linux-kernel - Re: [PATCH 1/2] perf sched: Introduce timehist command

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Date:	Mon, 02 Dec 2013 11:33:06 +0200
From:	Pekka Enberg <penberg@....fi>
To:	David Ahern <dsahern@...il.com>, acme@...stprotocols.net,
	linux-kernel@...r.kernel.org
CC:	namhyung@...nel.org, Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Mike Galbraith <efault@....de>, Jiri Olsa <jolsa@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: [PATCH 1/2] perf sched: Introduce timehist command - v2

On 12/02/2013 02:23 AM, David Ahern wrote:
> 'perf sched timehist' provides an analysis of scheduling events.
>
> Example usage:
>      perf sched record -- sleep 1
>      perf sched timehist
>
> By default it shows the individual schedule events, including the time between
> sched-in events for the task, the task scheduling delay (time between wakeup
> and actually running) and run time for the task:
>
>             time cpu  task name[tid/pid]    b/n time sch delay  run time
>    ------------- ---- -------------------- --------- --------- ---------
>     79371.874569 [11] gcc[31949]               0.014     0.000     1.148
>     79371.874591 [10] gcc[31951]               0.000     0.000     0.024
>     79371.874603 [10] migration/10[59]         3.350     0.004     0.011
>     79371.874604 [11] <idle>                   1.148     0.000     0.035
>     79371.874723 [05] <idle>                   0.016     0.000     1.383
>     79371.874746 [05] gcc[31949]               0.153     0.078     0.022

What does "b/n time" mean?

I'm seeing rather large "sch delay" numbers on Fedora 19's default 
kernel that seem like a data error of some sort:

     4500.663117 [02] fix_client[7216]         0.007 
18446744073708.033     1.786

Scheduling delays don't seem to be part of "-s" summary output. Why?

                             Pekka
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