[PATCH V2] perf test: Add a perf event fallback test

[PATCH V2] perf test: Add a perf event fallback test

[Zide Chen]

This adds test cases to verify the precise ip fallback logic:

- If the system supports precise ip, for an event given with the maximum
  precision level, it should be able to decrease precise_ip to find a
  supported level.
- The same fallback behavior should also work in more complex scenarios,
  such as event groups or when PEBS is involved

Additional fallback tests, such as those covering missing feature cases,
can be added in the future.

Suggested-by: Ian Rogers <irogers@google.com>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
---
v2:
- Incorporated Namhyung's suggestion to change cycles:ppp to cycles:P

 .../tests/shell/test_event_open_fallback.sh   | 86 +++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100755 tools/perf/tests/shell/test_event_open_fallback.sh

diff --git a/tools/perf/tests/shell/test_event_open_fallback.sh b/tools/perf/tests/shell/test_event_open_fallback.sh
new file mode 100755
index 000000000000..9c411153c01b
--- /dev/null
+++ b/tools/perf/tests/shell/test_event_open_fallback.sh
@@ -0,0 +1,86 @@
+#!/bin/bash
+# Perf event open fallback test
+# SPDX-License-Identifier: GPL-2.0
+
+skip_cnt=0
+ok_cnt=0
+err_cnt=0
+
+cleanup()
+{
+	rm -f perf.data
+	rm -f perf.data.old
+	trap - EXIT TERM INT
+}
+
+trap_cleanup()
+{
+	cleanup
+	exit 1
+}
+
+trap trap_cleanup EXIT TERM INT
+
+perf_record()
+{
+	perf record "$@" -- true 1>/dev/null 2>&1
+}
+
+test_decrease_precise_ip()
+{
+	echo "Decrease precise ip test"
+
+	perf list pmu | grep -q 'cycles' || return 2
+
+	if ! perf_record -e cycles; then
+		return 2
+	fi
+
+	# It should reduce precision level down to 0 if needed.
+	if ! perf_record -e cycles:P; then
+		return 1
+	fi
+	return 0
+}
+
+test_decrease_precise_ip_complicated()
+{
+	echo "Decrease precise ip test (complicated case)"
+
+	perf list pmu | grep -q 'mem-loads-aux' || return 2
+
+	if ! perf_record -e '{cpu/mem-loads-aux/S,cpu/mem-loads/PS}'; then
+		return 1
+	fi
+	return 0
+}
+
+count_result()
+{
+	if [ "$1" -eq 2 ] ; then
+		skip_cnt=$((skip_cnt + 1))
+		return
+	fi
+	if [ "$1" -eq 0 ] ; then
+		ok_cnt=$((ok_cnt + 1))
+		return
+	fi
+	err_cnt=$((err_cnt + 1))
+}
+
+ret=0
+test_decrease_precise_ip		|| ret=$? ; count_result $ret ; ret=0
+test_decrease_precise_ip_complicated	|| ret=$? ; count_result $ret ; ret=0
+
+cleanup
+
+if [ ${err_cnt} -gt 0 ] ; then
+	exit 1
+fi
+
+if [ ${ok_cnt} -gt 0 ] ; then
+	exit 0
+fi
+
+# Skip
+exit 2
-- 
2.51.1

Re: [PATCH V2] perf test: Add a perf event fallback test

[Ian Rogers]

On Wed, Nov 12, 2025 at 8:55 AM Zide Chen <zide.chen@intel.com> wrote:
>
> This adds test cases to verify the precise ip fallback logic:
>
> - If the system supports precise ip, for an event given with the maximum
>   precision level, it should be able to decrease precise_ip to find a
>   supported level.
> - The same fallback behavior should also work in more complex scenarios,
>   such as event groups or when PEBS is involved
>
> Additional fallback tests, such as those covering missing feature cases,
> can be added in the future.
>
> Suggested-by: Ian Rogers <irogers@google.com>
> Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
> Signed-off-by: Zide Chen <zide.chen@intel.com>
> ---
> v2:
> - Incorporated Namhyung's suggestion to change cycles:ppp to cycles:P
>
>  .../tests/shell/test_event_open_fallback.sh   | 86 +++++++++++++++++++
>  1 file changed, 86 insertions(+)
>  create mode 100755 tools/perf/tests/shell/test_event_open_fallback.sh
>
> diff --git a/tools/perf/tests/shell/test_event_open_fallback.sh b/tools/perf/tests/shell/test_event_open_fallback.sh
> new file mode 100755
> index 000000000000..9c411153c01b
> --- /dev/null
> +++ b/tools/perf/tests/shell/test_event_open_fallback.sh
> @@ -0,0 +1,86 @@
> +#!/bin/bash
> +# Perf event open fallback test
> +# SPDX-License-Identifier: GPL-2.0
> +
> +skip_cnt=0
> +ok_cnt=0
> +err_cnt=0
> +
> +cleanup()
> +{
> +       rm -f perf.data
> +       rm -f perf.data.old
> +       trap - EXIT TERM INT
> +}
> +
> +trap_cleanup()
> +{
> +       cleanup
> +       exit 1
> +}
> +
> +trap trap_cleanup EXIT TERM INT
> +
> +perf_record()
> +{
> +       perf record "$@" -- true 1>/dev/null 2>&1
> +}
> +
> +test_decrease_precise_ip()
> +{
> +       echo "Decrease precise ip test"
> +
> +       perf list pmu | grep -q 'cycles' || return 2

nit: I don't think this test can ever fail.

Reviewed-by: Ian Rogers <irogers!@google.com>

Thanks,
Ian

> +
> +       if ! perf_record -e cycles; then
> +               return 2
> +       fi
> +
> +       # It should reduce precision level down to 0 if needed.
> +       if ! perf_record -e cycles:P; then
> +               return 1
> +       fi
> +       return 0
> +}
> +
> +test_decrease_precise_ip_complicated()
> +{
> +       echo "Decrease precise ip test (complicated case)"
> +
> +       perf list pmu | grep -q 'mem-loads-aux' || return 2
> +
> +       if ! perf_record -e '{cpu/mem-loads-aux/S,cpu/mem-loads/PS}'; then
> +               return 1
> +       fi
> +       return 0
> +}
> +
> +count_result()
> +{
> +       if [ "$1" -eq 2 ] ; then
> +               skip_cnt=$((skip_cnt + 1))
> +               return
> +       fi
> +       if [ "$1" -eq 0 ] ; then
> +               ok_cnt=$((ok_cnt + 1))
> +               return
> +       fi
> +       err_cnt=$((err_cnt + 1))
> +}
> +
> +ret=0
> +test_decrease_precise_ip               || ret=$? ; count_result $ret ; ret=0
> +test_decrease_precise_ip_complicated   || ret=$? ; count_result $ret ; ret=0
> +
> +cleanup
> +
> +if [ ${err_cnt} -gt 0 ] ; then
> +       exit 1
> +fi
> +
> +if [ ${ok_cnt} -gt 0 ] ; then
> +       exit 0
> +fi
> +
> +# Skip
> +exit 2
> --
> 2.51.1
>

Re: [PATCH V2] perf test: Add a perf event fallback test

[Namhyung Kim]

On Wed, 12 Nov 2025 08:48:23 -0800, Zide Chen wrote:
> This adds test cases to verify the precise ip fallback logic:
> 
> - If the system supports precise ip, for an event given with the maximum
>   precision level, it should be able to decrease precise_ip to find a
>   supported level.
> - The same fallback behavior should also work in more complex scenarios,
>   such as event groups or when PEBS is involved
> 
> [...]
Applied to perf-tools-next, thanks!

Best regards,
Namhyung