perf(build): set dev profile to line-tables-only debug info#515
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The dev profile uses cargo's default `debug = 2` (full DWARF). Linking the `nori` binary then has to mmap the full debug info of ~600 crates; on memory-constrained machines (and CI/cloud VMs with little RAM and no swap) the kernel evicts and re-reads those pages, sending the linker into disk thrash. A clean debug build was observed reading tens of GB at the final link and failing to complete in 35+ minutes. `debug = "line-tables-only"` keeps file:line in panics and backtraces while dropping the bulk of the DWARF, which removes the thrash: clean build ~9 min, incremental relink ~30s on the same constrained box. Scoped to profile.dev, so test/ci-test profiles are unaffected. 🤖 Generated with [Nori](https://noriagentic.com) Co-Authored-By: Nori <contact@tilework.tech>
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Summary
Sets
profile.dev.debug = "line-tables-only"innori-rs/Cargo.toml. This keepsfile:lineinfo in backtraces while dropping the full DWARF that makes the final link of thenoribinary memory-bound on low-RAM machines.Why
While benchmarking clean
noribuilds across cargo/rustc/linker configurations, the dominant cost was not the linker choice (mold/lld/bfd are all within run-to-run noise). It was the debug-info footprint.On a RAM-constrained machine (no swap,
target/on overlayfs), the defaultdebuginfo=2makes the final link mmap huge DWARF inputs across ~600 crates. Under memory pressure the kernel evicts and re-reads those pages from disk, so the linker sits in disk-sleep reading tens of GB. A clean default-profile debug build never completed in 35+ min.Measured clean build of the
noribin by debug-info level (same machine, mold):debuginfo=2(default)"line-tables-only"0(none)"line-tables-only"is the sweet spot: it removes the thrash while preserving thefile:linedata that makes panic backtraces useful during development.Scope
profile.devis affected.profile.release,profile.test, andprofile.ci-testare unchanged.debug = "line-tables-only"is the explicit string form — notedebug = 1maps to"limited", which is a different (larger) level.Test plan
cargo metadata --no-depsparses the manifest cleanlycargo buildon a dev machine still produces usable backtraces withfile:line