Page 8: "To fix this bug, we alter the code that is executed when a thread wakes up. We wake up the thread on the local core—i.e., the core where the thread was scheduled last— if it is idle; otherwise, if there are idle cores in the system, we wake up the thread on the core that has been idle for the longest amount of time."

I don't quite understand the choice for picking the core that was idle for the longest time. I think they use that as a predictor of future load of the CPU, and scheduling based on future load see,s a good idea, but I think this could lead to cases where it prevents one of more CPUs to go to low power states when the system doesn't have enough work to keep all its cores fully occupied.

(Edit: how did I overlook the following paragraph, where they discuss this issue?)

Also, in general, I think they too easily call changes that remove the corner cases they find fixes. Chances are that they introduce other corner cases, either on workloads they didn't test or on hardware they didn't test (caveat: I know very little about the variation in hardware that is out there)