I received a lot of questions about Hyperthreading and NUMA in ESX 4.1 after writing the ESX 4.1 NUMA scheduling article. A common misconception is that Hyperthreading is ignored and therefore not used on a NUMA system. This is not entirely true and due to the improved Hyperthreading code on Nehalems, the CPU scheduler is [...]

VMware has made some changes to the CPU scheduler in ESX 4.1; one of the changes is the support for Wide virtual machines. A wide virtual machine contains more vCPUs than the total amount of available cores in one NUMA node. Wide VM’s will be discussed after a quick rehash of NUMA. NUMA NUMA stands [...]

Note: This article describes NUMA scheduling on ESX 3.5 and ESX 4.0 platform, vSphere 4.1 introduced wide NUMA nodes, information about this can be found in my new article: ESX4.1 NUMA scheduling With the introduction of vSphere, VM configurations with 8 CPUs and 255 GB of memory are possible. While I haven’t seen that much [...]