[PATCH v6 0/4] Rewrite jevents program in python

[Ian Rogers]

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 3.6 (released Dec. 2016) 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.

v6. Fixes an annotation and use of removesuffix that aren't present in
    Python 3.6. Linter issues are also fixed.The code was tested on
    Python 3.6 and 3.8 with docker.
v5. Adds a 2>/dev/null as suggested by David Laight
    <David.Laight@xxxxxxxxxx>.
v4. Fixes the build for systems with python2 installed by adding a
    patch that makes python3 the preferred python (Reported-by: John
    Garry <john.garry@xxxxxxxxxx>). It also fixes a bash-ism in the
    jevents-test.sh and fixes the handling of an empty string for a
    metric BriefDescription as one was added for sapphirerapids in the
    metric Execute.
v3. Updates the patches for merged changes (on
    acme/tmp.perf/core). Re-runs all comparisons to make sure the
    generated pmu-events.c isn't altered at all by this change. Adds
    the jevents.c ExtSel fix in:
    https://lore.kernel.org/lkml/20220525140410.1706851-1-zhengjun.xing@xxxxxxxxxxxxxxx/
    Bumps the python version from 3.5 to 3.6, as f-strings weren't
    introduced until 3.6.

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

Ian Rogers (4):
  perf python: Prefer python3
  perf jevents: Add python converter script
  perf jevents: Switch build to use jevents.py
  perf jevents: Remove jevents.c

 tools/perf/Makefile.config               |   27 +-
 tools/perf/Makefile.perf                 |   16 +-
 tools/perf/pmu-events/Build              |   15 +-
 tools/perf/pmu-events/empty-pmu-events.c |   21 +
 tools/perf/pmu-events/jevents.c          | 1342 ----------------------
 tools/perf/pmu-events/jevents.py         |  409 +++++++
 tools/perf/pmu-events/jsmn.h             |   68 --
 tools/perf/pmu-events/json.c             |  162 ---
 tools/perf/pmu-events/json.h             |   39 -
 9 files changed, 465 insertions(+), 1634 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

-- 
2.36.1.476.g0c4daa206d-goog