[not-matthias]

Always pass --deterministic-rng=yes to valgrind in simulation mode, so AT_RANDOM, getrandom(), /dev/urandom and hardware RNG instructions return fixed values. This removes one source of run-to-run variance.

Blocked on a valgrind-codspeed release: the currently pinned 3.26.0-0codspeed10 does not know --deterministic-rng and would reject it. The pin must be bumped before this merges.

Closes COD-4083

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I suggest merging this and releasing a new beta to properly test the feature

[codspeed]

Merging this PR will degrade performance by 13.13%

1 warning

⚠️ 7 benchmarks are dominated by system calls

System calls cannot be simulated consistently and are left out of the measure. The reported value understates the real cost. Switch to the Walltime instrument to measure them.

Learn more about system calls

See affected benchmarks

❌ 1 regressed benchmark
✅ 37 untouched benchmarks
⏩ 9 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Walltime	memtrack track tar	8.2 s	9.4 s	-13.13%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing cod-4083-enable-deterministic-rng-in-runner (93b6701) with main (ea54386)}

Footnotes

1. 9 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[greptile-apps]

Confidence Score: 5/5

[Medium impact] No additional changes are requested beyond the Valgrind release prerequisite already documented by the author.

Summary

Adds --deterministic-rng=yes to every simulation run, covering both Callgrind and Tracegrind.

• Valgrind simulation runs now ask for fixed random values.

_{Reviews (1) · Last reviewed commit: "feat(valgrind): always enable determinis..." · Reviewed by Greptile}

[GuillaumeLagrange]

lgtm, I think all thee commits can be squashed though 🙈