linux-kernel - Re: [PATCH 1/4] arm_pmu: Add PERF_PMU_CAP_EXTENDED_HW

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Message-ID: <20230721102131.GA12457@willie-the-truck>
Date:   Fri, 21 Jul 2023 11:21:31 +0100
From:   Will Deacon <will@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     James Clark <james.clark@....com>, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Anshuman Khandual <anshuman.khandual@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.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>,
        Kan Liang <kan.liang@...ux.intel.com>,
        linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH 1/4] arm_pmu: Add PERF_PMU_CAP_EXTENDED_HW_TYPE capability

On Thu, Jul 20, 2023 at 10:12:21AM -0700, Ian Rogers wrote:
> On Tue, Jul 11, 2023 at 7:12 AM James Clark <james.clark@....com> wrote:
> >
> >
> >
> > On 11/07/2023 13:01, Anshuman Khandual wrote:
> > >
> > >
> > > On 7/10/23 17:51, James Clark wrote:
> > >> This capability gives us the ability to open PERF_TYPE_HARDWARE and
> > >> PERF_TYPE_HW_CACHE events on a specific PMU for free. All the
> > >> implementation is contained in the Perf core and tool code so no change
> > >> to the Arm PMU driver is needed.
> > >>
> > >> The following basic use case now results in Perf opening the event on
> > >> all PMUs rather than picking only one in an unpredictable way:
> > >>
> > >>   $ perf stat -e cycles -- taskset --cpu-list 0,1 stress -c 2
> > >>
> > >>    Performance counter stats for 'taskset --cpu-list 0,1 stress -c 2':
> > >>
> > >>          963279620      armv8_cortex_a57/cycles/                (99.19%)
> > >>          752745657      armv8_cortex_a53/cycles/                (94.80%)
> > >>
> > >> Fixes: 55bcf6ef314a ("perf: Extend PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE")
> > >> Suggested-by: Ian Rogers <irogers@...gle.com>
> > >> Signed-off-by: James Clark <james.clark@....com>
> 
> Hi ARM Linux and ARM Linux PMU people,
> 
> Could this patch be picked up for Linux 6.5? I don't see it in the
> tree and it seems a shame to have to wait for it. The other patches do
> cleanup and so waiting for 6.6 seems okay.

I'm only taking fixes for 6.5 and I don't think this qualifies.

If it was an oversight introduced during the recent merge window, then
I'd be happier fixing it up, but 55bcf6ef314a was merged ages ago (v5.12?),
so I think we can wait.

I'll be queuing perf changes for 6.6 next week, so I'll look at this
then.

Cheers,

Will