Describe the performance issue

Using this repo as a test: https://github.com/KieranP/Github-Releases-Feed (Vite + Svelte + LightningCSS)

Ran old vite 5 times nad new rolldown-vite 5 times using time (i.e. real wall time, not just vites reported build time, since build time alone doesn't give an accurate picture of all parts involved), the final outcome is below.

Building (warm cache) is roughly 14.96% faster with enableNativePlugin false (0.909s down to 0.773s), and up to 27.72% faster with enableNativePlugin true (0.909s down to 0.657s). But the resulting package is ~31% bigger in both cases (62.62 kB up to 81.97 kB).

Nothing changes in application code, I simply swapped vite with rolldown-vite as per blog post. And the project is small, not much if any dead code within my code. So best guess is something is not getting tree-shaken correctly, some lib is including more than it should?

Reproduction

https://github.com/KieranP/Github-Releases-Feed

Performance Metrics

vite:

› time yarn build
vite v6.3.5 building for production...
✓ 444 modules transformed.
dist/index.html                  0.51 kB │ gzip:  0.31 kB
dist/assets/index-QWt4X0jk.css   8.21 kB │ gzip:  1.68 kB
dist/assets/index-0q1ncWN4.js   62.62 kB │ gzip: 23.16 kB
✓ built in 369ms
yarn build  1.07s user 0.16s system 134% cpu 0.909 total

rolldown-vite (enableNativePlugin = false)

› time yarn build
rolldown-vite v6.3.18 building for production...
✓ 441 modules transformed.
dist/index.html                  0.51 kB │ gzip:  0.31 kB
dist/assets/index-QWt4X0jk.css   8.21 kB │ gzip:  1.68 kB
dist/assets/index-CsmkX_yS.js   81.97 kB │ gzip: 29.30 kB
✓ built in 200ms
yarn build  0.70s user 0.30s system 129% cpu 0.773 total

rolldown-vite (enableNativePlugin = true)

› time yarn build
rolldown-vite v6.3.18 building for production...
✓ 441 modules transformed.
dist/index.html                  0.50 kB │ gzip:  0.30 kB
dist/assets/index-QWt4X0jk.css   8.21 kB │ gzip:  1.67 kB
dist/assets/index-DIRflXaC.js   81.97 kB │ gzip: 29.29 kB
✓ built in 129ms
yarn build  0.59s user 0.27s system 131% cpu 0.657 total

Steps to reproduce

time yarn build (which is alias for vite build)

System Info

System:
    OS: macOS 15.5
    CPU: (12) arm64 Apple M3 Pro
    Memory: 214.84 MB / 18.00 GB
    Shell: 5.9 - /opt/homebrew/bin/zsh
  Binaries:
    Node: 23.10.0 - ~/.asdf/installs/nodejs/23.10.0/bin/node
    Yarn: 4.9.1 - ~/.asdf/installs/nodejs/23.10.0/bin/yarn
    npm: 10.9.2 - ~/.asdf/plugins/nodejs/shims/npm
    bun: 1.2.15 - /opt/homebrew/bin/bun
  Browsers:
    Safari: 18.5
  npmPackages:
    vite: ^6.3.5 => 6.3.5

Used Package Manager

yarn

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs and the Rolldown-related guide.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.