[Zope] Number of Zope process on Linux

Hi, I am running Zope on Linux (RH 9). Performance is not that great (to say the least). I can see only two Zope processes and only one seems to use any cpu time. Is that supposed to be like that? Should I do anything about it? If so, what do I need to do? I realize that this has been discussed before, I just couldn't find the thread in the archives or through Google. TIA Ulrich