Use OnceLock for SingleCache

[Zoxc]

This uses OnceLock for SingleCache instead of Lock<Option<T>> so lookups are lock-free.

r? @cjgillot

[cjgillot]

@bors r+

[bors]

📌 Commit 90f5f94 has been approved by cjgillot

It is now in the queue for this repository.

[bors]

⌛ Testing commit 90f5f94 with merge 9dc11a1...

[bors]

☀️ Test successful - checks-actions
Approved by: cjgillot
Pushing 9dc11a1 to master...

[bors]

☀️ Test successful - checks-actions
Approved by: cjgillot
Pushing 9dc11a1 to master...

[rust-timer]

Finished benchmarking commit (9dc11a1): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	2
Improvements ✅ (secondary)	-0.5%	[-0.6%, -0.3%]	8
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	2

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.9%	[1.2%, 2.3%]	3
Regressions ❌ (secondary)	7.7%	[7.7%, 7.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.9%	[-4.9%, -4.9%]	1
All ❌✅ (primary)	1.9%	[1.2%, 2.3%]	3

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 629.86s -> 631.705s (0.29%)
Artifact size: 316.61 MiB -> 316.63 MiB (0.01%)