Re: [PATCH 1/1] perf tools: Bump the minimum Python version to 3.9

[Mauro Carvalho Chehab <mchehab+huawei@kernel.org>]

On Sat, 26 Sep 2026 01:01:12 +0200
Arnaldo Carvalho de Melo <acme@kernel.org> wrote:

> perf's build only refused interpreters older than 3.6, the check added
> when jevents.py started using f-strings, and jevents.py carried a
> removesuffix() shim to stay usable on them.
> 
> The kernel itself requires Python 3.9.x since 5e25b972a22be224 ("docs:
> changes: update Python minimal version"), so tools in the tree are
> expected to work with it, and staying compatible with older
> interpreters stopped paying off:
> 
>  - the PEP 585 generics, list[...], used by the type annotations in
>    jevents.py and util/setup.py are only subscriptable from Python 3.9
>    and, being evaluated at import or definition time, they break the
>    build on RHEL 8's python3.6.8 with:
> 
>    TypeError: 'type' object is not subscriptable

If it is just for type, you probably could do something like:

	from __future__ import annotations

if you have a too old python version and you use import typing
(I didn't test it myself - no idea it it would make any difference).

But yeah, 3.6 is too old for my taste ;-)

>  - ProcessPoolExecutor(initializer=, initargs=) requires Python 3.7, so
>    generating pmu-events.c fails there as well.

Double-checked with vermin:

 $ vermin -vv ./tools/perf/pmu-events/jevents.py
...
  'concurrent.futures.ProcessPoolExecutor(initargs)' requires !2, 3.7
  'concurrent.futures.ProcessPoolExecutor(initializer)' requires !2, 3.7

> Rather than spreading version guards and typing.List() workarounds for
> interpreters that cannot be supported anyway, make 3.9 the floor: check
> for it in Makefile.config, where the jevents generation check already
> lives, and drop the removesuffix() shim, since str.removesuffix() was
> added in 3.9.
> 
> RHEL 8 is in feature freeze, so those wanting a new perf and its python
> features have to vendor a newer interpreter, just as
> Documentation/process/changes.rst already asks for the kernel itself.
> 
> Tested with Python 3.9.22: perf builds, generating pmu-events.c and the
> python binding, with byte for byte identical output to the build made
> with the shim, while Python 3.8.20 and 3.6.15 are rejected with the
> "older than 3.9" error. vermin reports no perf build file as requiring
> more than 3.9, the only offender being the runtime script
> scripts/python/mem-phys-addr.py, which the build doesn't run.
> 
> Suggested-by: Ian Rogers <irogers@google.com>
> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> Assisted-by: LLM
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Patch LGTM.

Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

> ---
>  tools/perf/Makefile.config       |  8 +++++---
>  tools/perf/pmu-events/jevents.py | 16 +++-------------
>  2 files changed, 8 insertions(+), 16 deletions(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index b288ae0191acf7ef..92ac7c620b3ccd49 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -885,10 +885,12 @@ ifneq ($(NO_JEVENTS),1)
>    ifndef PYTHON
>      $(error ERROR: No python interpreter needed for jevents generation. Install python or build with NO_JEVENTS=1.)
>    else
> -    # jevents.py uses f-strings present in Python 3.6 released in Dec. 2016.
> -    JEVENTS_PYTHON_GOOD := $(shell $(PYTHON) -c 'import sys;print("1" if(sys.version_info.major >= 3 and sys.version_info.minor >= 6) else "0")' 2> /dev/null)
> +    # Minimum Python version, the same one the kernel requires, see
> +    # Documentation/process/changes.rst: jevents.py needs PEP 585 generics,
> +    # list[...] and friends, that are subscriptable from Python 3.9.
> +    JEVENTS_PYTHON_GOOD := $(shell $(PYTHON) -c 'import sys;print("1" if sys.version_info >= (3, 9) else "0")' 2> /dev/null)
>      ifneq ($(JEVENTS_PYTHON_GOOD), 1)
> -      $(error ERROR: Python interpreter needed for jevents generation too old (older than 3.6). Install a newer python or build with NO_JEVENTS=1.)
> +      $(error ERROR: Python interpreter needed for jevents generation too old (older than 3.9). Install a newer python or build with NO_JEVENTS=1.)
>      endif
>    endif
>  endif
> diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
> index 074daae5308b110b..296bf68d10810952 100755
> --- a/tools/perf/pmu-events/jevents.py
> +++ b/tools/perf/pmu-events/jevents.py
> @@ -65,15 +65,6 @@ _json_metric_attributes = [
>  _json_enum_attributes = ['aggr_mode', 'deprecated', 'event_grouping', 'perpkg',
>                           'default_show_events']
>  
> -def removesuffix(s: str, suffix: str) -> str:
> -  """Remove the suffix from a string
> -
> -  The removesuffix function is added to str in Python 3.9. We aim for 3.6
> -  compatibility and so provide our own function here.
> -  """
> -  return s[0:-len(suffix)] if s.endswith(suffix) else s
> -
> -
>  def file_name_to_table_name(prefix: str, parents: Sequence[str],
>                              dirname: str) -> str:
>    """Generate a C table name from directory names."""
> @@ -214,9 +205,8 @@ class JsonEvent:
>        """Fix formatting issue for the desc string."""
>        if s is None:
>          return None
> -      return removesuffix(removesuffix(removesuffix(s, '.  '),
> -                                       '. '), '.').replace('\n', '\\n').replace(
> -                                           '\"', '\\"').replace('\r', '\\r')
> +      return s.removesuffix('.  ').removesuffix('. ').removesuffix('.').replace(
> +          '\n', '\\n').replace('\"', '\\"').replace('\r', '\\r')
>  
>      def convert_aggr_mode(aggr_mode: Optional[str]) -> Optional[str]:
>        """Returns the aggr_mode_class enum value associated with the JSON string."""
> @@ -641,7 +631,7 @@ static const struct pmu_table_entry {_pending_metrics_tblname}[] = {{
>  def get_topic(topic: str) -> str:
>    if topic.endswith('metrics.json'):
>      return 'metrics'
> -  return removesuffix(topic, '.json').replace('-', ' ')
> +  return topic.removesuffix('.json').replace('-', ' ')
>  
>  def preprocess_one_file(parents: Sequence[str], item: os.DirEntry) -> None:
>    if item.is_dir():



Thanks,
Mauro