Description of problem:
Boot win2012 guest which is gluster Fuse mount backend. Copy files inside guest and check CPU utilization in "task manager", the CPU utilization is about 99%, the detailed CPU utilization, pls refer to the attachment file cpu_utilization_fuse_mount.png

Use nfs mount backend to start guest and do same copying operation, the CPU utilization is < 10%. The detailed CPU utilization, pls refer to the attachment file cpu_utilization_nfs_mount.png.

Version-Release number of selected component (if applicable):
Host kernel: kernel-3.10.0-4.el7.x86_64
qemu version: qemu-kvm-1.5.2-2.el7.x86_64
gluster server kernel: kernel-2.6.32-358.el6.x86_64
gluster version: glusterfs-3.4.0-8.el6.x86_64

How reproducible:
100%

Steps to Reproduce:
1. On host, mount gluster volume
# mount -t glusterfs [gluster-server]:/gv0 /mnt

2. Boot win2012 guest
/usr/libexec/qemu-kvm -M pc -cpu SandyBridge -enable-kvm -m 4G -smp 4,sockets=2,cores=2,threads=1 -no-kvm-pit-reinjection -rtc base=localtime,clock=host,driftfix=slew -drive file=/mnt/win2012-64-2.raw,if=none,id=drive-system-disk,format=raw,cache=none,aio=native,werror=stop,rerror=stop -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x4 -device scsi-hd,drive=drive-system-disk,bus=scsi0.0,id=system-disk,bootindex=1 -netdev tap,id=macvtap_netdev,fd=4 -device virtio-net-pci,netdev=macvtap_netdev,mac=5e:93:7f:e9:69:21 4<>/dev/tap4 -monitor stdio -drive file=/root/en_windows_server_2012_x64_dvd_915478.iso,if=none,media=cdrom,format=raw,id=drive-ide1-0-1 -device ide-drive,drive=drive-ide1-0-1,id=ide1-0-1,bus=ide.1,unit=0  -drive file=/root/driver.iso,if=none,media=cdrom,format=raw,id=drive-ide1-0-2 -device ide-drive,drive=drive-ide1-0-2,id=ide1-0-2,bus=ide.1,unit=1 -vnc :1 -vga qxl -global qxl-vga.vram_size=67108864 -spice disable-ticketing,port=5912

3. Inside guest copy some files to C:\ and check CPU utilization in "task manager"


Actual results:
The CPU utilization is more than 90%

Expected results:
The CPU utilization should be < 10%

Additional info: