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

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Date:   Sat, 18 Feb 2017 18:52:25 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Jiri Olsa <jolsa@...hat.com>,
        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>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCHv2 4/5] perf stat: Add -a as a default target

On Fri, Feb 17, 2017 at 06:48:13PM +0100, Boris Petkov wrote:
> LGTM.
> 
> Acked-by: me

Well, it looks good but actually trying it is a different story. For
example:

$ ./perf stat -e amd_nb/event=0xe0,umask=0x1f/ sleep 1

still says <not supported> because argc is not 0.

So how about the below diff instead?

$ ./perf stat -e amd_nb/event=0xe0,umask=0x1f/

without args dumps the usage message and

$ ./perf stat -e amd_nb/event=0xe0,umask=0x1f/ sleep 1

actually does the system-wide thing:

 Performance counter stats for 'system wide':

           196,469      amd_nb/event=0xe0,umask=0x1f/

       1.001815180 seconds time elapsed

Hmmm?

 tools/perf/Documentation/perf-stat.txt | 2 +-
 tools/perf/builtin-stat.c              | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

Index: linux/tools/perf/Documentation/perf-stat.txt
===================================================================
--- linux.orig/tools/perf/Documentation/perf-stat.txt	2017-02-18 18:38:23.751960730 +0100
+++ linux/tools/perf/Documentation/perf-stat.txt	2017-02-18 18:38:23.743960730 +0100
@@ -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::
Index: linux/tools/perf/builtin-stat.c
===================================================================
--- linux.orig/tools/perf/builtin-stat.c	2017-02-18 18:38:23.751960730 +0100
+++ linux/tools/perf/builtin-stat.c	2017-02-18 18:48:33.531959828 +0100
@@ -2445,8 +2445,12 @@ int cmd_stat(int argc, const char **argv
 	} else if (big_num_opt == 0) /* User passed --no-big-num */
 		big_num = false;
 
-	if (!argc && target__none(&target))
-		usage_with_options(stat_usage, stat_options);
+	/* Make system wide (-a) the default target. */
+	if (target__none(&target)) {
+		if (!argc)
+			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");


-- 
Regards/Gruss,
    Boris.

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