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

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Date:	Tue, 7 Apr 2009 13:37:17 +0900
From:	GeunSik Lim <leemgs1@...il.com>
To:	Steven Rostedt <srostedt@...hat.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

 > What's the chrt for?
 We often need simple test to get  latency result  of realtime using
"current_tracers" file.
 In this case, We can run easy testcase as realtime task with the chrt command.

 Although we usually use function tracer for tracing internal kernel
functions by ftraced.
 I think that we need simple example like the chrt for monitoring
latencies and the kernel
functoins using sleep command as realtime task.


2009/4/7 Steven Rostedt <srostedt@...hat.com>:
>
> 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
>
>
>



-- 
Regards,
GeunSik Lim
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