Configure CPU QoS

About CPU QoS

CPU QoS controls the ratio of CPU resources allocated to VMs to ensure VM performance and avoid unbalanced computing capability distribution.

CPU scheduling priority

A CPU scheduling priority determines the sequence in which VMs are assigned physical CPU resources. When physical CPU resources are insufficient, the VMs with high CPU scheduling priority take precedence.

CPU scheduling priorities can be high, medium, or low. The system allocates CPU resources to VMs with high, medium, and low CPU scheduling priorities in a ratio of 4:2:1. For example, three VMs run on a host that has a single-core 2.8GHz CPU, and the CPU scheduling priorities for the VMs are high, medium, and low, respectively. When the VMs run at full load, the CPU frequency allocated to them is 1600 MHz, 800 MHz, and 400 MHz, respectively.

A CPU scheduling priority takes effect only when VMs are competing for CPU resources. If CPU resources are sufficient, a VM can use all physical CPU resources of a host. For example, if only one of the VMs on a host is in running state, the VM can obtain all computing capability of the host's CPU.

CPU frequency reservation

The reserved CPU frequency is the lowest computing capability that a VM can obtain. Reserve CPU frequency to ensure correct operation of a VM when CPU resources are insufficient.

CPU frequency limit

A CPU frequency limit is the maximum computing capability that a VM can obtain. Limit the CPU frequency allocated to a VM to leave enough CPU resources for other VMs.

If you set the reserved CPU frequency, the minimum value of the CPU frequency limit is the reserved CPU frequency.

If you enable overall CPU limit, the system does not limit CPU frequency on a per-core basis.

 

Procedure

  1. On the top navigation bar, click Resources.

  1. From the left navigation pane, select Host Pool Name > Cluster Name > Host Name > VM Name or Host Pool Name > Host Name > VM Name.

  1. Click Edit.

  1. Expand advanced settings on the CPU tab.

  1. Configure the following settings:

Figure-1 Editing advanced CPU settings