Building a Linux Distribution for Space Computers
Typ
Examensarbete för masterexamen
Program
Publicerad
2021
Författare
LAGERQUIST SERGEL, LINA
PETTERSSON, GUSTAV
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Computer platforms used in mission- or safety-critical applications are often designed
to support execution of hard real-time tasks. Linux has traditionally not
been used as a real-time operating system for these applications but has become a
more viable option within recent years.
In this thesis, we explore how embedded Linux distributions can be built to be
used as a real-time operating system for space computers. We compare how the
build systems Yocto Project and Buildroot can generate the components required
to boot Linux on two reference design boards provided by RUAG Space. By using
the benchmark tools cyclictest and lat_ctx we evaluate the latency of response
to an interrupt and context switching latency. This is done for two builds on one
of the reference design boards. Further, we provide pointers on how an implementation
can be made on RUAG Space’s custom space computer, and discuss what
components should be included in such a build.
Based on our benchmark results, we conclude that a Linux kernel equipped with
the PREEMPT_RT patch has an improved deterministic behaviour. The patched
kernel compared to a basic version of the kernel has a reduced maximum latency
when reacting to an interrupt. The patched kernel also has a more consistent increasing
context switching latency based on the number of involved processes. Regarding
the build systems we can, through our observations, conclude that Buildroot is more
user-friendly than Yocto. However, we perceive that Buildroot can be more limiting
because of its reduced complexity and available packages.
Beskrivning
Ämne/nyckelord
Linux , PREEMPT_RT , cyclictest , rt-tests , LMbench , Yocto Project , Buildroot , RTOS