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Knowledge Base

High CPU usage and slow performance on all virtual machines on an ESX host (1005239)

Last Updated: 5/9/2008Categories: Total Views: 33386Language:
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Symptoms

All of the virtual machines on an ESX host experience:

Slow performance

High CPU usage

Resolution

IOWAIT occurs when the CPU cannot perform computations because it is waiting on I/O operations. Disk and network I/O operations are the slowest components in the system and are a common cause of IOWAIT. Launching a large application or an application running off the network may also cause IOWAIT.

IOWAIT is a normal part of system operation. It is a problem when it occurs too frequently or when it negatively affects system performance.

In the VMware environment, IOWAIT can be caused by:

Swapping performed because of a shortage of RAM on the host or on the guest operating system.

Paging performed if the guest operating system is short on RAM. Paging causes the guest to write to its virtual disk, which in turn causes disk I/O.

To determine if the Service Console is using swap space, execute the top command. The output appears similar to:

11:46:59 up 7:41, 2 users, load average: 0.00, 0.00, 0.00
197 processes: 196 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 0.0% 0.0% 0.0% 0.0% 0.9% 0.0% 99.0%
Mem: 268568k av, 260856k used, 7712k free, 0k shrd, 46336k buff
192980k actv, 36860k in_d, 2688k in_c
Swap: 554856k av, 0k used, 554856k free 88400k cached

PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
1 root 15 0 496 496 436 S 0.0 0.1 0:04 0 init

This output shows that swap usage is 0k. If the swap usage is higher, increase the memory assigned to service console. Fore more information, see Increasing the amount of RAM assigned to the ESX Server service console (1003501).

Related Information

For more information about interpreting esxtop output, refer to the VMware Communities article Interpreting esxtop Statistics.

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End Of General Availability of the Free vSphere Hypervisor (ESXi 7.x and 8.x) (2107518)

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在 vRealize Operations Manager 6.x 及更高版本中，具有长 ID 的警示定义阻止分析服务启动 (65102)

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Download and Install VMware Fusion (2014097)

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VMware ESX Server

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