linux-kernel - Re: [PATCH 2/7] perf: Create a symlink for a PMU

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Date:   Fri, 25 Jun 2021 11:57:18 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Andi Kleen <ak@...ux.intel.com>, Greg KH <greg@...ah.com>
Cc:     peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, eranian@...gle.com,
        namhyung@...nel.org, acme@...nel.org, jolsa@...hat.com
Subject: Re: [PATCH 2/7] perf: Create a symlink for a PMU



On 6/25/2021 11:44 AM, Andi Kleen wrote:
> 
>> We have an attribute "caps/pmu_name" for the core PMU. Maybe we should 
>> add it for uncore PMU as well. For example,
>>
>> $ cat /sys/devices/uncore_type_0_0/caps/pmu_name
>> cha_0
>>
>> Userspace tool can get clues about what type_0_0 is.
> 
> It would break all the old tools, but I suppose it could work for 
> updated tools.
> 

Right, users have to update their perf tool to use the new name, 
uncore_cha_0.

> It isn't only perf that is parsing this, but some other libraries too. 
> They all would need to be updated too.
>

Yes, I will update the Documentation/ABI/ in V2 to indicate the changes. 
If any other libraries are broken, they may get clues from the Document.

Thanks,
Kan

> I think I still prefer the symlink. It would just work and keep full 
> compatibility.
> 
> But yes maybe there is no choice.
> 
> -Andi
> 
>