It would be helpful to be able to see the changes to the logging levels before hitting 'apply', so instead of setting these server side, do it client side.  Using Ajax to retrieve the new set of logging levels would work well here.  It would also help the page organization to move the select box below the horizontal line and to update the info ('i') text to describe what the box does.  Right now the info text says nothing about what selecting a 'log set' does.