distcc only builds locally when using rpmbuild

[Suvayu Ali]

Hi Sam,

On Sun, May 31, 2015 at 08:05:44PM -0400, Sam Varshavchik wrote:
> Suvayu Ali writes:
> >
> >How does rpmbulid decide how many threads to run?  I think it looks at
> >the local machine and decides.  I also recall some variable called
> >RPMBUILD_NCPU or something like that.  That would explain why it only
> >uses as many threads as the local machine can handle.
> >
> >Hope this helps,
> 
> Sadly, no it doesn't.  As I wrote above:
> 
> >> >> >> ps shows the maximum number of "/usr/bin/distcc /usr/bin/g++
> >[options]"
> >> >> >> processes running locally,
> 
> rpmbuild uses the _smp_mflags macro to pass the -j parameter to make, and I
> have it correctly configured to kick off ten parallel processes, to match
> the maximum number of ten processes distcc is configured (4 local, 6
> remote). Yet, despite the fact that a manual build distributes the compiles
> correctly, with rpmbuild distcc throttles the number of concurrent parallel
> jobs that it kicks off to four, and runs them locally.

I think you misunderstood me, I wasn't clear either.  I saw you set
_smp_mflags, what I mean is rpmbuild still does some magic underneath.
I.e. after you have set that flag, afaik, rpmbuild will fiddle with the
value and pass an "appropriate" -j<n> flag to Make in the regular case.
It makes this choice based on how many threads it can run locally.  At
least that's what I think it does.

Okay I did some digging.  This is what rpmbuild does with _smp_mflags
(output from rpmbuild --showrc).

-14: _smp_mflags        %([ -z "$RPM_BUILD_NCPUS" ] \
        && RPM_BUILD_NCPUS="`/usr/bin/getconf _NPROCESSORS_ONLN`"; \
        ncpus_max=%{?_smp_ncpus_max}; \
        if [ -n "$ncpus_max" ] && [ "$ncpus_max" -gt 0 ] && [ "$RPM_BUILD_NCPUS" -gt "$ncpus_max" ]; then RPM_BUILD_NCPUS="$ncpus_max"; fi; \
        if [ "$RPM_BUILD_NCPUS" -gt 1 ]; then echo "-j$RPM_BUILD_NCPUS"; fi)
-14: _smp_ncpus_max     16

I don't have the time to check the above snippet, maybe you can take a
look?  Hope this time we follow each other.  If this doesn't help, I'm
out of ideas :-(.

Cheers,

-- 
Suvayu

Open source is the future. It sets us free.