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

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Message-ID: <5876adba-0507-6bfd-6ede-74f8e7aa55f2@arm.com>
Date:   Mon, 24 Jul 2023 14:46:35 +0100
From:   James Clark <james.clark@....com>
To:     Will Deacon <will@...nel.org>, Ian Rogers <irogers@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org,
        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 21/07/2023 11:21, Will Deacon wrote:
> 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

Hi Will,

Thanks for looking at this. I've sent a v2 with Anshuman's fixes.

James