linux-kernel - Re: [PATCH] Update old Mini-HOWTO for ftrace

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Date:	Mon, 06 Apr 2009 21:46:52 -0400
From:	Steven Rostedt <srostedt@...hat.com>
To:	GeunSik Lim <leemgs1@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	rt-users <linux-rt-users@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Nikanth Karthikensan <knikanth@...e.de>
Subject: Re: [PATCH] Update old Mini-HOWTO for ftrace


On Mon, 2009-04-06 at 23:02 +0900, GeunSik Lim wrote:
> Dear Steven,
> 
>    The author of ftrace(Internal kernel Function Tracer) feature
> renamed the ftrace tracer
>     to function to avoid further confusion between the ftrace
> infrastructure and the
>     function tracer on Oct-20, 2008.
> 
>     But, Update of Mini-HOWTO document are still not working
>     .
>     Most of the developers often utilize "/debug/tracing/README" file
> as Mini-HOWTO.
>     They will confuse definition and usage about ftrace  between
> README(ftrace) file
>     and available_tracers(function) file after linux-2.6.27 like me.
>     And, I want you to append "chrt -f 5 sleep 1" command as simple
> example for latency.
> 
>     Signed-off-by: GeunSik Lim <leemgs1@...il.com>
>     Signed-off-by: Steven Rostedt <srostedt@...hat.com>
>     Signed-off-by: Ingo Molnar <mingo@...e.hu>
> ---
>  kernel/trace/trace.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index a0174a4..15f0eec 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2358,7 +2358,7 @@ static const char readme_msg[] =
>         "# mkdir /debug\n"
>         "# mount -t debugfs nodev /debug\n\n"
>         "# cat /debug/tracing/available_tracers\n"
> -       "wakeup preemptirqsoff preemptoff irqsoff ftrace sched_switch none\n\n"
> +       "wakeup preemptirqsoff preemptoff irqsoff function
> sched_switch none\n\n"
>         "# cat /debug/tracing/current_tracer\n"
>         "none\n"
>         "# echo sched_switch > /debug/tracing/current_tracer\n"
> @@ -2368,6 +2368,7 @@ static const char readme_msg[] =
>         "noprint-parent nosym-offset nosym-addr noverbose\n"
>         "# echo print-parent > /debug/tracing/trace_options\n"
>         "# echo 1 > /debug/tracing/tracing_enabled\n"
> +       "# chrt -f 5 sleep 1\n"
>         "# cat /debug/tracing/trace > /tmp/trace.txt\n"
>         "echo 0 > /debug/tracing/tracing_enabled\n"
>  ;
> 

Actually Nikanth sent a similar patch a month ago, but somehow it
slipped under the radar. I'll be picking that one up instead.

http://lkml.org/lkml/2009/3/23/24

But thanks anyway.

-- Steve


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