Re: [PATCH] perf test: Fix perf stat --bpf-counters on hybrid machines

[Ian Rogers]

On Tue, Mar 17, 2026 at 12:00 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> The test constantly fails on my Intel hybrid machine.  The issue was it
> has two events in the output even if I only gave it one event.
>
>   $ perf stat -e instructions -- perf test -w sqrtloop
>
>    Performance counter stats for 'perf test -w sqrtloop':
>
>          910,856,421      cpu_atom/instructions/                                                  (28.05%)
>       14,852,865,997      cpu_core/instructions/                                                  (96.79%)
>
>          1.014313341 seconds time elapsed
>
>          1.004114000 seconds user
>          0.008174000 seconds sys
>
> Let's modify the awk script to add the values for each line and print
> the total.  That way it should work on any platforms.

Thanks Namhyung! Sashiko noted a regression in the "not
counted/supported" logic caused by this change:
https://sashiko.dev/#/patchset/20260317070032.41934-1-namhyung%40kernel.org

Does this modification to the awk script prevent the detection of unsupported
or uncounted events?

When perf stat outputs strings like "<not counted>" or "<not supported>",
the first field is "<not". In awk arithmetic, adding a non-numeric string
evaluates to 0. The script will output 0 instead of the string.

The check_counts() function explicitly checks for these uncounted events:

  check_counts()
  {
    if [ "$1" = "<not" ]; then
    printf "[Skipped]\n"

Since awk now returns 0, it seems the test will bypass the skip logic,
proceed to compare the numbers (0 and 0), and falsely report success. Can the
awk script be adjusted to preserve non-numeric strings?

Thanks,
Ian

> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
>  tools/perf/tests/shell/stat_bpf_counters.sh | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/tests/shell/stat_bpf_counters.sh b/tools/perf/tests/shell/stat_bpf_counters.sh
> index f43e28a136d3c9bc..e04808ed871e3f08 100755
> --- a/tools/perf/tests/shell/stat_bpf_counters.sh
> +++ b/tools/perf/tests/shell/stat_bpf_counters.sh
> @@ -41,8 +41,10 @@ check_counts()
>  test_bpf_counters()
>  {
>         printf "Testing --bpf-counters "
> -       base_instructions=$(perf stat --no-big-num -e instructions -- $workload 2>&1 | awk '/instructions/ {print $1}')
> -       bpf_instructions=$(perf stat --no-big-num --bpf-counters -e instructions -- $workload  2>&1 | awk '/instructions/ {print $1}')
> +       base_instructions=$(perf stat --no-big-num -e instructions -- $workload 2>&1 | \
> +                               awk -v i=0 '/instructions/ {i += $1} END {print i}')
> +       bpf_instructions=$(perf stat --no-big-num --bpf-counters -e instructions -- $workload  2>&1 | \
> +                              awk -v i=0 '/instructions/ {i += $1} END {print i}')
>         check_counts $base_instructions $bpf_instructions
>         compare_number $base_instructions $bpf_instructions
>         echo "[Success]"
> @@ -52,8 +54,8 @@ test_bpf_modifier()
>  {
>         printf "Testing bpf event modifier "
>         stat_output=$(perf stat --no-big-num -e instructions/name=base_instructions/,instructions/name=bpf_instructions/b -- $workload 2>&1)
> -       base_instructions=$(echo "$stat_output"| awk '/base_instructions/ {print $1}')
> -       bpf_instructions=$(echo "$stat_output"| awk '/bpf_instructions/ {print $1}')
> +       base_instructions=$(echo "$stat_output"| awk -v i=0 '/base_instructions/ {i += $1} END {print i}')
> +       bpf_instructions=$(echo "$stat_output"| awk -v i=0 '/bpf_instructions/ {i += $1} END {print i}')
>         check_counts $base_instructions $bpf_instructions
>         compare_number $base_instructions $bpf_instructions
>         echo "[Success]"
> --
> 2.53.0
>