Bypassing the Branch Predictor
nicula.xyz
nicula.xyz
It's weird to want your CPU to be slow on average and fast in the exceptional case but sometimes you want that. The CPU won't behave that way so you have to fake exceptional cases until they become the majority again.
I bet this is helpful for HFT.
However, I did hear a few times about cases where you'd trade better average performance that comes with spikes (e.g. in terms of response time) in favor of worse average performance that has lower variance.