Re: [PATCH v1] perf test: Be more tolerant of metricgroup failures

[Ian Rogers]

On Mon, Apr 22, 2024 at 4:51 AM Veronika Molnarova <vmolnaro@redhatcom> wrote:
>
> Hi Ian,
>
> On Wed, Apr 3, 2024 at 6:48 PM Ian Rogers <irogers@xxxxxxxxxx> wrote:
>>
>> Previously "set -e" meant any non-zero exit code from perf stat would
>> cause a test failure. As a non-zero exit happens when there aren't
>> sufficient permissions, check for this case and make the exit code
>> 2/skip for it.
>>
>> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
>> ---
>>  .../perf/tests/shell/stat_all_metricgroups.sh | 28 +++++++++++++++----
>>  1 file changed, 22 insertions(+), 6 deletions(-)
>>
>> diff --git a/tools/perf/tests/shell/stat_all_metricgroups.sh b/tools/perf/tests/shell/stat_all_metricgroups.sh
>> index 55ef9c9ded2d..d6db192b9f18 100755
>> --- a/tools/perf/tests/shell/stat_all_metricgroups.sh
>> +++ b/tools/perf/tests/shell/stat_all_metricgroups.sh
>> @@ -1,9 +1,7 @@
>> -#!/bin/sh
>> +#!/bin/bash
>>  # perf all metricgroups test
>>  # SPDX-License-Identifier: GPL-2.0
>>
>> -set -e
>> -
>>  ParanoidAndNotRoot()
>>  {
>>    [ "$(id -u)" != 0 ] && [ "$(cat /proc/sys/kernel/perf_event_paranoid)" -gt $1 ]
>> @@ -14,11 +12,29 @@ if ParanoidAndNotRoot 0
>>  then
>>    system_wide_flag=""
>>  fi
>> -
>> +err=0
>>  for m in $(perf list --raw-dump metricgroups)
>>  do
>>    echo "Testing $m"
>> -  perf stat -M "$m" $system_wide_flag sleep 0.01
>> +  result=$(perf stat -M "$m" $system_wide_flag sleep 0.01 2>&1)
>> +  result_err=$?
>> +  if [[ $result_err -gt 0 ]]
>> +  then
>> +    if [[ "$result" =~ \
>> +          "Access to performance monitoring and observability operations is limited" ]]
>> +    then
>> +      echo "Permission failure"
>> +      echo $result
>> +      if [[ $err -eq 0 ]]
>> +      then
>> +        err=2 # Skip
>> +      fi
>> +    else
>> +      echo "Metric group $m failed"
>> +      echo $result
>> +      err=1 # Fail
>> +    fi
>> +  fi
>>  done
>>
>> -exit 0
>> +exit $err
>> --
>> 2.44.0.478.gd926399ef9-goog
>>
>>
>
> The patch looks good and thanks for taking care of it.
>
> Just wanted to check what is the desired outcome for metric groups
> with events that are invalid in per-thread mode causing the test to fail.
>
> ```
> $ ./stat_all_metricgroups.sh
> Testing smi
> Metric group smi failed
> Error: Invalid event (msr/smi/u) in per-thread mode, enable system wide with '-a'.
> ```
>
> Wouldn't it be better if in these cases the test would result in skip instead of fail?

Hi Veronika,

I agree that fail isn't best here. I'm wondering:

 - why doesn't msr/smi/ support per-thread mode? Can't we save/restore
the count on a context switch? The implementation is here:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/arch/x86/events/msr.c?h=perf-tools-next#n234
There's clearly something going on as pperf appears to have other restrictions:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/arch/x86/events/msr.c?h=perf-tools-next#n115
I'm wondering if aggregation is working right if these counters are
more than per hyperthread (I'm guessing why the restrictions exist).

 - the tool error message is doing pretty good. In the test I guess we
can spot the per-thread error and turn the fail to a skip. It's a
shame to bucket things as skip, but it seems easier than listing
metrics in the test or spotting particular events.

I can do a v2 to add this.

Thanks,
Ian

> Thanks,
> Veronika
>