Messages in this thread Patch in this message | | | From | Daniel Bristot de Oliveira <> | Subject | [PATCH v2] sched/rt: Disable RT_RUNTIME_SHARE by default | Date | Wed, 16 Nov 2016 21:19:21 +0100 |
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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 <bristot@redhat.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Clark Williams <williams@redhat.com> Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com> Cc: linux-kernel@vger.kernel.org Acked-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
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
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