Re: [RFC PATCH v10 0/8] TPEBS counting mode support
From: Namhyung Kim
Date: Fri May 31 2024 - 02:37:41 EST
Hello,
On Tue, May 28, 2024 at 11:43 PM <weilin.wang@xxxxxxxxx> wrote:
>
> From: Weilin Wang <weilin.wang@xxxxxxxxx>
>
> I have tried not to count retire_latency events but did not succeed.
> In particular, I tried the following methods:
> - Convert retire_latency event to dummy event in event parser.
> - Early bail out in evsel__open_cpu() and store_evsel_ids().
>
> The first method fails and causes non-retire_latency events with the same event
> name return 0 count.
>
> The second method fails and causes all the events in the same group returning
> "<not counted>" results.
Can you please describe where it fails? Is it failing on other events
because the tpebs event is a leader of the group? I think you wanted
to avoid having it in the leader position. If we can skip any actual
operations (open/close/enable/disable/read) for the tpebs events, then
it could be fine..
Thanks,
Namhyung
>
> Because of above, the retire_latency event will still run in counting mode.
>
> Other changes in v10:
> - Change perf record fork from perf stat to evsel. All the major operations
> like tpebs start, stop, read_evsel should directly work through evsel.
> - Make intel-tpebs x86_64 only. This change is cross-compiled to arm64.
> - Put tpebs code to intel-tepbs and simplify intel-tpebs APIs to minimum number
> of functions and variables. Update funtion name and variable names to use
> consistent prefix. Also improve error handling.
> - Integrate code patch from Ian for the :R parser.
> - Update MTL metrics to TMA 4.8.
>
> V9: https://lore.kernel.org/all/20240521173952.3397644-1-weilin.wang@xxxxxxxxx/
>
> 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@xxxxxxxxxx/
> 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
>
>
> Ian Rogers (1):
> perf parse-events: Add a retirement latency modifier
>
> Weilin Wang (7):
> 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 vendor events intel: Add MTL metric json files
> 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 | 8 +
> .../arch/x86/meteorlake/metricgroups.json | 140 +
> .../arch/x86/meteorlake/mtl-metrics.json | 2595 +++++++++++++++++
> .../perf/tests/shell/test_stat_intel_tpebs.sh | 19 +
> tools/perf/util/Build | 1 +
> tools/perf/util/data.c | 7 +-
> tools/perf/util/evsel.c | 26 +
> tools/perf/util/evsel.h | 6 +
> tools/perf/util/intel-tpebs.c | 397 +++
> tools/perf/util/intel-tpebs.h | 48 +
> tools/perf/util/parse-events.c | 2 +
> tools/perf/util/parse-events.h | 1 +
> tools/perf/util/parse-events.l | 3 +-
> 16 files changed, 3288 insertions(+), 2 deletions(-)
> 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
>