linux-kernel - Re: [PATCH 10/54] perf stat: Forbid user passing improper config terms

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Date:	Fri, 12 Feb 2016 13:45:17 -0200
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Wang Nan <wangnan0@...wei.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Cody P Schafer <dev@...yps.com>,
	"David S. Miller" <davem@...emloft.net>,
	He Kuang <hekuang@...wei.com>,
	Jérémie Galarneau 
	<jeremie.galarneau@...icios.com>, Jiri Olsa <jolsa@...nel.org>,
	Kirill Smelkov <kirr@...edi.com>,
	Li Zefan <lizefan@...wei.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, pi3orama@....com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/54] perf stat: Forbid user passing improper config
 terms

Em Fri, Feb 12, 2016 at 02:49:08PM +0100, Jiri Olsa escreveu:
> On Fri, Feb 05, 2016 at 02:01:35PM +0000, Wang Nan wrote:
> > 'perf stat' accepts some config terms but doesn't apply them. For
> > example:
> > 
> >  # perf stat -e 'instructions/no-inherit/' -e 'instructions/inherit/' bash
> >  # ls
> >  # exit
> > 
> >  Performance counter stats for 'bash':
> > 
> >          266258061      instructions/no-inherit/
> >          266258061      instructions/inherit/
> 
> hum, but we support no-/inherit in stat, it'd be better to
> implement this one for stat IMO
> 
> 
> > 
> >        1.402183915 seconds time elapsed
> > 
> > The result is confusing, because user may expect the first
> > 'instructions' event exclude the 'ls' command.
> > 
> > This patch forbit most of those config terms for 'perf stat'.
> > 
> > Result:
> > 
> >  # ./perf stat -e 'instructions/no-inherit/' -e 'instructions/inherit/' bash
> >  event syntax error: 'instructions/no-inherit/'
> >                       \___ Don't use record mode only config terms
> 
> and there's bunch of others which are sampling related:
>   PARSE_EVENTS__TERM_TYPE_SAMPLE_*
>   PERF_EVSEL__CONFIG_TERM_CALLGRAPH
>   PERF_EVSEL__CONFIG_TERM_STACK_USER
>   ...
> 
> probably all from get_config_terms apart from the 'inherot' ones,
> which should end up with the error message, which could be more
> user friendly like:
> 
>   - Can't use stack-size term in stat event.

'stat' event? If this is the term you want to use maybe:

    'stack-size' is not usable in 'perf stat'.

But perhaps it would be better as:

    'stack-size' can only be used when sampling.

Or even more verbose:

    The 'stack-size' can only be configured when sampling, not when just
    counting events.

No?

- Arnaldo