Flags GPUs that reach one or more peers only via a SYS-class PCIe hop
(crossing the CPU/NUMA-node boundary) in nvidia-smi topo -m. On servers
where GPUs are only bridged pairwise via NVLink bridge (no switched
NVLink fabric), this is the exact path that traffic between different
bridge pairs has to cross, and can cut multi-GPU throughput by 2x+ for
workloads spanning more than one pair.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Mikhail Chusavitin
9db651c75a