I’m in the same situation. I was toying with elegant Mandelbrot Set generator from Haskell, when I stumbled on massive performance bottlenecks. That was a year ago. I have reduced the issue to inconsistent optimizations when composing sequence operations. I’m in the process of writing benchmarks to help pinpoint these performance traps, but I took a detour through improving measurement process for Swift Benchmark Suite.
With all that said, I think Jens is onto something with the suggestion for a category for discussing possible performance problems. What about sticking to the #swift-users with a performance tag? We could spin off a topic about “How to diagnose performance issues” and “How to reduce performance bugs” documenting these processes that can allow community to ease the burden for core developers…