[Zope] how to generate debug.log for requestprofiler

At some point btn Zope 2.6.2 and 2.7.4, it seems way you set up a logfile to be used by requestprofiler.py has changed. Now I need "debug.log" - whats the proper way to generate one? I've just been googling and can't find explicit instructions about this. Doing runzope or zopectl with -M aren't working, and there is no obvious directive in zope.conf for it. Unless I am supposed to configure a logger at DEBUG level myself, from the zope.conf and make sure it's called debug.log, but this doesn't seem right.... Any suggestions? Thanks, Jim