Date: Wed, 22 May 2024 21:03:56 -0700
From: Ian Rogers <irogers@...gle.com>
To: weilin.wang@...el.com
Cc: Namhyung Kim <namhyung@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.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>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Perry Taylor <perry.taylor@...el.com>, Samantha Alt <samantha.alt@...el.com>, 
	Caleb Biggers <caleb.biggers@...el.com>
Subject: Re: [RFC PATCH v9 0/7] TPEBS counting mode support

On Tue, May 21, 2024 at 10:39 AM <weilin.wang@...el.com> wrote:
>
> From: Weilin Wang <weilin.wang@...el.com>
>
> Changes in v9:
> - Update the retire_latency result print and metric calculation method. Plugin
> the value to evsel so that no special code is required.
> - Update --control:fifo to use pipe instead of named pipe.
> - Add test for TPEBS counting mode.
> - Update Document with more details.
>
> Changes in v8:
> - In this revision, the code is updated to base on Ian's patch on R modifier
> parser https://lore.kernel.org/lkml/20240428053616.1125891-3-irogers@google.com/

I pulled the first patch of these 3, to clean up the tool events into
its own patch and hopefully addressed Namhyung's feedback:
https://lore.kernel.org/lkml/20240503232849.17752-1-irogers@google.com/
It is looking for review.

I think in general it'd be useful when posting the series to include
the patches it is dependent on, that way we can also make changes to
those patches (for example the missed perf-list documentation of the
'R' modifier).

Thanks,
Ian



> After this change, there is no special code required for R modifier in
> metricgroup.c and metricgroup.h files.
>
> Caveat of this change:
>   Ideally, we will need to add special handling to skip counting events with R
> modifier in evsel. Currently, this is not implemented so the event with :R will
> be both counted and sampled. Usually, in a metric formula that uses retire_latency,
> it would already require to count the event. As a result, we will endup count the
> same event twice. This should be able to be handled properly when we finalize our
> design on evsel R modifier support.
>
> - Move TPEBS specific code out from main perf stat code to separate files in
> util/intel-tpebs.c and util/intel-tpebs.h. [Namhyung]
> - Use --control:fifo to ack perf stat from forked perf record instead of sleep(2) [Namhyung]
> - Add introductions about TPEBS and R modifier in Documents. [Namhyung]
>
>
> Changes in v7:
> - Update code and comments for better code quality [Namhyung]
> - Add a separate commit for perf data [Namhyung]
> - Update retire latency print function to improve alignment [Namhyung]
>
> Changes in v6:
> - Update code and add comments for better code quality [Namhyung]
> - Remove the added fd var and directly pass the opened fd to data.file.fd [Namhyung]
> - Add kill() to stop perf record when perf stat exists early [Namhyung]
> - Add command opt check to ensure only start perf record when -a/-C given [Namhyung]
> - Squash commits [Namhyung]
>
> Changes in v5:
> - Update code and add comments for better code quality [Ian]
>
> Changes in v4:
> - Remove uncessary debug print and update code and comments for better
> readability and quality [Namhyung]
> - Update mtl metric json file with consistent TmaL1 and TopdownL1 metricgroup
>
> Changes in v3:
> - Remove ':' when event name has '@' [Ian]
> - Use 'R' as the modifier instead of "retire_latency" [Ian]
>
> Changes in v2:
> - Add MTL metric file
> - Add more descriptions and example to the patch [Arnaldo]
>
> Here is an example of running perf stat to collect a metric that uses
> retire_latency value of event MEM_INST_RETIRED.STLB_HIT_STORES on a MTL system.
>
> In this simple example, there is no MEM_INST_RETIRED.STLB_HIT_STORES sample.
> Therefore, the MEM_INST_RETIRED.STLB_HIT_STORES:p count and retire_latency value
> are all 0.
>
> ./perf stat -M tma_dtlb_store -a -- sleep 1
>
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.000 MB - ]
>
>  Performance counter stats for 'system wide':
>
>        181,047,168      cpu_core/TOPDOWN.SLOTS/          #      0.6 %  tma_dtlb_store
>          3,195,608      cpu_core/topdown-retiring/
>         40,156,649      cpu_core/topdown-mem-bound/
>          3,550,925      cpu_core/topdown-bad-spec/
>        117,571,818      cpu_core/topdown-fe-bound/
>         57,118,087      cpu_core/topdown-be-bound/
>             69,179      cpu_core/EXE_ACTIVITY.BOUND_ON_STORES/
>              4,582      cpu_core/MEM_INST_RETIRED.STLB_HIT_STORES/
>         30,183,104      cpu_core/CPU_CLK_UNHALTED.DISTRIBUTED/
>         30,556,790      cpu_core/CPU_CLK_UNHALTED.THREAD/
>            168,486      cpu_core/DTLB_STORE_MISSES.WALK_ACTIVE/
>               0.00 MEM_INST_RETIRED.STLB_HIT_STORES:p       0        0
>
>        1.003105924 seconds time elapsed
>
> v1:
> TPEBS is one of the features provided by the next generation of Intel PMU.
> Please refer to Section 8.4.1 of "Intel® Architecture Instruction Set Extensions
> Programming Reference" [1] for more details about this feature.
>
> This set of patches supports TPEBS in counting mode. The code works in the
> following way: it forks a perf record process from perf stat when retire_latency
> of one or more events are used in a metric formula. Perf stat would send a
> SIGTERM signal to perf record before it needs the retire latency value for
> metric calculation. Perf stat will then process sample data to extract the
> retire latency data for metric calculations. Currently, the code uses the
> arithmetic average of retire latency values.
>
> [1] https://www.intel.com/content/www/us/en/content-details/812218/intel-architecture-instruction-set-extensions-programming-reference.html?wapkw=future%20features
>
>
> Weilin Wang (7):
>   perf vendor events intel: Add MTL metric json files
>   perf data: Allow to use given fd in data->file.fd
>   perf stat: Fork and launch perf record when perf stat needs to get
>     retire latency value for a metric.
>   perf stat: Plugin retire_lat value from sampled data to evsel
>   perf stat: Add command line option for enabling tpebs recording
>   perf Document: Add TPEBS to Documents
>   perf test: Add test for Intel TPEBS counting mode
>
>  tools/perf/Documentation/perf-list.txt        |    1 +
>  tools/perf/Documentation/topdown.txt          |   30 +
>  tools/perf/arch/x86/util/evlist.c             |    6 +
>  tools/perf/builtin-stat.c                     |   24 +
>  .../arch/x86/meteorlake/metricgroups.json     |  127 +
>  .../arch/x86/meteorlake/mtl-metrics.json      | 2551 +++++++++++++++++
>  .../perf/tests/shell/test_stat_intel_tpebs.sh |   27 +
>  tools/perf/util/Build                         |    1 +
>  tools/perf/util/data.c                        |    7 +-
>  tools/perf/util/evsel.c                       |   53 +
>  tools/perf/util/evsel.h                       |    5 +
>  tools/perf/util/intel-tpebs.c                 |  301 ++
>  tools/perf/util/intel-tpebs.h                 |   30 +
>  tools/perf/util/stat.h                        |    1 +
>  14 files changed, 3163 insertions(+), 1 deletion(-)
>  create mode 100644 tools/perf/pmu-events/arch/x86/meteorlake/metricgroups.json
>  create mode 100644 tools/perf/pmu-events/arch/x86/meteorlake/mtl-metricsjson
>  create mode 100755 tools/perf/tests/shell/test_stat_intel_tpebs.sh
>  create mode 100644 tools/perf/util/intel-tpebs.c
>  create mode 100644 tools/perf/util/intel-tpebs.h
>
> --
> 2.43.0
>

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