linux-kernel - Re: [RFC PATCH v2 1/2] perf tools: Set evsel->system_wide field for global system wide recording

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Message-ID: <562E2452.104@intel.com>
Date:	Mon, 26 Oct 2015 15:02:10 +0200
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	"Wangnan (F)" <wangnan0@...wei.com>, acme@...nel.org,
	ast@...mgrid.com
Cc:	linux-kernel@...r.kernel.org, pi3orama@....com, lizefan@...wei.com,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RFC PATCH v2 1/2] perf tools: Set evsel->system_wide field for
 global system wide recording

On 26/10/15 14:39, Wangnan (F) wrote:
> 
> 
> On 2015/10/26 20:24, Adrian Hunter wrote:
>> On 26/10/15 13:41, Wang Nan wrote:
>>> evsel->system_wide is introduced by commit bf8e8f4b832972c76d64ab2e2837
>>> (perf evlist: Add 'system_wide' option), which is used for mixing evsels
>>> that aren't system-wide with ones that are [1]. However, for global
>>> system wide recording (perf record -a ...), evsel->system_wide is set
>>> to false, which is confusion.
>>>
>>> This patch set evsel->system_wide to true if the target.system_wide is
>>> set, which makes evsel->system_wide a reliable way to describe whether
>>> itself is system_wide or not.
>>>
>>> [1] http://lkml.kernel.org/r/562DF19B.2080608@intel.com
>>>
>>> Signed-off-by: Wang Nan <wangnan0@...wei.com>
>>> Cc: Adrian Hunter <adrian.hunter@...el.com>
>>> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
>>> Cc: Alexei Starovoitov <ast@...mgrid.com>
>>> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>>> Cc: Li Zefan <lizefan@...wei.com>
>>> Cc: pi3orama@....com
>>> Link: http://lkml.kernel.org/n/ebpf-qm3gtwidc1o5ktjd9tgjex25@git.kernel.org
>>> ---
>>>   tools/perf/util/evsel.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
>>> index 3ac4ee9c..36ecf0e 100644
>>> --- a/tools/perf/util/evsel.c
>>> +++ b/tools/perf/util/evsel.c
>>> @@ -734,6 +734,7 @@ void perf_evsel__config(struct perf_evsel *evsel,
>>> struct record_opts *opts)
>>>       int track = evsel->tracking;
>>>       bool per_cpu = opts->target.default_per_cpu &&
>>> !opts->target.per_thread;
>>>   +    evsel->system_wide = opts->target.system_wide;
>> Well that breaks the way evsel->system_wide is used i.e. it is a parameter
>> to the evsel and here you just overwrote it.
> 
> Currently the only user of evsel->system_wide is IPT:
> 
> auxtrace_record__options -> intel_pt_recording_options
> 
> and it only set it to true.
> 
> So I think changing to this should make it safe:
> 
> evsel->system_wide = (evsel->system_wide || opt->target.system_wide);
> 
> Thought?

That would work although it looks like a kludge.

Have you looked at properly validating opts->no_inherit ?

Also, aren't you neglecting target->cpu_list ?

> 
> If we want to add further config terms we can put it to apply_config_terms(),
> where we can implement something like:
> 
>  # perf record -e cycles/system-wide/ -e instruction/no-system-wide/ ...
> 
> But currently I don't have such requirement.
> 
> Thank you.
> 
> 

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