linux-kernel - Re: [PATCH 2/3] perf list: Collapse similar events across PMUs

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Message-ID: <20250305093545.GD13418@e132581.arm.com>
Date: Wed, 5 Mar 2025 09:35:45 +0000
From: Leo Yan <leo.yan@....com>
To: James Clark <james.clark@...aro.org>
Cc: 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>,
	Robin Murphy <robin.murphy@....com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] perf list: Collapse similar events across PMUs

On Tue, Mar 04, 2025 at 01:49:14PM +0000, James Clark wrote:
> Instead of showing multiple line items with the same event name and
> description, show a single line and concatenate all PMUs that this
> event can belong to.
> 
> Don't do it for json output. Machine readable output doesn't need to be
> minimized, and changing the "Unit" field to a list type would break
> backwards compatibility.
> 
> Before:
>  $ perf list -v
>  ...
>  br_indirect_spec
>        [Branch speculatively executed,indirect branch. Unit: armv8_cortex_a53]
>  br_indirect_spec
>        [Branch speculatively executed,indirect branch. Unit: armv8_cortex_a57]
> 
> After:
> 
>  $ perf list -v
>  ...
>  br_indirect_spec
>        [Branch speculatively executed,indirect branch. Unit: armv8_cortex_a53,armv8_cortex_a57]

>From my testing, based on the latest tmp.perf-tools-next branch, I
need to remove the option '-v'.  Otherwise, the '-v' option will
enable long event descriptions, in this case, it does _not_ print Unit
strings at all (see default_print_event() in builtin-list.c).

  default_print_event()
  {
    ...
    if (long_desc && print_state->long_desc) {
            fprintf(fp, "%*s", 8, "[");
            wordwrap(fp, long_desc, 8, pager_get_columns(), 0);
            fprintf(fp, "]\n");
    } else if (desc && print_state->desc) {
    ...
  }

The command `perf list` would be sufficent.

Thanks,
Leo