KVM increase CPU and RAM during runtime

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KVM - Increase CPU and RAM during runtime

The page summarises the necessary steps for increasing the amount of CPUs and RAM allocated to KVM guests during runtime.

Increase RAM during runtime

  • activate the kernel module Virtio balloon driver on the guest system (maybe also on the host)

 modprobe virtio_balloon

  • connect to the virtual machine

 ssh user@hostmaschine -L 5900:localhost:5900 
 xvncviewer localhost

  • in the opening qemu window press Ctrl+Alt+2 (press ‘‘Ctrl+Alt+1 to return)

 info ballon - shows the allocated memory
 balloon 256 - sets the memory to 256MB

CPU hotpluging

  • start virtual machine with the maximum of cores
  • disable a cpu (in Debian)

 echo 0 > /sys/devices/system/cpu/cpu1/online

  • to enable a CPU (in Debian)

 echo 1 > /sys/devices/system/cpu/cpu1/online