6.0

Resource allocation
You can change CPU resource allocation seings, such as shares, reservation,
and limit, when available resource capacity does not meet demands. For
example, if at year end, the workload on accounting increases, you can
increase the accounting resource pool reserve.
vSphere Virtual
Symmetric
Multiprocessing (Virtual
SMP)
Virtual SMP or vSphere Virtual Symmetric Multiprocessingis a feature that
enables a single virtual machine to have multiple processors.
Virtual CPU Limitations
The maximum number of virtual CPUs that you can assign to a virtual machine depends on the hardware
version number of the virtual machine, the number of logical CPUs on the host, and the type of guest
operating system that is installed on the virtual machine.
Be aware of the following limitations:
n
A virtual machine cannot have more virtual CPUs than the number of logical cores on the host. The
number of logical cores is equal to the number of physical cores if hyperthreading is disabled. The
number of logical cores is equal to twice the number of physical cores if hyperthreading is enabled.
n
Not every guest operating system supports Virtual SMP, and guest operating systems that support this
function might support fewer processors than are available on the host. For information about Virtual
SMP support, see the VMware Compatibility Guide at hp://www.vmware.com/resources/compatibility.
n
Hyperthreaded hosts might aect virtual machine performance, depending on the workload. The best
practice is to test your workload to determine whether to enable or disable hyperthreading on your
hosts.
Configuring Multicore Virtual CPUs
VMware multicore virtual CPU support lets you control the number of cores per virtual socket in a virtual
machine. This capability lets operating systems with socket restrictions use more of the host CPU's cores,
which increases overall performance.
I When you congure your virtual machine for multicore virtual CPU seings, you must ensure
that your conguration complies with the requirements of the guest operating system EULA.
Using multicore virtual CPUs can be useful when you run operating systems or applications that can take
advantage of only a limited number of CPU sockets.
You can congure a virtual machine that runs on an ESXi host 6.0 and later to have up to 128 virtual CPUs.
A virtual machine cannot have more virtual CPUs than the actual number of logical CPUs on the host. The
number of logical CPUs means the number of physical processor cores or two times that number if
hyperthreading is enabled. For example, if a host has 128 logical CPUs, you can congure the virtual
machine for 128 virtual CPUs.
You congure how the virtual CPUs are assigned in terms of cores and cores per socket. Determine how
many CPU cores you want in the virtual machine, then select the number of cores you want in each socket,
depending on whether you want a single core CPU, dual-core CPU, tri-core CPU, and so on. Your selection
determines the number of sockets that the virtual machine has.
For more information about multicore CPUs, see the vSphere Resource Management documentation.
Chapter 3 Virtual Machine Management with the VMware Host Client
VMware, Inc. 51