Memory leak in optimizeCss

[dmgawel]

Link to the code that reproduces this issue

https://codesandbox.io/p/devbox/old-currying-xtd57t

To Reproduce

1. Enable experimental optimizeCss
2. Keep the site running for longer time under some traffic
3. Watch the memory grows indefinitely until the app crashes

Current vs. Expected behavior

There's some kind of memory leak when the optimizeCss (Critters) is enabled. The memory usage grows linearly to traffic and is not freed, if the pages are SSG. This eventually results in the app crash.

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 22.6.0: Wed Jul  5 22:22:05 PDT 2023; root:xnu-8796.141.3~6/RELEASE_ARM64_T6000
Binaries:
  Node: 16.18.1
  npm: 8.19.2
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 13.5.6
  eslint-config-next: N/A
  react: 18.2.0
  react-dom: 18.2.0
  typescript: N/A
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Not sure

Which stage(s) are affected? (Select all that apply)

next start (local), Other (Deployed)

Additional context

Memory usage graph of our app:

The drops are manual restarts to keep the app running. The moment it finally stabilizes is when we disabled optimizeCss.

[rusakovic]

I think we have the issue not only with optimizeCss but with opengraph and wasm.
My ticket: #61047