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

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Date:	Mon, 06 Apr 2009 21:26:56 -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>
Subject: Re: [PATCH] Update old Mini-HOWTO for ftrace


On Mon, 2009-04-06 at 23:17 +0900, GeunSik Lim wrote:
> I attached patch file again because no-operation is changed
> from "none"word to "nop" word.
> 
> for example,
> -       "wakeup preemptirqsoff preemptoff irqsoff ftrace sched_switch none\n\n"
> +       "wakeup preemptirqsoff preemptoff irqsoff function sched_switch nop\n\n"
> 
> ./trace_nop.c:struct tracer nop_trace __read_mostly =
> 	.name	= "nop",
> 	.init		= nop_trace_init,
> 	.reset	= nop_trace_reset,
> 	.selftest	= trace_selftest_startup_nop,
> 	.flags	= &nop_flags,
> 	.set_flag	= nop_set_flag
> 
> 
> 
> 2009/4/6 GeunSik Lim <leemgs1@...il.com>:
> >   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"


What's the chrt for?

-- Steve


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