linux-kernel - Re: [PATCH 0/4] perf sched: Fix task state report

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Message-ID: <CAM9d7cgXKaKTnfx9YJae2qqv0pXtWLVQPBN=2H0WZkenBjHFnQ@mail.gmail.com>
Date: Tue, 16 Jan 2024 17:35:17 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Ze Gao <zegao2021@...il.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Ian Rogers <irogers@...gle.com>, Ingo Molnar <mingo@...hat.com>, 
	Jiri Olsa <jolsa@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Peter Zijlstra <peterz@...radead.org>, Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, Ze Gao <zegao@...cent.com>
Subject: Re: [PATCH 0/4] perf sched: Fix task state report

Hello,

On Sun, Jan 14, 2024 at 11:23 PM Ze Gao <zegao2021@...il.com> wrote:
>
> Hi,
>
> The problems of task state report in both libtraceevent
> and perf sched has been reported in [1]. In short, they
> parsed the wrong state due to relying on the outdated
> hardcoded state string to interpret the raw bitmask
> from the record, which left the messes to maintain the
> backward compatibilities for both tools.
>
> [1] has not managed to make itself into the kernel, the
> problems and the solutions are well studied though.
>
> Luckily, as suggested by Steven, perf/libtraceevent
> records the print format, especially the __print_flags()
> part of the in-kernel tracepoint sched_switch in its
> metadata, and we have a chance to build the state str
> on the fly by parsing it.
>
> Now that libtraceevent has landed this solution in [2],
> we now apply the same idea to perf as well.

Thanks for your work.  But perf links libtraceevent
conditionally so you need to make sure if it works without
that too.

I think all libtraceevent related stuff should be in the
util/trace-event.c which is included only if the library is
available.  Maybe util/trace-event-parse.c is a better
place but then you need to tweak the python-ext-sources
and Makefile.perf for the case it's not available.

Thanks,
Namhyung

>
> Regards,
>
>         -- Ze
>
> [1]: https://lore.kernel.org/lkml/20230803083352.1585-1-zegao@tencent.com/
> [2]: https://lore.kernel.org/linux-trace-devel/20231224140732.7d41698d@rorschach.local.home/
>
> Ze Gao (4):
>   perf sched: Sync state char array with the kernel
>   perf util: Add helpers to parse task state string from libtraceevent
>   perf util: Add evsel__taskstate() to parse the task state info instead
>   perf sched: Commit to evsel__taskstate() to parse task state info
>
>  tools/perf/builtin-sched.c |  57 +++------------
>  tools/perf/util/evsel.c    | 146 +++++++++++++++++++++++++++++++++++++
>  tools/perf/util/evsel.h    |   1 +
>  3 files changed, 157 insertions(+), 47 deletions(-)
>
> --
> 2.41.0
>