As I see, this recently hit git master. I want to say big thanks since it improved git rebase from tens of minutes to just minutes here (warm disk caches).
However, I can't say I'm completely satisfied with git rebase speed (I'd like it to be < 1 min). So, are there known performance hotspots in 'git rev-list --cherry-pick'/'git format-patch --ignore-if-in-upstream' (these are two flags have biggest impact on git rebase [-i] speed) or I should run some kind of profiles in order to determine what else could be improved?