Show HN: Dial9, a tool for diagnosing p99+ performance in Rust programs

- p99+ refers to extreme tail latency: the slowest 1% (or less) of requests. In distributed systems, these outliers often cause cascading timeouts and degraded user experience, even if average latency looks fine. - Dial9 is a new open-source Rust diagnostic tool that attaches to a running program and samples stack traces only during high-latency events, letting developers pinpoint exactly which code paths are causing the worst slowdowns. - Prior tools either sample everything (producing noisy data that buries rare slow paths) or require expensive instrumentation. Dial9's key innovation is "p99+ targeted sampling" — it ignores normal requests and focuses exclusively on the pathological tail cases. - The project emerged from the Rust ecosystem, where performance tooling (perf,火焰图) is mature for average-case analysis but tail-latency debugging remains underserved.