linux-kernel - Re: [PATCH v4 05/18] perf: add minimal support for PERF_SAMPLE

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Date:	Mon, 7 Jan 2013 14:10:20 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Namhyung Kim <namhyung.kim@....com>
Subject: Re: [PATCH v4 05/18] perf: add minimal support for PERF_SAMPLE_WEIGHT

On Wed, Jan 2, 2013 at 3:07 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Thu, Dec 20, 2012 at 04:41:35PM +0100, Stephane Eranian wrote:
>> Ensure we grab the weight from  raw sample struct
>> and that we can dump it via perf report -D.
>>
>> Signed-off-by: Stephane Eranian <eranian@...gle.com>
>> ---
>>  tools/perf/util/event.h   |    1 +
>>  tools/perf/util/evsel.c   |    5 +++++
>>  tools/perf/util/session.c |    3 +++
>>  3 files changed, 9 insertions(+)
>>
>> diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
>> index 0d573ff..cf52977 100644
>> --- a/tools/perf/util/event.h
>> +++ b/tools/perf/util/event.h
>> @@ -90,6 +90,7 @@ struct perf_sample {
>>       u64 period;
>>       u32 cpu;
>>       u32 raw_size;
>> +     u64 weight;
>>       void *raw_data;
>>       struct ip_callchain *callchain;
>>       struct branch_stack *branch_stack;
>> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
>> index 1b16dd1..4374c07 100644
>> --- a/tools/perf/util/evsel.c
>> +++ b/tools/perf/util/evsel.c
>> @@ -1058,6 +1058,11 @@ int perf_evsel__parse_sample(struct perf_evsel *evsel, union perf_event *event,
>>               }
>>       }
>>
>> +     if (type & PERF_SAMPLE_WEIGHT) {
>> +             data->weight= *array;
>> +             array++;
>> +     }
>> +
>
> this bit should be placed right after PERF_SAMPLE_PERIOD (where
> you placed it in kernel path), otherwise you get wrong data
>

Thought some more about this. I think this new WEIGHT sample type is
in the wrong place in Andi's patch.
It's new, it should be put at the end of perf_output_sample(). That's
necessary to ensure older versions
of perf (without the knowledge about WEIGHT) can still decode
PERF_SAMPLE_READ in case
PERF_SAMPLE_WEIGHT is present in the perf.data file.

I will update his patch to reflect this change.
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