NativeAOT CLI size and startup analysis for dotnet/sdk PR #55497

pr55497-nativeaot-size-and-startup.md

NativeAOT CLI size and startup analysis for dotnet/sdk#55497

PR: dotnet/sdk#55497 — Enable MSBuild-backed commands in the Native AOT CLI

Test setup

• OS/RID: Windows x64 (win-x64)
• Configuration: Release
• PR base: 2e5fa46b2d150671d77cf313930d4de322907118
• PR head: 3df559618a8d1776b58dd71c3b4c2ab424b46ab8
• SDK used to build: 11.0.100-preview.5.26302.115
• NativeAOT compiler/runtime packs: 11.0.0-preview.7.26365.101
• Each bundle was force-recompiled to prevent incremental output reuse.
• Bundle size is the native dotnet-aot.dll only. PDB size is excluded.
• Commands were launched through the NativeAOT dn host with DOTNET_CLI_ENABLEAOT=true.

Bundle size

Optimization	Invariant globalization	Base	PR	PR increase
Speed	false	20.60 MiB	45.79 MiB	+25.18 MiB / 122.2%
Size	false	17.16 MiB	36.28 MiB	+19.12 MiB / 111.4%
Speed	true	20.39 MiB	45.54 MiB	+25.15 MiB / 123.3%
Size	true	16.97 MiB	36.06 MiB	+19.09 MiB / 112.5%

On the PR head:

• OptimizationPreference=Size saves 9.51 MiB / 20.8% with normal globalization.
• OptimizationPreference=Size plus invariant globalization saves 9.73 MiB / 21.3% versus the default.
• InvariantGlobalization=true alone saves only 0.22–0.25 MiB / ~0.6% on Windows.

Native section growth at default settings

PE section	Base	PR	Increase	Share of growth
.text	8.43 MiB	18.03 MiB	+9.60 MiB	38.1%
.rdata	10.35 MiB	23.45 MiB	+13.09 MiB	52.0%
.data	0.82 MiB	1.72 MiB	+0.90 MiB	3.6%
.pdata	0.48 MiB	1.08 MiB	+0.60 MiB	2.4%
.reloc	0.52 MiB	1.50 MiB	+0.99 MiB	3.9%

Most of the increase is code and read-only data, consistent with resolver registration rooting the MSBuild/NuGet dependency closure.

Command startup on the PR head

These are medians from 150 launches per command/configuration. Commands were rotated across three passes to reduce ordering effects. Output was identical across all four configurations.

Command	Speed	Size	Speed + invariant	Size + invariant
--version	27.40 ms	40.47 ms	26.28 ms	39.58 ms
--info	55.47 ms	68.87 ms	45.45 ms	58.61 ms
--help	27.79 ms	40.84 ms	26.93 ms	39.93 ms
build --help	27.97 ms	41.36 ms	27.75 ms	40.12 ms
restore --help	28.74 ms	41.89 ms	27.41 ms	40.88 ms
sdk check	108.06 ms	117.27 ms	90.30 ms	106.41 ms

Relative to the default

Command	Size	Speed + invariant	Size + invariant
--version	+47.7%	-4.1%	+44.5%
--info	+24.2%	-18.1%	+5.7%
--help	+47.0%	-3.1%	+43.7%
build --help	+47.9%	-0.8%	+43.4%
restore --help	+45.8%	-4.6%	+42.2%
sdk check	+8.5%	-16.4%	-1.5%

Conclusions

• The PR more than doubles the native DLL at default settings: 20.60 MiB to 45.79 MiB.
• OptimizationPreference=Size recovers about 9.5 MiB, but adds a largely fixed ~9–13 ms with normal globalization and ~12–16 ms with invariant globalization in this command matrix.
• The fixed absolute cost makes the percentage regression look largest for parser-only commands and smaller for commands that do more work.
• Invariant globalization has little size benefit on Windows, but reduced measured startup for --info and sdk check by roughly 16–18%.
• --list-sdks and --list-runtimes were excluded because they used managed fallback in the minimal benchmark harness.

These timings are process-launch microbenchmarks on one machine. They are useful for comparing these builds under the same conditions, not as universal absolute startup numbers.