Knowledge Base

The VMware Knowledge Base provides support solutions, error messages and troubleshooting guides
 
Search the VMware Knowledge Base (KB)   View by Article ID
 

Linux Guest Clock Runs Slowly on ESX Server 2 (1518)

Details

Why does the clock in my Linux guest run more slowly than real time?

Solution

Note: For ESX Server 3, see http://kb.vmware.com/kb/2219 Linux Guest Clock Runs Slowly on ESX Server 3
 
By default, ESX Server versions 2.x and earlier program the real timer hardware to deliver a maximum of 1000 clock interrupts per second per CPU. However, SMP-capable Linux 2.6 kernels, as well as some 2.4 kernels with vendor patches, can require a total of 2000 or more virtual clock interrupts per second; ESX Server generally cannot sustain a virtual clock interrupt rate higher than the real hardware rate.

With ESX Server 2.5, you can increase the hardware clock interrupt rate to correct this problem. To do so, perform the following steps:

  1. Connect the VMware Management Interface to the ESX Server machine, and log on as root.
  2. Click the Options tab.
  3. Click the Advanced Settings link. This opens a new window with a list of configuration parameters.
  4. Scroll to the Misc.TimerHardPeriod parameter and click the current value. This opens a new window where you can update the value.
  5. Type a new value of 333, then click the OK button to exit.

    Values other than 333 can only make the guest clock run too slow, not too fast. The period must be short enough to give the system frequent enough chances to check whether a virtual timer interrupt is due on the guest.

Neither ESX Server nor the guest need to be rebooted after changing TimerHardPeriod.

This workaround does not apply to VMware products other than ESX Server. For a similar workaround that applies to some Linux hosts with VMware Workstation or GSX Server, refer to http://kb.vmware.com/kb/892 Virtual Machine Seems Slow when Running a Particular Program (Clock Issue)
 

For additional information about timekeeping in virtual machines, see the following white paper Timekeeping in VMware Virtual Machines at www.vmware.com/pdf/vmware_timekeeping.pdf.

Keywords

1518; urlz; esx3update

Request a Product Feature

To request a new product feature or to provide feedback on a VMware product, please visit the Request a Product Feature page.

Feedback

  • 5 Ratings

Did this article help you?
This article resolved my issue.
This article did not resolve my issue.
This article helped but additional information was required to resolve my issue.
What can we do to improve this information? (4000 or fewer characters)
  • 5 Ratings
Actions
KB: