rustdoc: use with_capacity and reserve to reduce reallocation

[lolbinarycat]

No description provided.

[lolbinarycat]

@bors try @rust-timer queue

[lolbinarycat]

Oops, forgot we can do more focused perf runs now, hopefully this overwrites the perf run and doesn't start a second one.

@rust-timer queue profiles=doc

[lolbinarycat]

@bors try cancel

[rust-bors]

Try build cancelled. Cancelled workflows:

• https://github.com/rust-lang/rust/actions/runs/21924761758

[lolbinarycat]

@bors try

[rust-bors]

☀️ Try build successful (CI)
Build commit: 08f322c (08f322c258c616d236bf389f7abf02202a524729, parent: 7057231bd78d6c7893f905ea1832365d4c5efe17)

[rust-timer]

Finished benchmarking commit (08f322c): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (secondary -4.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.5%	[-4.9%, -4.0%]	2
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -2.4%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.0%	[3.0%, 3.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.2%	[-5.5%, -2.8%]	3
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 476.438s -> 474.386s (-0.43%)
Artifact size: 397.88 MiB -> 397.89 MiB (0.00%)