You'd have to know the source code quite intimately to answer that. My hunch is that when it slows down, what you'd see under the covers is a tangled mess of lo

You'd have to know the source code quite intimately to answer that. My hunch is that when it slows down, what you'd see under the covers is a tangled mess of locks and some kind of leaking resource(s). If the tabs were more isolated, you'd be able to at least kill the ones most responsible and the others would survive. Chrome consciously chose to isolate tabs in separate processes; having more explicit separation probably discourages tangled dependency chains and that might be the best explanation for why, even though you could, you don't have to resort to actually killing processes that often.