Re: problem with 'perf script -F weight'

["Liang, Kan" <kan.liang@linux.intel.com>]

On 9/29/2021 2:08 AM, Jiri Olsa wrote:
> On Tue, Sep 28, 2021 at 05:35:51PM -0400, Liang, Kan wrote:
>>
>>
>> On 9/28/2021 3:20 PM, Jiri Olsa wrote:
>>> Joe reported broken -F weight in perf script with (on x86):
>>>
>>>     # ./perf mem record
>>>     # ./perf script -F weight
>>>     Samples for 'dummy:HG' event do not have WEIGHT attribute set. Cannot print 'weight' field.
>>>
>>> the problem seems to be introduced with the WEIGHT_STRUCT change:
>>>     ea8d0ed6eae3 perf tools: Support PERF_SAMPLE_WEIGHT_STRUCT
>>>
>>> which enables WEIGHT_STRUCT sample_type on x86 instead of WEIGHT,
>>> and leaves 'perf script -F weight' in the dark
>>
>> Right, I missed the support for the perf script. Because the default perf
>> script worked. It didn't ring the bell. :(
>>
>>>
>>> I'm not sure what the fix should look like.. should we allow user
>>> to use just 'WEIGHT' sample type? or is there a way to get original
>>> weight from 'WEIGHT_STRUCT' data, so we could fix just perf script?
>>
>> Just fix the perf script is enough.
>> Could you please try the below patch?
>>
>> (I probably need to split the patch into two patches, since it fixed two
>> issues, one is this error, the other is to print the instruction latency.
>> Anyway, let's try it first.)
>>
>>  From 99443f49a6236ef6e3bea3930792967a7863f753 Mon Sep 17 00:00:00 2001
>> From: Kan Liang <kan.liang@linux.intel.com>
>> Date: Tue, 28 Sep 2021 13:57:18 -0700
>> Subject: [PATCH] perf script: Fix PERF_SAMPLE_WEIGHT_STRUCT support
>>
>> -F weight in perf script is broken.
>>
>>    # ./perf mem record
>>    # ./perf script -F weight
>>    Samples for 'dummy:HG' event do not have WEIGHT attribute set. Cannot
>> print 'weight' field.
>>
>> The sample type, PERF_SAMPLE_WEIGHT_STRUCT, is an alternative of the
>> PERF_SAMPLE_WEIGHT sample type. They share the same space, weight. The
>> lower 32 bits are exactly the same for both sample type. The higher 32
>> bits may be different for different architecture. For a new kernel on
>> x86, the PERF_SAMPLE_WEIGHT_STRUCT is used. For an old kernel or other
>> ARCHs, the PERF_SAMPLE_WEIGHT is used.
>>
>> With -F weight, current perf script will check the input string "weight"
>> with the corresponding sample type. However, the commit ID ea8d0ed6eae3
>> ("perf tools: Support PERF_SAMPLE_WEIGHT_STRUCT") didn't update the
>> sample type for perf script. The check fails with a new kernel on x86.
>>
>> Use PERF_SAMPLE_WEIGHT_TYPE, which supports both sample types, to
>> replace PERF_SAMPLE_WEIGHT.
>>
>> Also, print the instruction latency for PERF_SAMPLE_WEIGHT_STRUCT type.
>>
>> Reported-by: Joe Mario <jmario@redhat.com>
>> Fixes: ea8d0ed6eae3 ("perf tools: Support PERF_SAMPLE_WEIGHT_STRUCT")
>> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
>> ---
>>   tools/perf/builtin-script.c | 7 +++++--
>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
>> index 6211d0b..fd73bbc 100644
>> --- a/tools/perf/builtin-script.c
>> +++ b/tools/perf/builtin-script.c
>> @@ -459,7 +459,7 @@ static int evsel__check_attr(struct evsel *evsel, struct
>> perf_session *session)
>>   		return -EINVAL;
>>
>>   	if (PRINT_FIELD(WEIGHT) &&
>> -	    evsel__check_stype(evsel, PERF_SAMPLE_WEIGHT, "WEIGHT",
>> PERF_OUTPUT_WEIGHT))
>> +	    evsel__check_stype(evsel, PERF_SAMPLE_WEIGHT_TYPE, "WEIGHT",
>> PERF_OUTPUT_WEIGHT))
>>   		return -EINVAL;
>>
>>   	if (PRINT_FIELD(SYM) &&
>> @@ -2036,8 +2036,11 @@ static void process_event(struct perf_script *script,
>>   	if (PRINT_FIELD(DATA_SRC))
>>   		data_src__fprintf(sample->data_src, fp);
>>
>> -	if (PRINT_FIELD(WEIGHT))
>> +	if (PRINT_FIELD(WEIGHT)) {
>>   		fprintf(fp, "%16" PRIu64, sample->weight);
>> +		if (attr->sample_type & PERF_SAMPLE_WEIGHT_STRUCT)
>> +			fprintf(fp, ",0x%" PRIx16, sample->ins_lat);
> 
> this will add extra number to weight.. should we add separate column
> for that -F 'insn-lat' ? users expect just single value for -F weight
> 

Sure, I will send out a patch set to LKML for review shortly.

Thanks,
Kan