Optimize performance in Docker containers used by Embedded Systems Consulting business
In 3mdeb we use Docker heavily. Main tasks that we perform using it are:
firmware and embedded software building - each software in Embedded System
requires little bit different building environment, configuring those
development environments on your host may quickly make a mess in your system for
daily use, because of that we created various containers which I enumerate
below
trainings/workshops - when we perform trainings we don’t want to waste time
for users to reconfigure the environment. In general, we have 2 choices: VM or
containers. Since we use containers for building and development we prefer
containers or containers in VMs while performing trainings.
rootfs building for infrastructure deployment - we maintain pxe-server
project which helps us in firmware testing and development. In that project we
have a need for custom rootfs and kernels, we decided to combine Docker and
Ansible for a reliable building of that infrastructure
Some are actively maintained, some are not, some came from other projects, some
were created from scratch, but all of them have value for Embedded Systems
Developers.
Those solutions are great but we think it is very important in all those use
cases to optimize performance. To clarify we have to distinguish the most
time-consuming tasks in above containers:
code compilation - there are books about that topic, but since we use mostly
Linux, we think that key factor is to have support for
ccache and this is our first goal in this post
packages installation - even when you are using httpredir for apt you
still will spent a significant amount of time installing and downloading,
because of that it is very important to have locally or on server in LAN apt
caching proxy like apt-cacher-ng, we will show how to use it with Docker on
build and runtime
ccache
Following example will show ccache usage with xen-docker. Great post about
that topic was published by Tim Potter here.
Of course, to use ccache in our container we need it installed, so make sure
your Dockerfile contains that package. You can take a look at xen-docker Dockerfile.
I installed ccache on my host to control its content:
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cache directory /home/pietrushnic/.ccache
primary config /home/pietrushnic/.ccache/ccache.conf
secondary config (readonly) /etc/ccache.conf
cache hit (direct) 0
cache hit (preprocessed) 0
cache miss 0
cache hit rate 0.00 %
cleanups performed 0
files in cache 0
cache size 0.0 kB
max cache size 5.0 GB
Moreover it is important to pay attention to directory structure and
volumes, because we can easy end up with not working ccache. Of course clear
indication that ccache works is that it show some statistics. Configuration
of ccache in Docker files should look like this:
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ENV PATH="/usr/lib/ccache:${PATH}"
RUN mkdir /home/xen/.ccache && \
chown xen:xen /home/xen/.ccache
Then to run container with ccache we can pass our ~/.ccache as volume. For
single-threaded compilation assuming you checked out correct code and called
./configure:
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Before we start testing performance we also have to mention terminology little
bit, below we use terms cold cache and hot cache, this was greatly
explained on StackOverflow
so I will not repeat myself. In short cold means empty and hot means that there
are some values from previous runs.
Performance measures
No ccache single-threaded:
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docker run --rm -it -v $PWD:/home/xen -w /home/xen 3mdeb/xen-docker \
make debball| ts -s '[%.T]'
(...)
[00:13:10.006206] dpkg-deb: building package 'xen-upstream' in 'xen-upstream-4.8.4.deb'.
No ccache multi-threaded:
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docker run --rm -it -v $PWD:/home/xen -w /home/xen 3mdeb/xen-docker \
make -j$(nproc) debball| ts -s '[%.T]'
(...)
[00:07:53.910527] dpkg-deb: building package 'xen-upstream' in 'xen-upstream-4.8.4.deb'.
cache directory /home/pietrushnic/.ccache
primary config /home/pietrushnic/.ccache/ccache.conf
secondary config (readonly) /etc/ccache.conf
stats zero time Wed Aug 22 23:29:32 2018
cache hit (direct) 38
cache hit (preprocessed) 19
cache miss 3750
cache hit rate 1.50 %
called for link 133
called for preprocessing 1498
compiler produced empty output 61
compile failed 6
preprocessor error 12
bad compiler arguments 10
unsupported source language 2
autoconf compile/link 56
unsupported compiler option 2
output to stdout 4
no input file 5998
cleanups performed 0
files in cache 8887
cache size 203.1 MB
max cache size 5.0 GB
Hot cache:
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docker run --rm -it -e CCACHE_DIR=/home/xen/.ccache -v $PWD:/home/xen \
-v $HOME/.ccache:/home/xen/.ccache -w /home/xen 3mdeb/xen-docker make -j$(nproc) \
debball | ts -s '[%.T]'
(...)
[00:05:40.766517] dpkg-deb: building package 'xen-upstream' in 'xen-upstream-4.8.4.deb'.
cache directory /home/pietrushnic/.ccache
primary config /home/pietrushnic/.ccache/ccache.conf
secondary config (readonly) /etc/ccache.conf
stats zero time Wed Aug 22 23:29:32 2018
cache hit (direct) 3557
cache hit (preprocessed) 229
cache miss 3767
cache hit rate 50.13 %
called for link 266
called for preprocessing 2945
compiler produced empty output 122
compile failed 12
preprocessor error 14
bad compiler arguments 14
unsupported source language 4
autoconf compile/link 64
unsupported compiler option 4
output to stdout 8
no input file 8811
cleanups performed 0
files in cache 9023
cache size 204.4 MB
max cache size 5.0 GB
I’m not ccache expert and cannot explain all results e.g. why hit rate is so
low, when we compile the same code?
To conclude, we can gain even 30% with hot cache. Biggest gain we have when
using multithreading, but this highly depends on CPU, in my case I had 8 jobs
run simultaneously and gain was 40% in compilation time.
apt-cacher-ng
There 2 use case for apt-cacher-ng in our workflows. One is Docker build
time, which can be time-consuming since all packages and its dependencies are
installed in the base image. Second is runtime, when you need some package that
may have extensive dependencies e.g. xen-systema-amd64.
First, let’s setup apt-cacher-ng. Some guide may be found in Docker documentation, but we will modify it a little bit.
Ideally, we would like to use docker compose to set up apt-cacher-ng
container whenever it is not set, or have dedicated VM which serves this
purpose. In this post, we consider local cache. Dockerfile may look like this:
Assuming that the network conditions did not change between runs to extent of
30s delay we can conclude:
using cacher even with cold cache is better than nothing, it gives the
speedup of about 5%
using hot cache can spare ~20% of normal container build time, if significant
amount of that time is package installation
Of course, those numbers should be confirmed statistically.
Let’s try something more complex
Finally we can try to run much more sophisticated stuff like our
debian-rootfs-builder. This
code contain mostly compilation and package installation through apt-get.
Tuesday 21 August 2018 22:48:46 +0000 (0:00:53.340) 0:26:40.226 ********
===============================================================================
linux-kernel --------------------------------------------------------- 1272.91s
debootstrap ----------------------------------------------------------- 265.41s
command ---------------------------------------------------------------- 53.34s
setup ------------------------------------------------------------------- 8.29s
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
total ---------------------------------------------------------------- 1599.95s
Tuesday 21 August 2018 22:48:46 +0000 (0:00:53.341) 0:26:40.225 ********
===============================================================================
linux-kernel : make deb-pkg ------------------------------------------- 608.31s
linux-kernel : make deb-pkg ------------------------------------------- 510.51s
debootstrap : debootstrap second stage -------------------------------- 194.68s
compress rootfs -------------------------------------------------------- 53.34s
debootstrap : debootstrap first stage ---------------------------------- 52.27s
linux-kernel : decompress Linux "4.14.65" ------------------------------ 25.45s
linux-kernel : make mrproper ------------------------------------------- 24.57s
linux-kernel : decompress Linux "4.9.122" ------------------------------ 22.61s
debootstrap : install packages ----------------------------------------- 18.45s
linux-kernel : get Linux "4.14.65" ------------------------------------- 17.44s
linux-kernel : get Linux "4.9.122" ------------------------------------- 16.96s
linux-kernel : make mrproper ------------------------------------------- 12.19s
linux-kernel : make olddefconfig --------------------------------------- 10.54s
linux-kernel : remove everything except artifacts ----------------------- 7.96s
linux-kernel : remove everything except artifacts ----------------------- 7.15s
Gathering Facts --------------------------------------------------------- 4.62s
Gathering Facts --------------------------------------------------------- 3.68s
linux-kernel : make olddefconfig ---------------------------------------- 3.63s
linux-kernel : copy bzImage to known location --------------------------- 1.67s
linux-kernel : copy bzImage to known location --------------------------- 1.58s
Playbook run took 0 days, 0 hours, 26 minutes, 40 seconds
After adding ccache with hot cache:
ccache stats:
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cache directory /home/pietrushnic/.ccache
primary config /home/pietrushnic/.ccache/ccache.conf
secondary config (readonly) /etc/ccache.conf
cache hit (direct) 4595
cache hit (preprocessed) 89
cache miss 4871
cache hit rate 49.02 %
called for link 178
called for preprocessing 12551
compiler produced no output 12
ccache internal error 2
unsupported code directive 21
no input file 3687
cleanups performed 0
files in cache 14582
cache size 1.5 GB
max cache size 5.0 GB
Thursday 23 August 2018 00:41:15 +0000 (0:02:02.608) 0:23:19.962 *******
===============================================================================
linux-kernel ---------------------------------------------------------- 701.42s
packages -------------------------------------------------------------- 246.51s
debootstrap ----------------------------------------------------------- 243.14s
command --------------------------------------------------------------- 123.05s
linux-install ---------------------------------------------------------- 72.47s
setup ------------------------------------------------------------------ 10.10s
config ------------------------------------------------------------------ 3.21s
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
total ---------------------------------------------------------------- 1399.91s
Thursday 23 August 2018 00:41:15 +0000 (0:02:02.608) 0:23:19.961 *******
===============================================================================
linux-kernel : make deb-pkg ------------------------------------------- 388.91s
packages : install packages ------------------------------------------- 246.51s
linux-kernel : make deb-pkg ------------------------------------------- 223.72s
debootstrap : debootstrap second stage -------------------------------- 189.56s
compress rootfs ------------------------------------------------------- 122.61s
linux-install : install Linux "4.14.65" -------------------------------- 37.36s
debootstrap : debootstrap first stage ---------------------------------- 36.00s
linux-install : install Linux "4.9.122" -------------------------------- 35.12s
debootstrap : install packages ----------------------------------------- 17.58s
linux-kernel : get Linux "4.9.122" ------------------------------------- 16.67s
linux-kernel : get Linux "4.14.65" ------------------------------------- 16.18s
linux-kernel : decompress Linux "4.14.65" ------------------------------ 13.82s
linux-kernel : decompress Linux "4.9.122" ------------------------------ 12.72s
linux-kernel : make mrproper -------------------------------------------- 8.21s
linux-kernel : make mrproper -------------------------------------------- 6.55s
Gathering Facts --------------------------------------------------------- 4.81s
linux-kernel : remove everything except artifacts ----------------------- 3.40s
linux-kernel : remove everything except artifacts ----------------------- 3.11s
linux-kernel : make olddefconfig ---------------------------------------- 3.08s
Gathering Facts --------------------------------------------------------- 2.74s
Playbook run took 0 days, 0 hours, 23 minutes, 19 seconds
This is not significant but we gain another 13% and now build time is
reasonable. Still most time-consuming tasks belong to compilation and package
installation bucket.
Summary
If you have any other ideas about optimizing code compilation or container
build time please feel free to comment. If this post will gain popularity we
would probably reiterate it with best advices from our readers.
If you looking for Embedded Systems DevOps, who will optimize your firmware or
embedded software build environment, look no more and contact us
here.
Founder and Embedded Systems Consultant at 3mdeb as well as freelance CTO of Vitro Technology and CEO of LPN Plant. Passionate about building firmware that enables advanced hardware features in modern products. Dedicated to customers that treat embedded software security and upgradeability as forethought. Open source firmware evangelist interested in platform security and trusted computing. In favor of fixed price projects with a clear definition of success.
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