linux-kernel - Re: [PATCH v3 2/7] perf metric: Event "Compat" value supports matching multiple identifiers

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Date:   Fri, 16 Jun 2023 12:41:40 +0100
From:   John Garry <john.g.garry@...cle.com>
To:     Jing Zhang <renyu.zj@...ux.alibaba.com>,
        Ian Rogers <irogers@...gle.com>, Will Deacon <will@...nel.org>,
        Shuai Xue <xueshuai@...ux.alibaba.com>,
        Robin Murphy <robin.murphy@....com>
Cc:     James Clark <james.clark@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Ilkka Koskinen <ilkka@...amperecomputing.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org,
        Zhuo Song <zhuo.song@...ux.alibaba.com>
Subject: Re: [PATCH v3 2/7] perf metric: Event "Compat" value supports
 matching multiple identifiers

On 15/06/2023 03:18, Jing Zhang wrote:
>>>>> Unit is the format of the event_source device name. We should match based on that as well as compat. I need to check the code again to understand how that is done... it has changed a good bit in 3 years.
>>>>>
>>>> This situation only happens on uncore metric. I happened to write wrong Unit, but the metric still matches.
>>>>
>>> I'm just double checking this now. I think any possible fix should be easy enough for current code but may be tricky for backport with lots of metric code changes.
>> I also have code to re-work sys event metric support such that we don't require "compat" or "Unit" values for a metric when the metric is described in terms of event aliases. That code is 2 years old, so may take a bit of time to rebase. I'll look to do that now.
>>
> Sounds good!

BTW, I am just looking at your cmn JSONs in this series, and we have 
something like this:

index 0000000..e70ac1a
--- /dev/null
+++ b/tools/perf/pmu-events/arch/arm64/arm/cmn/sys/metrics.json
@@ -0,0 +1,74 @@
+[
+	{
+		"MetricName": "slc_miss_rate",
+		"BriefDescription": "The system level cache miss rate include.",
+		"MetricGroup": "arm_cmn",
+		"MetricExpr": "hnf_cache_miss / hnf_slc_sf_cache_access",

So this expression uses event aliases hnf_cache_miss and 
hnf_slc_sf_cache_access - where are they defined in a JSON?

I could not see them. If they are not needed, then I may be missing 
something...

Thanks,
John