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

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Message-ID: <ce24cf21-422f-45fe-838e-1e36858b93be@redhat.com>
Date: Mon, 29 Apr 2024 16:49:06 +0200
From: Veronika Molnarova <vmolnaro@...hat.com>
To: Ian Rogers <irogers@...gle.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 4/22/24 17:42, Ian Rogers wrote:
> On Mon, Apr 22, 2024 at 4:51 AM Veronika Molnarova <vmolnaro@...hat.com> 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).
> 

Hi Ian,

I am not really sure why the msr/smi/ does not support per-thread mode but
I encountered multiple instances of events that aren't supported in per-thread
mode during testing. Generally, we cannot be sure that there won't be such event,
whether the msr/smi event should be able to handle per-thread mode is another
question.

Thanks for checking it out and would be great if you could add it to v2.

Thanks,
Veronika 

>  - 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
>>
>