Support a TUI "live view" version of -Z self-profile.

[eddyb]

Using tui and by passing, say, the entire query stack to an "UI" thread 60 times per second, we can provide both a live view of the query stack, including when each entry started, and overall stats.

cc @nikomatsakis @michaelwoerister @wesleywiser @solson

[retep998]

But would it work on Windows?

[nagisa]

My personal preference is that we output some sort of file that can be inspected with some external tool instead (either live or after-the-fact). This generally allows way more control and significantly greater insight into operation of the code.

This is fairly popular in embedded and works extremely well. Not sure if there’s a generic libre tool for this, though, but I had a fair amount of success producing similar graphs out of perf record output.

[wesleywiser]

FYI, passing -Zprofile-json causes a self_profiler_results.json file to be created in the working directory with all of the same info presented in the -Zself-profile option.

[eddyb]

@wesleywiser Can you mention that in #53631 as well?

For the record, this issue is about an user-friendly live view that can give you "a feel" for what the compiler is doing, at an insignificant cost (i.e. without recording every single relevant event).
We can do multiple things here, but among them I also want this.

[eddyb]

Potentially relevant now that we've moved to tracing: tokio-rs/tracing#884 (learned of it thanks to @hawkw, who mentioned it in a related discussion about interactive log viewers).