Received-SPF: pass (google.com: domain of linux-kernel+bounces-46843-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Precedence: bulk
MIME-Version: 1.0
References: <20240111081914.3123-1-adrian.hunter@intel.com> <31bae596-ecb1-4b9c-9f1c-aaec4bcefd38@intel.com>
In-Reply-To: <31bae596-ecb1-4b9c-9f1c-aaec4bcefd38@intel.com>
From: Ian Rogers <irogers@google.com>
Date: Wed, 31 Jan 2024 08:53:06 -0800
Message-ID: <CAP-5=fUo96EABpH6=7i2cXFmZhAB2MM=UsnG-+vL4HJtLGS=bA@mail.gmail.com>
Subject: Re: [PATCH V4 00/11] perf/core: Add ability for an event to "pause"
 or "resume" AUX area tracing
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, 
	Mark Rutland <mark.rutland@arm.com>, 
	Alexander Shishkin <alexander.shishkin@linux.intel.com>, Heiko Carstens <hca@linux.ibm.com>, 
	Thomas Richter <tmricht@linux.ibm.com>, Hendrik Brueckner <brueckner@linux.ibm.com>, 
	Suzuki K Poulose <suzuki.poulose@arm.com>, Mike Leach <mike.leach@linaro.org>, 
	James Clark <james.clark@arm.com>, coresight@lists.linaro.org, 
	linux-arm-kernel@lists.infradead.org, Yicong Yang <yangyicong@hisilicon.com>, 
	Jonathan Cameron <jonathan.cameron@huawei.com>, Will Deacon <will@kernel.org>, 
	Arnaldo Carvalho de Melo <acme@kernel.org>, Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>, 
	linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Mon, Jan 29, 2024 at 4:49=E2=80=AFAM Adrian Hunter <adrian.hunter@intel.=
com> wrote:
>
> On 11/01/24 10:19, Adrian Hunter wrote:
> > Hi
> >
> > Hardware traces, such as instruction traces, can produce a vast amount =
of
> > trace data, so being able to reduce tracing to more specific circumstan=
ces
> > can be useful.
> >
> > The ability to pause or resume tracing when another event happens, can =
do
> > that.
> >
> > These patches add such a facilty and show how it would work for Intel
> > Processor Trace.
> >
> > Maintainers of other AUX area tracing implementations are requested to
> > consider if this is something they might employ and then whether or not
> > the ABI would work for them.
> >
> > Changes to perf tools are now (since V4) fleshed out.
> >
> >
> > Changes in V4:
> >
> >     perf/core: Add aux_pause, aux_resume, aux_start_paused
> >       Rename aux_output_cfg -> aux_action
> >       Reorder aux_action bits from:
> >               aux_pause, aux_resume, aux_start_paused
> >       to:
> >               aux_start_paused, aux_pause, aux_resume
> >       Fix aux_action bits __u64 -> __u32
> >
> >     coresight: Have a stab at support for pause / resume
> >       Dropped
> >
> >     perf tools
> >       All new patches
> >
> > Changes in RFC V3:
> >
> >     coresight: Have a stab at support for pause / resume
> >       'mode' -> 'flags' so it at least compiles
> >
> > Changes in RFC V2:
> >
> >       Use ->stop() / ->start() instead of ->pause_resume()
> >       Move aux_start_paused bit into aux_output_cfg
> >       Tighten up when Intel PT pause / resume is allowed
> >       Add an example of how it might work for CoreSight
>
> Any more comments?

I think the tools side looks good. The parsing changes match the
existing style. I wonder if it wouldn't be better to handle the valid
strings (pause, resume, etc.) in the lexer rather than a separate
parse function, but the pattern used matches the existing one. You can
have my Acked-by on the tools changes, although the subtleties of ARM
PMUs makes me somewhat nervous in this regard.

Thanks,
Ian