Only using huge page may filter the usable host

[zhangtralon]

when only using huge page parameter without numa to create vms, the current code can generate an instance numatopology with a numa cell.

the solution will filter some hosts which meet the
need of huge page but no numa.

I think that binding the huge page with numa so closely is unreasonable.

[Nikola Đipanov (ndipanov)]

Hmmm are you sure that this is correct - in the current libvirt implementation - even single node hosts will report a topology (with a single cell) so I am not sure this will filter any hosts out unless they are running a very old version of libvirt which would not support large pages anyway.

[Daniel Berrange (berrange)]

Yep, every single compute host should always be reporting at least a single NUMA node containing all CPUs/RAM, so if a guest has only requested hugepages, the NUMA logic shouldn't cause hosts to be filtered out. So I don't see any reason to separate numa/hugepage scheduling for that case

[zhangtralon (zhangchunlong1)]

yeah, Daniel and Nikola, you are right.
Before, I find no numa in a host by the numactl --hardware, so I think that there may be no numa topo.
I made the following test, and find that the libvirt return a numa even if the value from the numactl is zero.
thanks.

root@tralon-Vostro-1400:~# virsh --version
1.2.2
root@tralon-Vostro-1400:~# numactl --hardware
available: 0 nodes ()
root@tralon-Vostro-1400:~# virsh capabilities
<capabilities>

  <host>
    <uuid>44454c4c-3500-1039-8038-b4c04f433258</uuid>
    <cpu>
      <arch>i686</arch>
      <model>n270</model>
      <vendor>Intel</vendor>
      <topology sockets='1' cores='2' threads='1'/>
      <feature name='lahf_lm'/>
      <feature name='lm'/>
      <feature name='pdcm'/>
      <feature name='xtpr'/>
      <feature name='cx16'/>
      <feature name='tm2'/>
      <feature name='est'/>
      <feature name='vmx'/>
      <feature name='ds_cpl'/>
      <feature name='dtes64'/>
      <feature name='pbe'/>
      <feature name='tm'/>
      <feature name='ht'/>
      <feature name='ss'/>
      <feature name='acpi'/>
      <feature name='ds'/>
      <feature name='pse36'/>
    </cpu>
    <power_management>
      <suspend_mem/>
      <suspend_disk/>
      <suspend_hybrid/>
    </power_management>
    <migration_features>
      <live/>
      <uri_transports>
        <uri_transport>tcp</uri_transport>
      </uri_transports>
    </migration_features>
    <topology>
      <cells num='1'>
        <cell id='0'>
          <memory unit='KiB'>3106852</memory>
          <cpus num='2'>
            <cpu id='0' socket_id='0' core_id='0' siblings='0'/>
            <cpu id='1' socket_id='0' core_id='1' siblings='1'/>
          </cpus>
        </cell>
      </cells>
    </topology>
    <secmodel>
      <model>apparmor</model>
      <doi>0</doi>
    </secmodel>
    <secmodel>
      <model>dac</model>
      <doi>0</doi>
      <baselabel type='kvm'>+117:+126</baselabel>
      <baselabel type='qemu'>+117:+126</baselabel>
    </secmodel>
  </host>

</capabilities>