I wanted to ask before sending all the data, just in case someone has the same problem.
The command "/usr/bin/php -f /var/www/owncloud/cron.php", executed by cron, is consuming up to 70 % of 4 GB of RAM, and some swap.
When it finishes, RAM is recovered, but not swap.
This is an Owncloud on a Debian Jessie server, with PHP5.5.
This problem happened in previous versions too, I was just waiting to check if new versions solved it.
Has anyone any clue to start addressing this?