diff --git a/src/building/bootstrapping/debugging-bootstrap.md b/src/building/bootstrapping/debugging-bootstrap.md index 3f907e85..04fa5b20 100644 --- a/src/building/bootstrapping/debugging-bootstrap.md +++ b/src/building/bootstrapping/debugging-bootstrap.md @@ -121,6 +121,14 @@ For `#[instrument]`, it's recommended to: - Explicitly pick an instrumentation name via `name = ".."` to distinguish between e.g. `run` of different steps. - Take care to not cause diverging behavior via tracing, e.g. building extra things only when tracing infra is enabled. +### Profiling bootstrap + +You can use the `COMMAND` tracing target to trace execution of most commands spawned by bootstrap. If you also use the `BOOTSTRAP_PROFILE=1` environment variable, bootstrap will generate a Chrome JSON trace file, which can be visualized in Chrome's `chrome://tracing` page or on https://ui.perfetto.dev. + +```bash +$ BOOTSTRAP_TRACING=COMMAND=trace BOOTSTRAP_PROFILE=1 ./x build library +``` + ### rust-analyzer integration? Unfortunately, because bootstrap is a `rust-analyzer.linkedProjects`, you can't ask r-a to check/build bootstrap itself with `tracing` feature enabled to get relevant completions, due to lack of support as described in .