next.js

80cb3447 - [ci] Add an `TURBO_TASKS_AVAILABLE_PARALLELISM` environment variable that overrides `std::thread::available_parallelism` callsites (#93995)

[ci] Add an `TURBO_TASKS_AVAILABLE_PARALLELISM` environment variable that overrides `std::thread::available_parallelism` callsites (#93995) We want to use this to potentially improve efficiency in e2e tests where we're running many instances of Turbopack at once. By default, turbo-tasks will try to use every available CPU core. **This environment variable does not strictly limit Turbopack to using 4 cores, it just restricts the number of main tokio worker threads and changes how we shard dashmaps.** This option will not make sense for the vast majority of users, it only makes sense when you are running *many* instances of Turbopack at once, and the exact semantics are potentially confusing, as it is not a hard limit. ## Test Plan Build vercel-site with this set to 1 and see a little over 100% CPU usage. Set it to 8 and see around 800% CPU usage. ``` TURBO_TASKS_AVAILABLE_PARALLELISM=1 pnpm next build --experimental-build-mode=compile ```