linux-kernel - Re: [RFC PATCH v3 00/17] x86/resctrl : Support AMD Assignable Bandwidth Monitoring Counters (ABMC)

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Date: Wed, 8 May 2024 13:41:58 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: <babu.moger@....com>, <corbet@....net>, <fenghua.yu@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
	<rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
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	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>, <james.morse@....com>
Subject: Re: [RFC PATCH v3 00/17] x86/resctrl : Support AMD Assignable
 Bandwidth Monitoring Counters (ABMC)

Hi Babu,

On 5/8/2024 1:07 PM, Moger, Babu wrote:
> Hi Reinette,
> 
> On 5/7/24 15:26, Reinette Chatre wrote:
>> Hi Babu,
>>
>> On 5/6/2024 10:18 AM, Moger, Babu wrote:
>>> On 5/3/24 18:24, Reinette Chatre wrote:
>>>> On 3/28/2024 6:06 PM, Babu Moger wrote:
>>>>
>>>>> a. Check if ABMC support is available
>>>>> 	#mount -t resctrl resctrl /sys/fs/resctrl/
>>>>>
>>>>> 	#cat /sys/fs/resctrl/info/L3_MON/mbm_assign
>>>>> 	[abmc] 
>>>>> 	legacy_mbm
>>>>>
>>>>> 	Linux kernel detected ABMC feature and it is enabled.
>>>>
>>>> Please note that this adds the "abmc" feature to the resctrl
>>>> *filesystem* that supports more architectures than just AMD. Calling the
>>>> resctrl filesystem feature "abmc" means that (a) AMD needs to be ok with
>>>> other architectures calling their features that are
>>>> similar-but-maybe-not-identical-to-AMD-ABMC "abmc", or (b) this needs
>>>> a new generic name.
>>>
>>> It should not a problem if other architecture calling abmc for similar
>>> feature. But generic name is always better if there is a suggestion.
>>
>> "should not a problem" does not instill confidence that AMD is
>> actually ok with this.
> 
> The feature "ABMC" has been used in the public document already to refer
> this feature.
> https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/programmer-references/24594.pdf

It is clear to me that Assignable Bandwidth Monitoring Counters (ABMC) is the
name of the AMD feature. The question is whether users can use the 
same name to interact with "similar but maybe not identical" features from other
architectures, which is what this series enables.

> If there comes a conflict then we can change it to amd_abmc. Didn't see
> any conflict at this pint.

How do you envision this? The resctrl filesystem interface is intended to be
architecture neutral so it is not obvious to me how "amd_abmc" is expected
to look? Why would it be necessary to have different architecture specific names
for a similar feature from different architectures that users interact with in
the same way? Sounds to me as though this just needs a new non-AMD marketing name. 

Reinette