[alexdowad]

Be tactful and kind, but straightforward about what you can't/don't want to spend time reviewing.

"Thanks for the effort, but my time and energy is limited and I can't practically review this much code, so I'm closing this PR. We are interested in performance improvements, so you are welcome to pick out your #1 best idea for performance improvement, discuss it with the maintainers via ..., and then (possibly) open a focused PR which implements that improvement only."

[ivanjermakov]

Depends on context of course, but in my book "my time and energy is limited" is not a valid reason for a reject. Get back once you have time, review in chunks.

[alexdowad]

ivanjermakov, I don't know if you are an open source maintainer or not (I am, for several projects). If you are, and you follow the policy that "I will never reject PRs because of having no time, I will always get to it eventually", then I salute you. That is a self-sacrificing, altruistic position to take. It's also a very difficult position to maintain for the long term. If you can do it: congratulations!

As for me, my position is: "My project is my house. You want to be a guest in my house, you follow my rules. I really like people and am usually happy to answer questions from people who are reasonably polite, to review and provide feedback on their PRs, and so on. But I won't be pressured to prioritize your GitHub issue or PR over my work, my family, my friends, my health, or my personal goals in life. If you try to force me, I'll block you and there will be no further interaction."

If you don't like that position, well, I understand your feelings.

[wiseowise]

> is not a valid reason for a reject

As a reviewer or as a submitter?