linux-kernel - Re: [RFC PATCH 1/4] perf: Read cache instance ID when building cache topology

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Date:   Mon, 3 Apr 2023 08:13:35 +0530
From:   K Prateek Nayak <kprateek.nayak@....com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        peterz@...radead.org, mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        namhyung@...nel.org, ravi.bangoria@....com, sandipan.das@....com,
        ananth.narayan@....com, gautham.shenoy@....com, eranian@...gle.com
Subject: Re: [RFC PATCH 1/4] perf: Read cache instance ID when building cache
 topology

Hello Arnaldo,

Thank you for taking a look at the series.

On 3/31/2023 5:24 PM, Arnaldo Carvalho de Melo wrote:
> Em Fri, Mar 31, 2023 at 10:21:14AM +0530, K Prateek Nayak escreveu:
>> CPU cache level data currently stores cache level, type, line size,
>> associativity, sets, total cache size, and the CPUs sharing the cache.
>> Also read and store the cache instance ID from
>> "/sys/devices/system/cpu/cpuX/cache/indexY/id" in the cache level data.
>> Use instance ID as well when comparing cache levels.
> 
> And if a new perf tool is used in an older kernel without this new 'id'
> file?
> 
> Please check if the file exists, if it doesn't don't fail, just
> initialize with a zero, this way the latest perf will be usable in older
> kernels.

That makes sense. I'll handle this case as you suggested in the next
version.

> 
> - Arnaldo
>  
>> [..snip..]
> 

 
--
Thanks and Regards,
Prateek