Intel's Sub-NUMA Clustering Support Linux Patches Spun A 19th Time

Written by Michael Larabel in Intel on 29 May 2024 at 06:22 AM EDT. Add A Comment
The past year there's been a big Linux kernel patch series in the work by Intel to improve Sub-NUMA Clustering "SNC" support so it behaves well with Intel Resource Director Technology (RDT) on modern Intel hardware. Hopefully that work will soon be ready for mainlining in the Linux kernel while this week brought the 19th revision to those patches.

Intel's Tony Luck continues working on this Sub-NUMA Clustering so that it works out better on modern platforms:
"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 CPUs support an MSR that can partition the RMID counters in the same way. This allows monitoring features to be used. Legacy monitoring files provide the sum of counters from each SNC node for backwards compatibility. Additional files per SNC node provide details per node.

Cache and memory bandwidth allocation features continue to operate at the scope of the L3 cache."

The 19th iteration of these SNC patches are quite light on alterations that give hope this work might finally be ready soon for merging into the Linux kernel.

SNC in splitting of the CPU cores / cache / memory into multiple NUMA domains can help enhance the performance of NUMA-aware workloads. Intel Resource Director Technology is their feature over monitoring/controlling of shared resources around memory bandwidth, cache utilization, etc.

Intel Xeon 5th Gen CPU

Those interested in pairing SNC on RDT-enabled servers can find the v19 patches for now on the Linux kernel mailing list.
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