linux-kernel - Re: [RFC PATCH v3 6/6] libtraceevent: prefer to use prev_state_char introduced in sched

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Message-ID: <20230801101908.4ccc81c8@gandalf.local.home>
Date:   Tue, 1 Aug 2023 10:19:08 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Ze Gao <zegao2021@...il.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org,
        linux-trace-devel@...r.kernel.org, Ze Gao <zegao@...cent.com>
Subject: Re: [RFC PATCH v3 6/6] libtraceevent: prefer to use prev_state_char
 introduced in sched_switch

On Tue,  1 Aug 2023 17:01:24 +0800
Ze Gao <zegao2021@...il.com> wrote:

> Since the sched_switch tracepoint introduces a new variable to
> report sched-out task state in symbolic char, we prefer to use
> it to spare from knowing internal implementations in kernel.
> 
> Also we keep the old parsing logic intact but sync the state char
> array with the latest kernel.

This should be two patches. First sync the state char array and then add
your state_char change. The two changes are agnostic to each other, and
should be separate commits. Same goes for the perf changes.

-- Steve


> 
> Signed-off-by: Ze Gao <zegao@...cent.com>
> ---
>  plugins/plugin_sched_switch.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/plugins/plugin_sched_switch.c b/plugins/plugin_sched_switch.c
> index 8752cae..4c57322 100644
> --- a/plugins/plugin_sched_switch.c
> +++ b/plugins/plugin_sched_switch.c
> @@ -11,7 +11,7 @@
>  
>  static void write_state(struct trace_seq *s, int val)
>  {
> -	const char states[] = "SDTtZXxW";
> +	const char states[] = "SDTtXZPIp";
>  	int found = 0;
>  	int i;
>  
> @@ -99,7 +99,12 @@ static int sched_switch_handler(struct trace_seq *s,
>  	if (tep_get_field_val(s, event, "prev_prio", record, &val, 1) == 0)
>  		trace_seq_printf(s, "[%d] ", (int) val);
>  
> -	if (tep_get_field_val(s,  event, "prev_state", record, &val, 1) == 0)
> +	//find if has prev_state_char, otherwise fallback to prev_state
> +	if (tep_find_field(event, "prev_state_char")) {
> +		if (tep_get_field_val(s,  event, "prev_state_char", record, &val, 1) == 0)
> +			trace_seq_putc(s, (char) val);
> +	}
> +	else if (tep_get_field_val(s,  event, "prev_state", record, &val, 1) == 0)
>  		write_state(s, val);
>  
>  	trace_seq_puts(s, " ==> ");