linux-kernel - Re: [RFC 00/12] ARM: MPAM: add support for priority partitioning control

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Message-ID: <ddbc280a-1a53-b6ce-ea83-5b08eb1f5c6f@intel.com>
Date:   Thu, 17 Aug 2023 13:29:37 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Amit Singh Tomar <amitsinght@...vell.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <fenghua.yu@...el.com>, <james.morse@....com>,
        <gcherian@...vell.com>, <robh@...nel.org>,
        <peternewman@...gle.com>, "Luck, Tony" <tony.luck@...el.com>
Subject: Re: [RFC 00/12] ARM: MPAM: add support for priority partitioning
 control

Hi Amit,

On 8/17/2023 12:11 PM, Reinette Chatre wrote:
> On 8/15/2023 8:27 AM, Amit Singh Tomar wrote:

>>
>> Within the DDR QoS traffic class.
>>
>> 0--5 ----> Low priority value
>> 6-10 ----> Medium priority value
>> 11-15 ----> High priority value
>>
>> Benchmark[4] used is multichase.
>>
>> Two partition P1 and P2:
>>
>> Partition P1:
>> -------------
>> Assigned core 0
>> 100% BW assignment
>>
>> Partition P2:
>> -------------
>> Assigned cores 1-79
>> 100% BW assignment
>>
>> Test Script:
>> -----------
>> mkdir p1
>> cd p1
>> echo 1 > cpus
>> echo L3:1=8000,5 > schemata   ##### DSPRI set as 5 (lpr)
>> echo "MB:0=100" > schemata

I peeked at the next commit and I am missing something. 

It looks like indeed resource instances need to
support different controls, so that seems to answer my earlier
question. How to let user know what is supported where
remains an open, now with understanding that the information
is required to be per resource instance.

The first commit mentions that #0 has the Priority
partitioning feature but in these examples the schemata
of #1 is updated to modify the priority. Also, if I
understand correctly CPOR and priority partitioning
are mutually exclusive so I find it confusing to
see a bitmap and a priority written to a single resource.

Reinette