Message-ID: <6a3f6867-04cf-4691-a0f4-a722b603ec32@amd.com>
Date: Thu, 22 May 2025 14:15:18 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>,
 Peter Newman <peternewman@...gle.com>
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Subject: Re: [PATCH v13 00/27] x86/resctrl : Support AMD Assignable Bandwidth
 Monitoring Counters (ABMC)

Hi Reinette,

On 5/22/25 11:33, Reinette Chatre wrote:
> Hi Babu,
> 
> On 5/22/25 8:44 AM, Moger, Babu wrote:
>> On 5/21/25 18:03, Reinette Chatre wrote:
> 
> ...
> 
>>> This is why I proposed in [3] that the name of the mode reflects how user can interact
>>> with the system. Instead of one "mbm_cntr_assign" mode there can be "mbm_cntr_event_assign"
>>> that is used for ABMC and "mbm_cntr_group_assign" that is used for soft-ABMC. The mode should
>>> make it clear what the system is capable of wrt counter assignments.
>>
>> Yes, that makes sense. Perhaps we can also simplify it further:
>>
>> # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode:
>> [mbm_cntr_evt_assign] <- for ABMC
>>  mbm_cntr_grp_assign  <- for soft-ABMC
> 
> Looks good to me. Thank you.
> 
>>> Considering this the interface should be clear:
>>> num_mbm_cntrs: reflects the number of counters in each domain that can be assigned. In
>>> "mbm_cntr_event_assign" this will be the number of counters that can be assigned to 
>>> each event within a monitoring group, in "mbm_cntr_group_assign" this will be the number
>>> of counters that can be assigned to entire monitoring groups impacting all MBM events.
>>>
>>> mbm_L3_assignments: manages the counter assignment in each group. When user knows the mode
>>> is "mbm_cntr_event_assign"/"mbm_cntr_group_assign" then it should be clear to user space how the
>>> interface behaves wrt assignment, no surprises of multiple events impacted when
>>> assigning/unassigning single event.
>>>
>>> For soft-ABMC I thus find it most intuitive for num_mbm_cntrs to be the exact number
>>> of "active" RMIDs that the system can support *and* changing the name of the modes
>>> to help user interpret num_mbm_cntrs.
>>
>> Sure. The option A: fits well here then.
>>
>>  Option A (counters are RMIDs):
>>  # cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs
>>  0=31;1=31
> 
> Thank you for considering.
> 
> Please add the requirements from this discussion to your running list. Also please keep in mind
> how soft-ABMC intends to use the interfaces created by this work so that the documentation that
> accompanies the ABMC support in this series leaves enough "wiggle room" for soft-ABMC to be built on top.

Sure. Thanks

> 
>>>> [1] https://lore.kernel.org/lkml/CALPaoChSzzU5mzMZsdT6CeyEn0WD1qdT9fKCoNW_ty4tojtrkw@mail.gmail.com/
>>>
>>> Reinette
>>>
>>> [2] https://lore.kernel.org/lkml/b9e48e8f-3035-4a7e-a983-ce829bd9215a@intel.com/
>>> [3] https://lore.kernel.org/lkml/b3babdac-da08-4dfd-9544-47db31d574f5@intel.com/
>>>
>>
> 
> Reinette
> 

-- 
Thanks
Babu Moger

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