On Wed, Aug 14, 2024 at 12:15 PM Monsees, Steven C (US) via lists.yoctoproject.org <steven.monsees=baesystems...@lists.yoctoproject.org> wrote: > > Hello: > > I am looking for some clarity with regards too parallel builds under Yocto… > > I think I had a false assumption on setting PARALEL_MAKE… > > To increase thread usage: You add following to your local.conf inside the > build/conf directory. Replace x and y with your wanted configuration. > > PARALLEL_MAKE = "-j x" > > > > BB_NUMBER_THREADS = "y" > > > > Is the following true ? > > > > PARALLEL_MAKE defines how many threads should be used/dedicated when using > make -j command during do_compile. > >
seems correct. > > BB_NUMBER_THREADS defines number of threads dedicated for bitbake. It means how many jobs/tasks can bitbake spawn in parallel, its higher order than parallel make. > > > > I set up like so: > > > > There are 12 cores my board > > > > Yocto supporters say threads should be 2 times the number of cores, but don’t > go above 20…, or just the number cores, also under 20… depending on what you > read. > > > > They also say, increasing PARALLEL_MAKE to higher values, increases your > chance for a race condition. > > > > Is the following true ? > > > > PARALLEL_MAKE = "-j x" # For do_compile > > > > BB_NUMBER_THREADS = "y" # For bitbake > > > > PARALLEL_MAKEINST = "-j x" # For do_install > > > > If so, does this mean for 12 cores: > > > > BB_NUMBER_THREADS="8", will this dedicate 8 cores just for bitbake to use ? No, it will not reserve 8 cores, rather it tells bitbake to launch 8 task executions in parallel if bitbake deems them not dependent upon each other, e.g. every recipe has several tasks during build do_confgure, do_compile, do_install etc. and there are several recipes in build queue, then bitbake's task manager can find out non-dependent tasks and execute them in parallel, now be aware that in some cases it could be executing 8 tasks which could be all do_compile tasks for different recipes, in this case your parallelism will become -j 8*8 systemwide. > > > > And does this dedicate the remaining 4 for do_compile and do_install ? > > > > PARALLEL_MAKE="-j 2" > > PARALLEL_MAKEINST="-j 2” > > > > Thank you… > > > > Steve > > > > > >
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