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On Thu, 29 Nov 2012, David G. Miller wrote:
> Setting -j to be equal to the number of cores/CPUs is just playing it
> safe.
Yes, this is the default behavior of rpmbuild:
%_smp_mflags is defined in /usr/lib/rpm/redhat/macros:
%_smp_mflags %([ -z "$RPM_BUILD_NCPUS" ] \\\
&& RPM_BUILD_NCPUS="`/usr/bin/getconf _NPROCESSORS_ONLN`"; \\\
if [ "$RPM_BUILD_NCPUS" -gt 16 ]; then echo "-j16"; \\\
elif [ "$RPM_BUILD_NCPUS" -gt 1 ]; then echo "-j$RPM_BUILD_NCPUS"; fi)
> This is especially true when building a rpm which involves not just
> compiles and link but also packaging, dependency resolution and
> documentation tasks which are even more disk I/O intensive than
> compiles. Chances are that several of these operations that not
> dependent on successfully compiling the code are fired off in parallel
> rather than doing them sequentially and that old workhorse make gets the
> task of managing each of these tasks.
I disagree with you here. You build a rpm in stages: "%prep", "%build",
"%install", "list check for %files" and packaging (dependency
resolution/debug-info/etc). Each stage is dependent on the previous one.
All the stages are run sequentially.
make (%build stage) and make install (%install stage) may run things in
parallel. But this is something else (as I understand the process).
> Thus, you end up with multiple copies of make running at the same time
> even on a single core/CPU system to perform these tasks.
Exactly. This is what I was trying to explain to JD( jd1008@).
make != cc1.
make can spawn more make processes which eventually can run cc1.
Sorry but English is not my first language.
> My best results were with -j 12.
Wow! :-)
Gabriel
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