On Mon, Jun 15, 2015 at 09:14:52PM +0800, cauchy-love wrote: > 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.
Please post the iozone command-line you are using and the output. Your QEMU command-line uses the IDE storage controller, which is not optimized for performance. Usually virtio-blk is used when good performance is required: -drive if=virtio,cache=none,format=raw,aio=native,file=guest.img The guest OS needs virtio-blk device drivers in order for this to work. Stefan
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