Faster Ruby: Thoughts from the outside
> What kind of speedup is available for big Rails applications? If 90% of the time in an application is spent in database calls, then there’s little opportunity for improvement via JIT technologies.This is written as speculation of course, but it matches some long-time "conventional wisdom", that most Rails apps spend most of their time on I/O waiting for something external.That may have been true once, but i don't believe it's true anymore.My Rails apps now, when things like "n+1 database query problems" are properly eliminated, all spend more of their time on CPU than I/O, 60-80%. (I think most of that CPU time is ActionView rendering. Unsure about CPU parts of ActiveRecord, that aren't waiting on DB, but converting db results to in-memory AR objects etc).When this comes up and I ask around on social media who else has actually looked at their app and can confirm or deny, almost all who respond agree. I would be curious to see here too.Definitely some more systematic rather than anecdotal investigation is called for. But I think it's time to stop repeating that it's likely that a Rails app is I/O-bound rather than CPU-bound, my experience leads me to think the reverse is currently likely.[*edit* after I wrote this comment, I noticed multiple other comments in this thread saying basically the same thing. OK, so. Can we put this rumor to rest?]