Slow KVM Virtual Machine Performance Solved - Choose the right architecture with the CPU flag

I am running a 64-bit host and was running a 32-bit XP guest which was crawling no matter what I was doing with it,in fact it frequently used 100% CPU power while having no real work load.  I experienced with this other guests and wondered why KVM was slow compared to say Xen or Virtualbox.

This is because you need to use the "-cpu" flag.

For a full list of options run:

/usr/libexec/qemu-kvm -cpu \?

x86           qemu64
x86           qemu32
x86         pentium3

The option you need to pass is either "-cpu qemu64" or "-cpu qemu32".  Obviously qemu64 is for 64bit guests and qemu32 is for 32bit guests.

Make sure you specify this or your guest will be extremely slow since it will be emulating the architecture and won't give you native performance if you choose the wrong architecture. 

Also note that if you don't specify the -cpu flag it defaults to your host's architecture (eg. 64bit Centos or 32bit Centos).

So again, the solution is to use the -cpu flag and make sure you specify the correct architecture for the guest.


Tags:

kvm, virtual, architecture, cpu, flagi, xp, frequently, xen, virtualbox, quot, usr, libexec, qemu, pentium, specify, emulating, native, defaults, eg, centos,

Latest Articles

  • ssh Too many authentication failures not prompting for password
  • LightDM Mint Ubuntu Debian won't start errors Nvidia Graphics
  • WARNING: Unable to determine the path to install the libglvnd EGL vendor library config files. Check that you have pkg-config and the libglvnd development libraries installed, or specify a path with --glvnd-egl-config-path. Linux Ubuntu Mint Debian E
  • How To Upgrade Linux Mint 18.2 to 18.3 to 19.x and 20.x
  • MP3s Won't Play / ID3 Version 2.4 Issues in Cars and Other MP3 Players/CDs/DVDs Solution
  • LXC Containers LXD How to Install and Configure Tutorial Ubuntu Debian Mint
  • GlusterFS HowTo Tutorial For Distributed Storage in Docker, Kubernetes, LXC, KVM, Proxmox
  • Ubuntu Mint audio output not working pulseaudio "pulseaudio[13710]: [pulseaudio] sink-input.c: Failed to create sink input: too many inputs per sink."
  • How To Shrink Dynamically Allocated VM QEMU KVM VMware Disk Image File
  • How To Enable Linux Swapfile Instead of Partition Ubuntu Mint Debian Centos
  • 404 Not Found [IP: 151.101.194.132 80] apt update Debian 11 Bullseye Solution The repository 'http://security.debian.org bullseye/updates Release' does not have a Release file.
  • WARNING: Can't download daily.cvd from db.local.clamav.net freshclam clamav error solution
  • (firefox:9562): LIBDBUSMENU-GLIB-WARNING **: Unable to get session bus: Failed to execute child process "dbus-launch" (No such file or directory) Solution
  • Debian Mint Ubuntu Which Package Provides missing top, ps and w Solution
  • Vbox Virtualbox DNS NAT Network Mode NOT working
  • Docker Tutorial HowTo Install Docker, Use and Create Docker Container Images Clustering Swarm Mode Monitoring Service Hosting Provider
  • Zoom Password Error 'That passcode was incorrect' - Solution Wrong Passcode Wrong Meeting Name
  • How To Startup and Open Remote/Local Folder/Directory in Ubuntu Linux Mint automatically upon login
  • How To Reset Windows Server Password 2019, 2022, 7, 8, 10, 11 Recovery and Removal Guide Using Linux Ubuntu Mint Debian
  • How To Create OpenVPN Server for Secure Remote Corporate Access in Linux Debian/Mint/Ubuntu with client public key authentication