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References: <20240122070859.1394479-2-zegao@tencent.com> <20240122070859.1394479-6-zegao@tencent.com>
In-Reply-To: <20240122070859.1394479-6-zegao@tencent.com>
From: Namhyung Kim <namhyung@kernel.org>
Date: Mon, 22 Jan 2024 16:38:03 -0800
Message-ID: <CAM9d7cjWdZa9oh-6CmydvtzOEkkWMip8yfxTS4L_PZnq4K7B1w@mail.gmail.com>
Subject: Re: [PATCH v2 4/4] perf sched: Commit to evsel__taskstate() to parse
 task state info
To: Ze Gao <zegao2021@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>, 
	Alexander Shishkin <alexander.shishkin@linux.intel.com>, 
	Arnaldo Carvalho de Melo <acme@kernel.org>, Ian Rogers <irogers@google.com>, Ingo Molnar <mingo@redhat.com>, 
	Jiri Olsa <jolsa@kernel.org>, Mark Rutland <mark.rutland@arm.com>, 
	Peter Zijlstra <peterz@infradead.org>, Steven Rostedt <rostedt@goodmis.org>, linux-kernel@vger.kernel.org, 
	linux-perf-users@vger.kernel.org, Ze Gao <zegao@tencent.com>
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Hello,

On Sun, Jan 21, 2024 at 11:11=E2=80=AFPM Ze Gao <zegao2021@gmail.com> wrote=
:
>
> Now that we have evsel__taskstate() which no longer relies on the
> hardcoded task state string and has good backward compatibility,
> we have a good reason to use it.
>
> Note TASK_STATE_TO_CHAR_STR and task bitmasks are useless now so
> we remove them for good. And now we pass the state info back and
> forth in a symbolic char which explains itself well instead.
>
> Signed-off-by: Ze Gao <zegao@tencent.com>
> ---
>  tools/perf/builtin-sched.c | 46 +++++++++-----------------------------
>  1 file changed, 10 insertions(+), 36 deletions(-)
>
> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
> index ced6fffe8110..f1d62f6b6cab 100644
> --- a/tools/perf/builtin-sched.c
> +++ b/tools/perf/builtin-sched.c
> @@ -92,13 +92,6 @@ struct sched_atom {
>         struct task_desc        *wakee;
>  };
>
> -#define TASK_STATE_TO_CHAR_STR "RSDTtXZPI"
> -
> -/* task state bitmask, copied from include/linux/sched.h */
> -#define TASK_RUNNING           0
> -#define TASK_INTERRUPTIBLE     1
> -#define TASK_UNINTERRUPTIBLE   2
> -
>  enum thread_state {
>         THREAD_SLEEPING =3D 0,
>         THREAD_WAIT_CPU,
> @@ -255,7 +248,7 @@ struct thread_runtime {
>         u64 total_preempt_time;
>         u64 total_delay_time;
>
> -       int last_state;
> +       char last_state;
>
>         char shortname[3];
>         bool comm_changed;
> @@ -425,7 +418,7 @@ static void add_sched_event_wakeup(struct perf_sched =
*sched, struct task_desc *t
>  }
>
>  static void add_sched_event_sleep(struct perf_sched *sched, struct task_=
desc *task,
> -                                 u64 timestamp, u64 task_state __maybe_u=
nused)
> +                                 u64 timestamp, const char task_state __=
maybe_unused)
>  {
>         struct sched_atom *event =3D get_new_event(task, timestamp);
>
> @@ -849,7 +842,7 @@ static int replay_switch_event(struct perf_sched *sch=
ed,
>                    *next_comm  =3D evsel__strval(evsel, sample, "next_com=
m");
>         const u32 prev_pid =3D evsel__intval(evsel, sample, "prev_pid"),
>                   next_pid =3D evsel__intval(evsel, sample, "next_pid");
> -       const u64 prev_state =3D evsel__intval(evsel, sample, "prev_state=
");
> +       const char prev_state =3D evsel__taskstate(evsel, sample, "prev_s=
tate");
>         struct task_desc *prev, __maybe_unused *next;
>         u64 timestamp0, timestamp =3D sample->time;
>         int cpu =3D sample->cpu;
> @@ -1039,13 +1032,6 @@ static int thread_atoms_insert(struct perf_sched *=
sched, struct thread *thread)
>         return 0;
>  }
>
> -static char sched_out_state(u64 prev_state)
> -{
> -       const char *str =3D TASK_STATE_TO_CHAR_STR;
> -
> -       return str[prev_state];
> -}
> -
>  static int
>  add_sched_out_event(struct work_atoms *atoms,
>                     char run_state,
> @@ -1121,7 +1107,7 @@ static int latency_switch_event(struct perf_sched *=
sched,
>  {
>         const u32 prev_pid =3D evsel__intval(evsel, sample, "prev_pid"),
>                   next_pid =3D evsel__intval(evsel, sample, "next_pid");
> -       const u64 prev_state =3D evsel__intval(evsel, sample, "prev_state=
");
> +       const char prev_state =3D evsel__taskstate(evsel, sample, "prev_s=
tate");
>         struct work_atoms *out_events, *in_events;
>         struct thread *sched_out, *sched_in;
>         u64 timestamp0, timestamp =3D sample->time;
> @@ -1157,7 +1143,7 @@ static int latency_switch_event(struct perf_sched *=
sched,
>                         goto out_put;
>                 }
>         }
> -       if (add_sched_out_event(out_events, sched_out_state(prev_state), =
timestamp))
> +       if (add_sched_out_event(out_events, prev_state, timestamp))
>                 return -1;
>
>         in_events =3D thread_atoms_search(&sched->atom_root, sched_in, &s=
ched->cmp_pid);
> @@ -2022,24 +2008,12 @@ static void timehist_header(struct perf_sched *sc=
hed)
>         printf("\n");
>  }
>
> -static char task_state_char(struct thread *thread, int state)
> -{
> -       static const char state_to_char[] =3D TASK_STATE_TO_CHAR_STR;
> -       unsigned bit =3D state ? ffs(state) : 0;
> -
> -       /* 'I' for idle */
> -       if (thread__tid(thread) =3D=3D 0)
> -               return 'I';
> -
> -       return bit < sizeof(state_to_char) - 1 ? state_to_char[bit] : '?'=
;
> -}
> -
>  static void timehist_print_sample(struct perf_sched *sched,
>                                   struct evsel *evsel,
>                                   struct perf_sample *sample,
>                                   struct addr_location *al,
>                                   struct thread *thread,
> -                                 u64 t, int state)
> +                                 u64 t, const char state)
>  {
>         struct thread_runtime *tr =3D thread__priv(thread);
>         const char *next_comm =3D evsel__strval(evsel, sample, "next_comm=
");
> @@ -2080,7 +2054,7 @@ static void timehist_print_sample(struct perf_sched=
 *sched,
>         print_sched_time(tr->dt_run, 6);
>
>         if (sched->show_state)
> -               printf(" %5c ", task_state_char(thread, state));
> +               printf(" %5c ", thread->tid =3D=3D 0 ? 'I' : state);

This resulted in a build error with reference count checker.

  $ make EXTRA_CFLAGS=3D-DREFCNT_CHECKING=3D1
  ...
  builtin-sched.c: In function =E2=80=98timehist_print_sample=E2=80=99:
  builtin-sched.c:2057:39: error: =E2=80=98struct thread=E2=80=99 has no me=
mber named =E2=80=98tid=E2=80=99
   2057 |                 printf(" %5c ", thread->tid =3D=3D 0 ? 'I' : stat=
e);
        |

The struct thread is protected by the refcount checker so
you should not access the members directly.  Instead,
please use a help function like thread__tid().

Thanks,
Namhyung

>
>         if (sched->show_next) {
>                 snprintf(nstr, sizeof(nstr), "next: %s[%d]", next_comm, n=
ext_pid);
> @@ -2152,9 +2126,9 @@ static void timehist_update_runtime_stats(struct th=
read_runtime *r,
>                 else if (r->last_time) {
>                         u64 dt_wait =3D tprev - r->last_time;
>
> -                       if (r->last_state =3D=3D TASK_RUNNING)
> +                       if (r->last_state =3D=3D 'R')
>                                 r->dt_preempt =3D dt_wait;
> -                       else if (r->last_state =3D=3D TASK_UNINTERRUPTIBL=
E)
> +                       else if (r->last_state =3D=3D 'D')
>                                 r->dt_iowait =3D dt_wait;
>                         else
>                                 r->dt_sleep =3D dt_wait;
> @@ -2579,7 +2553,7 @@ static int timehist_sched_change_event(struct perf_=
tool *tool,
>         struct thread_runtime *tr =3D NULL;
>         u64 tprev, t =3D sample->time;
>         int rc =3D 0;
> -       int state =3D evsel__intval(evsel, sample, "prev_state");
> +       const char state =3D evsel__taskstate(evsel, sample, "prev_state"=
);
>
>         addr_location__init(&al);
>         if (machine__resolve(machine, &al, sample) < 0) {
> --
> 2.41.0
>