Dez 012008
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This issue occurs because of changes in the architecture of certain CPUs. These changes affect the way that ESX Servers perform COW (Copy-on-Write) memory operations when using vSMP in a virtual machine.
There are two common ways to workaround this problem. Perform one of the following workarounds:
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Instead of rebooting the virtual machine, power-off and then power it back on. By doing this the problem is not noticed because the COW memory is cleared and repopulated upon startup of the virtual machine.
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Alternatively, you can disable pagesharing which resolves the slow performance. Pagesharing is used to reclaim duplicated memory pages across and within virtual machines. With pagesharing disabled we no longer share memory in this way, therefore the virtual machine consumes more physical memory because all memory pages are duplicated for each virtual machine running on the ESX host.
Note: Turning pagesharing off can potentially cause an increase in the amount of swapping if you are overcommitting the ESX host memory resources.
To disable page sharing on the ESX Server:
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Log in to VirtualCenter (or the ESX Server directly) with an administrative account using the VMware Infrastructure Client.
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Click on the ESX Server that you want to disable page sharing on.
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Click the Configuration tab.
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Click the Advanced Settings link.
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Click Mem in the Advanced Settings window.
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Look for the Mem.ShareScanGHz option and set the value to 0.
Note: By default Mem.ShareScanGHz is set to 4.
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Click OK.
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Reboot the ESX host.
VMware engineering is currently investigating this behavior in more depth. A permanent fix is expected in a future release of ESX.
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VMware, slow performance, virtual machines, vSMP, ESX Server, hardware
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