[Buildroot] Antw: build speedup possible?

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Dear Fabio Porcedda,

On Fri, 7 Feb 2014 16:54:20 +0100, Fabio Porcedda wrote:

> > 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.

IMO this is not a corner case, this is precisely the problem we have
been pointing out since the beginning when mixing a global sysroot with
top-level parallelization.

> > 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.

I don't really see how to reproduce the exact build order, so the
support problem will be here. That's really why I have been a bit
skeptical and resistant to this patch series from the very beginning. I
am obviously very interested in ways to reduce the build time. But
doing that at the expense of reliability is not a good idea in my
opinion, as users will face spurious failures that we will not be able
to reproduce and fix.

If we want to get this to the next level, someone need to experiment
with per-package sysroot. Of course, this would be a long experiment,
without necessarily at the end the guarantee that we will accept it,
because it may be too complex to match Buildroot simplicity principle.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com