Re: problem with 'perf script -F weight'

[Jiri Olsa <jolsa@redhat.com>]

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

thanks,
jirka

> +	}
> 
>  	if (PRINT_FIELD(IP)) {
>  		struct callchain_cursor *cursor = NULL;
> -- 
> 2.7.4
> 
> Thanks,
> Kan
>