Go 1.20 has been released! I’m most excited about the addition of profile-guided optimization (PGO). Now you can run on production a copy of your service with the profiler enabled, redirect there a small percent of users, export the collected profile, and recompile the service with
-pgo=/path/to/profile. The compiler will use the information from the profile about which lines of code are executed more often and optimize the binary for them. More specifically, Go 1.20 compiler will do more aggressive inline for the hot parts, which adds 2-4% of performance on average. That’s not much but it might be much more in the future versions of the compiler.
I always liked the idea of PGO. There were many blog posts about people moving around parts of code (and also many PRs into Go itself doing the same for stdlib) to get a better performance for the most often executed path. And it always bothered me as one of the things that the compiler should do instead of humans. Well, now it can!
More in the Go documentation: Profile-guided optimization.