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Little things I didn’t know: difference between _enable_NUMA_support and numactl

In preparation for a research project and potential UKOUG conference papers I am researching the effect of NUMA on x86 systems.

NUMA is one of the key features to understand in modern computer organisation, and I recommend reading “Computer Architecture, Fifth Edition: A Quantitative Approach” from Hennessy and Patterson (make sure you grab the 5th edition). Read the chapter about cache optimisation and also the appendix about the memory hierarchy!

Now why should you know NUMA? First of all there is an increasing number of multi-socket systems. AMD has pioneered the move to a lot of cores, but Intel is not far behind. Although AMD is currently leading in the number of cores (“modules”) on a die, Intel doesn’t need to: the Sandy-Bridge EP processors are way more powerful on a one-to-one comparison than anything AMD has at the moment.