[Nix-dev] Re: Another approach at parallelizing in-build jobs

[Lluís Batlle i Rossell]

Hello Peter,

On Sat, Jun 19, 2010 at 08:36:24PM +0200, Peter Simons wrote:
> Hi Lluís,
> I see, thank you for the quick response. What I don't see, however, is how
> substituters might accomplish in-build parallelization?

I thought of a substituter that could take the derive file, change it, and issue
an output path build.

>  > I have a fear (not necesarily irrational) that not many people wrote good
>  > Makefiles (in terms of reproduceability of results in parallel builds).
> 
> It sounds a lot like your fear *is* irrational, because it is in stark contrast
> to the real world. Virtually everyone who owns a multi-core machine does enable
> parallel building, because without that feature build times for packages like
> the Linux kernel, GHC, GCC, glibc, etc. would be so immense that it would be
> extremely unpleasant to actually work on that code. Consequently, build systems
> of packages of a significant size tend to be extremely well tested with regard
> to parallel building. Also, other Linux distributions like Gentoo or ArchLinux
> utilize parallel building, and that seems to work, too. So I wonder on what
> rational criteria your fear might be based?

That my fear is related to people that may have written bad the Makefiles, and
that fear makes me simply against the opt-out approach, but I sure favour the
opt-in.  I trust projects like those you mention, and I'd also build them in
parallel without any fear, and in preference over single-task build.

> It is no secret that some packages don't support parallel building for whatever
> reason, and the commonly utilized approach to deal with that situation is to
> build them single-threadedly.
Also mine.

Regards,
Lluís.