linux-kernel - Re: [PATCH] perf script: Update brstack syntax documentation

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Message-ID: <20250311081443.GI9682@e132581.arm.com>
Date: Tue, 11 Mar 2025 08:14:43 +0000
From: Leo Yan <leo.yan@....com>
To: Yujie Liu <yujie.liu@...el.com>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Martin Liska <martin.liska@....com>
Subject: Re: [PATCH] perf script: Update brstack syntax documentation

Hi Yujie,

Sorry I missed this patch.

On Tue, Feb 25, 2025 at 02:17:36PM +0800, Yujie Liu wrote:
> 
> The following commits appended new fields to the end of the branch info
> list, such as branch type and branch speculation info.
> 
> commit 1f48989cdc7d ("perf script: Output branch sample type")
> commit 6ade6c646035 ("perf script: Show branch speculation info")
> 
> Update brstack syntax documentation to be consistent with the latest
> branch info list. Improve the descriptions to help users interpret the
> fields accurately.
> 
> Signed-off-by: Yujie Liu <yujie.liu@...el.com>
> ---
>  tools/perf/Documentation/perf-script.txt | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/perf/Documentation/perf-script.txt b/tools/perf/Documentation/perf-script.txt
> index b72866ef270b..8bd105084280 100644
> --- a/tools/perf/Documentation/perf-script.txt
> +++ b/tools/perf/Documentation/perf-script.txt
> @@ -239,13 +239,15 @@ OPTIONS
>         i.e., -F "" is not allowed.
> 
>         The brstack output includes branch related information with raw addresses using the
> -       /v/v/v/v/cycles syntax in the following order:
> -       FROM: branch source instruction
> -       TO  : branch target instruction
> -        M/P/-: M=branch target mispredicted or branch direction was mispredicted, P=target predicted or direction predicted, -=not supported
> -       X/- : X=branch inside a transactional region, -=not in transaction region or not supported
> -       A/- : A=TSX abort entry, -=not aborted region or not supported
> -       cycles
> +       FROM/TO/PRED/INTX/ABORT/CYCLES/TYPE/SPEC syntax in the following order:
> +       FROM  : branch source instruction
> +       TO    : branch target instruction
> +       PRED  : M=branch target mispredicted or branch direction was mispredicted, P=target predicted or direction predicted, -=not supported

Can we use a more generic naming (e.g., EVENT) for this field?

My patches have added a 'N' flag in this field, which stands for
"Not taken branch".  Later we might extend this field for support new
event types.

Thanks,
Leo

> +       INTX  : X=branch inside a transactional region, -=not in transaction region or not supported
> +       ABORT : A=TSX abort entry, -=not aborted region or not supported
> +       CYCLES: the number of cycles that have elapsed since the last branch was recorded
> +       TYPE  : branch type
> +       SPEC  : branch speculation info
> 
>         The brstacksym is identical to brstack, except that the FROM and TO addresses are printed in a symbolic form if possible.
> 
> --
> 2.34.1
> 
>