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

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Message-ID: <20170217142747.GD4109@kernel.org>
Date:   Fri, 17 Feb 2017 11:27:47 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     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: Re: [PATCH 4/5] perf stat: Add -a as a default target

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?

BTW, this is how 'perf trace' works since day one, i.e. no target means
system wide syscall tracing.

- Arnaldo

>   ...
> 
> 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>
> Cc: Borislav Petkov <bp@...en8.de>
> Link: http://lkml.kernel.org/n/tip-tq11of2qlz8kxpxzva05d54l@git.kernel.org
> ---
>  tools/perf/Documentation/perf-stat.txt | 2 +-
>  tools/perf/builtin-stat.c              | 6 ++++--
>  2 files changed, 5 insertions(+), 3 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..0d09ec7029d3 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -2445,8 +2445,10 @@ 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;
>  
> -	if (!argc && target__none(&target))
> -		usage_with_options(stat_usage, stat_options);
> +	if (!argc && target__none(&target)) {
> +		pr_warning("Warning: No target specified, setting system-wide collection (-a).\n");
> +		target.system_wide = true;
> +	}
>  
>  	if (run_count < 0) {
>  		pr_err("Run count must be a positive number\n");
> -- 
> 2.7.4