linux-kernel - Re: [PATCH v2 0/9] jevents/pmu-events improvements

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Date:   Mon, 23 Jan 2023 13:25:46 +0000
From:   John Garry <john.g.garry@...cle.com>
To:     Ian Rogers <irogers@...gle.com>, Will Deacon <will@...nel.org>,
        James Clark <james.clark@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        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>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Kim Phillips <kim.phillips@....com>,
        Florian Fischer <florian.fischer@...q.space>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Xing Zhengjun <zhengjun.xing@...ux.intel.com>,
        Rob Herring <robh@...nel.org>,
        Kang Minchul <tegongkang@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sandipan Das <sandipan.das@....com>,
        Jing Zhang <renyu.zj@...ux.alibaba.com>,
        linuxppc-dev@...ts.ozlabs.org, Kajol Jain <kjain@...ux.ibm.com>
Cc:     Stephane Eranian <eranian@...gle.com>,
        Perry Taylor <perry.taylor@...el.com>,
        Caleb Biggers <caleb.biggers@...el.com>
Subject: Re: [PATCH v2 0/9] jevents/pmu-events improvements

On 21/12/2022 22:34, Ian Rogers wrote:
> Add an optimization to jevents using the metric code, rewrite metrics
> in terms of each other in order to minimize size and improve
> readability. For example, on Power8
> other_stall_cpi is rewritten from:
> "PM_CMPLU_STALL / PM_RUN_INST_CMPL - PM_CMPLU_STALL_BRU_CRU / PM_RUN_INST_CMPL - PM_CMPLU_STALL_FXU / PM_RUN_INST_CMPL - PM_CMPLU_STALL_VSU / PM_RUN_INST_CMPL - PM_CMPLU_STALL_LSU / PM_RUN_INST_CMPL - PM_CMPLU_STALL_NTCG_FLUSH / PM_RUN_INST_CMPL - PM_CMPLU_STALL_NO_NTF / PM_RUN_INST_CMPL"
> to:
> "stall_cpi - bru_cru_stall_cpi - fxu_stall_cpi - vsu_stall_cpi - lsu_stall_cpi - ntcg_flush_cpi - no_ntf_stall_cpi"
> Which more closely matches the definition on Power9.
> 
> A limitation of the substitutions are that they depend on strict
> equality and the shape of the tree. This means that for "a + b + c"
> then a substitution of "a + b" will succeed while "b + c" will fail
> (the LHS for "+ c" is "a + b" not just "b").
> 
> Separate out the events and metrics in the pmu-events tables saving
> 14.8% in the table size while making it that metrics no longer need to
> iterate over all events and vice versa. These changes remove evsel's
> direct metric support as the pmu_event no longer has a metric to
> populate it. This is a minor issue as the code wasn't working
> properly, metrics for this are rare and can still be properly ran
> using '-M'.
> 
> Add an ability to just build certain models into the jevents generated
> pmu-metrics.c code. This functionality is appropriate for operating
> systems like ChromeOS, that aim to minimize binary size and know all
> the target CPU models.

 From a glance, this does not look like it would work for arm64. As I 
see in the code, we check the model in the arch folder for the test to 
see if built. For arm64, as it uses arch/implementator/model folder org, 
and not just arch/model (like x86)

So on the assumption that it does not work for arm64 (or just any arch 
which uses arch/implementator/model folder org), it would be nice to 
have that feature also. Or maybe also support not just specifying model 
but also implementator.

> 
> v2. Rebase. Modify the code that skips rewriting a metric with the
>      same name with itself, to make the name check case insensitive.
> 


Unfortunately you might need another rebase as this does not apply to 
acme perf/core (if that is what you want), now for me at:

5670ebf54bd2 (HEAD, origin/tmp.perf/core, origin/perf/core, perf/core)
perf cs-etm: Ensure that Coresight timestamps don't go backwards

> Ian Rogers (9):
>    perf jevents metric: Correct Function equality
>    perf jevents metric: Add ability to rewrite metrics in terms of others
>    perf jevents: Rewrite metrics in the same file with each other
>    perf pmu-events: Separate metric out of pmu_event
>    perf stat: Remove evsel metric_name/expr
>    perf jevents: Combine table prefix and suffix writing
>    perf pmu-events: Introduce pmu_metrics_table
>    perf jevents: Generate metrics and events as separate tables
>    perf jevents: Add model list option

Thanks,
John