Benchmarks: AMD's 45nm 'Shanghai' Opteron

Christoph Hochstätter ZDNet Germany

Published: 20 Nov 2008

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Go to section: Introduction Virtualisation compatibility Expanded L3 cache Arithmetic performance Memory performance Virtualisation Conclusion

Full virtualisation without VMware
Like its Barcelona predecessor, Shanghai supports nested page tables, which AMD calls Rapid Virtualisation Indexing (RVI). Intel does not support this technology on its current server platforms but is expected to offer this feature with its Nehalem architecture.

Users who employ virtualisation software from market leader VMware are unlikely to see performance improvements from RVI because VMware's binary translation software is at least the equal of RVI. Technically, binary translation means nothing more than code patching, with the program code altered to match the virtual address space.

That technology only functions with supported operating systems, and is a possible source of errors — particularly when patching — if executables do not distinguish clearly between programming code and data. A hardware feature such as RVI is primarily a safe alternative to binary translation. Support for it has been implemented, or is planned, by all virtualisation vendors.

AMD's memory architecture is also useful for virtualisation. If a four- or eight-processor system is divided up so that each VM gets a physical processor with four cores, then main memory can be used optimally for each one. Memory throughput can cause problems in virtualised environments, particularly with Dunnington systems where bottlenecks can be caused by up to 24 cores depending on a single memory controller.

 

Go to section: Introduction Virtualisation compatibility Expanded L3 cache Arithmetic performance Memory performance Virtualisation Conclusion

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