linux-kernel - Re: [PATCH v2] perf doc: Document ring buffer mechanism

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Message-ID: <87v8dw6vp1.fsf@meer.lwn.net>
Date:   Thu, 03 Aug 2023 08:34:50 -0600
From:   Jonathan Corbet <corbet@....net>
To:     Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        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
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: Re: [PATCH v2] perf doc: Document ring buffer mechanism

Leo Yan <leo.yan@...aro.org> writes:

> 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>
> ---

So this seems like good material from a very brief scan.  I do have to
ask, though: why is it not in RST, and why not put it into the
user-space API book?

Thanks,

jon