Tuning Configurations

• Deploy single-threaded applications on uniprocessor virtual machines, instead of on SMP virtual machines, for the best performance and resource use.
• VMware advise against using CPU Affinity as it generally constrains the scheduler BD can cause an improperly balanced load
• Use DRS where you can as this will balance the load for you
• Don’t configure your VMs for more vCPUs then their workloads require. Configuring a VM with more vCPUs then it needs will cause additional, unnecessary CPU utilization due to the increased overhead relating to multiple vCPUs
• Enable Hyperthreading in the BIOS. Check this in the BIOS and in vCenter, click on the host, select Configuration, select Properties and check that Hyperthreading is enabled
• When dealing with NUMA systems, ensure that node interleaving is disabled in the BIOS. If node interleaving is set to enabled it essentially disables NUMA capability on that host
• When possible configure the number of vCPUs to equal or less than the number of physical cores on a single NUMA node. When you configure equal or less vCPUs:physical cores the VM will get all its memory from that single NUMA node, resulting in lower memory access and latency times
• Sometimes for certain machines it may be beneficial to schedule all of the vCPUs on the same sockets in under committed systems which gives that VM full access to a Shared Last Level cache rather than spread across multiple processors. Adjust sched.cpu.vsmpConsolidate=”true” in the VMX Configuration file
• Pay attention to the Manufacturers recommendations for resources, especially application multithreading support
• Use processors which support Hardware-Assisted CPU Virtualization (Intel VT-x and AMD AMD-V)
• Use processors which support Hardware-Assisted MMU Virtualization (Intel EPT and AMD RVI)
• When configuring virtual machines, the total CPU resources needed by the virtual machines running on the system should not exceed the CPU capacity of the host. If the host CPU capacity is overloaded, the performance of individual virtual machines may degrade