Most Wordpress sites causing realpath errors

Question

recently installed some debugging software on our server and realised that most errors are coming from realpath() in Wordpress sites.

realpath() [<a href='function. realpath'>function. realpath</a>]: open_basedir restriction in effect. File(/var/www/vhosts/ xxx. com) is not within the allowed path(s): (/var/www/vhosts/ xxx. com/httpdocs/:/tmp/)

The sites are working OK but these are bugging me. Mostly because its hard to see any serious errors coming up!

Would errors like this also affect performance?