[PATCH v4 0/4] Rewrite jevents program in python

Ian Rogers
2022-06-15T03:05:17Z

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.

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@huawei.com>). 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@linux.intel.com/
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@huawei.com>) and fixes the
build for python not being present or too old (Suggested-by: Peter
Zijlstra <peterz@infradead.org>/John Garry <john.garry@huawei.com>).

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 | 394 +++++++
tools/perf/pmu-events/jsmn.h | 68 --
tools/perf/pmu-events/json.c | 162 ---
tools/perf/pmu-events/json.h | 39 -
9 files changed, 450 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

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2.34.1