linux-kernel - Re: [PATCH] perf parser: Improve error message for PMU address filters

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Date:   Thu, 19 Oct 2017 16:57:30 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jack Henschel <jackdev@...lbox.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        Taeung Song <treeze.taeung@...il.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf parser: Improve error message for PMU address
 filters

Em Thu, Oct 19, 2017 at 09:37:13PM +0200, Jack Henschel escreveu:
> On 09/05/2017 11:08 AM, Jack Henschel wrote:
> > This patch improves the error message of the perf events parser
> > when the PMU hardware does not support address filters.
> > 
> > Previously, the perf returned the following error:
> >> --filter option should follow a -e tracepoint or HW tracer option
> > This implies there is some syntax error present in the command line,
> > which is not true. Rather, notify the user that the CPU does not have
> > support for this feature.
> > 
> > For example, Intel chips based on the Broadwell micro-archticture have
> > the Intel PT PMU, but do not support address filtering.
> > 
> > Signed-off-by: Jack Henschel <jackdev@...lbox.org>
> > ---
> >  tools/perf/util/parse-events.c | 20 ++++++++++----------
> >  1 file changed, 10 insertions(+), 10 deletions(-)
> > 
> > diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> > index f44aeba51d1f..672b6d9423e9 100644
> > --- a/tools/perf/util/parse-events.c
> > +++ b/tools/perf/util/parse-events.c
> > @@ -1833,8 +1833,11 @@ static int set_filter(struct perf_evsel *evsel, const void *arg)
> >  	int nr_addr_filters = 0;
> >  	struct perf_pmu *pmu = NULL;
> >  
> > -	if (evsel == NULL)
> > -		goto err;
> > +	if (evsel == NULL) {
> > +		fprintf(stderr,
> > +			"--filter option should follow a -e tracepoint or HW tracer option\n");
> > +		return -1;
> > +	}
> >  
> >  	if (evsel->attr.type == PERF_TYPE_TRACEPOINT) {
> >  		if (perf_evsel__append_tp_filter(evsel, str) < 0) {
> > @@ -1856,8 +1859,11 @@ static int set_filter(struct perf_evsel *evsel, const void *arg)
> >  		perf_pmu__scan_file(pmu, "nr_addr_filters",
> >  				    "%d", &nr_addr_filters);
> >  
> > -	if (!nr_addr_filters)
> > -		goto err;
> > +	if (!nr_addr_filters) {
> > +		fprintf(stderr,
> > +			"This CPU does not support address filtering\n");
> > +		return -1;
> > +	}
> >  
> >  	if (perf_evsel__append_addr_filter(evsel, str) < 0) {
> >  		fprintf(stderr,
> > @@ -1866,12 +1872,6 @@ static int set_filter(struct perf_evsel *evsel, const void *arg)
> >  	}
> >  
> >  	return 0;
> > -
> > -err:
> > -	fprintf(stderr,
> > -		"--filter option should follow a -e tracepoint or HW tracer option\n");
> > -
> > -	return -1;
> >  }
> >  
> >  int parse_filter(const struct option *opt, const char *str,
> > 
> 
> Is there any interest in this patch? Did it get lost?
 
> > For example, Intel chips based on the Broadwell micro-archticture have
> > the Intel PT PMU, but do not support address filtering.

Can you provide this example with the tool output before and after? I
happen to have a Broadwell machine as my current notebook and would just
use this to test your patch.

And generally before/after command lines + output is good to quickly
show, in more concrete terms what the problem is and how it gets fixed.

- Arnaldo