linux-kernel - Re: [PATCH v2] trace-cmd: Add record --clock option to specify a trace clock

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Date:	Thu, 14 May 2015 10:32:09 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>
Cc:	Ian Webster <ian@...netaryresources.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] trace-cmd: Add record --clock option to specify a
 trace clock

On Mon, 16 Dec 2013 13:10:52 +0900
Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com> wrote:

> Hi Ian,
> 
> (2013/12/13 8:30), Ian Webster wrote:
> > This change adds a --clock option to trace-cmd record. It simply writes
> > trace_clock on debugfs. Examples of valid choices on most systems are: local,
> > global, counter, and any other choice compatible with ftrace.
> 
> Nice work!
> Please see my following comments.

Hmm, I was waiting for a reply back with an update against these
comments and never saw one. I eventually forgot about this patch :-(

I went to add it now, and noticed that I already added a -C option for
trace-clock which also works for instances.

Sorry about forgetting about this patch (just found it buried in my
inbox).

I'll be releasing 2.6 soon, with a bunch of new updates.

-- Steve

> 
> > This complements Yoshihiro Yunomae's change 8c9867c (trace-cmd: Add support for
> > extracting trace_clock in report).
> >
> > Signed-off-by: Ian Webster <ian@...netaryresources.com>
> >
> > ---
> > Changes per Steven's comments:
> >    * add missing const
> >    * preserve tab whitespace
> >
> >   Documentation/trace-cmd-record.1.txt |    5 +++++
> >   trace-record.c                       |   19 +++++++++++++++++++
> >   trace-usage.c                        |    1 +
> >   3 files changed, 25 insertions(+)
> >
> > diff --git a/Documentation/trace-cmd-record.1.txt b/Documentation/trace-cmd-record.1.txt
> > index 832a257..5e83454 100644
> > --- a/Documentation/trace-cmd-record.1.txt
> > +++ b/Documentation/trace-cmd-record.1.txt
> > @@ -240,6 +240,11 @@ OPTIONS
> >       timestamp to gettimeofday which will allow wall time output from the
> >       timestamps reading the created 'trace.dat' file.
> >
> > +*--clock* 'clock_name'::
> > +    When an event is recorded into the ring buffer, a timestamp is added. This
> > +    stamp comes from the specified clock. Ftrace uses the "local" clock by
> > +    default. Other common clocks include: global, counter, uptime, perf, x86-tsc.
> > +
> >   EXAMPLES
> >   --------
> >
> > diff --git a/trace-record.c b/trace-record.c
> > index 0199627..2143080 100644
> > --- a/trace-record.c
> > +++ b/trace-record.c
> > @@ -399,6 +399,20 @@ static int set_ftrace(int set, int use_proc)
> >   	return 0;
> >   }
> >
> > +static void set_trace_clock(const char *clock_choice)
> > +{
> > +	FILE *fp;
> > +	char *path;
> > +
> > +	path = tracecmd_get_tracing_file("trace_clock");
> > +	fp = fopen(path, "w");
> > +	if (!fp)
> > +		die("writing to '%s'", path);
> > +	tracecmd_put_tracing_file(path);
> > +	fwrite(clock_choice, 1, strlen(clock_choice), fp);
> 
> Please add an error check for fwrite(). If clock_choice is invalid,
> trace-cmd would better output the error report and die.
> 
> > +	fclose(fp);
> > +}
> > +
> >   static char *
> >   get_instance_file(struct buffer_instance *instance, const char *file)
> >   {
> > @@ -2279,6 +2293,7 @@ static void record_all_events(void)
> >   }
> >
> >   enum {
> > +	OPT_clock = 252,
> >   	OPT_nosplice	= 253,
> >   	OPT_funcstack	= 254,
> >   	OPT_date	= 255,
> > @@ -2351,6 +2366,7 @@ void trace_record (int argc, char **argv)
> >   			{"func-stack", no_argument, NULL, OPT_funcstack},
> >   			{"nosplice", no_argument, NULL, OPT_nosplice},
> >   			{"help", no_argument, NULL, '?'},
> > +			{"clock", required_argument, NULL, OPT_clock},
> >   			{NULL, 0, NULL, 0}
> >   		};
> >
> > @@ -2530,6 +2546,9 @@ void trace_record (int argc, char **argv)
> >   		case OPT_nosplice:
> >   			recorder_flags |= TRACECMD_RECORD_NOSPLICE;
> >   			break;
> > +		case OPT_clock:
> > +			set_trace_clock(optarg);
> > +			break;
> 
> This implementation does not support multiple buffers.
> trace_clock had better be changed after sub-buffers are created, I
> think.
> 
> Example:
> trace-cmd record -e sched --clock local -B foo -e block --clock x86-tsc
> 
> Thanks,
> Yoshihiro YUNOMAE
> 

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