linux-kernel - Re: [PATCH 1/2] tracing, function_graph: fix micro seconds notation in comment

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Date:	Fri, 24 Oct 2014 10:07:42 +0900
From:	Byungchul Park <byungchul.park@....com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	rostedt@...dmis.org, mingo@...hat.com, jolsa@...hat.com,
	vanilla@...ckduck.lge.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] tracing, function_graph: fix micro seconds notation
 in comment

On Fri, Oct 24, 2014 at 09:20:11AM +0900, Namhyung Kim wrote:
> Hi Byungchul,
> 
> On Thu, 23 Oct 2014 17:17:21 +0900, byungchul park wrote:
> > From: Byungchul Park <byungchul.park@....com>
> >
> > Usually, "msecs" notation means milli-seconds, and "usecs" notation
> > means micro-seconds. Since the unit used in the code is
> > micro-seconds, the notation should be replaced from msecs to usecs.
> > This confusing notation prevents us from understanding the code
> > correctly.
> >
> > Signed-off-by: Byungchul Park <byungchul.park@....com>
> > ---
> >  kernel/trace/trace_functions_graph.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> > index f0a0c98..c18a1e3 100644
> > --- a/kernel/trace/trace_functions_graph.c
> > +++ b/kernel/trace/trace_functions_graph.c
> > @@ -822,10 +822,10 @@ print_graph_duration(unsigned long long duration, struct trace_seq *s,
> >  
> >  	/* Signal a overhead of time execution to the output */
> >  	if (flags & TRACE_GRAPH_PRINT_OVERHEAD) {
> > -		/* Duration exceeded 100 msecs */
> > +		/* Duration exceeded 100 usecs */
> >  		if (duration > 100000ULL)
> >  			ret = trace_seq_puts(s, "! ");
> > -		/* Duration exceeded 10 msecs */
> > +		/* Duration exceeded 10 usecs */
> >  		else if (duration > 10000ULL)
> 
> I thought the duration was in usec, but it seems not, it's in nsec, hmm.
> Then this exceeding 10/100 usec is not meaningful - what about increaing
> numbers in the conditional so that it can match to the comment?  That
> will eliminate the need of the patch 2.

The approach you suggested also looks good to me. But I just wonder if it
would be ok even if it changes meaning of the marks, "!", "+", because the
marks have used with the meaning of exceeding 10/100 usec until now.

Isn't there anything wrong with increasing numbers in the conditions? :)

> 
> Also I think msecs_str in trace_print_graph_duration() should be renamed
> to usecs_str.

I agree. It should be also renamed. Such words made me hard to understand
the code correctly. :(

> 
> Thanks,
> Namhyung
> 
> 
> >  			ret = trace_seq_puts(s, "+ ");
> >  	}
> --
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