Based on what @Bob_Zimmerman said, you can check below link and also output of one of my lab R81.20 fw's
Andy
https://phoenixnap.com/kb/linux-commands-check-memory-usage
[Expert@CP-TEST-FIREWALL:0]# cat /proc/meminfo
MemTotal: 24452428 kB
MemFree: 13928244 kB
MemAvailable: 18893096 kB
Buffers: 2264 kB
Cached: 5337508 kB
SwapCached: 0 kB
Active: 3722584 kB
Inactive: 2470948 kB
Active(anon): 860788 kB
Inactive(anon): 728 kB
Active(file): 2861796 kB
Inactive(file): 2470220 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 8388604 kB
SwapFree: 8388604 kB
Dirty: 316 kB
Writeback: 0 kB
AnonPages: 853328 kB
Mapped: 118340 kB
Shmem: 7756 kB
Slab: 475072 kB
SReclaimable: 209936 kB
SUnreclaim: 265136 kB
KernelStack: 6384 kB
PageTables: 10476 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 20614816 kB
Committed_AS: 3163716 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 2855152 kB
VmallocChunk: 34356225224 kB
Percpu: 1312 kB
AnonHugePages: 391168 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 505720 kB
DirectMap2M: 24659968 kB
[Expert@CP-TEST-FIREWALL:0]# free -g
total used free shared buff/cache available
Mem: 23 4 13 0 5 18
Swap: 7 0 7
[Expert@CP-TEST-FIREWALL:0]# vmstat
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
3 0 0 13929532 2264 5812372 0 0 0 1 3 3 0 1 98 0 0
[Expert@CP-TEST-FIREWALL:0]# top
top - 12:28:38 up 9 days, 21:38, 1 user, load average: 0.10, 0.16, 0.10
Tasks: 257 total, 2 running, 255 sleeping, 0 stopped, 0 zombie
%Cpu0 : 0.0 us, 0.0 sy, 0.0 ni, 99.0 id, 0.0 wa, 1.0 hi, 0.0 si, 0.0 s
%Cpu1 : 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 s
%Cpu2 : 1.0 us, 1.0 sy, 0.0 ni, 95.1 id, 0.0 wa, 1.0 hi, 1.0 si, 1.0 s
%Cpu3 : 1.0 us, 1.0 sy, 0.0 ni, 96.1 id, 0.0 wa, 1.0 hi, 0.0 si, 1.0 s
%Cpu4 : 0.0 us, 0.0 sy, 0.0 ni, 99.0 id, 0.0 wa, 1.0 hi, 0.0 si, 0.0 s
%Cpu5 : 1.0 us, 0.0 sy, 0.0 ni, 98.0 id, 0.0 wa, 1.0 hi, 0.0 si, 0.0 s
%Cpu6 : 0.0 us, 0.0 sy, 0.0 ni, 98.0 id, 0.0 wa, 2.0 hi, 0.0 si, 0.0 s
%Cpu7 : 0.0 us, 1.0 sy, 0.0 ni, 97.0 id, 0.0 wa, 1.0 hi, 0.0 si, 1.0 s
KiB Mem : 24452428 total, 13929440 free, 4708328 used, 5814660 buff/cache
KiB Swap: 8388604 total, 8388604 free, 0 used. 18894328 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ P COMMAND
5629 admin 20 0 0 0 0 S 1.0 0.0 55:02.64 7 fw_wor+
5630 admin 20 0 0 0 0 R 1.0 0.0 51:53.48 6 fw_wor+
5632 admin 20 0 0 0 0 S 1.0 0.0 51:55.74 4 fw_wor+
5633 admin 20 0 0 0 0 S 1.0 0.0 50:21.71 3 fw_wor+
5634 admin 20 0 0 0 0 S 1.0 0.0 50:59.78 2 fw_wor+
16079 admin 20 0 3756 1488 1032 R 1.0 0.0 0:00.03 3 top
1 admin 20 0 2632 676 576 S 0.0 0.0 0:08.64 4 init
[Expert@CP-TEST-FIREWALL:0]#