Showing memory usage in Linux by process and user

top - 14:22:38 up 12 min,  3 users,  load average: 0.02, 0.22, 0.32
MiB Mem :   3784.7 total,    967.8 free,   1249.0 used,   1567.9 buff/cache
MiB Swap:   3784.0 total,   3737.2 free,     46.8 used.   2170.7 avail Mem
PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
3953 fedora    20   0 1785992 537936  76568 S   0.0  13.9   0:37.63 gnome-software
3590 fedora    20   0 3868704 147920  96512 S   0.0   3.8   0:07.35 gnome-shell
5885 root      20   0  664948 131048  24632 S   0.0   3.4   0:07.94 packagekitd
5444 fedora    20   0  690380  77988  26884 S   0.0   2.0   0:02.11 python

The list will be limited by your window size, but the most significant processes with respect to memory usage will show up at the top of the process list.

If you want to focus on a single user, top can be used much in the same way that it is used above. Just add a username with the -U option as shown below and press the shift+m keys to order by memory usage:

$ top -U nemo
top - 14:28:54 up 18 min,  3 users,  load average: 0.01, 0.08, 0.22
Tasks: 242 total,   1 running, 241 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.3 us,  0.5 sy,  0.0 ni, 99.2 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
MiB Mem :   3784.7 total,    761.7 free,   1118.5 used,   1904.5 buff/cache
MiB Swap:   3784.0 total,   3741.2 free,     42.8 used.   2298.2 avail Mem
PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
6906 nemo      20   0  225276   3712   2944 R   1.0   0.1   0:00.10 top
5681 nemo      20   0   30604  16004  10496 S   0.0   0.4   0:00.29 systemd
5702 nemo      20   0  168976  22256   2048 S   0.0   0.6   0:00.00 (sd-pam)
5718 nemo      20   0   17192   7224   5120 S   0.0   0.2   0:00.04 sshd
5732 nemo      20   0  224656   5248   3584 S   0.0   0.1   0:00.06 bash

Using htop

The htop command will run interactively – updating its display of all running processes, along with CPU, memory, and swap usage. You can also specify options when launching htop. For example, you can add a delay between its update using the -d option.