Enable/Disable SMT on PowerKVM Guest

Note: SMT is not supported on the host and must be disabled.

To use SMT in your guest, enable it in your guest XML configuration file by setting the number of threads per core. The number set must be a multiple of 2 (1, 2, 4, or 8). The number of virtual processors (vCPUs) must be the product of the number of threads per core and the number of cores. For example, to specify a guest with 2 cores and 8 threads per core, you need to assign 16 virtual processors to the guest (2 cores times 4 threads = 16 vCPUs). The xml configuration file for the guest includes the following markup.

<vcpu placement=’static’>16
<model>power8</model>
<topology sockets=’1′ cores=’2′ threads=’8’/>
</cpu>

[root@localhost ~]# ppc64_cpu –info
Core 0: 0* 1* 2* 3* 4* 5* 6* 7*
Core 1: 8* 9* 10* 11* 12* 13* 14* 15*

Note: * indicates that the thread is enabled for the processor

[root@localhost ~]# ppc64_cpu –smt
SMT is on
[root@localhost ~]#

To disable SMT, run ppc64_cpu –smt=off.

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3 thoughts on “Enable/Disable SMT on PowerKVM Guest

  1. Pingback: Bring Up PowerKVM | Pradeep K Surisetty

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