I have a simple problem that I always face when using qemu on Linux with Windows VM. When it’s paused, the CPU usage kept racking up for no reason… Until… I found this thread on linux question https://www.linuxquestions.org/questions/linux-virtualization-and-cloud-90/best-way-to-pause-kvm-qemu-windows-guest-4175549274/.

So in simple term, we can pause the CPU usage on the qemu process after pausing the windows VM. The question is how? It’s simple, just run this command as super user


$ sudo pkill -SIGSTOP qemu



Then you are set. Now you will see the qemu process won’t rack up again the CPU, it’s useful when you are far from charger plug, and you need the VM resume as fast as possible. But, when I resume my process, the process hang up, why? Because the qemu process still in SIGSTOP mode. You need to run this command to continue the process again.


$ sudo pkill -SIGCONT qemu



It’s better to resume the qemu process first, then unpause the Windows VM, so there’re no crash or other problem. I really forgot this trick when on VirtualBox… And I hate Virtualbox, because it’s racking CPU twice as much than qemu… it sucks… I don’t do games on Windows VM, just all pure works, so low FPS with spice isn’t problem for me. This make my experience with qemu much better.

I hope this also help all of you who tried to find answer.