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

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Date:   Fri, 17 Feb 2017 11:41:28 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
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: Re: [PATCH 4/5] perf stat: Add -a as a default target

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! :-)

- Arnaldo