linux-kernel - Re: [PATCH v1] perf test: Avoid hard coded metrics in stat std output test

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Date: Fri, 19 Apr 2024 13:39:14 -0400
From: "Liang, Kan" <kan.liang@...ux.intel.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>,
 Yicong Yang <yangyicong@...ilicon.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: Avoid hard coded metrics in stat std output
 test



On 2024-04-19 11:23 a.m., Ian Rogers wrote:
> On Fri, Apr 19, 2024 at 8:09 AM Liang, Kan <kan.liang@...ux.intel.com> wrote:
>>
>>
>>
>> On 2024-04-19 10:40 a.m., Ian Rogers wrote:
>>> On Fri, Apr 19, 2024 at 6:54 AM Liang, Kan <kan.liang@...ux.intel.com> wrote:
>>>>
>>>>
>>>>
>>>> On 2024-04-17 2:32 p.m., Ian Rogers wrote:
>>>>> Hard coded metric names fail on ARM testing.
>>>>>
>>>>> Signed-off-by: Ian Rogers <irogers@...gle.com>
>>>>> ---
>>>>>  tools/perf/tests/shell/stat+std_output.sh | 2 +-
>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/tools/perf/tests/shell/stat+std_output.sh b/tools/perf/tests/shell/stat+std_output.sh
>>>>> index cbf2894b2c84..845f83213855 100755
>>>>> --- a/tools/perf/tests/shell/stat+std_output.sh
>>>>> +++ b/tools/perf/tests/shell/stat+std_output.sh
>>>>> @@ -13,7 +13,7 @@ stat_output=$(mktemp /tmp/__perf_test.stat_outputstd.XXXXX)
>>>>>
>>>>>  event_name=(cpu-clock task-clock context-switches cpu-migrations page-faults stalled-cycles-frontend stalled-cycles-backend cycles instructions branches branch-misses)
>>>>>  event_metric=("CPUs utilized" "CPUs utilized" "/sec" "/sec" "/sec" "frontend cycles idle" "backend cycles idle" "GHz" "insn per cycle" "/sec" "of all branches")
>>>>> -skip_metric=("stalled cycles per insn" "tma_" "retiring" "frontend_bound" "bad_speculation" "backend_bound")
>>>>> +skip_metric=($(perf list --raw Default 2> /dev/null))
>>>>
>>>>
>>>> The "perf list --raw Default" only gives the topdown metrics.
>>>> The "stalled cycles per insn" is not covered.
>>>> The check should skip the line of "stalled cycles per insn" as well.
>>>>
>>>>      3,856,436,920 stalled-cycles-frontend   #   74.09% frontend cycles idle
>>>>      1,600,790,871 stalled-cycles-backend    #   30.75% backend  cycles idle
>>>>      2,603,501,247 instructions              #    0.50  insns per cycle
>>>>                                              #    1.48  stalled cycles
>>>> per insn
>>>>        484,357,498 branches                  #  283.455 M/sec
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/builtin-stat.c#n24
>>>>
>>>> The newer Intel CPU doesn't have the stalled-cycles-* events. But it
>>>> seems power and older x86 CPU have the events.
>>>
>>> Oh, sigh. This test should really ignore lines like that. How much do
>>> we care about these metrics? The RISC-V event parsing change:
>>> https://lore.kernel.org/lkml/20240416061533.921723-1-irogers@google.com/
>>> means that legacy hardware events will be uncommon and we need to
>>> adapt the hard coded metrics in stat-shadow.c to json ones. Once they
>>> are json metrics they will be in Default.
>>
>> It seems except the newer Intel CPU, all the other ARCHs support the two
>> stalled-cycles-* events and the metric. For Intel, there are Topdown
>> metrics. But it seems an important metrics for the other ARCHs.
>>
>> RISC-V
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/perf/riscv_pmu_sbi.c#n134
>> Power
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/perf/power9-pmu.c#n279
>> Arm
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/perf/arm_pmuv3.c#n53
>>
>> So almost all json files have to be updated. I'm not sure if it's a
>> practical way to fix the issue.
> 
> So I'd very much like to get rid of the hard coded metrics:
>  - they don't use or respect event groups,
>  - their ad hoc printing can introduce extra metric results
> unexpectedly in output,
>  - they fall outside of optimizations like Weilin's metric event grouping work.
> I'm hoping the python json generation of metrics makes their removal practical:
> https://lore.kernel.org/lkml/20240314055919.1979781-1-irogers@google.com/
>

It seems I wasn't listed in the Cc list, so it's missed in my main
inbox. But I was added to the same series for the Arm and AMD. :)

I will take a look at the patches.

> That's a lot to get landed for this fix:
>  - 40+ patches for python based json generation.
>  - 10+ patches for parse events changes.
> So I think a version that hard codes ignoring the hard coded metrics
> is in order.

Sounds good to me.

Thanks,
Kan