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authorRenato Golin <renato.golin@linaro.org>2013-11-15 08:42:14 +0000
committerRenato Golin <renato.golin@linaro.org>2013-11-15 08:42:14 +0000
commit868e74bdce7a2c49d60e2ef56a077b0aa7f2ba08 (patch)
tree3c720783578986ac87ba8314a48b650f0410373d /docs
parent42cb3abaddfcff16ab18b114c3de034839c85e05 (diff)
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Adding some info about stability of ARM boards
Patch by Mikael Lyngvig git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194794 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs')
-rw-r--r--docs/HowToBuildOnARM.rst30
1 files changed, 26 insertions, 4 deletions
diff --git a/docs/HowToBuildOnARM.rst b/docs/HowToBuildOnARM.rst
index b58dfac..f2edaef 100644
--- a/docs/HowToBuildOnARM.rst
+++ b/docs/HowToBuildOnARM.rst
@@ -25,15 +25,15 @@ on the ARMv6 and ARMv7 architectures and may be inapplicable to older chips.
process will very likely fail due to insufficient memory. In any
case it is probably a good idea to set up a swap partition.
-#. If you want to run ``make
- check-all`` after building LLVM/Clang, to avoid false alarms (eg, ARCMT
- failure) please use at least the following configuration:
+#. If you want to run ``make check-all`` after building LLVM/Clang, to avoid
+ false alarms (e.g., ARCMT failure) please use at least the following
+ configuration:
.. code-block:: bash
$ ../$LLVM_SRC_DIR/configure --with-abi=aapcs-vfp
-#. The most popular linaro/ubuntu OS's for ARM boards, eg, the
+#. The most popular Linaro/Ubuntu OS's for ARM boards, e.g., the
Pandaboard, have become hard-float platforms. The following set
of configuration options appears to be a good choice for this
platform:
@@ -45,3 +45,25 @@ on the ARMv6 and ARMv7 architectures and may be inapplicable to older chips.
--target=armv7l-unknown-linux-gnueabihf --with-cpu=cortex-a9 \
--with-float=hard --with-abi=aapcs-vfp --with-fpu=neon \
--enable-targets=arm --enable-optimized --enable-assertions
+
+#. ARM development boards can be unstable and you may experience that cores
+ are disappearing, caches being flushed on every big.LITTLE switch, and
+ other similar issues. To help ease the effect of this, set the Linux
+ scheduler to "performance" on **all** cores using this little script:
+
+ .. code-block:: bash
+
+ # The code below requires the package 'cpufrequtils' to be installed.
+ for ((cpu=0; cpu<`grep -c proc /proc/cpuinfo`; cpu++)); do
+ sudo cpufreq-set -c $cpu -g performance
+ done
+
+#. Running the build on SD cards is ok, but they are more prone to failures
+ than good quality USB sticks, and those are more prone to failures than
+ external hard-drives (those are also a lot faster). So, at least, you
+ should consider to buy a fast USB stick. On systems with a fast eMMC,
+ that's a good option too.
+
+#. Make sure you have a decent power supply (dozens of dollars worth) that can
+ provide *at least* 4 amperes, this is especially important if you use USB
+ devices with your board.