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

[PATCH] 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>
---
 .../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..72c1ac32c785
--- /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:ppp; 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] perf test: Add a perf event fallback test

[Namhyung Kim]

On Tue, Nov 11, 2025 at 02:42:46PM -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
> 
> 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>
> ---
>  .../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..72c1ac32c785
> --- /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:ppp; then

I think you need 'P' instead of 'ppp' for automatic precision.

Thanks,
Namhyung


> +		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] perf test: Add a perf event fallback test

[Chen, Zide]

On 11/11/2025 5:06 PM, Namhyung Kim wrote:
> On Tue, Nov 11, 2025 at 02:42:46PM -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
>>
>> 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>
>> ---
>>  .../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..72c1ac32c785
>> --- /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:ppp; then
> 
> I think you need 'P' instead of 'ppp' for automatic precision.

Yes, it's better with "-e cycles:P" to explicitly set evsel.precise_max
to 1.

> Thanks,
> Namhyung
> 
> 
>> +		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
>>