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

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Date:	Mon, 26 Oct 2015 20:39:07 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Adrian Hunter <adrian.hunter@...el.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 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?

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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