The flame graphs on https://performance.wikimedia.org/php-profiling/ are based on Excimer CPU-time profiles. It'd be useful to have wall-clock profiling too.
For one-shot profiling, we run two Excimer instances (one wall-clock, the other CPU) in parallel. Can we do the same for production profiling? It looks pretty easy to do.
The wall-clock profiler would publish samples to a different channel, and the end result would be an additional set of log files and flame graphs, existing alongside the current CPU-based ones.