The central processing unit or "processor" inside a computer which executes the instructions in a computer program.
An interrupt request is a hardware signal sent to the processor that temporarily stops a running program and allows to handle a hardware event.
"In some cases irq constitutes more than 8 of cpu for a process"
from question "Should irq% be included in cpu% of a process?"
"Cannot sleep run atomically in soft irq context and are guaranteed to never run on more than one cpu of a given processors for a given tasklet"
from question "What is the difference between tasklet and workqueue"