From: Steven Rostedt <rostedt@goodmis.org>
To: Yajun Deng <yajun.deng@linux.dev>
Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
vschneid@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched/rt: Add pid and comm when RT throttling activated
Date: Fri, 9 Dec 2022 16:36:06 -0500 [thread overview]
Message-ID: <20221209163606.53a2370e@gandalf.local.home> (raw)
In-Reply-To: <20221206083641.103832-1-yajun.deng@linux.dev>
On Tue, 6 Dec 2022 16:36:41 +0800
Yajun Deng <yajun.deng@linux.dev> wrote:
> It is difficult to know which process consumes time when RT throttling
> activated.
>
> So add pid and comm for this case.
>
Unfortunately, that only shows the process that "broke the camel's
back"[1]. The things is, it is the amount of time *all* RT tasks use to
trigger throttling. You are only printing the task that the throttling
occurred on.
Try running https://rostedt.org/code/migrate.c . It will create a bunch of
RT tasks, and they all will throttle once it hits 950ms ever second.
trace-cmd record -e sched_switch ./migrate
kernelshark
Then plot all the migrate tasks.
The above will demonstrate it very well.
-- Steve
[1] https://en.wikipedia.org/wiki/Straw_that_broke_the_camel%27s_back
> Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
> ---
> kernel/sched/rt.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index ed2a47e4ddae..1f267ab1b59a 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1012,6 +1012,7 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
>
> if (rt_rq->rt_time > runtime) {
> struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
> + struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
>
> /*
> * Don't actually throttle groups that have no runtime assigned
> @@ -1019,7 +1020,8 @@ 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("pid: %d, comm: %s, sched: RT throttling activated\n",
> + curr->pid, curr->comm);
> } else {
> /*
> * In case we did anyway, make it go away,
next prev parent reply other threads:[~2022-12-09 21:36 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-06 8:36 [PATCH] sched/rt: Add pid and comm when RT throttling activated Yajun Deng
2022-12-09 21:36 ` Steven Rostedt [this message]
2022-12-12 2:05 ` Yajun Deng
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20221209163606.53a2370e@gandalf.local.home \
--to=rostedt@goodmis.org \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=vincent.guittot@linaro.org \
--cc=vschneid@redhat.com \
--cc=yajun.deng@linux.dev \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).