OpCache - Recommended Configuration for Magento2

opcache.max_accelerated_files=16000 is definitely low for Magento 2.
find . -type f -print | xargs grep "<?php" | wc -l gives me 30736 for my Magento 2 installation (with a code generated in the var/generation folder and with some external extensions installed).
I recommend set opcache.max_accelerated_files to 65406 if your server has a single Magento 2 installation and has not other PHP sites.
If you have multiple PHP sites on the server then consider the value 130986.