[yocto] ref manual, 2.5, "Speeding Up the Build, " seems a bit confusing

[Robert P. J. Day]

  from that section:

"If you need to achieve even faster builds than what the build system
produces by default, you can consider and implement some of the
following:

  * BB_NUMBER_THREADS, BB_NUMBER_PARSE_THREADS, and PARALLEL_MAKE: As
previously mentioned, the build system scales the values for these
variables. However, you can manually override them in your local.conf
file if you are not satisfied with the defaults."

  but, as i read it from bitbake.conf and bitbake's cooker.py, all
three of those values are already calculated to max out on whatever
dev host is being used:

self.num_processes = int(self.cfgdata.getVar("BB_NUMBER_PARSE_THREADS", True) or
          multiprocessing.cpu_count())

# Default to setting automatically based on cpu count
BB_NUMBER_THREADS ?= "${@oe.utils.cpu_count()}"

# Default to setting automatically based on cpu count
PARALLEL_MAKE ?= "-j ${@oe.utils.cpu_count()}"

  so given these dev host-based calculations, how exactly would the
developer manually set them to get even *better* performance? or am i
misreading something?

rday

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
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