waf default number of jobs

Joel Sherrill joel at rtems.org
Thu Oct 1 19:53:15 UTC 2020

On Thu, Oct 1, 2020 at 2:39 PM Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> On 01/10/2020 20:09, Joel Sherrill wrote:
> > What was the rationale behind the choice of the default for the number
> > of jobs for the waf build system?
> I don't know. It is the default behaviour of waf. I noticed also
> scalability problems but had no time to track them down. It could be
> also a limitation of the Python multiprocessing capabilities. I am also
> not a waf expert, I may have produced some bottlenecks.

I don't think you produced any bottlenecks. Here are a couple of fragments
from my build. I have attached the ini file so you can double check that it
does match. Please let me know if the ini matches the configure command
or not. If it doesn't, then I have a lot of bogus builds. :(

 ../rtems/configure --target=arm-rtems6 --enable-rtemsbsp=gumstix
--prefix=/home/joel/rtems-cron-6/tools/6/bsp-install --disable-networking
--enable-posix --disable-smp --disable-multiprocessing --enable-rtems-debug
--enable-profiling --enable-tests --enable-cxx --enable-maintainer-mode
+ make -j24

real    1m53.064s
user    7m14.675s
sys     1m45.913s

+ ./waf -j 24

real    1m1.404s
user    0m9.601s
sys     0m1.547s

Notice how the build time for waf is 50 seconds faster but that doesn't
match the user and system time. Perhaps the Python jobs model doesn't
keep them as children the same way so time doesn't get to count them.

I honestly can't explain that.

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