# Qemu performance problem under Debian

**URL:** <https://linux-tips.com/t/qemu-performance-problem-under-debian/312>\
**Category:** Distributions\
**Created:** [December 25, 2015, 12:22pm UTC](https://linux-tips.com/t/qemu-performance-problem-under-debian/312 "2015-12-25T12:22:27Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Greg](https://linux-tips.com/letter_avatar_proxy/v4/letter/g/71c47a/32.png) [@Greg](https://linux-tips.com/u/Greg)\
**Post date:** [December 25, 2015, 12:22pm UTC](https://linux-tips.com/t/qemu-performance-problem-under-debian/312/1 "2015-12-25T12:22:27Z")

</div>

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:

```auto
$ 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?

---

<div class="post-metadata">

**Author:** ![Debuser](https://linux-tips.com/letter_avatar_proxy/v4/letter/d/96bed5/32.png) [@Debuser](https://linux-tips.com/u/Debuser)\
**Post date:** [December 25, 2015, 1:11pm UTC](https://linux-tips.com/t/qemu-performance-problem-under-debian/312/2 "2015-12-25T13:11:14Z")

</div>

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](http://wiki.qemu.org/KVM)

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

```auto
$ 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:

```auto
$ kvm -m 1024 -hda vm.img

```