<p>My understanding is that NUMA helps optimize RAM usage by 'preferring' RAM which is physically closer to the CPU on which the instructions are running. With a single, multi-core processor, I wouldn't think there's much advantage. With more than one processor, you often have your RAM slots split with each proc getting its own bank or bus. If instructions or data are located on the other processor's bus, there is a time penalty incurred on every access.</p>
<p>Virtualization technologies can request affinity to a processor to keep a particular vm on a single processor, but if the amount of RAM needed exeeds that available locally to the processor, then the non-preffered RAM on the other processor's bus will be used, resulting in a small performance hit.</p>
<p>That, at least, is my understanding. Please correct me if I'm wrong!</p>
<p><blockquote type="cite">On Jun 18, 2010 2:32 PM, "Nathan C. Smith" <<a href="mailto:nathan.smith@ipmvs.com">nathan.smith@ipmvs.com</a>> wrote:<br><br><br>
Sort of a virtualization question I guess.<br>
<br>
Is using NUMA still preferred when doing virtualization on a single processor machine with multiple cores, or is NUMA purely for multiple physical processor clusters?<br>
<br>
What about NUMA when virtualization is not in use? Any benefit or performance penalty on a single or multiple processor machine?<br>
<br>
Thanks.<br>
<br>
-Nate<br>
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