2014-01-28 11:08, Koen Kooi skrev:
Op 27 jan. 2014, om 15:39 heeft Richard Purdie
<richard.pur...@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.pur...@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,
We discussed this 2.3 months ago.
Did some studies on my dual hex-core machine (24 H/W treads) while
building a cloud9-gnome-image derivative.
This did about 7500 tasks.
Enabled the CPU supervisors in the panel.
Everything seems to be ok with BB_NUMBER_THREADS = "24" for about 4-4500
tasks.
Then the CPUs are mostly inactive and only 1-2 running for ~500 tasks.
Then parallellism is resumed until about task 7000, and again
only a few CPUs are active.
I believe that some tools use "make" within the Makefile,
and they are written badly, and do not use "-j <n>" for
that part of the build.
Got my build down to 83 minutes.
Since I have 96 GB of RAM, I tried creating an 80 GB tmpfs for the build,
and copied the download and the recipes to the ram.
That shaved only 2 monutes from the build, and some stuff,
still built using only a single CPU.
BR
Ulf Samuelsson
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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--
Best Regards
Ulf Samuelsson
eMagii
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