Re: [libvirt] Problem with setting up KVM guests to use HugePages

On Wed, Jun 10, 2015 at 09:20:40PM +0000, Vivi L wrote: > Michal Privoznik <mprivozn <at> redhat.com> writes: > >> >> On 10.06.2015 01:05, Vivi L wrote: >>> Kashyap Chamarthy <kchamart <at> redhat.com> writes: >>> >>> >>>> You might want re-test by explicitly setting the 'page' element and >>>> 'size' attribute? From my test, I had something like this: >>>> >>>> $ virsh dumpxml f21-vm | grep hugepages -B3 -A2 >>>> <memory unit='KiB'>2000896</memory> >>>> <currentMemory unit='KiB'>2000000</currentMemory> >>>> <memoryBacking> >>>> <hugepages> >>>> <page size='2048' unit='KiB' nodeset='0'/> >>>> </hugepages> >>>> </memoryBacking> >>>> <vcpu placement='static'>8</vcpu> >>>> >>>> I haven't tested this exhaustively, but some basic test notes here: >>>> >>>> https://kashyapc.fedorapeople.org/virt/test-hugepages-with-libvirt.txt >>> >>> Current QEMU does not support setting <page> element. Could it be the >>> cause of my aforementioned problem? >>> >>> unsupported configuration: huge pages per NUMA node are not supported >>> with this QEMU >>> >> >> So this is explanation why the memory for you guest is not backed by >> hugepages. > > I thought setting hugepages per NUMA node is a nice-to-have feature. > Is it required to enable the use of hugepages for the guest? No, it should not be mandatory. You should be able to use <memoryBacking> <hugepages/> </memoryBacking> With pretty much any KVM/QEMU version that exists. If that's broken then its a libvit bug.