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

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Date: Mon, 22 Apr 2024 08:42:17 -0700
From: Ian Rogers <irogers@...gle.com>
To: Veronika Molnarova <vmolnaro@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] perf test: Be more tolerant of metricgroup failures

On Mon, Apr 22, 2024 at 4:51 AM Veronika Molnarova <vmolnaro@...hatcom> wrote:
>
> Hi Ian,
>
> On Wed, Apr 3, 2024 at 6:48 PM Ian Rogers <irogers@...gle.com> 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@...gle.com>
>> ---
>>  .../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
>