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

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Date:	Thu, 3 Sep 2015 21:38:16 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...hat.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

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
>>>>>> 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

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

>
> 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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