Can someone confirm what the below item is in the "umbracoLog" database, and why it's slow / crippling our website?

"ContentService.RebuildXmlStructures completed, the xml has been regenerated in the database"

and

"MediaService.RebuildXmlStructures completed, the xml has been regenerated in the database"

Everytime this happens, the website becomes slow to non responsive. How can we stop this event from happening, its logged as publish but no one is publishing anything?