6.5.1

Table 1‑46. Counters
Name Description
virtual_machine Amount of CPU actively being used by each virtual machine on the host. 100% represents all
CPUs.
For example, if a virtual machine has one virtual CPU that is running on a host with four
CPUs and the CPU usage is 100%, the virtual machine is using one CPU resource.
virtual CPU usage = usagemhz ÷ (number of virtual CPUs × core frequency)
N This is the host's view of the CPU usage, not the guest operating system view.
n
Counter: usage
n
Stats Type: Rate
n
Unit: Percentage (%). Precision is to 1/100%. A value between 0 and 100.
n
Rollup Type: Average (Minimum/Maximum)
n
Collection Level: 1 (4)
Chart Analysis
A short spike in CPU usage or CPU ready indicates that you are making the best use of the virtual machine
resources. However, if the CPU usage value for a virtual machine is above 90% and the CPU ready value is
above 20%, performance is being impacted.
If performance is impacted, consider taking the actions listed below.
Table 1‑47. 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 Compare the CPU usage value of a virtual machine with the CPU usage of other virtual machines on the host or in
the resource pool. The stacked line chart on the host's Virtual Machine view shows the CPU usage for virtual
machines on the host.
4 Determine whether the high ready time for the virtual machine resulted from its CPU usage time reaching the CPU
limit seing. If so, increase the CPU limit on the virtual machine.
5 Increase the CPU shares to give the virtual machine more opportunities to run. The total ready time on the host
might remain at the same level if the host system is constrained by CPU. If the host ready time doesn't decrease, set
the CPU reservations for high-priority virtual machines to guarantee that they receive the required CPU cycles.
6 Increase the amount of memory allocated to the virtual machine. This decreases disk and or network activity for
applications that cache. This might lower disk I/O and reduce the need for the host to virtualize the hardware.
Virtual machines with smaller resource allocations generally accumulate more CPU ready time.
7 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 benets from a single vCPU. But the
hypervisor's maintenance of the three idle vCPUs takes CPU cycles that could be used for other work.
8 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.
9 Upgrade the physical CPUs or cores on the host if necessary.
10 Use the newest version of hypervisor software, and enable CPU-saving features such as TCP Segmentation Ooad,
large memory pages, and jumbo frames.
Disk (KBps)
The Disk (KBps) chart displays disk I/O of the host.
This chart is located in the Home view of the host Performance tab.
vSphere Monitoring and Performance
36 VMware, Inc.