Hi all,
I am running a embedded OS on Qemu-2.3.0. However I found that the I/O performance was quite different for different CentOS release (CentOS 6.5 and CentOS 7.0). The CentOS 6.5 uses linux-2.6.32 while the CentOS 7.0 uses linux-3.10.0. The I/O throughput (write) of the former (CentOS 6.5) is about ten times of that on the latter (CentOS 7.0). All configurations are the same except the kernel version. And the command line is as following:
# qemu-kvm -m 2G -smp 4 -enable-kvm -hda guest.img ...
The I/O throughput of the host is almost the same for these two different kernels, as tested by Iozone tool. Actually, I found that the IO throughput degraded significantly since the 3.4 or later kernel version. I also tried different qemu versions such as qemu-1.5.3, qemu-2.1.3 but got no improvements.
Hope someone can provide helps.
Yi