We made some improvements to PerfTools and the SchedulerTrace module now not only prints the runtime status of your program, from the execution contexts and their schedulers to each individual fibers… but also the yield stack of suspended fibers when FiberTrace is loaded (warning: performance impact) and thus know what each fiber is waiting for (sleep, wait readable, channel send, …).
I hope this will be useful to better understand your programs, especially to understand situations as they happen (e.g. why a fiber hangs).