~$ free -m
              total        used        free      shared  buff/cache   available
Mem:           1998        1572          96          62         329         180
Swap:          2047         276        1771

$ vmstat -s
      2046616 K total memory
      1613984 K used memory
      1308792 K active memory
       510044 K inactive memory
        95116 K free memory
        46652 K buffer memory
       290864 K swap cache
      2097148 K total swap
       281576 K used swap
      1815572 K free swap
       204911 non-nice user cpu ticks
          880 nice user cpu ticks
        35471 system cpu ticks
     13420166 idle cpu ticks
        21318 IO-wait cpu ticks
            0 IRQ cpu ticks
          575 softirq cpu ticks
         6558 stolen cpu ticks
      2225368 pages paged in
     31869316 pages paged out
         6208 pages swapped in
        73631 pages swapped out
     13751094 interrupts
     20037148 CPU context switches
   1583328605 boot time
        26209 forks

$ cat /proc/meminfo
MemTotal:        2046616 kB
MemFree:          109320 kB
MemAvailable:     185604 kB
Buffers:           41012 kB
Cached:           210712 kB
SwapCached:         7820 kB
Active:          1298988 kB
Inactive:         504976 kB
Active(anon):    1204196 kB
Inactive(anon):   414780 kB
Active(file):      94792 kB
Inactive(file):    90196 kB
Unevictable:        3652 kB
Mlocked:            3652 kB
SwapTotal:       2097148 kB
SwapFree:        1805596 kB
Dirty:              2948 kB
Writeback:             0 kB
AnonPages:       1548464 kB
Mapped:            93412 kB
Shmem:             64312 kB
Slab:              75832 kB
SReclaimable:      46100 kB
SUnreclaim:        29732 kB
KernelStack:        7536 kB
PageTables:        12312 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     3120456 kB
Committed_AS:    3361808 kB
VmallocTotal:   34359738367 kB
VmallocUsed:           0 kB
VmallocChunk:          0 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
CmaTotal:              0 kB
CmaFree:               0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:       61440 kB
DirectMap2M:     2035712 kB

top - 03:38:08 up 1 day, 14:08,  1 user,  load average: 0.00, 0.03, 0.00
Tasks: 127 total,   1 running, 126 sleeping,   0 stopped,   0 zombie
%Cpu(s):  1.3 us,  0.0 sy,  0.0 ni, 98.7 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem :  2046616 total,   107464 free,  1610080 used,   329072 buff/cache
KiB Swap:  2097148 total,  1805600 free,   291548 used.   185192 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND
22679 daemon    20   0 1963044 953504  57124 S  1.0 46.6   4:03.54 httpd.bin
26215 daemon    20   0  310628  21116  17276 S  0.3  1.0   0:00.03 .php-fpm.bin
    1 root      20   0  119640   4160   2980 S  0.0  0.2   0:05.04 systemd
    2 root      20   0       0      0      0 S  0.0  0.0   0:00.00 kthreadd
    3 root      20   0       0      0      0 S  0.0  0.0   0:02.97 ksoftirqd/0
    5 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 kworker/0:0H
    7 root      20   0       0      0      0 S  0.0  0.0   0:07.62 rcu_sched
    8 root      20   0       0      0      0 S  0.0  0.0   0:00.00 rcu_bh
    9 root      rt   0       0      0      0 S  0.0  0.0   0:00.00 migration/0
   10 root      rt   0       0      0      0 S  0.0  0.0   0:00.52 watchdog/0
   11 root      20   0       0      0      0 S  0.0  0.0   0:00.00 kdevtmpfs
   12 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 netns
   13 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 perf
   14 root      20   0       0      0      0 S  0.0  0.0   0:00.02 xenwatch
   15 root      20   0       0      0      0 S  0.0  0.0   0:00.00 xenbus
   17 root      20   0       0      0      0 S  0.0  0.0   0:00.05 khungtaskd
   18 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 writeback
   19 root      25   5       0      0      0 S  0.0  0.0   0:00.00 ksmd
   20 root      39  19       0      0      0 S  0.0  0.0   0:00.52 khugepaged
   21 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 crypto
   22 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 kintegrityd
   23 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 bioset
   24 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 kblockd
   25 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 ata_sff
   26 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 md
   27 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 devfreq_wq
   30 root      20   0       0      0      0 S  0.0  0.0   0:01.69 kswapd0
   31 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 vmstat
   32 root      20   0       0      0      0 S  0.0  0.0   0:00.00 fsnotify_ma+
   33 root      20   0       0      0      0 S  0.0  0.0   0:00.00 ecryptfs-kt+
   49 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 kthrotld
   50 root       0 -20       0      0      0 S  0.0  0.0   0:00.00 bioset
...

$ sudo apt-get update
$ sudo apt install htop
$ htop