Messages in this thread Patch in this message | | | Date | Wed, 12 Dec 2012 14:27:35 -0500 | From | Steven Rostedt <> | Subject | [RFC][PATCH RT 2/4 v2] sched/rt: Try to migrate task if preempting pinned rt task |
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If a higher priority task is about to preempt a task that has been pinned to a CPU. Try to first see if the higher priority task can preempt another task instead.
That is, a high priority process wakes up on a CPU while a currently running task can still migrate, it will miss pushing that high priority task to another CPU. If by the time the task schedules, the task that it's about to preempt could have changed its affinity and is pinned. At this time, it may be better to move the task to another CPU if one exists that is currently running a lower priority task than the one about to be preempted.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Index: linux-rt.git/kernel/sched/rt.c =================================================================== --- linux-rt.git.orig/kernel/sched/rt.c +++ linux-rt.git/kernel/sched/rt.c @@ -1804,8 +1804,22 @@ skip: static void pre_schedule_rt(struct rq *rq, struct task_struct *prev) { + struct task_struct *p = prev; + + /* + * If we are preempting a pinned task see if we can push + * the higher priority task first. + */ + if (prev->on_rq && (prev->nr_cpus_allowed <= 1 || prev->migrate_disable) && + has_pushable_tasks(rq) && rq->rt.highest_prio.next < prev->prio) { + p = _pick_next_task_rt(rq); + + if (p != prev && p->nr_cpus_allowed > 1 && push_rt_task(rq)) + p = _pick_next_task_rt(rq); + } + /* Try to pull RT tasks here if we lower this rq's prio */ - if (rq->rt.highest_prio.curr > prev->prio) + if (rq->rt.highest_prio.curr > p->prio) pull_rt_task(rq); }
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