linux-kernel - [PATCH v1 0/2] Consistently prioritize legacy events

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Message-ID: <20250310195518.2012571-1-irogers@google.com>
Date: Mon, 10 Mar 2025 12:55:16 -0700
From: Ian Rogers <irogers@...gle.com>
To: 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>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	James Clark <james.clark@...aro.org>, Dominique Martinet <asmadeus@...ewreck.org>, 
	Yang Jihong <yangjihong@...edance.com>, Yang Li <yang.lee@...ux.alibaba.com>, 
	Weilin Wang <weilin.wang@...el.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	Leo Yan <leo.yan@....com>
Subject: [PATCH v1 0/2] Consistently prioritize legacy events

Legacy events were historically the priority over sysfs/json
events. This behavior was changed in commit a24d9d9dc096 ("perf
parse-events: Make legacy events lower priority than sysfs/JSON") to
fix issues on ARM Apple-M CPUs. Sysfs/json being the priority makes
most sense, was preferred by RISC-V and gives abilities impossible
with legacy events. Making this encoding consistent is proving
impossible with endless bike shedding, people saying they see
something as a fix then when that fix is provided continuing to
object, etc. Given that in the RFC [1] legacy events are seen as being
preferrable let's just follow up on that and make their use
consistent.

If it isn't clear, I think this is the wrong decision and landing [2]
should be the priority. When I try to have this conversation it just
gets ignored and I want consistency more than my preferred
prioritization.

[1] https://lore.kernel.org/lkml/Z7Z5kv75BMML2A1q@google.com/
[2] https://lore.kernel.org/linux-perf-users/20250109222109.567031-1-irogers@google.com/

Ian Rogers (2):
  perf parse-events: Make legacy events always have priority over
    sysfs/json
  Revert "perf evsel: Add alternate_hw_config and use in evsel__match"

 tools/perf/builtin-diff.c       |  6 +--
 tools/perf/tests/parse-events.c | 13 ++----
 tools/perf/util/evsel.c         | 21 ---------
 tools/perf/util/evsel.h         | 19 +++++++-
 tools/perf/util/parse-events.c  | 81 ++++++++++++---------------------
 tools/perf/util/parse-events.h  |  8 +---
 tools/perf/util/parse-events.y  |  2 +-
 tools/perf/util/pmu.c           |  6 +--
 tools/perf/util/pmu.h           |  2 +-
 9 files changed, 57 insertions(+), 101 deletions(-)

-- 
2.49.0.rc0.332.g42c0ae87b1-goog