linux-kernel - Re: [tip:perf/urgent] perf evlist: Open event on evsel cpus and threads

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Message-ID: <20150903152713.GA2537@redhat.com>
Date:	Thu, 3 Sep 2015 12:27:13 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	kan.liang@...el.com, mingo@...nel.org, jolsa@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [tip:perf/urgent] perf evlist: Open event on evsel cpus and
 threads

Em Thu, Sep 03, 2015 at 04:34:24PM +0300, Adrian Hunter escreveu:
> On 01/09/15 11:31, tip-bot for Kan Liang wrote:
> > Commit-ID:  d988d5ee647861706bc7a391ddbc29429b50f00e
> > Gitweb:     http://git.kernel.org/tip/d988d5ee647861706bc7a391ddbc29429b50f00e
> > Author:     Kan Liang <kan.liang@...el.com>
> > AuthorDate: Fri, 21 Aug 2015 02:23:14 -0400
> > Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
> > CommitDate: Mon, 31 Aug 2015 17:28:01 -0300
> > 
> > perf evlist: Open event on evsel cpus and threads
> > 
> > An evsel may have different cpus and threads than the evlist it is in.
> > 
> > Use it's own cpus and threads, when opening the evsel in 'perf record'.
> > 
> > Signed-off-by: Kan Liang <kan.liang@...el.com>
> > Cc: Jiri Olsa <jolsa@...nel.org>
> > Link: http://lkml.kernel.org/r/1440138194-17001-1-git-send-email-kan.liang@intel.com
> > Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> 
> Just noticed this breaks Intel PT.  Will have to investigate further.

What kind of breakage?

It all should be equivalent to before, its just that it uses
evsel->{threads,cpus} while before it was using evlist->{threads,cpus},
but that should point to the same thing if that
perf_evlist__propagate_maps() method was called, so I assume this is
some segfault?

Something we could catch in a 'test' entry? Even if that required Intel
PT hardware that would be something important to have, all this stuff is
growing in complexity, we need those tests...

- Arnaldo
 
> > ---
> >  tools/perf/builtin-record.c | 2 +-
> >  tools/perf/util/evlist.c    | 4 ++++
> >  2 files changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index a660022..1d14f38 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -279,7 +279,7 @@ static int record__open(struct record *rec)
> >  
> >  	evlist__for_each(evlist, pos) {
> >  try_again:
> > -		if (perf_evsel__open(pos, evlist->cpus, evlist->threads) < 0) {
> > +		if (perf_evsel__open(pos, pos->cpus, pos->threads) < 0) {
> >  			if (perf_evsel__fallback(pos, errno, msg, sizeof(msg))) {
> >  				if (verbose)
> >  					ui__warning("%s\n", msg);
> > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> > index 8d00039..d51a520 100644
> > --- a/tools/perf/util/evlist.c
> > +++ b/tools/perf/util/evlist.c
> > @@ -1181,6 +1181,10 @@ int perf_evlist__apply_filters(struct perf_evlist *evlist, struct perf_evsel **e
> >  		if (evsel->filter == NULL)
> >  			continue;
> >  
> > +		/*
> > +		 * filters only work for tracepoint event, which doesn't have cpu limit.
> > +		 * So evlist and evsel should always be same.
> > +		 */
> >  		err = perf_evsel__apply_filter(evsel, ncpus, nthreads, evsel->filter);
> >  		if (err) {
> >  			*err_evsel = evsel;
> > 
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