linux-kernel - Re: [PATCH v3 35/46] perf parse-events: Support hardware events as terms

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Date:   Tue, 2 May 2023 16:25:45 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     Ian Rogers <irogers@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ahmad Yasin <ahmad.yasin@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Perry Taylor <perry.taylor@...el.com>,
        Samantha Alt <samantha.alt@...el.com>,
        Caleb Biggers <caleb.biggers@...el.com>,
        Weilin Wang <weilin.wang@...el.com>,
        Edward Baker <edward.baker@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Florian Fischer <florian.fischer@...q.space>,
        Rob Herring <robh@...nel.org>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        John Garry <john.g.garry@...cle.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Sumanth Korikkar <sumanthk@...ux.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Leo Yan <leo.yan@...aro.org>,
        Yang Jihong <yangjihong1@...wei.com>,
        James Clark <james.clark@....com>,
        Suzuki Poulouse <suzuki.poulose@....com>,
        Kang Minchul <tegongkang@...il.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [PATCH v3 35/46] perf parse-events: Support hardware events as
 terms

> @@ -269,6 +279,16 @@ percore			{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_PERCORE); }
>  aux-output		{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_AUX_OUTPUT); }
>  aux-sample-size		{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE); }
>  metric-id		{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_METRIC_ID); }
> +cpu-cycles|cycles				{ return hw_term(yyscanner, PERF_COUNT_HW_CPU_CYCLES); }
> +stalled-cycles-frontend|idle-cycles-frontend	{ return hw_term(yyscanner, PERF_COUNT_HW_STALLED_CYCLES_FRONTEND); }
> +stalled-cycles-backend|idle-cycles-backend	{ return hw_term(yyscanner, PERF_COUNT_HW_STALLED_CYCLES_BACKEND); }
> +instructions					{ return hw_term(yyscanner, PERF_COUNT_HW_INSTRUCTIONS); }
> +cache-references				{ return hw_term(yyscanner, PERF_COUNT_HW_CACHE_REFERENCES); }
> +cache-misses					{ return hw_term(yyscanner, PERF_COUNT_HW_CACHE_MISSES); }
> +branch-instructions|branches			{ return hw_term(yyscanner, PERF_COUNT_HW_BRANCH_INSTRUCTIONS); }
> +branch-misses					{ return hw_term(yyscanner, PERF_COUNT_HW_BRANCH_MISSES); }
> +bus-cycles					{ return hw_term(yyscanner, PERF_COUNT_HW_BUS_CYCLES); }
> +ref-cycles					{ return hw_term(yyscanner, PERF_COUNT_HW_REF_CPU_CYCLES); }

These are generic terms and thus can be added to _any_ pmus. Ex:

Before:
```
$ sudo ./perf stat -e amd_l3/cycles/ -C 0 -- sleep 1
event syntax error: 'amd_l3/cycles/'
                            \___ unknown term 'cycles' for pmu 'amd_l3'
```

After:
```
$ sudo ./perf stat -e amd_l3/cycles/ -C 0 -vv -- sleep 1
Control descriptor is not initialized
------------------------------------------------------------
perf_event_attr:
  size                             136
  config                           0xb00000000
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid -1  cpu 0  group_fd -1  flags 0x8
sys_perf_event_open failed, error -2
Warning:
amd_l3/cycles/ event is not supported by the kernel.
failed to read counter amd_l3/cycles/

 Performance counter stats for 'CPU(s) 0':

   <not supported>      amd_l3/cycles/

       1.059391819 seconds time elapsed
```

Here `type=0` which means perf is trying to open event on HW pmu instead
of amd_l3//. `config` is 0xb00000000 where 0xb is amd_l3 pmu type:

$ cat /sys/bus/event_source/devices/amd_l3/type
11

Not sure if this is expected behavior.