Insufficient free host memory pages available to allocate guest RAM with Open vSwitch DPDK in Red Hat OpenStack Platform 10

Issue

When spawning an instance and scheduling it onto a compute node which still has sufficient pCPUs for the instance and also sufficient free huge pages for the instance memory, nova returns:

[stack@undercloud-4 ~]$ nova show 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc
(...)
| fault                                | {"message": "Exceeded maximum number of retries. Exceeded max scheduling attempts 3 for instance 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc. Last exception: internal error: process exited while connecting to monitor: 2017-11-23T19:53:20.311446Z qemu-kvm: -chardev pty,id=cha", "code": 500, "details": "  File \"/usr/lib/python2.7/site-packages/nova/conductor/manager.py\", line 492, in build_instances |
|                                      |     filter_properties, instances[0].uuid)                                                                                                                                                                                                                                                                                                                                                                   |
|                                      |   File \"/usr/lib/python2.7/site-packages/nova/scheduler/utils.py\", line 184, in populate_retry                                                                                                                                                                                                                                                                                                            |
|                                      |     raise exception.MaxRetriesExceeded(reason=msg)                                                                                                                                                                                                                                                                                                                                                          |
|                                      | ", "created": "2017-11-23T19:53:22Z"} 
(...)                                                                                                                                                                                                                                                                                          

And /var/log/nova/nova-compute.log on the compute node gives the following ERROR message:

2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [req-2ad59cdf-4901-4df1-8bd7-ebaea20b9361 5d1785ee87294a6fad5e2bdddd91cc20 8c307c08d2234b339c504bfdd896c13e - - -] [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc] Instance failed 
to spawn
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc] Traceback (most recent call last):
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/nova/compute/manager.py", line 2087, in _build_resources
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     yield resources
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/nova/compute/manager.py", line 1928, in _build_and_run_instance
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     block_device_info=block_device_info)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 2674, in spawn
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     destroy_disks_on_failure=True)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 5013, in _create_domain_and_network
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     destroy_disks_on_failure)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     self.force_reraise()
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     six.reraise(self.type_, self.value, self.tb)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 4985, in _create_domain_and_network
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     post_xml_callback=post_xml_callback)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 4903, in _create_domain
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     guest.launch(pause=pause)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/guest.py", line 144, in launch
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     self._encoded_xml, errors='ignore')
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     self.force_reraise()
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     six.reraise(self.type_, self.value, self.tb)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/guest.py", line 139, in launch
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     return self._domain.createWithFlags(flags)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/eventlet/tpool.py", line 186, in doit
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     result = proxy_call(self._autowrap, f, *args, **kwargs)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/eventlet/tpool.py", line 144, in proxy_call
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     rv = execute(f, *args, **kwargs)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/eventlet/tpool.py", line 125, in execute
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     six.reraise(c, e, tb)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib/python2.7/site-packages/eventlet/tpool.py", line 83, in tworker
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     rv = meth(*args, **kwargs)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]   File "/usr/lib64/python2.7/site-packages/libvirt.py", line 1069, in createWithFlags
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc]     if ret == -1: raise libvirtError ('virDomainCreateWithFlags() failed', dom=self)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc] libvirtError: internal error: process exited while connecting to monitor: 2017-11-23T19:53:20.311446Z qemu-kvm: -chardev pty,id=charserial1: char device redirected to /dev/pts/3 (label charserial1)
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc] 2017-11-23T19:53:20.477183Z qemu-kvm: -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/7-instance-00000006,share=yes,size=536870912,host-nodes=0,policy=bind: os_mem_prealloc: Insufficient free host memory pages available to allocate guest RAM
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc] 
2017-11-23 19:53:21.021 153615 ERROR nova.compute.manager [instance: 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc] 

Additionally, libvirt creates the following log file:

[root@overcloud-compute-1 qemu]# cat instance-00000006.log
2017-11-23 19:53:02.145+0000: starting up libvirt version: 3.2.0, package: 14.el7_4.3 (Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>, 2017-08-22-08:54:01, x86-039.build.eng.bos.redhat.com), qemu version: 2.9.0(qemu-kvm-rhev-2.9.0-10.el7), hostname: overcloud-compute-1.localdomain
LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin QEMU_AUDIO_DRV=none /usr/libexec/qemu-kvm -name guest=instance-00000006,debug-threads=on -S -object secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-5-instance-00000006/master-key.aes -machine pc-i440fx-rhel7.4.0,accel=kvm,usb=off,dump-guest-core=off -cpu SandyBridge,vme=on,hypervisor=on,arat=on,tsc_adjust=on,xsaveopt=on -m 512 -realtime mlock=off -smp 1,sockets=1,cores=1,threads=1 -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/5-instance-00000006,share=yes,size=536870912,host-nodes=0,policy=bind -numa node,nodeid=0,cpus=0,memdev=ram-node0 -uuid 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc -smbios 'type=1,manufacturer=Red Hat,product=OpenStack Compute,version=14.0.8-5.el7ost,serial=4f88fcca-0cd3-4e19-8dc4-4436a54daff8,uuid=1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc,family=Virtual Machine' -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-5-instance-00000006/monitor.sock,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=delay -no-hpet -no-shutdown -boot strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=/var/lib/nova/instances/1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc/disk,format=qcow2,if=none,id=drive-virtio-disk0,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -chardev socket,id=charnet0,path=/var/run/openvswitch/vhu9758ef15-d2 -netdev vhost-user,chardev=charnet0,id=hostnet0 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=fa:16:3e:d6:89:65,bus=pci.0,addr=0x3 -add-fd set=0,fd=29 -chardev file,id=charserial0,path=/dev/fdset/0,append=on -device isa-serial,chardev=charserial0,id=serial0 -chardev pty,id=charserial1 -device isa-serial,chardev=charserial1,id=serial1 -device usb-tablet,id=input0,bus=usb.0,port=1 -vnc 172.16.2.8:2 -k en-us -device cirrus-vga,id=video0,bus=pci.0,addr=0x2 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 -msg timestamp=on
2017-11-23T19:53:03.217386Z qemu-kvm: -chardev pty,id=charserial1: char device redirected to /dev/pts/3 (label charserial1)
2017-11-23T19:53:03.359799Z qemu-kvm: -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/5-instance-00000006,share=yes,size=536870912,host-nodes=0,policy=bind: os_mem_prealloc: Insufficient free host memory pages available to allocate guest RAM

2017-11-23 19:53:03.630+0000: shutting down, reason=failed
2017-11-23 19:53:10.052+0000: starting up libvirt version: 3.2.0, package: 14.el7_4.3 (Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>, 2017-08-22-08:54:01, x86-039.build.eng.bos.redhat.com), qemu version: 2.9.0(qemu-kvm-rhev-2.9.0-10.el7), hostname: overcloud-compute-1.localdomain
LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin QEMU_AUDIO_DRV=none /usr/libexec/qemu-kvm -name guest=instance-00000006,debug-threads=on -S -object secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-6-instance-00000006/master-key.aes -machine pc-i440fx-rhel7.4.0,accel=kvm,usb=off,dump-guest-core=off -cpu SandyBridge,vme=on,hypervisor=on,arat=on,tsc_adjust=on,xsaveopt=on -m 512 -realtime mlock=off -smp 1,sockets=1,cores=1,threads=1 -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/6-instance-00000006,share=yes,size=536870912,host-nodes=0,policy=bind -numa node,nodeid=0,cpus=0,memdev=ram-node0 -uuid 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc -smbios 'type=1,manufacturer=Red Hat,product=OpenStack Compute,version=14.0.8-5.el7ost,serial=4f88fcca-0cd3-4e19-8dc4-4436a54daff8,uuid=1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc,family=Virtual Machine' -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-6-instance-00000006/monitor.sock,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=delay -no-hpet -no-shutdown -boot strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=/var/lib/nova/instances/1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc/disk,format=qcow2,if=none,id=drive-virtio-disk0,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -chardev socket,id=charnet0,path=/var/run/openvswitch/vhu9758ef15-d2 -netdev vhost-user,chardev=charnet0,id=hostnet0 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=fa:16:3e:d6:89:65,bus=pci.0,addr=0x3 -add-fd set=0,fd=29 -chardev file,id=charserial0,path=/dev/fdset/0,append=on -device isa-serial,chardev=charserial0,id=serial0 -chardev pty,id=charserial1 -device isa-serial,chardev=charserial1,id=serial1 -device usb-tablet,id=input0,bus=usb.0,port=1 -vnc 172.16.2.8:2 -k en-us -device cirrus-vga,id=video0,bus=pci.0,addr=0x2 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 -msg timestamp=on
2017-11-23T19:53:11.466399Z qemu-kvm: -chardev pty,id=charserial1: char device redirected to /dev/pts/3 (label charserial1)
2017-11-23T19:53:11.729226Z qemu-kvm: -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/6-instance-00000006,share=yes,size=536870912,host-nodes=0,policy=bind: os_mem_prealloc: Insufficient free host memory pages available to allocate guest RAM

2017-11-23 19:53:12.159+0000: shutting down, reason=failed
2017-11-23 19:53:19.370+0000: starting up libvirt version: 3.2.0, package: 14.el7_4.3 (Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>, 2017-08-22-08:54:01, x86-039.build.eng.bos.redhat.com), qemu version: 2.9.0(qemu-kvm-rhev-2.9.0-10.el7), hostname: overcloud-compute-1.localdomain
LC_ALL=C PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin QEMU_AUDIO_DRV=none /usr/libexec/qemu-kvm -name guest=instance-00000006,debug-threads=on -S -object secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-7-instance-00000006/master-key.aes -machine pc-i440fx-rhel7.4.0,accel=kvm,usb=off,dump-guest-core=off -cpu SandyBridge,vme=on,hypervisor=on,arat=on,tsc_adjust=on,xsaveopt=on -m 512 -realtime mlock=off -smp 1,sockets=1,cores=1,threads=1 -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/7-instance-00000006,share=yes,size=536870912,host-nodes=0,policy=bind -numa node,nodeid=0,cpus=0,memdev=ram-node0 -uuid 1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc -smbios 'type=1,manufacturer=Red Hat,product=OpenStack Compute,version=14.0.8-5.el7ost,serial=4f88fcca-0cd3-4e19-8dc4-4436a54daff8,uuid=1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc,family=Virtual Machine' -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-7-instance-00000006/monitor.sock,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=delay -no-hpet -no-shutdown -boot strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=/var/lib/nova/instances/1b72e7a1-c298-4c92-8d2c-0a9fe886e9bc/disk,format=qcow2,if=none,id=drive-virtio-disk0,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -chardev socket,id=charnet0,path=/var/run/openvswitch/vhu9758ef15-d2 -netdev vhost-user,chardev=charnet0,id=hostnet0 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=fa:16:3e:d6:89:65,bus=pci.0,addr=0x3 -add-fd set=0,fd=29 -chardev file,id=charserial0,path=/dev/fdset/0,append=on -device isa-serial,chardev=charserial0,id=serial0 -chardev pty,id=charserial1 -device isa-serial,chardev=charserial1,id=serial1 -device usb-tablet,id=input0,bus=usb.0,port=1 -vnc 172.16.2.8:2 -k en-us -device cirrus-vga,id=video0,bus=pci.0,addr=0x2 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 -msg timestamp=on
2017-11-23T19:53:20.311446Z qemu-kvm: -chardev pty,id=charserial1: char device redirected to /dev/pts/3 (label charserial1)
2017-11-23T19:53:20.477183Z qemu-kvm: -object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages/libvirt/qemu/7-instance-00000006,share=yes,size=536870912,host-nodes=0,policy=bind: os_mem_prealloc: Insufficient free host memory pages available to allocate guest RAM

2017-11-23 19:53:20.724+0000: shutting down, reason=failed