How to increase memory_limit

If your site loads slow you have to increase memory_limit

Read https://docs.woothemes.com/document/increasing-the-wordpress-memory-limit/

For clear Woocommerce it needs to be minimum 64M. For VC plugin developers recommend 128M

If you use 40M it can slow down your site

php settings must be

1php_value upload_max_filesize 64M
2php_value post_max_size 64M
3php_value max_execution_time 3000
4php_value max_input_time 3000

Also read http://www.onlinemediamasters.com/slow-wordpress-admin-panel/