irq smp affinity on a fedora vm

Here is my askfedora post that didn't receive any reply. https://ask.fedoraproject.org/en/question/103915/what-kernel-relates-to-i... Description of the problem: In a network test setup, FC-23 (kernel-4.8) acts as bridge passing network traffic. TCP iperf tests are done from external (to the hypervisor) servers and clients for throughput 700Mbps. The bridge setup on the hypervisor is done through openvswitch and the VM relies on those bridge to pass traffic. Number of CPU core assigned to the FC VM is 2. Two test cases considered: #1) irqbalance not running #2) irqbalance running For test#1, CPU usage seen for the qemu-pid on the hypervisor stays close to 100% For test#2, CPU usage seen for the qemu-pid on the hypervisor goes to 200%, sometimes even more. For test#1, `smp_affinity` uses default value 3, where as for #2, it uses different values for three different virtio-input interrupts, 1,1,2. Question is, why turning on irqbalance (default for FC installation) makes it worse ?