Question about autoreconf to regenerate configuration files

[Mike Frysinger]

On 26 Jan 2022 05:02, Mike Frysinger wrote:
> On 21 Jan 2022 17:09, Mike Frysinger wrote:
> > On 21 Jan 2022 17:09, R. Diez via Newlib wrote:
> > > > [...]
> > > > The bootstrap time was large enough to
> > > > negatively impact our ability to do automated regression testing.
> > > 
> > > A very long bootstrap time could be an issue.
> > > 
> > > However, compilation time normally outweighs by far the Autotools regeneration step. Is that a problem in Newlib at the moment?
> > 
> > autotools (autoreconf really) doesn't run in parallel, so every subdir
> > with a configure script needs a separate serialized run of all the tools.
> > newlib has many many of these (arguably, too many).
> > 
> > on my quad core 4.2GHz AMD that is otherwise idle ...
> > 
> > $ time (cd newlib && autoreconf)
> > real    5m22.170s
> > user    3m13.709s
> > sys     0m12.332s
> > 
> > $ time (cd libgloss && autoreconf)
> > real    1m41.754s
> > user    0m43.505s
> > sys     0m3.618s
> > <this errored out, not sure why, so it might normally take even longer :p>
> > 
> > # Blackfin builds 8 copies (multilib) of newlib+libgloss by default.
> > $ time (cd build; ../configure --host=bfin-elf; make -j4)
> > real    1m40.950s
> > user    0m58.032s
> > sys     0m30.968s
> 
> updated timings on my system after recent work to delete many configure scripts
> $ time (cd newlib && autoreconf)
> real    1m0.619s
> user    0m45.249s
> sys     0m1.535s
> 
> $ time (cd libgloss && autoreconf -I$PWD -I$PWD/.. -I$PWD/../config)
> real    0m32.662s
> user    0m15.858s
> sys     0m1.205s
> 
> $ time (cd build; ../configure --host=bfin-elf; make -j4)
> real    1m2.337s
> user    0m44.987s
> sys     0m26.708s
> 
> so it's def better, but autotool generation still takes longer than actually
> compiling newlib+libgloss 8 times :).

things are looking up.  with all my pending changes, we have 1 configure script
in newlib and no recursive makes.

$ time (cd newlib && autoreconf)
real    0m8.740s
user    0m7.524s
sys     0m0.193s

i'm not sure if i'll "finish" libgloss.  there's still a lot of subdirs not
even using automake, so while i can kill most configure scripts, i prob won't
do them all, and i prob won't convert more to automake or non-recursive make.
the libgloss arches have a lot harrier logic in them that i don't care to try
to unpack, especially since i converted the dirs i most care about.

$ time (cd libgloss && autoreconf -I$PWD -I$PWD/.. -I$PWD/../config)
real    0m8.313s
user    0m5.015s
sys     0m0.259s

we can see that killing excessive configure scripts & recursive makes helps
with compilation times too.

$ time (cd build; ../configure --host=bfin-elf; make -j4)
real    0m28.831s
user    0m34.828s
sys     0m23.093s

generating autotools is now slightly faster that compiling 8 copies of
newlib+libgloss :).  not that i'm advocating for changing anything :P.
-mike
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