I have nginx 1.12.1, php-fpm 7.1, mariadb 10, memcached, fail2ban on a centos 7.5 (VPS at vultr 2GB RAM)
I just install only 1 joomla site on that server and traffic is too low (about 50-150 visitor a DAY), but sometime, my server show that it load full, something like this (i use nodequery to monitor):

Server: bienthuy.com
Last Update: 2017-08-16 08:27:39
Alert Trigger: 2017-08-16 08:28:01

Average: 4.95 1.40 0.51

System Load: 100%
Ram Usage: 34%
Disk Usage: 9%

mysqld 1.8% 180.93 MB mysql (1)
php-fpm 0.6% 279.33 MB nginx (6)
redis-server 0.2% 13.07 MB redis (1)
php-fpm 0% 44.28 MB root (1)
tuned 0% 15 MB root (1)
dhclient 0% 12.88 MB root (1)
fail2ban-server 0% 11.05 MB root (1)
nginx 0% 10.39 MB nginx (2)
polkitd 0% 8.97 MB polkitd (1)
crond 0% 3.88 MB root (2)

Could you please help me how to find out which one cause this high load?
Thank you so much