Use keepalive (requires a upstream block) + Open file cache

[melroy89]

• Use keepalive in Nginx, to actually keep the connection open. keepalive is not the max. amount of connections, but the amount of idle connections.
• Also add open_file_cache
• Increase gzip_comp_level to 5 for a better balance between performance/CPU usage.

For some reason Nginx think it's a good idea that this required an upstream block, so actually in order to leverage keepalive functionality in Nginx, you will need to define an upstream section...

Official keepalive documentation: http://nginx.org/en/docs/http/ngx_http_upstream_module.html#keepalive

And open file cache documentation here: http://nginx.org/en/docs/http/ngx_http_core_module.html#open_file_cache