The RT_RUNTIME_SHARE sched feature enables the sharing of rt_runtime between CPUs, allowing a CPU to run a real-time task up to 100% of the time while leaving more space for non-real-time tasks to run on the CPU that lend rt_runtime.
The problem is that a CPU can easily borrow enough rt_runtime to allow a spinning rt-task to run forever, starving per-cpu tasks like kworkers, which are non-real-time by design. This patch disables RT_RUNTIME_SHARE by default, avoiding this problem. The feature will still be present for users that want to enable it, though. It also documents this option. v1->v2: Unified the documentation and the disabling in a single patch Signed-off-by: Daniel Bristot de Oliveira <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Clark Williams <[email protected]> Cc: Luis Claudio R. Goncalves <[email protected]> Cc: [email protected] Acked-by: Steven Rostedt <[email protected]> Acked-by: Luis Claudio R. Goncalves <[email protected]> diff --git a/kernel/sched/features.h b/kernel/sched/features.h index 69631fa..d609ca9 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -65,7 +65,17 @@ SCHED_FEAT(RT_PUSH_IPI, true) #endif SCHED_FEAT(FORCE_SD_OVERLAP, false) -SCHED_FEAT(RT_RUNTIME_SHARE, true) + +/* + * Enables the sharing of rt_runtime between CPUs, allowing a CPU to + * run real-time tasks up to 100% of the time while leaving more + * space for non-real-time tasks to run on the CPU that lend rt_runtime. + * + * WARNING: This may allow the starvation of non-real-time tasks pinned + * to the CPU in which spinning rt-tasks run forever. + */ +SCHED_FEAT(RT_RUNTIME_SHARE, false) + SCHED_FEAT(LB_MIN, false) SCHED_FEAT(ATTACH_AGE_LOAD, true) -- 2.7.4
