I am currently testing running Openstack instance on Cinder volume with libgfapi. This instance is the Windows instance and i found that when running random 4k write workload, the CPU utilization is very high,  90% CPU utilization with about 86% in privileged time. I also tested the workload with volume from NFS and the CPU utilization is only around 5%. For gluster fuse, the CPU utilization is also not as high as 90%, around 30-40%. Is there any reason why is that so? Appreciate on any comments and suggestions.

Details.

Workload generator: IOMeter

Instance: Windows 2008R2

Openstack Host: CentOS 7

qemu-kvm version: qemu-kvm-ev-2.1.2-23.el7.1.x86_64

Workload: 4kb random write, 4 workers with each worker configure to have 4 outstanding IOs

Gluster server and client version: 3.7.8

Gluster info

Cw