Craft causing Apache2 to max out memory and swap Background: Our Craft 2 site has been working for years. Now I want to upgrade to Craft 3. On a test machine, I have been having problems with the upgrade process. I have tried 3 classes of things: 


Install Craft 3 from scratch. This is working, but I'd really like to bring the old database along.
Install Craft 3 and the old database, and try to do the upgrade.
Just duplicate the old Craft 2 system with the old database, to get something to work.


The problem: Anything I do with the old database (#2 or #3, above) is likely to cause Apache2 to go berserk, using up all memory and swap and bringing the system to a nearly complete halt. Not every page does this, but, for example, the CP Entries page does this when it attempts to list entries.

I haven't been able find any errors in logs, though I'm not especially adept at that.  Any thoughts?
I sent the Craft 2 database to Pixel and Tonic, and Brad kindly updated it for me.