bug#35139: Rust builds systematically time out

[Ludovic Courtès]

Ivan Petkov <address@hidden> skribis:

>> On Apr 4, 2019, at 1:59 AM, Ludovic Courtès <address@hidden> wrote:
>> 
>> The build nodes may be slower than the front-end, but still, it seems
>> unlikely that it would take more than 6h there.  (That could happen if
>> the test suite, which lasts 2.1h, were “embarrassingly parallel”, but
>> we’re running tests with ‘-j1’.)
>> 
>> To summarize, there are two problems:
>> 
>>  1. Rust takes too long to build.  What can we do about it?  Enable
>>     parallel builds?
>
> Rust tests are designed to run in parallel, as long as you have enough
> RAM, file descriptors, etc. available on the machine for the amount of
> concurrency being used. The compiler test suite is largely just compiling
> files, so the most important resource is probably available RAM/swap.

Perhaps we could start with:

  "-j" (number->string (min (parallel-job-count) 2))

?

> Maybe if the bootstrapped versions don’t ever change skipping the check
> phase will be safe, but I think we should try running parallel tests first
> and see how far that gets us.

Sounds like a good start.

So the only reason we’re running tests sequentially is because of memory
usage concerns?

Thanks,
Ludo’.