linux-kernel - Re: [PATCH 2/5] perf probe: Generate event name with line number

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Message-ID: <20191107135507.GE11372@kernel.org>
Date:   Thu, 7 Nov 2019 10:55:07 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH 2/5] perf probe: Generate event name with line number

Em Thu, Nov 07, 2019 at 10:43:41PM +0900, Masami Hiramatsu escreveu:
> Hi Arnaldo,
> 
> On Wed, 6 Nov 2019 16:54:32 -0300
> Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> 
> > Em Tue, Nov 05, 2019 at 09:16:59AM +0900, Masami Hiramatsu escreveu:
> > > Generate event name from function name with line number
> > > as <function>_L<line_number>. Note that this is only for
> > > the new event which is defined by function and lines.
> > > 
> > > If there is another event on same line, you have to use
> > > "-f" option. In that case, the new event has "_1" suffix.
> > 
> > So I don't like this, the existing practice of, if given a function
> > name, just create the probe:name looks more natural, if one states
> > kernel:1, then, sure, appending L1 to them is natural, better than the
> > previous naming convention,
> 
> OK, then what about adding L* only when the user add it on a
> specific line (like kernel_read:1) ?
> IOW, _L0 will be skipped.

Exactly, agreed.
 
> Thank you,
> 
> > 
> > Thanks,
> > 
> > - Arnaldo
> >  
> > >  e.g.
> > >   # perf probe -a kernel_read
> > >   Added new event:
> > >     probe:kernel_read_L0 (on kernel_read)
> > > 
> > >   You can now use it in all perf tools, such as:
> > > 
> > >   	perf record -e probe:kernel_read_L0 -aR sleep 1
> > > 
> > >   # perf probe -a kernel_read:1
> > >   Added new events:
> > >     probe:kernel_read_L1 (on kernel_read:1)
> > > 
> > >   You can now use it in all perf tools, such as:
> > > 
> > >   	perf record -e probe:kernel_read_L1_1 -aR sleep 1
> > > 
> > >   # perf probe -l
> > >     probe:kernel_read_L0 (on kernel_read@...ux/linux/fs/read_write.c)
> > >     probe:kernel_read_L1 (on kernel_read@...ux/linux/fs/read_write.c)
> > > 
> > > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> > > ---
> > >  tools/perf/util/probe-event.c |    8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> > > index 91cab5f669d2..d14b970a6461 100644
> > > --- a/tools/perf/util/probe-event.c
> > > +++ b/tools/perf/util/probe-event.c
> > > @@ -1679,6 +1679,14 @@ int parse_perf_probe_command(const char *cmd, struct perf_probe_event *pev)
> > >  	if (ret < 0)
> > >  		goto out;
> > >  
> > > +	/* Generate event name if needed */
> > > +	if (!pev->event && pev->point.function
> > > +			&& !pev->point.lazy_line && !pev->point.offset) {
> > > +		if (asprintf(&pev->event, "%s_L%d", pev->point.function,
> > > +			pev->point.line) < 0)
> > > +			return -ENOMEM;
> > > +	}
> > > +
> > >  	/* Copy arguments and ensure return probe has no C argument */
> > >  	pev->nargs = argc - 1;
> > >  	pev->args = zalloc(sizeof(struct perf_probe_arg) * pev->nargs);
> > 
> > -- 
> > 
> > - Arnaldo
> 
> 
> -- 
> Masami Hiramatsu <mhiramat@...nel.org>

-- 

- Arnaldo