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References: <20230829234426.64421-1-tony.luck@intel.com> <20230928191350.205703-1-tony.luck@intel.com>
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From:   Peter Newman <peternewman@google.com>
Date:   Fri, 29 Sep 2023 16:33:17 +0200
Message-ID: <CALPaoCjxW70h=rTNNiShEc8bmgwEaHpFnAHRB-m=ch47WdQsig@mail.gmail.com>
Subject: Re: [PATCH v6 0/8] Add support for Sub-NUMA cluster (SNC) systems
To:     Tony Luck <tony.luck@intel.com>
Cc:     Fenghua Yu <fenghua.yu@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Shuah Khan <skhan@linuxfoundation.org>, x86@kernel.org,
        Shaopeng Tan <tan.shaopeng@fujitsu.com>,
        James Morse <james.morse@arm.com>,
        Jamie Iles <quic_jiles@quicinc.com>,
        Babu Moger <babu.moger@amd.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        patches@lists.linux.dev
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Hi Tony,

On Thu, Sep 28, 2023 at 9:14=E2=80=AFPM Tony Luck <tony.luck@intel.com> wro=
te:
>
> 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.

Is an "SNC NUMA node" a "sub-NUMA node", or a NUMA node on which SNC
has been enabled?

Thanks!
-Peter