ra_prof: use tracing?

[kjeremy]

As seen on zulip: https://rust-lang.zulipchat.com/#narrow/stream/144729-wg-traits/topic/tracing.20in.20chalk/near/192417961

https://github.com/davidbarsky/tracing-tree/

[bjorn3]

Another option would be measureme which is used by rustc.

[Veetaha]

Not sure if we can use it in Rust, but the flamegraph impl is here: https://github.com/jonhoo/inferno

[davidbarsky]

(Hi, I'm David!)

I think I speak for Eliza when I say we'd be super happy if you did end up using tracing! Beyond the tracing-tree library I wrote, @yaahc has been working on flamegraph/inferno integration with tracing here: tokio-rs/tracing#631. I'll see what the status of that PR is and if it can be merged soon.

[yaahc]

just finished the fix with the thread_local so now it should give accurate samples for multiple threads, I'll see if we can't get it merged today.

[lnicola]

@davidbarsky I think we can close this, right?