linux-kernel - Re: Region aware RDT options for resctrl

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Message-ID: <4bec8924-6125-45ef-a212-f123ab2e4f5b@intel.com>
Date: Mon, 14 Apr 2025 10:30:18 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: "Luck, Tony" <tony.luck@...el.com>, Fenghua Yu <fenghuay@...dia.com>,
	Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>, Peter Newman
	<peternewman@...gle.com>, James Morse <james.morse@....com>, Babu Moger
	<babu.moger@....com>, Drew Fustini <dfustini@...libre.com>, Dave Martin
	<Dave.Martin@....com>, Anil Keshavamurthy <anil.s.keshavamurthy@...el.com>
CC: <linux-kernel@...r.kernel.org>
Subject: Re: Region aware RDT options for resctrl

Hi Tony,

Could you please help clarify how memory regions should be viewed?

On 4/11/25 1:56 PM, Luck, Tony wrote:
> On Fri, Apr 11, 2025 at 01:54:12PM -0700, Luck, Tony wrote:
> 
> Add Cc: lkml
> 
>> A future CPU from Intel will implement "region aware" memory bandwidth
>> monitoring and bandwidth allocation. This will provide for more granular
>> monitoring and control for heterogeneous memory configurations. BIOS
>> will populate an ACPI table that describes which system physical address
>> ranges belong to each region. E.g. for a two socket system with both
>> DDR and CXL memory regions could be assigned like this:
>>
>> Region 0: Local DDR
>> Region 1: Remote DDR
>> Region 2: Local CXL
>> Region 3: Remote CXL

If considering an assignment like above ...

...

>> Option 1: Per-memory regions might be described individually like this:
>>
>> 	$ cat schemata
>> 	RMB0:0=100;1=100
>> 	RMB1:0=75;1=75
>> 	RMB2:0=25;1=25
>>

... I assume "RMB0" represents "Region 0" and so forth. In this case, what do
the "domain IDs" used in above option represent?

Thank you.

Reinette