Ability to set concurrency to max (equal to CPU cores) --concurrency=max

[moltar]

Describe the feature you'd like to request

I am not an expert in this area, but I think it's counter-productive to set the concurrency to a higher number than there are CPU cores available for CPU-hungry processes, like tests and builds, as these processes would be competing for resources.

Thus, a default setting of 10 might be counter-productive in certain environments, like CI, where the number of cores can be lower.

For example, GitHub Actions only have 2 cores available for Windows and Linux, yet 3 for macOS.

Describe the solution you'd like

I think there should be a way to specify "max" or some other variation of that, that signals Turbo to sniff out the number of cores and set the concurrency to that value.

Describe alternatives you've considered

turbo run build --concurrency=$(node -r os -e 'process.stdout.write(os.cpus().length.toString())')

[marcelltoth]

In my opinion it would probably be even better if we could set the global default using an environment variable. I'm sure many people are like us: we have a long and complex CI pipeline with lots of jobs, adding --concurrency everywhere is cumbersome.

It would be much simpler if we could specify e.g. TURBO_DEFAULT_CONCURRENCY=4 globally, then we

1. wouldn't have to litter the CI config file with --concurrency settings everywhere.
2. would have a single place to change in case I were to change the executor size.

Note that simply changing turbo's default to the CPU count (like jest does for example) is not adequate, as some CI providers like CircleCI always show a lot of CPU cores (32 in CCI's case), regardless of the actually available size.

What do you think?

[moltar]

I think these are separate features and both have the place.