[OE-core] [PATCH] local.conf.sample: Add automatic defaults for BB_NUMBER_THREADS and PARALLEL_MAKE

[Koen Kooi]

Op 27 jan. 2014, om 15:39 heeft Richard Purdie <richard.purdie at linuxfoundation.org> het volgende geschreven:

> Its rather sad that people don't appear to read local.conf and then complain
> about slow builds when they're just using a single thread. Most systems have
> more than one core now so we might as well use a more automatic default
> for these values. This may lead to better experiences for new users.
> 
> [YOCTO #2528]
> 
> Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
> ---
> diff --git a/meta/conf/local.conf.sample b/meta/conf/local.conf.sample
> index 71856b8..36d33e1 100644
> --- a/meta/conf/local.conf.sample
> +++ b/meta/conf/local.conf.sample
> @@ -18,12 +18,18 @@
> # option determines how many tasks bitbake should run in parallel:
> #
> #BB_NUMBER_THREADS ?= "4"
> +#
> +# Default to setting automatically based on cpu count
> +BB_NUMBER_THREADS ?= "${@oe.utils.cpu_count()}"

I've noticed that after 4 threads IO becomes a big bottleneck when you have things like webkit, qt, asio etc in the buildqueue. Combine that with issues like every make -j thread taking >2GB ram with asio and webkit this default seems a bit high. I'd use 0.5*numcpu with a lower bound of 2.

regards,

Koen

> # 
> # The second option controls how many processes make should run in parallel when
> # running compile tasks:
> #
> #PARALLEL_MAKE ?= "-j 4"
> #
> +# Default to setting automatically based on cpu count
> +PARALLEL_MAKE ?= "-j ${@oe.utils.cpu_count()}"
> +#
> # For a quad-core machine, BB_NUMBER_THREADS = "4", PARALLEL_MAKE = "-j 4" would
> # be appropriate for example.
> 
> 
> 
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