linux-kernel - Re: [PATCH] perf docs: Refine the description for the buffer size

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Message-ID: <9b27533e-6dc6-4476-8f0b-4497388efde3@linaro.org>
Date: Mon, 12 Aug 2024 10:11:56 +0100
From: James Clark <james.clark@...aro.org>
To: Leo Yan <leo.yan@....com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
 "Liang, Kan" <kan.liang@...ux.intel.com>, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org, Govindarajan.Mohandoss@....com
Subject: Re: [PATCH] perf docs: Refine the description for the buffer size



On 10/08/2024 5:15 pm, Leo Yan wrote:
> Current description for the AUX trace buffer size is misleading. When a
> user specifies the option '-m,512M', it represents a size value in bytes
> (512MiB) but not 512M pages (512M x 4KiB regard to a page of 4KiB).
> 
> Make the document clear that the normal buffer and the AUX tracing
> buffer share the same semantics.
> 
> Signed-off-by: Leo Yan <leo.yan@....com>
> ---
>   tools/perf/Documentation/perf-record.txt | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 41e36b4dc765..242223240a08 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -273,10 +273,11 @@ OPTIONS
>   -m::
>   --mmap-pages=::
>   	Number of mmap data pages (must be a power of two) or size
> -	specification with appended unit character - B/K/M/G. The
> -	size is rounded up to have nearest pages power of two value.
> -	Also, by adding a comma, the number of mmap pages for AUX
> -	area tracing can be specified.
> +	specification in bytes with appended unit character - B/K/M/G.
> +	The size is rounded up to the nearest power-of-two page value.
> +	By adding a comma, an additional parameter with the same
> +	semantics used for the normal mmap areas can be specified for
> +	AUX tracing area.
>   
>   -g::
>   	Enables call-graph (stack chain/backtrace) recording for both

The same text is repeated on a few tools, probably makes sense to update 
them all at the same time.

With that change:

Reviewed-by: James Clark <james.clark@...aro.org>