linux-kernel - Re: [PATCH v1 0/3] Improve event groups for topdown, add X event modifier

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Message-ID: <3f481d00-2c9f-45a5-807b-037930903b1c@linux.intel.com>
Date: Tue, 26 Aug 2025 10:30:10 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Ian Rogers <irogers@...gle.com>, 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>,
 Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@...aro.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Yoshihiro Furudera <fj5100bi@...itsu.com>, Howard Chu
 <howardchu95@...il.com>, Thomas Falcon <thomas.falcon@...el.com>,
 Andi Kleen <ak@...ux.intel.com>, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/3] Improve event groups for topdown, add X event
 modifier


On 8/26/2025 5:12 AM, Ian Rogers wrote:
> In:
> https://lore.kernel.org/lkml/20250822082233.1850417-1-dapeng1.mi@linux.intel.com/#t
> Dapeng Mi and Xudong Hao reported that Intel topdown events have
> issues with parsing when events are duplicated. While some of that is
> intended, things could be better. These patches:
>
> 1) give error messages specific to topdown event grouping constraints,
> 2) fail groups if non-leaders fail to open (this appears to be old tech debt),
> 3) adds an 'X' event modifier to allow events to opt-out of being regrouped.
>
> The 'X' modifier should also give a means to side-step future issues
> in parse_events__sort_events_and_fix_groups should they come up.
>
> Ian Rogers (3):
>   perf evsel: Give warning for broken Intel topdown event grouping
>   perf stat: Don't skip failing group events
>   perf parse-events: Add 'X' modifier to exclude an event from being
>     regrouped
>
>  tools/perf/Documentation/perf-list.txt |  1 +
>  tools/perf/arch/x86/util/evsel.c       | 62 ++++++++++++++++++++++++--
>  tools/perf/builtin-stat.c              | 48 +++++++++-----------
>  tools/perf/util/evsel.c                |  7 ++-
>  tools/perf/util/evsel.h                |  3 +-
>  tools/perf/util/parse-events.c         |  5 ++-
>  tools/perf/util/parse-events.h         |  1 +
>  tools/perf/util/parse-events.l         |  5 ++-
>  8 files changed, 94 insertions(+), 38 deletions(-)

The whole patch-set looks good to me.

Reviewed-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>

Tested the patches on Intel Sapphire Rapids and Panther Lake, all results
are expected.

Tested-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>

Test results on Sapphire Rapids.

1. sudo ./perf stat -e slots,slots -a sleep 1

WARNING: events were regrouped to match PMUs
Error:
Topdown slots event can only be group leader in '{slots,slots}'.

2. sudo ./perf stat -e slots,slots:X -a sleep 1
 Performance counter stats for 'system wide':

    55,734,800,895      slots                                             
                     (49.99%)
    57,217,900,875      slots:X                                           
                     (50.01%)

       1.009697323 seconds time elapsed

3.  sudo ./perf stat -e slots,topdown-fe-bound,topdown-fe-bound -a sleep 1

WARNING: events were regrouped to match PMUs
Error:
Perf metric event 'topdown-fe-bound' is duplicated in the same group (only
one event is allowed) in '{slots,topdown-fe-bound,topdown-fe-bound}'.

4. Perf stats test

sudo ./perf test 100
100: perf stat tests                                                 : Ok

Test results on Panther Lake.

1. sudo ./perf stat -e slots,slots -a sleep 1
WARNING: events were regrouped to match PMUs
Error:
Topdown slots event can only be group leader in
'{cpu_core/slots/,cpu_core/slots/}'.

2. sudo ./perf stat -e slots,slots:X -a sleep 1

 Performance counter stats for 'system wide':

     1,592,899,478      cpu_core/slots/                                   
                     (49.98%)
     1,682,298,980      cpu_core/slots/X                                   
                    (50.02%)

       1.002821768 seconds time elapsed

3. sudo ./perf stat -e slots,topdown-fe-bound,topdown-fe-bound -a sleep 1
WARNING: events were regrouped to match PMUs
Error:
Perf metric event 'cpu_core/topdown-fe-bound/' is duplicated in the same
group (only one event is allowed) in
'{cpu_core/slots/,cpu_core/topdown-fe-bound/,cpu_core/topdown-fe-bound/},cpu_atom/topdown-fe-bound/,cpu_atom/topdown-fe-bound/'.

4. sudo ./perf test 99
 99: perf stat tests                                                 : Ok