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

From: Adrian Hunter
Date: Thu Sep 03 2015 - 14:38:24 EST

On 3/09/2015 9:19 p.m., Jiri Olsa wrote:
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
Author: Kan Liang <kan.liang@xxxxxxxxx>
AuthorDate: Fri, 21 Aug 2015 02:23:14 -0400
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
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@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

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

Yes but it would be nice to have a single function to do it that knows
the rules for when the evsel->cpus should be retained. Say:
int __perf_evlist__propagate_maps(struct perf_evlist *evlist, struct perf_evsel *evsel)
then call it from perf_evlist__propagate_maps(), perf_evlist__add() and
perf_evlist__splice_list_tail(). Probably need to add a member to perf_evlist
to know when the evlist->cpus should replace the evsel->cpus


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++)
+ 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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