linux-kernel - Re: [RFC V1 10/11] perf: Expand perf_branch

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Date:   Thu, 27 Jan 2022 16:11:15 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Rob Herring <robh@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-perf-users@...r.kernel.org,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [RFC V1 10/11] perf: Expand perf_branch_entry.type



On 1/26/22 10:17 PM, Rob Herring wrote:
> On Mon, Jan 24, 2022 at 10:00:52AM +0530, Anshuman Khandual wrote:
>> Current perf_branch_entry.type is a 4 bits field just enough to accommodate
>> 16 generic branch types. This is insufficient to accommodate platforms like
>> arm64 which has much more branch types. Lets just expands this field into a
>> 6 bits one, which can now hold 64 generic branch types. This also adds more
>> generic branch types and updates the BRBE driver as required.
>>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
>> Cc: Jiri Olsa <jolsa@...hat.com>
>> Cc: Namhyung Kim <namhyung@...nel.org>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-perf-users@...r.kernel.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>>  drivers/perf/arm_pmu_brbe.c           |  7 ++++++-
> 
> This patch should come before the BRBE support so that it can be applied
> sooner rather than later. If another field is added to the end before 
> expanding this field, then you will be stuck with assembling bits from 2 
> fields.

Should I just split this patch from the series and post it separately
right away, to be included in perf while BRBE support gets reviewed ?

> 
>>  include/uapi/linux/perf_event.h       | 10 ++++++++--
>>  tools/include/uapi/linux/perf_event.h | 10 ++++++++--
>>  tools/perf/util/branch.c              |  8 +++++++-
>>  4 files changed, 29 insertions(+), 6 deletions(-)