What's the cause of high LOC interrupts?
It's the process for managing multi-CPU threading. See SMP Affinity and Proper Interrupt Handling in Linux for the answers you seek on how to lower it down, but basically its the way the system handles masking the interrupts the are being caused by the CPU's needing to be fed more thread streams or memory and only CPU0 being able to take on the interrupts.
The higher the value, the better the threading of the system is happening, and this is a good thing.