Next 12 Build Performance on Windows

What version of Next.js are you using?

12.0.2 and 12.0.3-canary.9

What version of Node.js are you using?

v14.15.4

What browser are you using?

Any

What operating system are you using?

Windows

How are you deploying your application?

N/A

Describe the Bug

Despite the announcement (https://nextjs.org/blog/next-12#faster-builds-and-fast-refresh-with-rust-compiler) the build time of Next12 app on Windows was not improved:

• empty application created with create-next-app@latest - the build is the same comparing to create-next-app@11 (approx. 7.8 seconds)
• small-size application (5 pages, 2 API endpoints) - the build is ~50% slower after updating with npm i next@latest by 50% (22.4s vs 32.0)

Upgrading to next@canary makes no difference.

Others have reported similar or even worse results: https://www.tpjnorton.com/blog/posts/next-js-12-performance-test-builds-appear-to-be-slower-not-faster

Expected Behavior

Faster build with next12 comparing to next11.

To Reproduce

In Windows Powershell run:

npx create-next-app@latest
cd app-name
Measure-Command  {npm run build}
Measure-Command  {npm run build}

Compare results with:

npx create-next-app@11
cd app-name
Measure-Command  {npm run build} 
Measure-Command  {npm run build} 

Both build commands (with cold and hot cache) execution times are +/- the same.

[jamsinclair]

Seeing slower build times (30% increase) for a medium application after upgrading to Next 12.0.3 on Mac OS too.

Cold build times (with next build and type checking disabled)

• Next 11.1.0 ~30 seconds on MacOS Mojave
• Next 12.0.3 ~39 seconds on MacOS Mojave

Observed on CI too:

• Next 11.1.0 ~50 seconds on Ubuntu latest (GitHub Action CI)
• Next 12.0.3 ~64 seconds on Ubuntu latest (GitHub Action CI)

App

• 6 API Routes
• 2 base ISR Pages (hundreds of pages are later dynamically generated from here)
• Uses TypeScript
• Uses next-transpile-modules for one 200KB dependency
• ~Uses next-with-less~ I’ve removed this plugin and still observing ~10 second increase

Would a build trace help provide more visibility? Happy to share privately with a maintainer.

[TheThirdRace]

outputFileTracing: false

This also “solved” my problem. I’m on Window 10 too so you might have found the pattern.

The documentation on outputFileTracing: false make it sound scary to disable this, like the build could be missing files and not work… Should I be worried?

@timneutkens While my repo is private, I could send an invite for you to check it out if you still need examples of real repos. Furthermore, I’m in the midst of migrating from 11.1.2 to 12.0.7 so I could easily make 2 branches for testing purpose: nextjs-11-1-2 and nextjs-12-0-7.

Let me know if it’s something that you’re interested in validating.

Results of yarn build

11.1.2

Cold build: ~25s Warm build: ~14s

12.0.7

Cold build: ~35s (+10s average) Warm build: ~24s (+10s average)

12.0.7 + outputFileTracing: false

Cold build: ~19s (-6s average vs 11.1.2) Warm build: ~10s (-4s average vs 11.1.2)