Kvm VM slower after adding vcpus and RAM

by MathsStudent   Last Updated August 14, 2019 01:00 AM

I've created a kvm VM running Centos7 (host OS is Centos7 as well), assigning it a single vcpu and 2GB of RAM - it was painfully slow, so I decided to increase vcpus and RAM.

While adding RAM was fairly straightforward, I've encountered problems with adding vcpus - at first I've been simply changing (using virsh edit) the number on the line containing

<vcpu placement='static'>8</vcpu>

however the only effect of that was machine not booting. I've solved the booting issue by changing that line to

<vcpu placement='static' current='1'>8</vcpu>

and then hotpluging more vcpus once the machine was running.

It kind of works - the machine does indeed have 8 vcpus and assigned amount of RAM but the catch is - it's painfully slow, even slower than before. For example, starting the docker service (the daemon) takes more than 30 minutes.

How can I improve the performance?

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