GPU nodes - LUMI-G¶
The LUMI-G hardware partition consists of 2560 GPU-based nodes.
|2560||1x 64 cores AMD EPYC 7A53||512 GiB||4x AMD Instinct MI250X
|none||4x 200 Gb/s|
Each LUMI-G compute nodes is equipped with four AMD MI250X GPUs. Based on the 2nd Gen AMD CDNA architecture. A MI250x GPU is a multi-chip module (MCM) with two GPU dies named by AMD Graphics Compute Die (GCD). Each of these dies features 110 compute units (CU) and have access to a 64 GB slice of HBM memory for a total of 220 CUs and 128 GB total memory per MI250x module. An in-package Infinity Fabric interface between the GCDs deliver a theoretical peak bidirectional bandwidth of up to 400 GB/s. From a software perspective as well as from the Slurm perspective, one MI250x module is considered as two GPUs. It means the LUMI-G nodes can be considered as 8 GPUs nodes.
More information about the AMD MI250x can be found here:
In addition to the GPU, LUMI-G nodes feature a single 64-core AMD EPYC 7A53 "Trento" CPU configured as 4 NUMA nodes (NPS4). Each of these NUMA nodes have two links to one of the four MI250x modules: one link per GCD and a group of 8 cores + L3 cache with a peak bandwidth of 36 GB/s.
The figure below gives a general overview of a LUMI-G node as well as the topology of the CPU-GPU and GPU-GPU links.
From the figure above, you can see that there is no direct link between the GPU (GCD) numbering and the NUMA node numbering. Keep this in mind as prober NUMA and GPU binding is critical to achieve good performance.
The LUMI-G compute nodes each have four 200 Gb/s interfaces to the Slingshot-11 interconnect with one interface directly connected to each GPU. Thus, all network communication (even for the CPU) must go via one of the GPU network interfaces.
There is no local storage on the compute nodes in LUMI-G. You have to use one of the network based storage options.