Re: [PATCH 2/9] perf report: Remove the first overflow check for branch counters

Namhyung Kim
2024-08-02T20:26:12Z

On Wed, Jul 3, 2024 at 1:03 PM <kan.liang@linux.intel.com> wrote:
>
> From: Kan Liang <kan.liang@linux.intel.com>
>
> A false overflow warning is triggered if a sample doesn't have any LBRs
> recorded and the branch counters feature is enabled.
>
> The current code does OVERFLOW_CHECK_u64() at the very beginning when
> reading the information of branch counters. It assumes that there is at
> least one LBR in the PEBS record. But it is a valid case that 0 LBR is
> recorded especially in a high context switch.
>
> Remove the OVERFLOW_CHECK_u64(). The later OVERFLOW_CHECK() should be
> good enough to check the overflow when reading the information of the
> branch counters.
>
> Fixes: 9fbb4b02302b ("perf tools: Add branch counter knob")
> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung

> ---
> tools/perf/util/evsel.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index bc603193c477..a5dd031c9080 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2810,8 +2810,6 @@ int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
> array = (void *)array + sz;
>
> if (evsel__has_branch_counters(evsel)) {
> - OVERFLOW_CHECK_u64(array);
> -
> data->branch_stack_cntr = (u64 *)array;
> sz = data->branch_stack->nr * sizeof(u64);
>
> --
> 2.38.1
>