Re: [PATCH v9 12/12] x86/resctrl: Add MMIO-based LLC occupancy monitoring support

[Reinette Chatre]

Hi Chenyu,

On 10/27/26 4:22 AM, Chen Yu wrote:
> Hi Reinette,
> 
> On Fri, Oct 23, 2026 at 05:08:44PM -0700, Reinette Chatre wrote:
>> Hi Chenyu,
>>
>> On 10/13/26 8:01 PM, Chen Yu wrote:
>>> Add erdt_mon_read() to read LLC occupancy via MMIO and use it
>>> when the platform supports ERDT. Register the L3 occupancy event
>>> with ERDT enabled when available, falling back to the MSR-based
>>> path otherwise.
>>>
>>> Use the CMRC (Cache Monitoring Registers for CPU Agents Description)
>>> ACPI sub-table to read LLC occupancy counters for each RMID via MMIO
>>> when ERDT is enabled.
>>>
>>> Although the occupancy counters can now be read from any CPU via
>>> MMIO, keep the per-domain limbo handler. A global handler would
>>> still have to iterate over every domain and would save nr_domains - 1
>>
>> Please write what "nr_domains - 1" means in English since as it is written
>> it is not clear how this "does not justify maintaining two limbo handler
>> models."
>>
> 
> OK, I'll rephrase it to a simpler version, how about this:
> 
> Although the occupancy counters can now be read from any CPU via MMIO,
> keep the per domain limbo handler. A single global handler would still
> have to check the limbo RMIDs of every L3 domain, so it would do the same
> amount of work. The only saving would be running one limbo worker instead
> of one per L3 domain, which does not justify maintaining two limbo handler
> models.

ok. One nit, please let it start with "Keep the per domain limbo handler ...".

Thank you.

Reinette