)

free display amount of free and used memory in the system

free -h
             total        used        free      shared  buff/cache   available
Mem:           503G         21G         43G        2.1M        438G        478G
Swap:          975M         50M        925M

free
             total        used        free      shared  buff/cache   available
Mem:      528029540    22891532    48868648        2128   456269360   501718128
Swap:        999420       51456      947964

No swap configured:

free -h
             total        used        free      shared  buff/cache   available
Mem:           985M        468M         79M         65M        437M        302M
Swap:            0B          0B          0B

free -g

Activities

1. Emptying the buffers cache: free -h && sync && echo 3 > /proc/sys/vm/drop_caches && free -h
2. Use fio with direct=0 to fill up your cache.
3. Review historical memory usage with: sar -r --human
4. Review /proc/meminfo
5. ps -eo pid,user,s,comm,size,vsize,rss --sort -size | head

See also

• free (C)
• sync
• sar -r
• RAM and filesystem
• Swap, swapon, swapoff, mkswap, swaplabel, free,sar -r, sar -S, sar -W, vmstat, vm.swappiness, /proc/swaps, /etc/fstab, Add a swap disk, systemd.swap
• linux-ftools

http://man7.org/linux/man-pages/man1/free.1.html

https://unix.stackexchange.com/questions/87908/how-do-you-empty-the-buffers-and-cache-on-a-linux-system