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log_abi_compile_erasure rebuilds libwirelog inside a parallel meson test run

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
56/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
c
Domain
build-system, testing

Research direction

Start in tests/meson.build at the log_abi_compile_erasure registration, then inspect scripts/ci/check-log-erasure.sh and the related candidate_consumer_contract change in PR #1615. Add serial scheduling, review the timeout using check-shell-gate-walltime.py --fraction 0.5, and sweep registered scripts for other nested builds. Done means the acceptance checks pass and the added serial wall-clock is reported.

Written by the indexing model from the issue text.

Description

bug p2-medium

Triage — 2026-09-22

Target: Infra-0.A. Priority: p2-medium.

Address nested-build contention and scheduling in log erasure checks. #1799/#1808/#1663 separately own correctness; do not conflate scheduling improvement with their fixes.

This scheduling/ownership update supersedes older milestone assignments below; original acceptance criteria remain binding. A target milestone is a completion target, not a requirement to delay ready work.

Discovery context

Architect validation of PR #1615. That PR fixed candidate_consumer_contract, which ran a full from-scratch release build inside meson test and both exceeded its own budget and starved a neighbour into a timeout. The fix was is_parallel: false. A sweep for siblings found one.

The defect

tests/meson.build:

test('log_abi_compile_erasure',
     find_program(meson.project_source_root() / 'scripts/ci/check-log-erasure.sh'),
     suite: 'abi',
     timeout: 180)

scripts/ci/check-log-erasure.sh runs meson setup ... --buildtype=release -Dwirelog_log_max_level=error followed by meson compile -C "${BUILD_DIR}" wirelog. So it is a full library rebuild, and it has no is_parallel: false — it runs concurrently with the rest of the suite, where meson test parallelism is ncpu and the nested ninja takes ncpu+2.

The registration comment at tests/meson.build already acknowledges the cost ("log_abi_compile_erasure keeps 180 because it rebuilds libwirelog"), so the rebuild is known; what is not addressed is that it competes with every other test while doing it.

This is the same mechanism that produced PR #1615's two CI failures, measured there as a 5.6x spread on identical work across legs of one run, and a neighbour timing out at 30.08s while the offender passed at 112.17s.

Why it matters now

PR #1615 raised col_rel_deep_copy to timeout: 120 partly because this gate remains a parallel full-build neighbour on the TSan legs, where that test legitimately costs ~29s. In other words the col_rel_deep_copy raise is currently doing double duty: covering both the gate PR #1615 serialised and this one, which it did not. Serialising this gate would let that be re-examined on its own merits.

Scope

  • Add is_parallel: false to log_abi_compile_erasure, and re-check its timeout: 180 once it no longer runs contended — serialised it should be faster, but check-shell-gate-walltime.py requires measured duration to stay under 50% of the registered timeout, so the two move together.
  • Sweep for any other registered test that nests a build; check-log-erasure.sh and the candidate-consumer runner were the two found by grepping registered scripts for meson setup.

Acceptance criteria

  • No registered test runs a nested meson compile concurrently with the rest of the suite.
  • check-shell-gate-walltime.py --fraction 0.5 green with the adjusted timeout.
  • The added serial wall-clock is stated, since it is paid on every leg that runs an unfiltered meson test.

Related

  • PR #1615 — same mechanism, fixed for candidate_consumer_contract
Dominant language
C
Stars
18
Forks
2
Avg merge
6h 16m
Merged PRs (30d)
286

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