I know the new version of Photos in macOS Sierra analyzes all of your photos for faces and over 3,000 objects... but the analysis process runs whether Photos is open or not. This is a problem for me. I have something around 30,000 photos (my library dates back to 1999.) It's going to be running for a long time, and when it runs it hogs the CPU. If I kill it, it re-spawns half an hour later. If I put my Mac to sleep, I come back to it later with the process running. The biggest reason this is a problem is because today it's 35°C in my city (Toronto), we're under a heat warning, I don't have air conditioning, and my MBP has already locked up and reset twice today because of overheating due to this stupid resource-intensive process. I wish it had the sense to throttle back and not go wild.