Re: [PATCH 2/2 v3] perf test: Change event in perf test 114 perf record test subtest test_leader_sampling

[Liang, Kan]

On 2025-02-03 10:42 p.m., Namhyung Kim wrote:
> Add Kan and Dapeng to CC.
> 
> Thanks,
> Namhyung
> 
> 
> On Fri, Jan 31, 2025 at 11:27:56AM +0100, Thomas Richter wrote:
>> On s390 the event instructions can not be used for recording.
>> This event is only supported by perf stat.
>>
>> Change the event from instructions to cycles in
>> subtest test_leader_sampling.
>>
>> Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>
>> Suggested-by: James Clark <james.clark@xxxxxxxxxx>
>> Reviewed-by: James Clark <james.clark@xxxxxxxxxx>
>> ---
>>  tools/perf/tests/shell/record.sh | 10 +++++-----
>>  1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
>> index fe2d05bcbb1f..ba8d873d3ca7 100755
>> --- a/tools/perf/tests/shell/record.sh
>> +++ b/tools/perf/tests/shell/record.sh
>> @@ -231,7 +231,7 @@ test_cgroup() {
>>  
>>  test_leader_sampling() {
>>    echo "Basic leader sampling test"
>> -  if ! perf record -o "${perfdata}" -e "{instructions,instructions}:Su" -- \
>> +  if ! perf record -o "${perfdata}" -e "{cycles,cycles}:Su" -- \
>>      perf test -w brstack 2> /dev/null


As a non-precise test, using cycles instead should be fine. But we
should never use it for precise test, e.g., with p. Because cycles is a
non-precise event. It would not surprise me if there is a skid when
reading two cycles events at the point when the event overflow occurs.

Reviewed-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>

Thanks,
Kan

>>    then
>>      echo "Leader sampling [Failed record]"
>> @@ -243,15 +243,15 @@ test_leader_sampling() {
>>    while IFS= read -r line
>>    do
>>      # Check if the two instruction counts are equal in each record
>> -    instructions=$(echo $line | awk '{for(i=1;i<=NF;i++) if($i=="instructions:") print $(i-1)}')
>> -    if [ $(($index%2)) -ne 0 ] && [ ${instructions}x != ${prev_instructions}x ]
>> +    cycles=$(echo $line | awk '{for(i=1;i<=NF;i++) if($i=="cycles:") print $(i-1)}')
>> +    if [ $(($index%2)) -ne 0 ] && [ ${cycles}x != ${prev_cycles}x ]
>>      then
>> -      echo "Leader sampling [Failed inconsistent instructions count]"
>> +      echo "Leader sampling [Failed inconsistent cycles count]"
>>        err=1
>>        return
>>      fi
>>      index=$(($index+1))
>> -    prev_instructions=$instructions
>> +    prev_cycles=$cycles
>>    done < $script_output
>>    echo "Basic leader sampling test [Success]"
>>  }
>> -- 
>> 2.48.1
>>