linux-kernel - [PATCHv2 4/5] perf stat: Add -a as a default target

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Date:   Fri, 17 Feb 2017 18:00:34 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, David Ahern <dsahern@...il.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Borislav Petkov <bp@...en8.de>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCHv2 4/5] perf stat: Add -a as a default target

On Fri, Feb 17, 2017 at 11:41:28AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Fri, Feb 17, 2017 at 03:33:27PM +0100, Jiri Olsa escreveu:
> > On Fri, Feb 17, 2017 at 11:27:47AM -0300, Arnaldo Carvalho de Melo wrote:
> > > Em Fri, Feb 17, 2017 at 03:00:57PM +0100, Jiri Olsa escreveu:
> > > > Boris asked for default -a option in case we monitor
> > > > only uncore events. While implementing that I thought
> > > > it might be actually useful to make it overall default.
> 
> > > >   # perf stat
> > > >   Warning: No target specified, setting system-wide collection (-a).
> 
> > > Humm, would be interesting to disable this after a few warnings? Just
> > > one?
>  
> > not sure it's good idea to keep the count of that somewhere..
> > how about i make the warning smaller ;-)
>  
> >   # perf stat
> >   Forced system wide target.
> >   ...
>  
> > > BTW, this is how 'perf trace' works since day one, i.e. no target means
> > > system wide syscall tracing.
>  
> > or we could omit the warning completely as probably perf trace does
> 
> I think that we should have some note on the Documentation (have you
> added it?) and be done with it.
> 
> Another thing possiblity my mind, print that at the end? like:
> 
> perf record
> ^C[ perf record: Woken up 1 times to write data - system wide samples ]
> [ perf record: Captured and wrote 1.738 MB perf.data (7565 samples) ]
> 
> ----------
> 
> Then people will thing, hey, so now it does systemwide samples when I
> pass no target, I don't have anymore to type _three_ keys! cool! :-)

ok, posting the change with no warning

jirka

---
Boris asked for default -a option in case we monitor
only uncore events. While implementing that I thought
it might be actually useful to make it overall default.

Running 'perf stat' will now collect system wide data.

Requested-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
Cc: David Ahern <dsahern@...il.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/n/tip-tq11of2qlz8kxpxzva05d54l@git.kernel.org
---
 tools/perf/Documentation/perf-stat.txt | 2 +-
 tools/perf/builtin-stat.c              | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index d96ccd4844df..aecf2a87e7d6 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -63,7 +63,7 @@ report::
 
 -a::
 --all-cpus::
-        system-wide collection from all CPUs
+        system-wide collection from all CPUs (default if no target is specified)
 
 -c::
 --scale::
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index f28719178b51..70ed4f9d014e 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -2445,8 +2445,9 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
 	} else if (big_num_opt == 0) /* User passed --no-big-num */
 		big_num = false;
 
+	/* Make system wide (-a) the default target. */
 	if (!argc && target__none(&target))
-		usage_with_options(stat_usage, stat_options);
+		target.system_wide = true;
 
 	if (run_count < 0) {
 		pr_err("Run count must be a positive number\n");
-- 
2.7.4