[EXPERIMENTAL] bootstrap: add structured tracing to ./x test tests/ui and ./x build compiler/rustc_codegen_gcc flows

[jieyouxu]

Intended for bootstrap reading club's core infra session, to make it easier to play around with bootstrap to visualize the execution flow.

Not intended for merge because tracing + tracing_subscriber + tracing_tree are quite heavy dependencies for build times.

Example usage

$ BOOTSTRAP_LOG=bootstrap=TRACE,STEPS_TO_RUN=TRACE ./x build ./compiler/rustc_codegen_gcc/ --stage 1
$ BOOTSTRAP_LOG=bootstrap=TRACE ./x build ./compiler/rustc_codegen_gcc/ --stage 1
$ BOOTSTRAP_LOG=bootstrap=TRACE ./x test tests/ui --stage 1
$ BOOTSTRAP_LOG=bootstrap=TRACE ./x test tests/ui src/tools/run-make-support --stage 1

Screenshots

./x test tests --stage 1:

./x build compiler/rustc_codegen_gcc --stage 1:

r? @ghost

[bjorn3]

Maybe it would be possible to add it behind a cargo feature?

[jieyouxu]

Maybe it would be possible to add it behind a cargo feature?

Possibly. All the #[instrument(..)] attribute sites will have to be gated like

#[cfg_attr(feature = "logging", instrument(...))]

but tbh I would personally want that for debugging even if that is the case.

EDIT: implemented in #135391

[jieyouxu]

Maybe it would be possible to add it behind a cargo feature?

cf. https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Conditional.20.60tracing.60.20dep.3F, I also measured not gating behind conditionally and just measure the build time impact of taking on direct tracing* dependencies:

Build time measurements

Procedure

Preparation: rebase against latest master, commit 12445e0, ./x clean

The exploratory PR adds 3 (root) deps to bootstrap:

tracing = { version = "0.1.41", features = ["attributes"] }
tracing-subscriber = { version = "0.3.19", features = ["env-filter", "fmt", "registry", "std"] }
tracing-tree = "0.4.0"

Measured locally via

$ hyperfine --runs 5 --ignore-failure --prepare="./x clean" "./x build bootstrap" --show-output

• --prepare="./x clean": clear bootstrap build cache, not counted towards bootstrap build time measurement

Before tracing* deps

Time (mean ± σ): 16.831 s ± 0.233 s [User: 38.987 s, System: 3.404 s]
Range (min … max): 16.508 s … 17.159 s 5 runs

After tracing* deps

Time (mean ± σ): 17.540 s ± 0.084 s [User: 44.758 s, System: 3.900 s]
Range (min … max): 17.457 s … 17.666 s 5 runs

Conclusion

Approximately ~0.709 seconds slower (4.21% increase in build time).

[bors]

☔ The latest upstream changes (presumably #135281) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #135430) made this pull request unmergeable. Please resolve the merge conflicts.