Arch Linux

solskogen

Member

From: Norway

Registered: 2005-03-06

Posts: 145

Slow KVM and extremely high load

I've just installed Archlinux on a i7 920 with 24 GB of ram. Not the fastest machine in the world but it performs well.
But Virtual machines in KVM is quite slow and it shows a high load for the easiest of tasks. For instance, when installing CentOS 5 (or 6) (and no other virtual machines running) the load on my machine is ~25. Installing the OS takes about 15 minutes.
The setup is this:
3 1,5TB disk in raid5 (software)
lvm
/storage is ext4 (and a part of lvm) and this is the place where I have the disk images for the Virtual Machines.

When the Virtual machine (I only have one) top tells me that qemu-kvm is using 20% cpu.

Any hints?

mrxx

Member

Registered: 2011-12-24

Posts: 22

Re: Slow KVM and extremely high load

A common reason of high CPU load is qemu-only mode instead of kvm, as qemu emulates every instruction.

First of all, check if your kvm module is loaded:

$ lsmod|grep kvm
kvm_intel             125165  0 
kvm                   361546  1 kvm_intel

Then, check if your VM is actually using KVM.
Enter the VM's monitor and type "info kvm":

QEMU 0.13.0 monitor - type 'help' for more information
(qemu) info kvm
info kvm
kvm support: enabled