[Zope] Too many ZODB object loads...

On the database Activity tab in the Control Panel, I am seeing a high number of Object Loads (400K per hour). My cache size if 60K from what I see in the Cache Parameters tab, each of the 4 threads is well within this limit. My database has about 1M objects. The symptom is that Zope appears slow when adding/editing content. Any idea if this is a problem? Suresh