linux-kernel - Re: [PATCH v7 0/8] Add support for Sub-NUMA cluster (SNC) systems

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Message-ID: <a22ae684-faf7-c4e1-226b-7eab4e9caf65@intel.com>
Date:   Tue, 3 Oct 2023 09:34:13 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     "Luck, Tony" <tony.luck@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Peter Newman <peternewman@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Shuah Khan <skhan@...uxfoundation.org>,
        "x86@...nel.org" <x86@...nel.org>
CC:     Shaopeng Tan <tan.shaopeng@...itsu.com>,
        James Morse <james.morse@....com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Babu Moger <babu.moger@....com>,
        Randy Dunlap <rdunlap@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: Re: [PATCH v7 0/8] Add support for Sub-NUMA cluster (SNC) systems



On 10/3/2023 9:16 AM, Luck, Tony wrote:
>> The Sub-NUMA cluster feature on some Intel processors partitions
>> the CPUs that share an L3 cache into two or more sets. This plays
>> havoc with the Resource Director Technology (RDT) monitoring features.
>> Prior to this patch Intel has advised that SNC and RDT are incompatible.
>>
>> Some of these CPU support an MSR that can partition the RMID
>> counters in the same way. This allows for monitoring features
>> to be used (with the caveat that memory accesses between different
>> SNC NUMA nodes may still not be counted accuratlely.

The typo that I pointed out in V4 as well as V5 remains.
Not fixing something this fundamental reflects poorly on the rest
of this work.

Reinette