Johnny Zhang
In ESX 3.5, the CPU scheduler logically partitions a host's physical CPU into cells, by default, there are 4 cores per cell for scalability reason. The scheduler can make decision locally within a cell without affecting other cells. However, with the introduction of 6 cores CPU, this may lead into some cell span sockets. You might experience performance issue when VMs are using those cells. If you are using those CPUs. You can change it from both VIclient and command line.

Using the VI Client:

  1. Select the Configuration tab in the VI client.
  2. Select Advanced Settings.
  3. Select VMkernel.
  4. In the right pane, locate VMkernel.Boot.cpuCellSize .
  5. Change the value to 6 .
This will take effect the next time the ESX host is rebooted.

From the command line interface (on classic ESX):
esxcfg-advcfg --set-kernel 6 cpuCellSize
2. Reboot the ESX host.

From the remote command line interface (on ESXi):

vicfg-advcfg --set-kernel 6 cpuCellSize
2. Reboot the ESX host.

Note: ESX 4.0 uses per-pCPU locks instead of cell scheduler. You will not see the span socket performance issue on ESX 4.0
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