OPcache Control

OPcache is a PHP extension that caches code files in memory. Sometimes it can hiccup and need a cache clear. This module makes it easier by providing a reset button in the site, under OPcache reports.

OPcache description from php.net:

OPcache improves PHP performance by storing precompiled script bytecode in shared memory, thereby removing the need for PHP to load and parse scripts on each request.

https://www.php.net/manual/en/intro.opcache.php

When using opcache, you'll want to set opcache.enable_cli = 1 so drush cache clear also clears the opcache.