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

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Date:   Wed, 2 Aug 2023 11:08:04 +0800
From:   Ze Gao <zegao2021@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
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

Fair enough! Already did this in perf fixes. Will push a v4
to do this.

Thanks,
Ze


On Tue, Aug 1, 2023 at 10:19 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> 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, " ==> ");
>