A 9:1 performance drop after hibernation is a bug in my book but of course one mans bug is another mans feature.

Especially since hibernation is something you don't control (it kicks in by default in OTP when a process is idle for a while).

http://www.erlang.org/doc/man/gen_server.html

Does not contain any caveats about performance being substantially worse for some use cases after waking up a hibernated process.