The CPU (%) chart displays CPU usage for the host.

This chart is located in the Home view of the Host Performance tab.

Table 1. Data Counters

Chart Label

Description

Usage

Actively used CPU, as a percentage of the total available CPU, for each physical CPU on the host.

Active CPU is approximately equal to the ratio of the used CPU to the available CPU.

Available CPU = # of physical CPUs × clock rate.

100% represents all CPUs on the host. For example, if a four-CPU host is running a virtual machine with two CPUs, and the usage is 50%, the host is using two CPUs completely.

  • Counter: usage

  • Stats Type: Rate

  • Unit: Percentage (%)

  • Rollup Type: Average (Minimum/Maximum)

  • Collection Level: 1 (4)

Chart Analysis

A short spike in CPU usage indicates that you are making the best use of the host resources. However, if the value is constantly high, the host is probably lacking the CPU required to meet the demand. A high CPU usage value can lead to increased ready time and processor queuing of the virtual machines on the host.

If performance is impacted, consider taking the actions listed below.

Table 2. CPU Performance Enhancement Advice

#

Resolution

1

Verify that VMware Tools is installed on every virtual machine on the host.

2

Set the CPU reservations for all high-priority virtual machines to guarantee that they receive the CPU cycles required.

3

Reduce the number of virtual CPUs on a virtual machine to only the number required to execute the workload. For example, a single-threaded application on a four-way virtual machine only benefits from a single vCPU. But the hypervisor's maintenance of the three idle vCPUs takes CPU cycles that could be used for other work.

4

If the host is not already in a DRS cluster, add it to one. If the host is in a DRS cluster, increase the number of hosts and migrate one or more virtual machines onto the new host.

5

Upgrade the physical CPUs or cores on the host if necessary.

6

Use the newest version of hypervisor software, and enable CPU-saving features such as TCP Segmentation Offload, large memory pages, and jumbo frames.