sched_ext tasks currently are starved by RT hoggers especially since RT throttling was replaced by deadline servers to boost only CFS tasks. Several users in the community have reported issues with RT stalling sched_ext tasks. Add a sched_ext deadline server as well so that sched_ext tasks are also boosted and do not suffer starvation. A kselftest is also provided to verify the starvation issues are now fixed. Btw, there is still something funky going on with CPU hotplug and the relinquish patch. Sometimes the sched_ext's hotplug self-test locks up (./runner -t hotplug). Reverting that patch fixes it, so I am suspecting something is off in dl_server_remove_params() when it is being called on offline CPUs. v2->v3: - Removed code duplication in debugfs. Made ext interface separate. - Fixed issue where rq_lock_irqsave was not used in the relinquish patch. - Fixed running bw accounting issue in dl_server_remove_params. Link to v1: https://lore.kernel.org/all/20250315022158.2354454-1-joelagnelf@xxxxxxxxxx/ Link to v2: https://lore.kernel.org/all/20250602180110.816225-1-joelagnelf@xxxxxxxxxx/ Andrea Righi (1): selftests/sched_ext: Add test for sched_ext dl_server Joel Fernandes (9): sched/debug: Fix updating of ppos on server write ops sched/debug: Stop and start server based on if it was active sched/deadline: Clear the defer params sched: Add support to pick functions to take rf sched: Add a server arg to dl_server_update_idle_time() sched/ext: Add a DL server for sched_ext tasks sched/debug: Add support to change sched_ext server params sched/deadline: Add support to remove DL server bandwidth sched/ext: Relinquish DL server reservations when not needed include/linux/sched.h | 2 +- kernel/sched/core.c | 19 +- kernel/sched/deadline.c | 78 +++++-- kernel/sched/debug.c | 171 +++++++++++--- kernel/sched/ext.c | 108 ++++++++- kernel/sched/fair.c | 15 +- kernel/sched/idle.c | 4 +- kernel/sched/rt.c | 2 +- kernel/sched/sched.h | 13 +- kernel/sched/stop_task.c | 2 +- tools/testing/selftests/sched_ext/Makefile | 1 + .../selftests/sched_ext/rt_stall.bpf.c | 23 ++ tools/testing/selftests/sched_ext/rt_stall.c | 213 ++++++++++++++++++ 13 files changed, 579 insertions(+), 72 deletions(-) create mode 100644 tools/testing/selftests/sched_ext/rt_stall.bpf.c create mode 100644 tools/testing/selftests/sched_ext/rt_stall.c -- 2.34.1
