PHP 5.5, OpcodeCache, PHP-FPM, NGINX, Joomla

[brainforge]

After some struggling I've got that working in Plesk environment.

Opcache handling of Joomla configuration.php file.
If Joomla admin changes a system config setting the change gets saved OK.
If they pressed save+close no problem.
If they pressed save the screen redisplays with their original setting!
Presumably the old version of configuration.php gets read from opcache.

Tried to stop this happening using the black list in both Plesk PHP settings and opcache ini file.

I've tried the following:

opcache.blacklist_filename="configuration.php"
opcache.blacklist_filename="/var/www/vhosts/mydomain.com/httpdocs/configuration.php"

Any ideas?
I have 3 or 4 php-cgi processes running - so maybe they have their own opcode cache?
But tried to allow for that by restarting services and applying resets to the cache.
Next thing would be to make sure they share the same opcode cache - save a bit of memory.

Using htop I see the following processes:
user1 php-cgi
user1 php-cgi
user2 php-cgi
user2 php-cgi
user1 php-cgi
root php-fpm master pool # does very little
user3 php-fpm pool... # appears very occassinally
apache php-fpm pool www # idle
apache php-fpm pool www # idle