On Sept. 9, I upgraded NextGEN Gallery from 1.5.5 to 1.6.0, then 1.6.1, on all 15 of my WordPress blogs. Since then, I've noticed a remarkable increase in my sites' memory usage, as seen in this DreamHost graph:
(The CPU spike today was brief and was quickly eliminated with a server reboot.)
I can't say for sure that NGG is responsible, but there is definitely a correlation, if not a causation. But since NGG 1.6 required a database upgrade, I'm not sure I can safely revert to 1.5.5 to test this theory.
Any ideas what could be causing so much memory to be used, and how I might identify or resolve the issue?