making ./validate run tests on all CPUs by default

[Tuncer Ayaz]

On Tue, Aug 12, 2014 at 10:31 PM, Sergei Trofimovich wrote:
> Good evening all!
>
> Currently when being  ran './validate' script (without any parameters):
> - builds ghc using 2 parallel jobs
> - runs testsuite using 2 parallel jobs
>
> I propose to change the default value to amount of available CPUs:
> - build ghc using N+1 parallel jobs
> - run testsuite using N+1 parallel jobs
>
> Pros:
> - first-time users will get faster ./validate
> - seasoned users will need less tweaking for buildbots
>
> Cons:
> - for imbalanced boxes (32 cores, 8GB RAM) it might
>    be quite painful to drag box out of swap
>
> What do you think about it?

Isn't the memory use also a problem on boxes with a much lower
number of cores (e.g. 7.8 space leak(s))?

On one machine with 1GB per core, I had to limit cabal install's
parallelism when using 7.8.

Assuming the patch goes in, is there a way to limit parallel jobs
on the command line?