linux-kernel - Re: [PATCH v3] perf doc: Document ring buffer mechanism

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Date:   Tue, 3 Oct 2023 11:47:57 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3] perf doc: Document ring buffer mechanism


* Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Leo Yan <leo.yan@...aro.org> wrote:
> 
> > In the Linux perf tool, the ring buffer serves not only as a medium for
> > transferring PMU event data but also as a vital mechanism for hardware
> > tracing using technologies like Intel PT and Arm CoreSight, etc.
> > 
> > Consequently, the ring buffer mechanism plays a crucial role by ensuring
> > high throughput for data transfer between the kernel and user space
> > while avoiding excessive overhead caused by the ring buffer itself.
> > 
> > This commit documents the ring buffer mechanism in detail.  It provides
> > an in-depth explanation of the implementation of both the generic ring
> > buffer and the AUX ring buffer.  Additionally, it covers how these ring
> > buffers support various tracing modes and explains the synchronization
> > with memory barriers.
> > 
> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> > ---
> > 
> > Changes from v2:
> > - Refined doc for Thomas's suggestions (Thomas Richter).
> > 
> > Changes from v1:
> > - Addressed Ian's comments and suggestions (Ian Rogers).
> > 
> > 
> >  tools/perf/Documentation/perf-ring-buffer.txt | 762 ++++++++++++++++++
> >  1 file changed, 762 insertions(+)
> >  create mode 100644 tools/perf/Documentation/perf-ring-buffer.txt
> 
> Nice addition!
> 
> If it hasn't been picked up yet:
> 
>   Acked-by: Ingo Molnar <mingo@...nel.org>

Note that my ack is conditional on the conversion to RST and moving to 
Documentation/ - this documents an important aspect of the primary perf 
ABI, it deserves to be on the kernel side.

Thanks,

	Ingo