Hardware interrupts were introduced as a way to avoid wasting the processor’s valuable time in polling loops, waiting for external events. They may be implemented in hardware as a distinct system with control lines, or they may be integrated into the memory subsystem.Read More
[[email protected] ~]# cat /proc/interrupts CPU0 CPU1 <items removed> 30: 1543015844 70 IO-APIC-level eth0 33: 982 1125222804 IO-APIC-level eth1 NMI: 0 0 LOC: 312789123 312790125 ERR: 0 MIS: 0
As you can see from the list above the interrupts for the network card has been balanced betwen the Cores. How Irqbalance works is rather complex and i suggest you read more.