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Sometimes I do stupid things. Like overprovisioning my host's CPUs by creating an 16 vCore VM on a 2x8 cores host.

Just because you have two CPU sockets doesn't mean you should use them both for a single VM. Doing that means more complex memory sharing during CPU operations, which creates a significant performance penalty.

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/virtualization_tuning_and_optimization_guide/sect-virtualization_tuning_optimization_guide-numa-numa_and_libvirt

Now with only 8 cores attached, my Nextcloud VM runs faster than with 16 vCores. 🙂

#linux #kvm #virtualization