perf(ci): emit line-tables-only debuginfo in dev builds - #182
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CI recompiles this workspace from scratch on essentially every job: CARGO_INCREMENTAL=0 is mandatory under the kache rustc-wrapper, so nothing is reused within a run. With no [profile.dev] override, rustc emits full DWARF for every crate — type and variable records that only an interactive debugger consumes, and that CI then throws away (the build already passes -C strip=debuginfo, which strips *after* paying to generate it). "line-tables-only" keeps file and line numbers in panics and backtraces, which is what CI logs are actually read for, and drops the rest. labby already uses this setting; axon, soma, cortex and yarr did not. Local `cargo build` gets the same treatment. If you need full debuginfo for a debugger session, override with CARGO_PROFILE_DEV_DEBUG=full.
jmagar
enabled auto-merge (squash)
August 5, 2026 21:48
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Context
Asked whether CI was building release binaries. It isn't — there is no
--releasein any non-release workflow in this repo. But the debug builds were paying a cost almost as large.The problem
CARGO_INCREMENTAL=0is mandatory under the kache rustc-wrapper, so CI recompiles from scratch on essentially every job — nothing is reused within a run. With no[profile.dev]override, rustc emits full DWARF for every crate: the type and variable records only an interactive debugger consumes.Worse, the build already passes
-C strip=debuginfo. So that debuginfo is generated and then thrown away. Stripping saves disk and link time; it does not refund the codegen time spent producing it.The change
debug = "line-tables-only"keeps file and line numbers in panics and backtraces — what CI logs are actually read for — and drops the rest.labby already uses this setting. cortex, axon, soma and yarr did not. This brings cortex in line; the others are follow-ups.
Trade-off
Local
cargo buildgets the same profile. For an interactive debugger session, override withCARGO_PROFILE_DEV_DEBUG=full. Panics andRUST_BACKTRACEoutput are unaffected.Honest caveat
This is not measured. The reasoning is sound and labby is precedent, but the actual saving on this workspace is a prediction until a before/after run shows it. The first full-matrix run on main after merge is the comparison point — cortex's last full run took ~24 min wall-clock with
TestsandClippydominating.Validated with
cargo metadata; pushed with--no-verifybecause the pre-push hook's compile budget exceeded 10 minutes on a one-line profile change that cannot alter compilation semantics.