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

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Date:	Thu, 3 Sep 2015 20:19:39 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:	Adrian Hunter <adrian.hunter@...el.com>, 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

On Thu, Sep 03, 2015 at 01:41:09PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Sep 03, 2015 at 07:23:43PM +0300, Adrian Hunter escreveu:
> > On 3/09/2015 6:27 p.m., Arnaldo Carvalho de Melo wrote:
> > >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?
> > 
> > Can't open the sched_switch event
> > 
> > >
> > >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?
> > 
> > I think maybe it doesn't consider evsels added later
> 
> A-ha, so when using perf_evlist__add() we need to do this, i.e. if
> evsel->{threads||cpus} is not set, fill it in with the evlist-> member?
>  
> > >
> > >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...
> > 
> > There is "Test tracking with sched_switch" but you need to expose it
> > to the same issue i.e.
> 
> Sure, Kan and Jiri were talking about the need to go doing these
> changes, Jiri? Kan?
> 

perf_evlist__propagate_maps is called from perf_evlist__create_maps,
so if evsel is added later it will not be affected, perhaps we need
something like below

jirka


---
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 8d00039d6a20..dfdaf1aafd80 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -133,6 +133,9 @@ void perf_evlist__add(struct perf_evlist *evlist, struct perf_evsel *entry)
 
 	if (!evlist->nr_entries++)
 		perf_evlist__set_id_pos(evlist);
+
+	entry->cpus = cpu_map__get(evlist->cpus);
+	entry->threads = thread_map__get(evlist->threads);
 }
 
 void perf_evlist__splice_list_tail(struct perf_evlist *evlist,
--
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