Re: [PATCH v8 06/10] perf evsel: Assemble offcpu samples

[Namhyung Kim <namhyung@kernel.org>]

On Tue, Nov 12, 2024 at 04:28:14PM -0800, Howard Chu wrote:
> Use the data in bpf-output samples, to assemble offcpu samples.

Now it requires PERF_SAMPLE_RAW for the off-cpu events.  But it's not
compatible with the earlier format.  Can you please make sure if it can
read old off-cpu data recorded before your change?  Maybe you need to
check or add new info (like in a header.misc field) to distinguish them.

Thanks,
Namhyung

> 
> Suggested-by: Namhyung Kim <namhyung@kernel.org>
> Reviewed-by: Ian Rogers <irogers@google.com>
> Signed-off-by: Howard Chu <howardchu95@gmail.com>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: James Clark <james.clark@linaro.org>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Kan Liang <kan.liang@linux.intel.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Link: https://lore.kernel.org/r/20241108204137.2444151-7-howardchu95@gmail.com
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
>  tools/perf/util/evsel.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 8d0308f62484..654fb5196ecf 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2792,6 +2792,35 @@ static inline bool evsel__has_branch_counters(const struct evsel *evsel)
>  	return false;
>  }
>  
> +static int __set_offcpu_sample(struct perf_sample *data)
> +{
> +	u64 *array = data->raw_data;
> +	u32 max_size = data->raw_size, *p32;
> +	const void *endp = (void *)array + max_size;
> +
> +	if (array == NULL)
> +		return -EFAULT;
> +
> +	OVERFLOW_CHECK_u64(array);
> +	p32 = (void *)array++;
> +	data->pid = p32[0];
> +	data->tid = p32[1];
> +
> +	OVERFLOW_CHECK_u64(array);
> +	data->period = *array++;
> +
> +	OVERFLOW_CHECK_u64(array);
> +	data->callchain = (struct ip_callchain *)array++;
> +	OVERFLOW_CHECK(array, data->callchain->nr * sizeof(u64), max_size);
> +	data->ip = data->callchain->ips[1];
> +	array += data->callchain->nr;
> +
> +	OVERFLOW_CHECK_u64(array);
> +	data->cgroup = *array;
> +
> +	return 0;
> +}
> +
>  int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
>  			struct perf_sample *data)
>  {
> @@ -3143,6 +3172,9 @@ int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
>  		array = (void *)array + sz;
>  	}
>  
> +	if (evsel__is_offcpu_event(evsel))
> +		return __set_offcpu_sample(data);
> +
>  	return 0;
>  }
>  
> -- 
> 2.43.0
>