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SubjectRe: [PATCH] sched/rt: Print curr when RT throttling activated
On Thu, 3 Dec 2020 15:51:29 +0800
Xianting Tian <tian.xianting@h3c.com> wrote:

> We may meet the issue, that one RT thread occupied the cpu by 950ms/1s,
> The RT thread maybe is a business thread or other unknown thread.
>
> Currently, it only outputs the print "sched: RT throttling activated"
> when RT throttling happen. It is hard to know what is the RT thread,
> For further analysis, we need add more prints.
>
> This patch is to print current RT task when RT throttling activated,
> It help us to know what is the RT thread in the first time.

I think this can be useful information to include.

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve

>
> Signed-off-by: Xianting Tian <tian.xianting@h3c.com>
> ---
> kernel/sched/rt.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index f215eea6a..8913f38cb 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -946,7 +946,7 @@ static inline int rt_se_prio(struct sched_rt_entity *rt_se)
> return rt_task_of(rt_se)->prio;
> }
>
> -static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
> +static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq, struct task_struct *curr)
> {
> u64 runtime = sched_rt_runtime(rt_rq);
>
> @@ -970,7 +970,8 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
> */
> if (likely(rt_b->rt_runtime)) {
> rt_rq->rt_throttled = 1;
> - printk_deferred_once("sched: RT throttling activated\n");
> + printk_deferred_once("sched: RT throttling activated (curr: pid %d, comm %s)\n",
> + curr->pid, curr->comm);
> } else {
> /*
> * In case we did anyway, make it go away,
> @@ -1026,7 +1027,7 @@ static void update_curr_rt(struct rq *rq)
> if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
> raw_spin_lock(&rt_rq->rt_runtime_lock);
> rt_rq->rt_time += delta_exec;
> - if (sched_rt_runtime_exceeded(rt_rq))
> + if (sched_rt_runtime_exceeded(rt_rq, curr))
> resched_curr(rq);
> raw_spin_unlock(&rt_rq->rt_runtime_lock);
> }

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