linux-kernel - Re: [PATCH v1 1/3] perf ilist: Don't display deprecated events

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Message-ID: <CAP-5=fWDqE8SYfOLZkg_0=4Ayx6E7O+h7uUp4NDeCFkiN4b7-w@mail.gmail.com>
Date: Sun, 19 Oct 2025 16:04:17 -0700
From: Ian Rogers <irogers@...gle.com>
To: Howard Chu <howardchu95@...il.com>, Namhyung Kim <namhyung@...nel.org>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Gautam Menghani <gautam@...ux.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/3] perf ilist: Don't display deprecated events

On Sat, Oct 18, 2025 at 11:50 PM Howard Chu <howardchu95@...il.com> wrote:
>
> Hi Namhyung,
>
> On Sat, Oct 18, 2025 at 7:56 PM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > Hi Ian,
> >
> > On Thu, Oct 16, 2025 at 03:22:26PM -0700, Ian Rogers wrote:
> > > Unsupported legacy events are flagged as deprecated. Don't display
> > > these events in ilist as they won't open and there are over 1,000
> > > legacy cache events.
> >
> > Off-topic, any chance to integrate this into a perf command?
> > It'd be convenient if we can call this like `perf list --interactive`
> > or some other way.
>
> You have my vote, user-friendliness is important.
> I think Ian mentioned that the major drawback is the difficulty of
> forwarding arguments passed to the ilist.py program. A random thought:
> perf is known for binding everything under a single command, but to
> make scripting more flexible, perhaps some Bash scripts added to
> .bashrc could be considered. After all, perf is fundamentally a
> command-line tool.

Thanks Howard and Namhyung,

I think Arnaldo also raised this in the past.  My thought on how to do
this is to build in to `perf script`:

1) `perf script` currently uses libpython and then exposes a
trace_start, trace_end and process_event method. When building the
flamegraph work the only place that textual can run is in trace_end as
it needs to run on the main python thread. This means we can't do
incremental loading of data files while textual is showing the data as
perf wants to be the main thread. So step 1 is to create a python
version of the trace_start, trace_end and process_event callbacks. To
do this something like the session API needs wrapping or writing in
python. I'm not sure I'd keep the API the same as the C one. It'd be
interesting to think of async file processing. It'd be nice to make
the generation of strings.. in the event lazier. We could start with
the existing API though, and then migrate to something more complex
later.

2) Once we have a session like API in python we can convert the
existing `perf script` commands to be standalone tools similar to
ilist. So we can convert all the existing tools to be standalone.

3) Once we have standalone versions of the `perf script` scripts then
we can have `perf script` just exec the commands. The install step can
install the scripts like it currently does and we can move ilist into
the scripts location.

4) Once we run python things as tools in their own right we can
deprecate the libpython stuff, probably make it a build opt-in thing,
etc. It seems hard to delete unused features, like libbfd, from the
codebase. We did merge a patch deprecating libperl as a step in this
direction.

Thanks,
Ian