Best practices for KVM on NUMA servers

Tuneup

Conclusion

As the number of cores per CPU increases drastically, NUMA optimization matters for all multisocket servers. The Linux community understands this trend and, on a nearly day-to-day basis, adds new libvirt elements and attributes to optimize VM placement in the hypervisor. Manual NUMA optimization leads to the best results, but it can rapidly become tedious in terms of management and can lead to dangerous memory over-commitment situations.

An interesting automatic optimization alternative exists with numad, but this user mode service cannot take full advantage of some kernel data structures and does not provide the best response. To address this situation, a kernel-based solution called "automatic NUMA balancing" is under development and may appear in future Linux distributions with better results than numad.

Infos

NUMA: http://en.wikipedia.org/wiki/Non-uniform_memory_access
libvirt API: http://libvirt.org/
STREAM, STREAM2: http://www.cs.virginia.edu/stream/
LMbench: http://www.bitmover.com/lmbench/
memtester: http://pyropus.ca/software/memtester/

The Author

François Donzé is a senior technical consultant at HP living on the French Riviera. After 10 years of regional presales activities, he now works in the Linux R&D organization with a focus on various responsibilities, including virtualization, mission-critical server deployment optimization, and IPv6.

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