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 11:00:28 +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 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.
 * other_pmus: All other PMUs which are not part of core_pmus list. Does not
 *             matter whether it is a per SMT-thread or outside of the core in
 *             hw. i.e. PMUs belonging to other_pmus must have pmu->is_core=0
 *             but pmu->is_uncore could be 0 or 1.
 */
static LIST_HEAD(core_pmus);
static LIST_HEAD(other_pmus);

Thanks,
Ravi