next.js

88350cfe - [ci] Set `TURBO_TASKS_AVAILABLE_PARALLELISM` to 4 in most e2e tests (#93996)

[ci] Set `TURBO_TASKS_AVAILABLE_PARALLELISM` to 4 in most e2e tests (#93996) By default, turbo-tasks will try to use every available CPU core. While we do want it to use as many resources as possible if the CPU is otherwise idle, this may hurt us when the CPU is busy, as it will lead to more locking, more thread contention, more memory usage, etc. **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.** We currently are using 16 core CI machines, but I want to experiment with 32 core build machines with a higher `TEST_CONCURRENCY`, and the per-core scaling of Turbopack was a concern that came up, as wall time improvements are sub-linear starting somewhere around 16 cores. ## Test Plan Watch CI, compare build times in this commit and the parent one. Attempt with a value of 2: https://github.com/vercel/next.js/pull/94001 Attempt with a value of 8: https://github.com/vercel/next.js/pull/94002  I think this data is too noisy to draw any conclusions.