linux-kernel - [PATCH v2 0/7] Rewrite jevents program in python

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Date:   Wed, 11 May 2022 14:15:19 -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>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        John Garry <john.garry@...wei.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        Felix Fietkau <nbd@....name>, Qi Liu <liuqi115@...wei.com>,
        Like Xu <likexu@...cent.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Nick Forrington <nick.forrington@....com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        James Clark <james.clark@....com>,
        Andrew Kilroy <andrew.kilroy@....com>,
        "Paul A . Clarke" <pc@...ibm.com>, Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        ananth.narayan@....com, ravi.bangoria@....com,
        santosh.shukla@....com, sandipan.das@....com,
        Caleb Biggers <caleb.biggers@...el.com>,
        Perry Taylor <perry.taylor@...el.com>,
        Kshipra Bopardikar <kshipra.bopardikar@...el.com>
Cc:     Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH v2 0/7] Rewrite jevents program in python

New architectures bring new complexity, such as Intel's hybrid
models. jevents provides an alternative to specifying events in the
kernel and exposing them through sysfs, however, it is difficult to
work with. For example, an error in the json input would yield an
error message but no json file or location. It is also a challenge to
update jsmn.c given its forked nature.

The changes here switch from jevents.c to a rewrite in python called
jevents.py. This means there is a build time dependency on python, but
such a dependency already exists for asciidoc (used to generate perf's
man pages). If the build detects that python isn't present or is older
than version 3.5 (released Sept. 2015) then an empty file is
substituted for the generated one.

A challenge with this code is in avoiding regressions. For this reason
the jevents.py produces identical output to jevents.c, validated with a
test script and build target.

A difference in the python to the C approach is that the python loads
an entire json file in to memory, while the C code works from token to
token. In some cases the C approach was sensitive to the order of
dictionary items in the json file. To ensure matching output there are
two changes made to jevents.c to cause it to read all values before
creating output.

The changes also found a bug in Ivytown's UNC_M_ACT_COUNT.RD event
encoding, as well as unnecessary whitespace introduced in Alderlake's
metrics. In these cases the json input is fixed.

v2. Fixes the build for architectures that don't have pmu-events json
    (Suggested-by: John Garry <john.garry@...wei.com>) and fixes the
    build for python not being present or too old (Suggested-by: Peter
    Zijlstra <peterz@...radead.org>/John Garry <john.garry@...wei.com>).

Ian Rogers (7):
  perf jevents: Append PMU description later
  perf vendor events: Fix Alderlake metric groups
  perf vendor events: Fix Ivytown UNC_M_ACT_COUNT.RD umask
  perf jevents: Modify match field
  perf jevents: Add python converter script
  perf jevents: Switch build to use jevents.py
  perf jevents: Remove jevents.c

 tools/perf/Makefile.config                    |   19 +
 tools/perf/Makefile.perf                      |   16 +-
 tools/perf/pmu-events/Build                   |   15 +-
 .../arch/x86/alderlake/adl-metrics.json       |   32 -
 .../arch/x86/ivytown/uncore-memory.json       |    3 +-
 tools/perf/pmu-events/empty-pmu-events.c      |   21 +
 tools/perf/pmu-events/jevents.c               | 1322 -----------------
 tools/perf/pmu-events/jevents.py              |  392 +++++
 tools/perf/pmu-events/jsmn.h                  |   68 -
 tools/perf/pmu-events/json.c                  |  162 --
 tools/perf/pmu-events/json.h                  |   39 -
 tools/perf/tests/pmu-events.c                 |   30 +-
 12 files changed, 460 insertions(+), 1659 deletions(-)
 create mode 100644 tools/perf/pmu-events/empty-pmu-events.c
 delete mode 100644 tools/perf/pmu-events/jevents.c
 create mode 100755 tools/perf/pmu-events/jevents.py
 delete mode 100644 tools/perf/pmu-events/jsmn.h
 delete mode 100644 tools/perf/pmu-events/json.c
 delete mode 100644 tools/perf/pmu-events/json.h

-- 
2.36.0.512.ge40c2bad7a-goog