Cargo profiling improvements - #17411
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On large workspaces, the formatting `UnitGraph` can take a long time. Notably on Zed, it was taking over 300ms on my machine, meaningfully skewing the profiling results. This commit makes dumping the unit graph opt-in with `__CARGO_DUMP_UNIT_DEP_GRAPH`
This trace! was in a hot loop skewing the timings when cargo profiling is enabled. As a side note `build_sbom_graph` does appear to take up a meaninful amount of time in `prepare_rust` due to needing to walk the dependency graph.
Added profiling instrumentation on more profiler related functions to give more visiblity on where we spend time while preparing rustc jobs.
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### What does this PR try to resolve? Before this PR, the SBOM would be generated in memory and be thrown away instead of written to a file. For projects with a large dependency graph, this can add noticeable delay. Below is a profiling run on Zed. <img width="2065" height="908" alt="image" src="https://github.com/user-attachments/assets/8ca00cc0-3498-4161-8c2b-0415f2006d9e" /> On a cold build, this is a very small part of the work, but we have to pay this price on every build. But when trying to do repeated builds while iterating this time starts to add up. ### How to test and review this PR? I primarily was doing profiling on Zed when I found this. (also see: #17411) ```sh CARGO_LOG_PROFILE=true CARGO_LOG_PROFILE_CAPTURE_ARGS=true cargo build ``` I did not add any additional tests since there aren't really any outputs to compare against. Hoping the existing SBOM tests are good enough, but happy to add a test for this if there is a way I am missing :) r? @arlosi cc: @Shnatsel cc: #16565
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Update cargo submodule 26 commits in e8cb624d5701824f46a2ec5873cfd59ee3d2f66c..b2e9d5f9db3fb1c454ab84f10c16508984a266e2 2026-08-22 00:23:45 +0000 to 2026-09-02 14:49:16 +0000 - fix(parser): Resolve theoretical use-after-free (rust-lang/cargo#17428) - fix(trim-paths)!: remove default scope from release profile (rust-lang/cargo#17424) - fix(git): Use git's 429 retry, when available (rust-lang/cargo#17422) - Avoid passing search path (-L) args when they are passed as --extern (rust-lang/cargo#17410) - chore(deps): update crate-ci/typos action to v1.50.0 (rust-lang/cargo#17417) - test: Move -Z onto its own line (rust-lang/cargo#17416) - chore(triagebot): enable `@rustbot merge/delegate` (rust-lang/cargo#17415) - Micro-optimize two package dir functions (rust-lang/cargo#17413) - perf: Do not build SBOM if user has not set build.sbom (rust-lang/cargo#17412) - feat(manifest)!: implement feature-metadata RFC3416 (rust-lang/cargo#15056) - Cargo profiling improvements (rust-lang/cargo#17411) - test(git): Remove gix override run in CI and the mode in code (rust-lang/cargo#17405) - perf(git): Reduce extra work when using git-cli (rust-lang/cargo#17406) - feat(resolver): Stabilize min-publish-age (rust-lang/cargo#17335) - fix(git): Remove ref status update when showing progress (rust-lang/cargo#17400) - revert: refactor: move sysroot lookup to GlobalContext (rust-lang/cargo#17401) - fix(run): Printing a new line to avoid overwriting error code after \r (rust-lang/cargo#17373) - fix(trim-paths): custom workspace-relative member paths remap (rust-lang/cargo#17366) - fix(home): rustdoc lint (rust-lang/cargo#17394) - feat(diag): Stabilize cargo-lints (rust-lang/cargo#17298) - chore(deps): Update partial_ref to v0.3.4 (rust-lang/cargo#17392) - refactor: remove ad-hoc `subslice_range` (rust-lang/cargo#17390) - docs(changelog): move build-dir new layout to Changed (rust-lang/cargo#17387) - chore(deps): update msrv (1 version) to v1.98 (rust-lang/cargo#17386) - docs: Use mdbook admonitions (rust-lang/cargo#17384) - chore(ci): exclude resolver-tests from intra doc link checks (rust-lang/cargo#17385)
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What does this PR try to resolve?
This PR makes a couple of small improvements to our profiling by:
trace!()calls that log large objects (UnitGraph) or all called from a hot loop (in the case ofbuild_sbom_graph)fn compile()while trying to avoid instrumenting leaf functions.Below are some tracing examples from using profiling on the Zed repository.
Before
After
How to test and review this PR?
CARGO_LOG_PROFILE=true CARGO_LOG_PROFILE_CAPTURE_ARGS=true cargo buildon your favorite repo :)