This series introduces a comprehensive test suite for the SCHED_DEADLINE scheduler, providing coverage for core functionality, bandwidth admission control, and the fair_server (dl-server) mechanism.
I've been playing with/using this set of tests for a while and they helped me a little checking for regressions and corner cases. So, I guess I've also now found the courage to share this with everyone and see what happens. :P Motivation ---------- SCHED_DEADLINE currently lacks dedicated test coverage in kselftest. While the scheduler itself is well-tested in production, having automated tests helps catch regressions during development and provides examples of correct SCHED_DEADLINE usage for developers. Development Process ------------------- This series was developed using Claude Code (claude.ai/code), making it both a testing improvement and an experiment in itself. The goal is to explore what AI-assisted development can contribute to kernel testing efforts - from framework design to test implementation to documentation. All code has been reviewed and validated by the human maintainer, but the bulk of the implementation, test design, and even this cover letter were produced through iterative collaboration with Claude. This represents an experiment in whether AI tools can help scale testing efforts while maintaining code quality and kernel development standards. Feedback on both the test suite itself and this development approach is welcome. Design ------ The test framework follows the pattern established by sched_ext selftests, using ELF constructors for automatic test registration. This allows tests to be self-contained and easily extensible - new tests are added simply by defining a struct dl_test and calling REGISTER_DL_TEST(). The suite includes a utility library (dl_util) that provides reusable helpers for common operations: setting SCHED_DEADLINE parameters, managing bandwidth, controlling CPU topology, and process management. Series Overview --------------- Patch 1: Framework infrastructure with test discovery and structured output Patch 2: Utility library and cpuhog helper program Patch 3: Integration with kselftest build system Patch 4: Basic functionality tests (scheduling, parameter validation) Patch 5: Bandwidth admission control tests Patch 6: fair_server (dl-server) tests Patch 7: Regression test for ENQUEUE_REPLENISH bug Testing ------- All tests pass on x86_64 with both VM and bare-metal systems. The tests adapt automatically to system configuration, detecting available bandwidth and dl-server bandwidth allocations dynamically. Tests can be run via: make -C tools/testing/selftests TARGETS=sched run_tests make -C tools/testing/selftests/sched/deadline run_tests Or selectively: cd tools/testing/selftests/sched/deadline make ./runner -h Current test results: PASSED: 7 SKIPPED: 0 FAILED: 0 Series also available at [email protected]:jlelli/linux.git deadline-kselftests-rfc Signed-off-by: Juri Lelli <[email protected]> --- Juri Lelli (7): selftests/sched: Add SCHED_DEADLINE test framework infrastructure selftests/sched: Add SCHED_DEADLINE utility library selftests/sched: Integrate SCHED_DEADLINE tests into kselftest framework selftests/sched: Add basic SCHED_DEADLINE functionality tests selftests/sched: Add SCHED_DEADLINE bandwidth tests to kselftest selftests/sched: Add SCHED_DEADLINE fair_server tests to kselftest selftests/sched: Add SCHED_DEADLINE ENQUEUE_REPLENISH bug test tools/testing/selftests/sched/Makefile | 8 + tools/testing/selftests/sched/deadline/.gitignore | 3 + tools/testing/selftests/sched/deadline/Makefile | 54 +++ tools/testing/selftests/sched/deadline/bandwidth.c | 270 +++++++++++ tools/testing/selftests/sched/deadline/basic.c | 127 +++++ tools/testing/selftests/sched/deadline/cpuhog.c | 107 +++++ tools/testing/selftests/sched/deadline/dl_test.h | 238 +++++++++ tools/testing/selftests/sched/deadline/dl_util.c | 530 +++++++++++++++++++++ tools/testing/selftests/sched/deadline/dl_util.h | 294 ++++++++++++ .../testing/selftests/sched/deadline/fair_server.c | 260 ++++++++++ .../selftests/sched/deadline/replenish_bug.c | 337 +++++++++++++ tools/testing/selftests/sched/deadline/runner.c | 219 +++++++++ 12 files changed, 2447 insertions(+) --- base-commit: d658686a1331db3bb108ca079d76deb3208ed949 change-id: 20260306-upstream-deadline-kselftests-f7357ae20166 Best regards, -- Juri Lelli <[email protected]>
