Qemu performance problem under Debian


#1

I have several qemu disk images with some of them includes Xorg. All of the virtual machine runs quite fast under Ubuntu. But when I want to start same image under Debian like this:

$ qemu-system-x86_64 -m 1024 -hda vm.img

everything works but performance is too low.

What can be the main problem of this slowness while qemu versions are same?


#2

Most of the performance hit comes from KVM.

KVM (Kernel Virtual Machine) is a Linux kernel module that allows a user space program to utilize the hardware virtualization features of various processors: http://wiki.qemu.org/KVM

To enable kvm virtualization support under qemu, you need to pass -enable-kvm option:

$ qemu-system-x86_64 -enable-kvm -m 1024 -hda vm.img

Or you can install qemu-kvm package with apt and run kvm script like that:

$ kvm -m 1024 -hda vm.img