linux-kernel - Re: [RFC][PATCH 3/3 v2] sched: Add bandwidth ratio to /proc/sched

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Message-ID: <20160203175646.GD12132@e106622-lin>
Date:	Wed, 3 Feb 2016 17:56:46 +0000
From:	Juri Lelli <juri.lelli@....com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Juri Lelli <juri.lelli@...il.com>,
	Clark Williams <williams@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH 3/3 v2] sched: Add bandwidth ratio to
 /proc/sched_debug

Hi,

On 03/02/16 11:57, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
> 
> Playing with SCHED_DEADLINE and cpusets, I found that I was unable to create
> new SCHED_DEADLINE tasks, with the error of EBUSY as if the bandwidth was
> already used up. I then realized there wa no way to see what bandwidth is
> used by the runqueues to debug the issue.
> 
> By adding the dl_bw->bw and dl_bw->total_bw to the output of the deadline
> info in /proc/sched_debug, this allows us to see what bandwidth has been
> reserved and where a problem may exist.
> 
> For example, before the issue we see the ratio of the bandwidth:
> 
>  # cat /proc/sys/kernel/sched_rt_runtime_us
>  950000
>  # cat /proc/sys/kernel/sched_rt_period_us
>  1000000
> 
>   # grep dl /proc/sched_debug
>   dl_rq[0]:
>     .dl_nr_running                 : 0
>     .dl_bw->bw                     : 996147
>     .dl_bw->total_bw               : 0
>   dl_rq[1]:
>     .dl_nr_running                 : 0
>     .dl_bw->bw                     : 996147
>     .dl_bw->total_bw               : 0
>   dl_rq[2]:
>     .dl_nr_running                 : 0
>     .dl_bw->bw                     : 996147
>     .dl_bw->total_bw               : 0
>   dl_rq[3]:
>     .dl_nr_running                 : 0
>     .dl_bw->bw                     : 996147
>     .dl_bw->total_bw               : 0
>   dl_rq[4]:
>     .dl_nr_running                 : 0
>     .dl_bw->bw                     : 996147
>     .dl_bw->total_bw               : 0
>   dl_rq[5]:
>     .dl_nr_running                 : 0
>     .dl_bw->bw                     : 996147
>     .dl_bw->total_bw               : 0
>   dl_rq[6]:
>     .dl_nr_running                 : 0
>     .dl_bw->bw                     : 996147
>     .dl_bw->total_bw               : 0
>   dl_rq[7]:
>     .dl_nr_running                 : 0
>     .dl_bw->bw                     : 996147
>     .dl_bw->total_bw               : 0
>

I think this is already quite useful. But, do you think we can also
display information about the root_domain (like the span for example)?
Or do we have that some place else already?

Thanks,

- Juri