fixing the case where we use every single page in 1 vm

[Satish Patel]

Got this error: qemu-kvm: -object memory-backend-ram,id=ram-node0,size=12884901888,host-nodes=0,policy=bind: cannot set up guest memory 'ram-node0': Cannot allocate memory.

My Hardware: 32CPU / 32G memory

Flavor: 30 vCPU / 24000 MB (24G) memory

Grub hugemem setting: hugepagesz=2M hugepages=12288

[root@ostack-compute-sriov-196 ~]# cat /sys/devices/system/node/node*/meminfo | grep -i hugepage
Node 0 AnonHugePages: 0 kB
Node 0 HugePages_Total: 6144
Node 0 HugePages_Free: 394
Node 0 HugePages_Surp: 0
Node 1 AnonHugePages: 0 kB
Node 1 HugePages_Total: 6144
Node 1 HugePages_Free: 394
Node 1 HugePages_Surp: 0

Solution was set 23000 MB (23G) in flavor to make it work.

IRC: sean-k-mooney suggested to open bug to use every single page in 1 vm.

[sean mooney (sean-k-mooney)]

we used to have a bug in the libvirt driver where we effectly had an off by 1 error and could not use all pages. in this case i belive this might actully be a qemu issue but i asked for this to be filed so we can figure out if it is a qemu issue or not.