Model name : Intel(R) Core(TM) i7-3770 CPU 3.40GHz To verify that Turbo mode is being used stress the CPU in a VM and check that the CPU frequency is higher than the rated value: To determine whether Turbo mode is enabled, use the following command in dom0:
Hence the default configuration that uses all available C-states should give the best performance for processors supporting a Turbo mode.įor maximum performance, it is recommended that Turbo mode is enabled in the BIOS. Using all the available C-states gives the processor most thermal headroom to enter Turbo mode. To go back to the default configuration, use the following and reboot: /opt/xensource/libexec/xen-cmdline -delete-xen mwait-idle This is not a recommended configuration as it is likely to lead to reduced performance. After this, controlling C-states in the BIOS will have an effect on Citrix Hypervisor. To revert to the C-state configuration for Intel processors that was used by older versions of XenServer (6.2 and earlier), use the following command in dom0: /opt/xensource/libexec/xen-cmdline -set-xen mwait-idle=falseĪ reboot is required for this change to take effect. Modern CPUs can transition between C-states very quickly so the use of deep C-states has minimal performance impact but provides great potential for power saving.įalling back to use of BIOS C-state settings For example, C1 and C1E are treated as two separate states which gives Xen more flexibility in the choice of C-state. This improves performance because Xen can make more accurate decisions about which C-state to use. It chooses the correct information at boot based on the processor used.
Xen Project Hypervisor comes preloaded with the C-states and performance characteristics of each processor family (like Sandy Bridge, Haswell, etc). For AMD processors, changing C-state settings in the BIOS does have an effect for AMD processors.Ĭitrix Hypervisor uses Xen Project Hypervisor's means of enumerating and using C-states for newer Intel processors.For Intel processors, Citrix Hypervisor uses all the available C-states regardless of the BIOS C-state settings.It is recommended to use Citrix Hypervisor's default configuration and to enable OS-controlled frequency scaling and Turbo mode in the BIOS. Use the more power-friendly "ondemand" CPU frequency governor Use the BIOS settings to know which C-states are supported Use frequency scaling and Turbo mode as controlled by the BIOS settings Use the "performance" CPU frequency governor Use all available C-states regardless of BIOS settings
Configure turbo c how to#
This article explains how to handle your power settings and how you can change the configuration to fit your specific needs.Ĭitrix Hypervisor (formerly XenServer) has the following power settings:
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