Disabling Large Page Support in ESX Server

Disabling Large Page Support in ESX Server

ESX Server 3.5 and ESX Server 3i v3.5 enable large page support by default. When a virtual machine requests a large page, the ESX Server kernel tries to find a free machine large page. Both the virtual machine monitor and the guest operating system can request large pages. The virtual machine monitor requests large pages to improve its own performance. The guest operating system or an application running on the guest operating system requests large pages just as it would when running on a native machine. The ESX Server kernel supplies large pages to the virtual machine opportunistically. When there is no free large page available, ESX Server emulates a guest operating system large page using small machine pages.

 

In ESX Server 3.5 and ESX Server 3i v3.5, large pages cannot be shared as copy‐on‐write pages. This means, the ESX Server page sharing technique might share less memory when large pages are used instead of small pages. In order to recover from non-sharable large pages, ESX Server uses a “share‐before‐swap” technique. When free machine memory is low and before swapping happens, the ESX Server kernel attempts to share identical small pages even if they are parts of large pages. As a result, the candidate large pages on the host machine are broken into small pages. In rare cases, you might experience performance issues with large pages. If this happens, you can disable large page support for the entire ESX Server host or for the individual virtual machine.

 

To disable the large page support for the entire ESX Server host, take the following steps using the VMware Infrastructure Client:

 

1. In the left pane of the VI Client, choose the ESX Server host.
2. In the right pane of the VI Client, click the Configuration tab.
3. Choose Software > Advanced Settings. The Advanced Settings dialog box opens.
4. In the left pane of the Advanced Settings dialog box, choose Mem.
5. In the right pane of the Advanced Settings dialog box, set Mem.AllocGuestLargePage to 0.
6. Click OK to close the Advanced Settings dialog box.

To disable guest operating system large page support for a virtual machine, add the following line in the virtual machine’s configuration file(*.vmx): monitor_control.disable_mmu_largepages = TRUE

 

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Author
Administrator
Date Created
2012-06-15 15:33:20
Date Updated
2012-06-15 15:33:20
Views
15446


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