linux-kernel - Re: [PATCH] perf/ftrace: system_wide collection is not effective by default

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Message-ID: <CAM9d7cipbsg46=UNY8-h-e9RAsqeJRcL=mi_RXbtQwQUbwPehQ@mail.gmail.com>
Date:   Wed, 26 Jan 2022 15:47:48 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Changbin Du <changbin.du@...il.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...hat.com>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf/ftrace: system_wide collection is not effective by default

Hello,

On Wed, Jan 26, 2022 at 7:19 AM Changbin Du <changbin.du@...il.com> wrote:
>
> The ftrace.target.system_wide must be set before invoking
> evlist__create_maps(), otherwise it has no effect.

Oh, right.  Thanks for pointing that out.

>
> Fixes: 53be50282269 ("perf ftrace: Add 'latency' subcommand")
> Signed-off-by: Changbin Du <changbin.du@...il.com>
> ---
>  tools/perf/builtin-ftrace.c | 45 ++++++++++++++++++++-----------------
>  1 file changed, 24 insertions(+), 21 deletions(-)
>
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index dec24dc0e767..26bff29ad277 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -1115,6 +1115,7 @@ enum perf_ftrace_subcommand {
>  int cmd_ftrace(int argc, const char **argv)
>  {
>         int ret;
> +       int (*cmd_func)(struct perf_ftrace *) = NULL;
>         struct perf_ftrace ftrace = {
>                 .tracer = DEFAULT_TRACER,
>                 .target = { .uid = UINT_MAX, },
> @@ -1221,6 +1222,28 @@ int cmd_ftrace(int argc, const char **argv)
>                 goto out_delete_filters;
>         }
>
> +       switch (subcmd) {
> +       case PERF_FTRACE_TRACE:
> +               if (!argc && target__none(&ftrace.target))
> +                       ftrace.target.system_wide = true;

We can move only this part after parse_options().

> +               cmd_func = __cmd_ftrace;
> +               break;
> +       case PERF_FTRACE_LATENCY:
> +               if (list_empty(&ftrace.filters)) {
> +                       pr_err("Should provide a function to measure\n");
> +                       parse_options_usage(ftrace_usage, options, "T", 1);
> +                       ret = -EINVAL;
> +                       goto out_delete_evlist;

Otherwise, it should go to the out_delete_filters.

> +               }
> +               cmd_func = __cmd_latency;
> +               break;
> +       case PERF_FTRACE_NONE:
> +       default:
> +               pr_err("Invalid subcommand\n");
> +               ret = -EINVAL;
> +               goto out_delete_evlist;

Ditto.

Thanks,
Namhyung


> +       }
> +
>         ret = target__validate(&ftrace.target);
>         if (ret) {
>                 char errbuf[512];
> @@ -1248,27 +1271,7 @@ int cmd_ftrace(int argc, const char **argv)
>                         goto out_delete_evlist;
>         }
>
> -       switch (subcmd) {
> -       case PERF_FTRACE_TRACE:
> -               if (!argc && target__none(&ftrace.target))
> -                       ftrace.target.system_wide = true;
> -               ret = __cmd_ftrace(&ftrace);
> -               break;
> -       case PERF_FTRACE_LATENCY:
> -               if (list_empty(&ftrace.filters)) {
> -                       pr_err("Should provide a function to measure\n");
> -                       parse_options_usage(ftrace_usage, options, "T", 1);
> -                       ret = -EINVAL;
> -                       goto out_delete_evlist;
> -               }
> -               ret = __cmd_latency(&ftrace);
> -               break;
> -       case PERF_FTRACE_NONE:
> -       default:
> -               pr_err("Invalid subcommand\n");
> -               ret = -EINVAL;
> -               break;
> -       }
> +       ret = cmd_func(&ftrace);
>
>  out_delete_evlist:
>         evlist__delete(ftrace.evlist);
> --
> 2.32.0
>