linux-kernel - Re: [PATCH v12 14/26] x86/resctrl: Add the functionality to assign MBM events

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Message-ID: <1bfdcaed-35ae-4754-9b1b-f86ae10f9cd8@amd.com>
Date: Wed, 16 Apr 2025 14:29:41 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, tony.luck@...el.com,
 peternewman@...gle.com
Cc: corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
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 maciej.wieczor-retman@...el.com, eranian@...gle.com
Subject: Re: [PATCH v12 14/26] x86/resctrl: Add the functionality to assign
 MBM events

Hi Reinette,

On 4/16/25 14:02, Reinette Chatre wrote:
> Hi Babu,
> 
> On 4/16/25 10:09 AM, Moger, Babu wrote:
>> On 4/15/25 11:53, Reinette Chatre wrote:
>>> On 4/15/25 7:20 AM, Moger, Babu wrote:
>>>> On 4/11/25 16:04, Reinette Chatre wrote:
>>>>> On 4/3/25 5:18 PM, Babu Moger wrote:
>>>>>> The mbm_cntr_assign mode offers "num_mbm_cntrs" number of counters that
>>>>>> can be assigned to an RMID, event pair and monitor the bandwidth as long
>>>>>> as it is assigned.
>>>>>
>>>>> Above makes it sound as though multiple counters can be assigned to
>>>>> an RMID, event pair.
>>>>>
>>>>
>>>> Yes. Multiple counter-ids can be assigned to RMID, event pair.
>>>
>>> oh, are you referring to the assignments of different counters across multiple
>>> domains?
>>
>> May be I am confusing you here. This is what I meant.
>>
>> Here is one example.
>>
>> In a same group,
> 
> "same group" means single RMID, eg. RMID_A

Yes.

> 
>>   Configure cntr_id 0, to count reads only (This maps to total event).
> 
> This will be one event, event0, so one counter assigned to RMID_A, event0 pair.
> 
>>   Configure cntr_id 1, to count write only (This maps to local event).
> 
> ... event1, one counter assigned to RMID_A, event1 pair, ...
> 
>>   Configure cntr_id 2, to count dirty victims.
> 
> ... event2, one counter assigned to RMID_A, event2 pair, ...
> 
>>   so on..
>>   so on..
>>   Configure cntr_id 31, to count remote read only.
> 
> ... and event31, one counter assigned to RMID_A, event31 pair.

Yes. That is correct.

> 
> The example reflects that a *single* counter can be assigned to an RMID, event pair.
> 
> Considering above, perhaps changelog can start with something like:
> 	mbm_cntr_assign mode offers "num_mbm_cntrs" number of counters that
>         can be assigned to RMID, event pairs ....
> 

Sounds good.

-- 
Thanks
Babu Moger