linux-kernel - Re: [PATCH RFC v3 00/12] perf pmu-events: Support event aliasing for system PMUs

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Date:   Tue, 12 May 2020 11:13:11 +0100
From:   John Garry <john.garry@...wei.com>
To:     Joakim Zhang <qiangqing.zhang@....com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "acme@...nel.org" <acme@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "jolsa@...hat.com" <jolsa@...hat.com>,
        "namhyung@...nel.org" <namhyung@...nel.org>
CC:     "irogers@...gle.com" <irogers@...gle.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        Linuxarm <linuxarm@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Zhangshaokun <zhangshaokun@...ilicon.com>,
        "will@...nel.org" <will@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH RFC v3 00/12] perf pmu-events: Support event aliasing for
 system PMUs


> I have an aside question, do you have any idea? Thanks a lot!
> 
> For DDR PMU, I want to add bandwidth usage metric, but it depends on DDR controller clock frequency.
> For example, we have i.MX8MM LPDDR4 board which DDR controller clock is 800MHZ, and i.MX8MM DDR4 board which DDR controller is 600MHZ, but the SoC is the same.
> 
> So they can share all JSON metrics with identifier "i.mx8mm", except bandwidth metric. 

what is the bandwidth metric? how is it supposed to be calculated?

If I add separate JOSN metrics files for identifier "i.mx8mm-lpddr4" and 
identifier "i.mx8mm-ddr4", then it's going to be very redundant, since 
most metrics are same just the identifier is different.
> 
> Do you know how perf tool handle such case?

jirka is supporting user-defined metric here:
https://lore.kernel.org/lkml/20200511205307.3107775-1-jolsa@kernel.org/

So maybe you can use that somehow with separate scripts.

Thanks,
John