[root@localhost x86_64-softmmu]# ./qemu-system-x86_64 -d exec -enable-kvm -m 1024 -smp 2 -chardev socket,id=char0,path=/usr/local/var/run/openvswitch/vhost-user1 -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce  -device virtio-net-pci,netdev=mynet1,mac=52:54:00:02:d9:01 -object memory-backend-file,id=mem,size=1024M,mem-path=/dev/hugepages,share=on -numa node,memdev=mem -mem-prealloc -net user,hostfwd=tcp::10021:22 -net nic /var/lib/libvirt/images/centos-vm1.qcow2 
qemu-system-x86_64: -object memory-backend-file,id=mem,size=1024M,mem-path=/dev/hugepages,share=on: unable to map backing store for hugepages: Cannot allocate memory

[root@localhost x86_64-softmmu]# 
[root@localhost x86_64-softmmu]# 
[root@localhost x86_64-softmmu]# dmesg | grep line
[    0.000000] Command line: BOOT_IMAGE=/vmlinuz-3.10.0-229.11.1.el7.x86_64 root=/dev/mapper/centos-root ro rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet intel_iommu=on default_hugepagesz=2M hugepagesz=2M hugepages=2048 isolcpus=1,2,3,4,5,12,13,14,15,16,17,7,8,9,10,11,18,19,20,21,22,23
[    0.000000] Base memory trampoline at [ffff880000094000] 94000 size 24576
[    0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-3.10.0-229.11.1.el7.x86_64 root=/dev/mapper/centos-root ro rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet intel_iommu=on default_hugepagesz=2M hugepagesz=2M hugepages=2048 isolcpus=1,2,3,4,5,12,13,14,15,16,17,7,8,9,10,11,18,19,20,21,22,23
[    0.055970] TSC deadline timer enabled
[    0.652409] PCI: pci_cache_line_size set to 64 bytes
[    1.008080] io scheduler deadline registered (default)
[    1.070864] ehci-pci 0000:00:1a.0: cache line size of 64 is not supported
[    1.080484] ehci-pci 0000:00:1d.0: cache line size of 64 is not supported
[    1.086735] xhci_hcd 0000:00:14.0: cache line size of 64 is not supported
[    2.188516] systemd[1]: Started dracut ask for additional cmdline parameters.
[    2.188618] systemd[1]: Starting dracut cmdline hook...
[root@localhost x86_64-softmmu]# clear
[3;J
[root@localhost x86_64-softmmu]# ./qemu-system-x86_64 -d exec -enable-kvm -m 1024 -smp 2 -chardev socket,id=char0,path=/usr/local/var/run/openvswitch/vhost-user1 -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce  -device virtio-net-pci,netdev=mynet1,mac=52:54:00:02:d9:01 -object memory-backend-file,id=mem,size=1024M,mem-path=/dev/hugepages,share=on -numa node,memdev=mem -mem-prealloc -net user,hostfwd=tcp::10021:22 -net nic /var/lib/libvirt/images/centos-vm1.qcow2 
qemu-system-x86_64: -object memory-backend-file,id=mem,size=1024M,mem-path=/dev/hugepages,share=on: unable to map backing store for hugepages: Cannot allocate memory

[root@localhost x86_64-softmmu]# dmesg | grep -i "command line"
[    0.000000] Command line: BOOT_IMAGE=/vmlinuz-3.10.0-229.11.1.el7.x86_64 root=/dev/mapper/centos-root ro rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet intel_iommu=on default_hugepagesz=2M hugepagesz=2M hugepages=2048 isolcpus=1,2,3,4,5,12,13,14,15,16,17,7,8,9,10,11,18,19,20,21,22,23
[    0.000000] Kernel command line: BOOT_IMAGE=/vmlinuz-3.10.0-229.11.1.el7.x86_64 root=/dev/mapper/centos-root ro rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet intel_iommu=on default_hugepagesz=2M hugepagesz=2M hugepages=2048 isolcpus=1,2,3,4,5,12,13,14,15,16,17,7,8,9,10,11,18,19,20,21,22,23
[root@localhost x86_64-softmmu]# 
[root@localhost x86_64-softmmu]# cat /proc/meminfo 
MemTotal:       32740436 kB
MemFree:        26507864 kB
MemAvailable:   26665440 kB
Buffers:             764 kB
Cached:           295348 kB
SwapCached:            0 kB
Active:           340760 kB
Inactive:         225492 kB
Active(anon):     288096 kB
Inactive(anon):    10932 kB
Active(file):      52664 kB
Inactive(file):   214560 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:      16449532 kB
SwapFree:       16449532 kB
Dirty:                 4 kB
Writeback:             0 kB
AnonPages:        278332 kB
Mapped:            67872 kB
Shmem:             20696 kB
Slab:             348152 kB
SReclaimable:     228212 kB
SUnreclaim:       119940 kB
KernelStack:        8672 kB
PageTables:        17792 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    30722596 kB
Committed_AS:    1792216 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      388556 kB
VmallocChunk:   34342302716 kB
HardwareCorrupted:     0 kB
AnonHugePages:    102400 kB
HugePages_Total:    2048
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      160036 kB
DirectMap2M:     7073792 kB
DirectMap1G:    28311552 kB
[root@localhost x86_64-softmmu]#