https://fedoraproject.org/wiki/Features/KVM_Huge_Page_Backed_Memory contains this checklist to get hugetlbfs to work: 1. mount -t hugetlbfs hugetlbfs /dev/hugepages I have done this - /dev/hugepages didn't exist - I created it 2. Reserve some memory for huge pages - sysctl vm.nr_hugepages=516 Done - I created 600 pages to fit a 1024 MB vm (on amd64): (from meminfo): HugePages_Total: 600 HugePages_Free: 600 HugePages_Rsvd: 0 HugePages_Surp: 0 3. Run an existing KVM guest with libvirt done (I also restarted libvirtd) 4. Confirm the guest has booted correctly done 5. Confirm the guest is using hugepages by checking HugePages_Free in /proc/meminfo it doesn't - HugePages_Free is still 600 Selinux is disabled, my kvm-commandline: /usr/bin/qemu-kvm -S -M pc-0.11 -m 1024 -smp 1 -name f11-x86_64 -uuid 61563594-3d8f-17c8-1b87-7d727689a9a0 -monitor unix:/var/lib/libvirt/qemu/f11-x86_64.monitor,server,nowait -boot c -drive file=,if=ide,media=cdrom,index=2 -drive file=/var/lib/libvirt/images/f1164.img,if=virtio,index=0,boot=on -net nic,macaddr=00:16:36:74:aa:8f,vlan=0,model=virtio,name=virtio.0 -net tap,fd=17,vlan=0,name=tap.0 -serial pty -parallel none -usb -usbdevice tablet -vnc 127.0.0.1:0 -vga cirrus
Hugepages are not enabled by default for guests, so merely mounting hugetlbfs won't make them be used. You need to add the following to the guest <memoryBacking> <hugepages/> </memoryBacking> To enable use of hugepages for RAM allocation.
Sven, thanks for the report - I've added a note to "How to test" section in the wiki