linux-kernel - Re: [PATCH 4/4] perf: Remove unused PERF_PMU_CAP_HETEROGENEOUS

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Date:   Tue, 11 Jul 2023 17:40:09 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, irogers@...gle.com
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        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>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Will Deacon <will@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/4] perf: Remove unused PERF_PMU_CAP_HETEROGENEOUS_CPUS
 capability



On 7/10/23 17:51, James Clark wrote:
> Since commit bd2756811766 ("perf: Rewrite core context handling") the
> relationship between perf_event_context and PMUs has changed so that
> the error scenario that PERF_PMU_CAP_HETEROGENEOUS_CPUS originally
> silenced no longer exists.
> 
> Remove the capability to avoid confusion that it actually influences
> any perf core behavior. This change should be a no-op.
> 
> Signed-off-by: James Clark <james.clark@....com>
> ---
>  include/linux/perf_event.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index d5628a7b5eaa..3f4d941fd6c5 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -288,7 +288,7 @@ struct perf_event_pmu_context;
>  #define PERF_PMU_CAP_EXTENDED_REGS		0x0008
>  #define PERF_PMU_CAP_EXCLUSIVE			0x0010
>  #define PERF_PMU_CAP_ITRACE			0x0020
> -#define PERF_PMU_CAP_HETEROGENEOUS_CPUS		0x0040
> +/* Unused					0x0040 */

Small nit, "Unused" marking might not be required here.

>  #define PERF_PMU_CAP_NO_EXCLUDE			0x0080
>  #define PERF_PMU_CAP_AUX_OUTPUT			0x0100
>  #define PERF_PMU_CAP_EXTENDED_HW_TYPE		0x0200