Re: [libvirt] with vhostuser I cannot use hugepages

From: Mooney, Sean K Sent: Wednesday, January 24, 2018 8:52 PM To: Adnan Mundres <amundres(a)yahoo.com>; libvir-list(a)redhat.com Cc: Mooney, Sean K <sean.k.mooney(a)intel.com&gt; Subject: RE: [libvirt] with vhostuser I cannot use hugepages From: libvir-list-bounces@redhat.com<mailto:libvir-list-bounces@redhat.com> [mailto:libvir-list-bounces@redhat.com] On Behalf Of Adnan Mundres Sent: Wednesday, January 24, 2018 6:54 PM To: libvir-list@redhat.com<mailto:libvir-list@redhat.com> Subject: [libvirt] with vhostuser I cannot use hugepages In my setup I am using qemu-kvm without openstack. I am trying to use ovs with dpdk. In my xml file I added following lines for the dpdkvhostuser <cpu mode='host-passthrough'> <numa> <cell id="0" cpus="0-6" memory="16777216" unit='KiB' memAccess="shared"/> </numa> </cpu> [Mooney, Sean K] this xml snippit is not requsting the use of huge page memory. It is requesting memory to be allocated form a single numa node and for that to be mmaped shared. Dpdk does not actually need the guest to use hugepages it just improves the performance. What it requires Is that the gues uses file descriptor backed, pre allocated, locked, shared memory. e.g. <memoryBacking> <locked/> <source type='file'/> <access mode='shared'/> <allocation mode='immediate'/> </memoryBacking> Hugepages will enable all of the above features implicitly. to enable hugepages add <memoryBacking> <hugepages> <page size="16" unit="G" nodeset="0"/> </hugepages> </memoryBacking> [Mooney, Sean K] oh I forgot to say you can find the relevant documentation here https://libvirt.org/formatdomain.html#elementsMemoryBacking I have enabled hugepages during boot time ot@mvmgptb11hyp01 hyp-1]# cat /proc/meminfo | grep -i huge AnonHugePages: 126976 kB HugePages_Total: 100 HugePages_Free: 80 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 1048576 kB But When I start my vm (virsh start vm1.xml) I am seeing that this vm is not using memory from hugepages, rather it is taking memory from total memory. When I checked the log file I see that it is using -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/var/lib/libvirt/qemu/ram,share=yes It should use backend memory as following -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/vm1,share=yes Any idea how can I use memory from hugepages