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The first ever KernelCI hackfest

By Blog, Community

The first KernelCI test development and coverage hackfest took place from 27th May to 4th June 2021. For a total of seven days, developers from the KernelCI team, Google, and Collabora worked to improve many different aspects of KernelCI testing capabilities.

The hackfest was a community event promoted by the KernelCI team. It aimed at bringing developers and companies together to improve testing for areas of the Linux kernel they care about. Through this effort, the KernelCI team also expects to increase awareness for continuous kernel testing and validation – more hackfests will happen in the future, so stay tuned if you want to join.

The first-ever KernelCI hackfest was a success. It kicked off the work to enable kernel testing through Chromium OS, a product-specific userspace. Enabling full userspace images and real-world tests like video call simulations adds a lot of complexity to the testing process. However, the benefits are a clear win for the community. They allow a more thorough kernel testing and validation through real application use cases, which can exercise several different kernel areas at the same time in an organized manner. Generally, it is not simple for lower-level kernel test suites like kselftests or LTP to orchestrate a similar use case.

Consider video call simulation for example. Once the user starts a video call, the test can begin by measuring the time needed to set up the video feed and show it in the browser rendered with the rest of the video call website. Then, as soon as the video call is up, many other measurements can be made: camera capture latency, camera stream to network latency, memory consumption, power consumption, GPU performance, background tasks latency, and user interaction latency. These types of tests stress the kernel in unique ways, exposing problems that might otherwise go unnoticed from release to release.

The support for the Chromium OS userspace is the start of full-stack tests in KernelCI. It is still quite experimental, but the support will evolve over the next few months, opening the path for other product-specific userspaces. Increased kernel testing diversity will definitely result in catching more regressions earlier. “Keeping upstream healthy is really important to us in the Chrome OS team (and Google broadly!) since we constantly pull in stable fixes and regularly push out major kernel version upgrades to our users.” said Jesse Barnes who leads the Base OS team of Chrome OS at Google.

On another front, there was progress enabling more testing for different kernel areas as well as improvements to the rootfs testing images used by KernelCI:

  • kselftests received new tests for the futex() system call, basic semantics validation, and soft-dirty page table entry mechanism corner cases;
  • improved LTP crypto tests by enabling missing kernel configs needed;
  • libcamera now has its first few tests running on KernelCI;
  • fs/unicode tests converted to the new Kunit mechanism;
  • bootr test to check if all CPUs went online successfully;
  • experimental support for including firmware files in the rootfs.

The overall results were significant for only a few days of work. Kernel testing through product-specific userspace opens a whole new avenue of possibilities for KernelCI. On top of that, there was an accomplishment for many test cases and test suites, as detailed above. “It has been an amazing week and a half. We’ve achieved a lot in such a short time, in spite of a few workflow weaknesses which we’re now addressing to help further grow the KernelCI community with new developers.” said Guillaume Tucker, KernelCI project lead and Senior Software Engineer at Collabora.

More hackfests will come in the future – this was only the first one. Dates are being discussed for the next hackfest to happen around the end of August, a few weeks before the Linux Plumbers Conference. The KernelCI team invites developers and companies to participate. Joining a hackfest is a great way to quickly evolve the kernel testing knowledge of your team, leading to products and services that work better with easier maintenance over time. So make sure to raise your hand and join the next time a KernelCI hackfest happens.

KernelCI is a Linux Foundation project. If you are interested in learning more or becoming a member contact us.