linux-kernel - Re: [PATCH] perf report: Set PERF_SAMPLE_DATA

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Date:   Wed, 13 Apr 2022 09:15:40 +0100
From:   German Gomez <german.gomez@....com>
To:     Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf report: Set PERF_SAMPLE_DATA_SRC bit for Arm SPE
 event

Hi Leo,

On 13/04/2022 08:51, Leo Yan wrote:
> Since commit bb30acae4c4d ("perf report: Bail out --mem-mode if mem info
> is not available") "perf mem report" and "perf report --mem-mode"
> don't report result if the PERF_SAMPLE_DATA_SRC bit is missed in sample
> type.
>
> The commit ffab48705205 ("perf: arm-spe: Fix perf report --mem-mode")
> partially fixes the issue.  It adds PERF_SAMPLE_DATA_SRC bit for Arm SPE
> event, this allows the perf data file generated by kernel v5.18-rc1 or
> later version can be reported properly.
>
> On the other hand, perf tool still fails to be backward compatibility
> for a data file recorded by an older version's perf which contains Arm
> SPE trace data.  This patch is a workaround in reporting phase, when
> detects ARM SPE PMU event and without PERF_SAMPLE_DATA_SRC bit, it will
> force to set the bit in the sample type and give a warning info.
>
> Fixes: bb30acae4c4d ("perf report: Bail out --mem-mode if mem info is not available")
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  tools/perf/builtin-report.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
> index 1ad75c7ba074..f26dd14eb852 100644
> --- a/tools/perf/builtin-report.c
> +++ b/tools/perf/builtin-report.c
> @@ -353,6 +353,7 @@ static int report__setup_sample_type(struct report *rep)
>  	struct perf_session *session = rep->session;
>  	u64 sample_type = evlist__combined_sample_type(session->evlist);
>  	bool is_pipe = perf_data__is_pipe(session->data);
> +	struct evsel *evsel;
>  
>  	if (session->itrace_synth_opts->callchain ||
>  	    session->itrace_synth_opts->add_callchain ||
> @@ -407,6 +408,21 @@ static int report__setup_sample_type(struct report *rep)
>  	}
>  
>  	if (sort__mode == SORT_MODE__MEMORY) {
> +		/*
> +		 * FIXUP: prior to kernel 5.18, Arm SPE missed to set
> +		 * PERF_SAMPLE_DATA_SRC bit in sample type.  For backward
> +		 * compatibility, set the bit if it's an old perf data file.
> +		 */
> +		evlist__for_each_entry(session->evlist, evsel) {
> +			if (strstr(evsel->name, "arm_spe_") &&

This didn't work for me when the file recorded "-e arm_spe//" instead of
"-e arm_spe_0//". Could you remove the trailing _? With that:

Tested-by: German Gomez <german.gomez@....com>

> +				!(sample_type & PERF_SAMPLE_DATA_SRC)) {
> +				ui__warning("PERF_SAMPLE_DATA_SRC bit is not set "
> +					    "for Arm SPE event.\n");
> +				evsel->core.attr.sample_type |= PERF_SAMPLE_DATA_SRC;
> +				sample_type |= PERF_SAMPLE_DATA_SRC;
> +			}
> +		}
> +
>  		if (!is_pipe && !(sample_type & PERF_SAMPLE_DATA_SRC)) {
>  			ui__error("Selected --mem-mode but no mem data. "
>  				  "Did you call perf record without -d?\n");