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

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Message-ID: <20191106195432.GB11935@kernel.org>
Date:   Wed, 6 Nov 2019 16:54:32 -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 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,

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