linux-kernel - Re: [PATCH v7 0/7] Hwmon PMUs

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Message-ID: <Zy5nKxruRDahwPue@google.com>
Date: Fri, 8 Nov 2024 11:31:55 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...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>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Ravi Bangoria <ravi.bangoria@....com>,
	Weilin Wang <weilin.wang@...el.com>,
	Yoshihiro Furudera <fj5100bi@...itsu.com>,
	James Clark <james.clark@...aro.org>,
	Athira Jajeev <atrajeev@...ux.vnet.ibm.com>,
	Howard Chu <howardchu95@...il.com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Changbin Du <changbin.du@...wei.com>, Ze Gao <zegao2021@...il.com>,
	Junhao He <hejunhao3@...wei.com>, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v7 0/7] Hwmon PMUs

On Fri, Nov 08, 2024 at 09:49:29AM -0800, Ian Rogers wrote:
> Following the convention of the tool PMU, create a hwmon PMU that
> exposes hwmon data for reading. For example, the following shows
> reading the CPU temperature and 2 fan speeds alongside the uncore
> frequency:
> ```
> $ perf stat -e temp_cpu,fan1,hwmon_thinkpad/fan2/,tool/num_cpus_online/ -M UNCORE_FREQ -I 1000
>      1.001153138              52.00 'C   temp_cpu
>      1.001153138              2,588 rpm  fan1
>      1.001153138              2,482 rpm  hwmon_thinkpad/fan2/
>      1.001153138                  8      tool/num_cpus_online/
>      1.001153138      1,077,101,397      UNC_CLOCK.SOCKET                 #     1.08 UNCORE_FREQ
>      1.001153138      1,012,773,595      duration_time
> ...
> ```
> 
> Additional data on the hwmon events is in perf list:
> ```
> $ perf list
> ...
> hwmon:
> ...
>   temp_core_0 OR temp2
>        [Temperature in unit coretemp named Core 0. crit=100'C,max=100'C crit_alarm=0'C. Unit:
>         hwmon_coretemp]
> ...
> ```
> 
> v7: Try to address feedback from Namhyung wrt size/comprehensibility
>     of the hwmon PMU patch. To better explain the config encoding put
>     the parser into a patch ahead of the PMU patch and add a unit
>     test. This shows how a hwmon filename can be moved back-and-forth
>     with a config value as a single patch (two with the test). The
>     hwmon PMU patch is then putting the wrapping around that for the
>     pmus', parse_event's and evsel reading's benefit.

Thanks for doing this!
Namhyung

>     
>     The alternate approach of not caring about the mapping, name to
>     config value, and using the evsel->name wasn't followed. In the
>     tool PMU it was made so we can go back-and-forth between event
>     names and a type+config, this removed the tool enum value from the
>     evsel as now tool events were more 1st class and evsel should
>     really just be a wrapper on a perf_event_attr. Using the
>     evsel->name wasn't doing that and so the approach of mapping
>     filenames and configs, as better highlighted in this series was
>     pursued.
> 
>     It is expected future PMUs won't be able to cleanly map fixed
>     strings to config values, in those cases tables would be
>     necessary. Making a hwmon PMU do this and then removing it to
>     follow the parsing/mapping done in patch 2 here, would have been a
>     lot of additional work which then would be removed.
> 
> v6: Add string.h #include for issue reported by kernel test robot.
> v5: Fix asan issue in parse_hwmon_filename caught by a TMA metric.
> v4: Drop merged patches 1 to 10. Separate adding the hwmon_pmu from
>     the update to perf_pmu to use it. Try to make source of literal
>     strings clearer via named #defines. Fix a number of GCC warnings.
> v3: Rebase, add Namhyung's acked-by to patches 1 to 10.
> v2: Address Namhyung's review feedback. Rebase dropping 4 patches
>     applied by Arnaldo, fix build breakage reported by Arnaldo.
> 
> Ian Rogers (7):
>   tools api io: Ensure line_len_out is always initialized
>   perf hwmon_pmu: Add hwmon filename parser
>   perf test: Add hwmon filename parser test
>   perf hwmon_pmu: Add a tool PMU exposing events from hwmon in sysfs
>   perf pmu: Add calls enabling the hwmon_pmu
>   perf test: Add hwmon "PMU" test
>   perf docs: Document tool and hwmon events
> 
>  tools/lib/api/io.h                     |   1 +
>  tools/perf/Documentation/perf-list.txt |  15 +
>  tools/perf/tests/Build                 |   1 +
>  tools/perf/tests/builtin-test.c        |   1 +
>  tools/perf/tests/hwmon_pmu.c           | 340 ++++++++++
>  tools/perf/tests/tests.h               |   1 +
>  tools/perf/util/Build                  |   1 +
>  tools/perf/util/evsel.c                |   9 +
>  tools/perf/util/hwmon_pmu.c            | 825 +++++++++++++++++++++++++
>  tools/perf/util/hwmon_pmu.h            | 156 +++++
>  tools/perf/util/pmu.c                  |  20 +
>  tools/perf/util/pmu.h                  |   2 +
>  tools/perf/util/pmus.c                 |   9 +
>  tools/perf/util/pmus.h                 |   3 +
>  14 files changed, 1384 insertions(+)
>  create mode 100644 tools/perf/tests/hwmon_pmu.c
>  create mode 100644 tools/perf/util/hwmon_pmu.c
>  create mode 100644 tools/perf/util/hwmon_pmu.h
> 
> -- 
> 2.47.0.277.g8800431eea-goog
>