linux-kernel - Re: [PATCH] perf ftrace: Make system wide the default target for latency subcommand

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Message-ID: <ZCF/Oa+dK4Wc/7r7@kernel.org>
Date:   Mon, 27 Mar 2023 08:34:17 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Yang Jihong <yangjihong1@...wei.com>, peterz@...radead.org,
        mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        irogers@...gle.com, adrian.hunter@...el.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf ftrace: Make system wide the default target for
 latency subcommand

Em Fri, Mar 24, 2023 at 06:39:25PM -0700, Namhyung Kim escreveu:
> Hello,
> 
> On Thu, Mar 23, 2023 at 8:29 PM Yang Jihong <yangjihong1@...wei.com> wrote:
> >
> > If no target is specified for 'latency' subcommand, the execution fails
> > because - 1 (invalid value) is written to set_ftrace_pid tracefs file.
> > Make system wide the default target, which is the same as the default
> > behavior of 'trace' subcommand.
> 
> I followed the convention to use -a for system-wide profiling.
> Not sure if it's ok to make it default, but I don't object. :)

I'll make that an Acked-by, ok?

- Arnaldo
 
> Thanks,
> Namhyung
> 
> >
> > Before the fix:
> >
> >   # perf ftrace latency -T schedule
> >   failed to set ftrace pid
> >
> > After the fix:
> >
> >   # perf ftrace latency -T schedule
> >   ^C#   DURATION     |      COUNT | GRAPH                                          |
> >        0 - 1    us |          0 |                                                |
> >        1 - 2    us |          0 |                                                |
> >        2 - 4    us |          0 |                                                |
> >        4 - 8    us |       2828 | ####                                           |
> >        8 - 16   us |      23953 | ########################################       |
> >       16 - 32   us |        408 |                                                |
> >       32 - 64   us |        318 |                                                |
> >       64 - 128  us |          4 |                                                |
> >      128 - 256  us |          3 |                                                |
> >      256 - 512  us |          0 |                                                |
> >      512 - 1024 us |          1 |                                                |
> >        1 - 2    ms |          4 |                                                |
> >        2 - 4    ms |          0 |                                                |
> >        4 - 8    ms |          0 |                                                |
> >        8 - 16   ms |          0 |                                                |
> >       16 - 32   ms |          0 |                                                |
> >       32 - 64   ms |          0 |                                                |
> >       64 - 128  ms |          0 |                                                |
> >      128 - 256  ms |          4 |                                                |
> >      256 - 512  ms |          2 |                                                |
> >      512 - 1024 ms |          0 |                                                |
> >        1 - ...   s |          0 |                                                |
> >
> > Fixes: 53be50282269 ("perf ftrace: Add 'latency' subcommand")
> > Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
> > ---
> >  tools/perf/builtin-ftrace.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> > index d7fe00f66b83..fb1b66ef2e16 100644
> > --- a/tools/perf/builtin-ftrace.c
> > +++ b/tools/perf/builtin-ftrace.c
> > @@ -1228,10 +1228,12 @@ int cmd_ftrace(int argc, const char **argv)
> >                 goto out_delete_filters;
> >         }
> >
> > +       /* Make system wide (-a) the default target. */
> > +       if (!argc && target__none(&ftrace.target))
> > +               ftrace.target.system_wide = true;
> > +
> >         switch (subcmd) {
> >         case PERF_FTRACE_TRACE:
> > -               if (!argc && target__none(&ftrace.target))
> > -                       ftrace.target.system_wide = true;
> >                 cmd_func = __cmd_ftrace;
> >                 break;
> >         case PERF_FTRACE_LATENCY:
> > --
> > 2.30.GIT
> >

-- 

- Arnaldo