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September 2020

KernelCI Notes from Plumbers 2020

By Blog, Community

The Linux Plumbers Conference 2020 was held as a virtual event this year. The online platform provided a really good experience, with talks and live discussions using Big Blue Button for the video and Rocket Chat for text-based discussions. KernelCI was mentioned many times in several micro-conferences, with two talks in Testing & Fuzzing which are now available on YouTube:

The notes below were gathered publicly from a number of attendees, they give a good insight into what was discussed. In short, while there is still a lot to be done, the KernelCI project is healthy and growing well in its role of a central CI system for the upstream Linux kernel.

Real-Time Linux

We’ve been making great progress with running LAVA jobs using the test-definitions repository from Linaro, thanks to Daniel Wagner’s help in particular. This was prompted by the discussions in the real-time micro-conference.

The next steps from a KernelCI infrastructure point of view is to be able to detect performance regressions, as these are different to binary pass/fail results. KernelCI can already handle measurements, but not yet compare them to detect regressions. Real-time getting merged upstream means it is becoming increasingly important to be able to support this.

There was also an interesting talk about determining the scheduler latency when using RT_PREEMPT and the introduction of a new tool “rtsl” to trace real-time latency.  This might be an interesting area to investigate and potentially run automated tests with:

Static Analysis

The topic of static analysis and CI systems came up during the Kernel Dependability MC, and in particular, they were looking for a place to do “common reporting” in order to collect results for the various types of static analysis and checkers available.  We pointed them to the KernelCI common reporting talks/BoFs.

Some static analysis can also be done by KernelCI “native” tests using the Cloud infrastructure via Kubernetes, which is currently only used to build kernels. This is probably where KUnit and devicetree validation will be run, but the rest still needs to be defined.



Tim Bird, the main developer of Fuego at SONY, started joined the KCIDB BoF  and we had a good discussion. Unfortunately he had not enough time to go through to an actual submission. We got about a quarter way through converting his mock data to KCIDB.

Gentoo Kernel CI

Alice Ferrazzi, maintainer of GKernelCI at Gentoo, had more time available for the KCIDB BoF and we talked through getting the data out of her system. A mockup of her data was made and successfully submitted to the KCIDB playground database setup.


Tim Orling, Yocto project architect at Intel, has expressed keen interest in KCIDB.  He said he would experiment at home and will push Intel internally to participate.


The recently added support for “LLVM=1” upstream means we can now have better support for making Clang builds. In particular, this means we’re now using all the LLVM binaries and not just clang. It also solved the issue with and the default CC=gcc in the top-level Makefile.

This was enabled in shortly after LPC.


The first kselftest results were produced on during Plumbers as a collective effort.  We have now started enabling them in production, so stay tuned as they should soon start appearing on

Initial set of results:


AutoFDO will hopefully get merged upstream, once it is it might be useful for CI systems to share profiling data from benchmarking runs in particular.

Building randconfig

The TuxML project carries out some research around Linux kernel builds: determining the build time, what can be optimised, which configurations are not valid… The project could benefit from the Cloud infrastructure to extend its build capacity while also providing more build coverage to This could be done by detecting kernel configurations that don’t build or lead to problems that can’t be found with the regular defconfigs.

Using tuxmake

The goal of tuxmake is to provide a way to reproduce Linux kernel builds in a controlled environment. This is used primarily by LKFT, but it should be generic enough to cover any use-case related to building kernels. KernelCI uses its kci_build tool to generate kernel configurations and produce kernel builds with some associated meta-data. It could reuse tuxmake to avoid some duplication of effort and only implement the KernelCI-specific aspects.