[OE-core] [PATCH] local.conf.sample: Suggest parallelism of twice the number of cores.

[Enrico Scholz]

Saul Wold <sgw-VuQAYsv1563Yd54FQh9/CA at public.gmane.org> writes:

>>   #PARALLEL_MAKE = "-j 4"
>>   #
>> -# For a quad-core machine, BB_NUMBER_THREADS = "4", PARALLEL_MAKE = "-j 4" would
>> -# be appropriate for example.
>> -
>> +# If you have a multi-core machine, you would normally set both of these variables
>> +# to twice the number of cores.  So for a quad-core machine, it would be appropriate
>> +# to set BB_NUMBER_THREADS = "8" and PARALLEL_MAKE = "-j 8".
>
> I think adding a note to ensure that hyperthreading is enabled would
> be appropriate, then number of threads = number of hyperthreaded cores
> (4 vs 8).

what about a general

| BB_NUMBER_THREADS ??= "${@os.sysconf(os.sysconf_names['SC_NPROCESSORS_ONLN'])}"

in bitbake.conf?  Or the sqrt() of it in in both PARALLEL_MAKE and
BB_NUMBER_THREADS...


Enrico