Extremely slow, timing out, taking twice the memory for the same queries in 3.1

since upgrading, my site has doubled in load times. It’s running very slow and taking double the memory for queries.

For example, I had one large one that ran every few days and then was cached. Before the update it took about 60-70mb and now it’s taking 130-190mb (according to TCP memory usage plugin).

Any ideas? I’ve tried disabling some plugins and it didn’t seem to help.