9.3.2. Domain Processes

As provided in Red Hat Enterprise Linux, libvirt uses libnuma to set memory binding policies for domain processes. The nodeset for these policies can be configured either as static (specified in the domain XML) or auto (configured by querying numad). Refer to the following XML configuration for examples on how to configure these inside the <numatune> tag:
<numatune>
	<memory mode='strict' placement='auto'/>
</numatune>
<numatune>
	<memory mode='strict' nodeset='0,2-3'/>
</numatune>
libvirt uses sched_setaffinity(2) to set CPU binding policies for domain processes. The cpuset option can either be static (specified in the domain XML) or auto (configured by querying numad). Refer to the following XML configuration for examples on how to configure these inside the <vcpu> tag:
<vcpu placement='auto' current='8'>32</vcpu>
<vcpu placement='static' cpuset='0-10,ˆ5'>8</vcpu>
There are implicit inheritance rules between the placement mode you use for <vcpu> and <numatune>:
  • The placement mode for <numatune> defaults to the same placement mode of <vcpu>, or to static if a <nodeset> is specified.
  • Similarly, the placement mode for <vcpu> defaults to the same placement mode of <numatune>, or to static if <cpuset> is specified.
This means that CPU tuning and memory tuning for domain processes can be specified and defined separately, but they can also be configured to be dependent on the other's placement mode.

Note

Refer to the following URLs for more information on vcpu and numatune: http://libvirt.org/formatdomain.html#elementsCPUAllocation and http://libvirt.org/formatdomain.html#elementsNUMATuning