[Buildroot] Antw: build speedup possible?

[Fabio Porcedda]

On Fri, Feb 7, 2014 at 4:29 PM, Thomas Petazzoni
<thomas.petazzoni at free-electrons.com> wrote:
> Dear Fabio Porcedda,
>
> On Fri, 7 Feb 2014 15:48:35 +0100, Fabio Porcedda wrote:
>
>> The build can be reproduced even when building packages in parallel,
>> we just need to record the order of the steps and replay that order if
>> needed.
>
> And in practice, how do you achieve this? When building in parallel,
> how do you record the fact that the test for libfoo in package A
> configure script was run before or after the installation of libfoo in
> the global sysroot? It's not only about recording the order of the
> build of the package: it's knowing whether each specific test of a
> configure script was run before or after the corresponding library was
> installed in the global sysroot.

Well i admit i haven't thought about that corner case, I don't know an
easy solution for that.

>> The sysroot copy is needed only to be sure that even if some package
>> has an unspecified optional dependency it generates every time the
>> same binary.
>
> Which is *the* very important thing. So saying it's needed "only to be
> sure" is quite minimizing the very important consequence of parallel
> build with a global sysroot, IMO.

Well minimizing was not my intention, but you are right to point it out.

>> I think that at least when doing development it will be useful to
>> build packages in parallel.
>> Maybe it will be best to avoid building packages in parallel just for releases.
>
> I don't agree.
>
> I do a lot of support on #buildroot, and I would *hate* to have people
> coming up with bug reports that are not reproducible because they
> depend on the specific scheduling of the build. I really don't want new
> comers to use this feature and then come back with bug reports that are
> basically unfixable because they cannot be reproduced.
>
> I think we should really not minimize the support problem that
> parallelization without per-package sysroot is going to cause.

My suggestion was based on the assumption that there is a way to
reproduce the exact build order.
But if that is not true i agree with you.

Best regards
-- 
Fabio Porcedda