linux-kernel - Re: [PATCH v5 28/34] perf pmus: Split pmus list into core and other

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Date:   Fri, 9 Jun 2023 11:25:01 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.g.garry@...cle.com>,
        Will Deacon <will@...nel.org>,
        James Clark <james.clark@....com>,
        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>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Jing Zhang <renyu.zj@...ux.alibaba.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Ming Wang <wangming01@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        Sandipan Das <sandipan.das@....com>,
        Dmitrii Dolgov <9erthalion6@...il.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Ali Saidi <alisaidi@...zon.com>, Rob Herring <robh@...nel.org>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Kang Minchul <tegongkang@...il.com>,
        linux-kernel@...r.kernel.org, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [PATCH v5 28/34] perf pmus: Split pmus list into core and other

On 09-Jun-23 11:05 AM, Ian Rogers wrote:
> On Thu, Jun 8, 2023 at 10:30 PM Ravi Bangoria <ravi.bangoria@....com> wrote:
>>
>> On 09-Jun-23 10:10 AM, Ian Rogers wrote:
>>> On Thu, Jun 8, 2023 at 9:01 PM Ravi Bangoria <ravi.bangoria@....com> wrote:
>>>>
>>>> Hi Ian,
>>>
>>> Hi Ravi,
>>>
>>>> On 27-May-23 12:52 PM, Ian Rogers wrote:
>>>>> Split the pmus list into core and other. This will later allow for
>>>>> the core and other pmus to be populated separately.
>>>>>
>>>>> Signed-off-by: Ian Rogers <irogers@...gle.com>
>>>>> Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
>>>>> ---
>>>>>  tools/perf/util/pmus.c | 52 ++++++++++++++++++++++++++++++------------
>>>>>  1 file changed, 38 insertions(+), 14 deletions(-)
>>>>>
>>>>> diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
>>>>> index 58ff7937e9b7..4ef4fecd335f 100644
>>>>> --- a/tools/perf/util/pmus.c
>>>>> +++ b/tools/perf/util/pmus.c
>>>>> @@ -12,13 +12,19 @@
>>>>>  #include "pmu.h"
>>>>>  #include "print-events.h"
>>>>>
>>>>> -static LIST_HEAD(pmus);
>>>>> +static LIST_HEAD(core_pmus);
>>>>> +static LIST_HEAD(other_pmus);
>>>>
>>>> AMD ibs_fetch// and ibs_op// PMUs are per SMT-thread and are independent of
>>>> core hw pmu. I wonder where does IBS fit. Currently it's part of other_pmus.
>>>> So, is it safe to assume that other_pmus are not just uncore pmus? In that
>>>> case shall we add a comment here?
>>>
>>> I'm a fan of comments. The code has landed in perf-tools-next:
>>> https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/util/pmus.c?h=perf-tools-next
>>> Do you have any suggestions on wording? I've had limited success
>>> adding glossary terms, for example, offcore vs uncore:
>>> https://perf.wiki.kernel.org/index.php/Glossary#Offcore
>>> I think offcore is a more interconnect related term, but I'd prefer
>>> not to be inventing the definitions. I'd like it if we could be less
>>> ambiguous in the code and provide useful information on the wiki, so
>>> help appreciated :-)
>>
>> Does this look good?
>>
>> /*
>>  * core_pmus:  A PMU belongs to core_pmus if it's name is "cpu" or it's sysfs
>>  *             directory contains "cpus" file. All PMUs belonging to core_pmus
>>  *             must have pmu->is_core=1. If there are more than one PMUs in
>>  *             this list, perf interprets it as a heterogeneous platform.
> 
> 
> Looks good but a nit here. It is heterogeneous from point-of-view of
> PMUs, there are ARM systems where they are heterogenous with big an> little cores but they have a single homogeneous PMU driver. The perf
> tool will treat them as homogeneous.

In that case number of entries in core_pmus list would still be 1 right?

Thanks,
Ravi