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:	Tue, 27 Oct 2015 11:23:37 +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 21:02, Adrian Hunter wrote:
> 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 ?

I need this because Alexei's bpf_perf_event_output() helper needs perf side
support, and it only accept no-inherit perf event. I have already made a
patch[1] to support setting inherit bit per-event, so even without this and
next patch I can continue my work on bpf output. I'd like to rethink this
patch after I finish perf support for bpf output.

Thank you.

[1] 
http://lkml.kernel.org/g/1445847884-143981-1-git-send-email-wangnan0@huawei.com

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