If I'm reading correctly you only have 8GiB of memory. If your Magento instance gets a decent amount of traffic and/or you're not serving your static files (css and js) from a CDN, Magento 2 will eat up your memory pretty quickly.
If you just want to ensure you're only spawning php-fpm workers as needed you can edit your php-fpm pool configuration file
www.conf. The location of this file depends on the Linux distro you're using, for instance on Ubuntu Server this file is located at
/etc/php/<php version>/pool.d/www.conf. Once you find the file open it and edit the following configuration options.
NOTE: These options are already present in the file so you'll need to find them and update the value, don't just paste this into the file
Note the values for
pm.max_spare_servers will more than likely need to be tweaks to your needs, and the values I provided are on the low side.
Now you just need to restart your php-fpm process for the changes to take effect.
pm is set to
dynamic the php-fpm master process will spawn php-fpm workers as needed based on the values set above. When
pm is set to
static the php-fpm master process will always spawn the the maximum number of workers allowed based on the value of