From: Steven Rostedt When a new task is woken, the code to balance the RT task is currently skipped in the select_task_rq() call. But it will be pushed if the rq is currently overloaded with RT tasks anyway. The issue is that we already queued the task, and if it does get pushed, it will have to be dequeued and requeued on the new run queue. The advantage with pushing it first is that we avoid this requeuing as we are pushing it off before the task is ever queued. See commit: 318e0893ce3f524ca045f9fd9dfd567c0a6f9446 for more details. (sched: pre-route RT tasks on wakeup) The return of select_task_rq() when it is not a wake up has also been changed to return task_cpu() instead of smp_processor_id(). This is more of a sanity because the current only other user of select_task_rq() besides wake ups, is an exec, where task_cpu() should also be the same as smp_processor_id(). But if it is used for other purposes, lets keep the task on the same CPU. Why would we mant to migrate it to the current CPU? Signed-off-by: Steven Rostedt --- kernel/sched_rt.c | 9 ++++++--- 1 files changed, 6 insertions(+), 3 deletions(-) diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 1546c1c..33636d2 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -1005,10 +1005,12 @@ select_task_rq_rt(struct task_struct *p, int sd_flag, int flags) struct rq *rq; int cpu; - if (sd_flag != SD_BALANCE_WAKE) - return smp_processor_id(); - cpu = task_cpu(p); + + /* For anything but wake ups, just return the task_cpu */ + if (sd_flag != SD_BALANCE_WAKE || sd_flag != SD_BALANCE_FORK) + goto out; + rq = cpu_rq(cpu); rcu_read_lock(); @@ -1047,6 +1049,7 @@ select_task_rq_rt(struct task_struct *p, int sd_flag, int flags) } rcu_read_unlock(); +out: return cpu; } -- 1.7.4.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/