test(gc): raise gc_write_barrier_stress timeout 120s→300s to de-flake CI

[proggeramlug]

Problem

The cargo-test CI job intermittently fails on crates/perry/tests/gc_write_barrier_stress.rs — tenured_mutation_stress (and structured_clone_gc_churn_stress) panic with compiled binary timed out after 120s, regardless of the PR's changes (it fails identically across unrelated PRs and passes on lucky/idle runs).

Root cause — it's a timeout flake, not a correctness failure

compile_and_run executes the stress binaries under the slowest GC configuration:

run.env("PERRY_GC_FORCE_EVACUATE", "1")     // copy every marked object, every cycle
   .env("PERRY_GC_VERIFY_EVACUATION", "1"); // full-heap pointer-verification scan per cycle

against a heavy churn workload (churn(5) + churn(4) rounds × 30 000 allocations + explicit gc() each). Measured wall-clock:

config	time
normal	~1.5s
FORCE_EVACUATE + VERIFY_EVACUATION	~21s (fast host)

~21s on a fast local host scales to roughly 60–130s on the slower, shared, heavily-parallel CI runners — straddling the old 120s deadline, so the run is killed (timeout panic) whenever the runner is loaded. (Issue #5029 fixed the underlying GC corruption and re-enabled these tests in #5043; this is purely the run deadline being too tight for the verify-evacuate config.)

Fix

Raise COMPILED_BINARY_TIMEOUT from 120s to 300s. The tests assert correctness (BARRIER_STRESS_OK), not speed, so widening the deadline de-flakes CI without trimming the stress coverage (still force-evacuate + full verify across all churn cycles). 300s is ~14× the measured fast-host time and ~2.5× the worst-case loaded-CI estimate.

Verified locally: both configs still print BARRIER_STRESS_OK; the verify-evacuate run completes in ~21s.

This de-flakes the cargo-test job for every open PR. No version bump / changelog per maintainer instruction.

Summary by CodeRabbit

• Tests
  • Adjusted garbage collection stress test timeout parameters to accommodate slower execution environments and allow adequate headroom for test completion.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 46129171-ed67-47bf-afe7-c60ba6daac44

📥 Commits

Reviewing files that changed from the base of the PR and between 5b61919 and 389e2ec.

📒 Files selected for processing (1)

• crates/perry/tests/gc_write_barrier_stress.rs

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📝 Walkthrough

Walkthrough

The COMPILED_BINARY_TIMEOUT constant in the GC write barrier stress test is increased from 120 seconds to 300 seconds. Explanatory comments are added noting that the test runs with forced GC evacuation and verification enabled, which can cause significantly longer runtimes on slower CI runners.

Changes

GC Write Barrier Stress Test Timeout

Layer / File(s)	Summary
Stress test timeout constant crates/perry/tests/gc_write_barrier_stress.rs	COMPILED_BINARY_TIMEOUT raised from 120s to 300s; comments added explaining forced evacuation and verification settings drive the longer allowed runtime.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

🐇 A bunny once waited with patience so grand,
Two minutes weren't enough — the GC had more planned!
With evacuation and verification in tow,
Five whole minutes now let the stress test flow.
Hop hop, no more timeouts — watch the barriers go! 🌟

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the main change: raising the GC write barrier stress test timeout from 120s to 300s to fix CI flakiness.
Description check	✅ Passed	The PR description provides a comprehensive explanation of the problem, root cause, fix, and verification, though it doesn't follow the template structure with explicit sections like Summary, Changes, Test plan, and Checklist.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
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• Create PR with unit tests
• Commit unit tests in branch fix/gc-stress-test-timeout

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