Occasionally when I am using iPhoto an app with a generic white Lego piece icon opens on the dock with the name "com.apple.MediaLibraryService.xpc".
Activity Monitor lists it as "(Not Responding)" and shows it using a pretty large amount of CPU time. When I quit iPhoto its % CPU drops to zero, but it remains in the dock and remains unresponsive in Activity Monitor.
It doesn't happen every time I use iPhoto, and there doesn't seem to be any particular action that triggers it to open. It does seem to correspond to a general slowing of responsiveness (already not great) in iPhoto. I am generally loathe to force quit something if I don't know what it is.
Does anyone know what this app does, why it is opening, and how to prevent it from hogging my CPU when I'm working?