Seems like syscalls are a lot more expensive, which may or not affect your daily work.

https://reverse.put.as/2018/01/07/measuring-osx-meltdown-pat...

This is the most info I've seen: https://twitter.com/aionescu/status/948609809540046849

I don't find any noticeable drop in day-to-day work like browsing, listening to music, or code in my IDEs. Compiling time might be impacted more, but I don't have any numbers.