[0ax1]

Problem

Concurrent first use can create more CUDA streams than the pool's configured capacity.

Solution

Use OnceCell::get_or_try_init for each pool slot, replacing the custom initialization lock and ArcSwap.

Assessment

Initialized access remains lock-free and failed initialization can be retried. Uses once_cell because the fallible std::sync::OnceLock API is unstable. Based on #10726.

[codspeed]

Merging this PR will regress 1 benchmark

2 warnings, 1 note

⚠️ Walltime results may be unreliable

Some benchmarks used the Walltime instrument outside CodSpeed Macro Runners, which can make the results inconsistent.

Learn more about Macro Runners

See affected benchmarks

⚠️ 20 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

ℹ️ 40 benchmarks have no flamegraph

The flamegraph wasn't generated: the symbols of the profiling trace could not be resolved, because no information about the language frames was collected.

See affected benchmarks

⚡ 4 improved benchmarks
❌ 1 regressed benchmark
✅ 2403 untouched benchmarks
⏩ 12 skipped benchmarks¹
🗄️ 43 archived benchmarks run²

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Walltime	bitpack_blocked_compress_avx2	6.8 µs	7.6 µs	-10.4%
⚡	CPU Simulation	decode_primitives[i64, (1000, 8)]	37.6 µs	24 µs	+56.62%
⚡	CPU Simulation	take[routing/alternating_chunks/primitive/nonnull/chunks=32/indices=1000]	247.1 µs	196.7 µs	+25.62%
⚡	Walltime	bitpack_blocked_compress_avx512	5.6 µs	4.8 µs	+15.94%
⚡	Walltime	words_gather_dispatch_neon[65536]	2 µs	1.8 µs	+10.18%

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 ad/cuda-stream-pool-init (ceea114) with develop (e083440)}

Footnotes

1. 12 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. ↩

2. 43 benchmarks were run, but are now archived. If they were deleted in another branch, consider rebasing to remove them from the report. Instead if they were added back, click here to restore them. ↩