Fully Automated Testing of the Linux Kernel

Some changes in the 2.6 development process have made fully automated testing vital to the ongoing stability of Linux. The pace of development is constantly increasing, with a rate of change that dwarfs most projects. The lack of a separate 2.7 development kernel means that we are feeding change more quickly and directly into the main stable tree. Moreover, the breadth of hardware types that people are running Linux on is staggering. Therefore it is vital that we catch at least a subset of introduced bugs earlier on in the development cycle, and keep up the quality of the 2.6 kernel tree.

Given a fully automated test system, we can run a broad spectrum of tests with high frequency, and find problems soon after they are introduced; this means that the issue is still fresh in the developers mind, and the offending patch is much more easily removed (not buried under thousands of dependant changes). This paper will present an overview of the current early testing publication system used on the test.kernel.org website. We then use our experiences with that system to define requirements for a second generation fully automated testing system.

Such a system will allow us to compile hundreds of different configuration files on every release, cross-compiling for multiple different architectures. We can also identify performance regressions and trends, adding statistical analysis. A broad spectrum of tests are necessary - boot testing, regression, function, performance, and stress testing; from disk intensive to compute intensive to network intensive loads. A fully automated test harness also empowers other other techniques that are impractical when testing manually, in order to make debugging and problem identification easier. These include automated binary chop search amongst thousands of patches to weed out dysfunctional changes.

In order to run all of these tests, and collate the results from multiple contributors, we need an open-source client test harness to enable sharing of tests. We also need a consistent output format in order to allow the results to be collated, analysed and fed back to the community effectively, and we need the ability to "pass" the reproduction of issues from test harness to the developer. This paper will describe the requirements for such a test client, and the new open-source test harness, Autotest, that we believe will address these requirements.

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