Assigning Interrupts to CPUs

Assigning Interrupts to CPUs

To minimize the latency of real-time interrupts, you can arrange for the VME bus interrupts with real-time significance to be delivered to a specified CPU where no other interrupts are handled. This is done with the IPL (Interrupt Priority Level) statement in the /var/sysgen/system/irix.sm file. The syntax is

IPL level# cpu#

Interrupts with the specified level initiated on any VME bus will be delivered to the specified CPU. After modifying irix.sm, rebuild the kernel using the command /etc/autoconfig -vf.

For more on how to handle time-critical interrupts see "Minimizing Interrupt Response Time").

The best way to handle non-critical interrupts is to allow the hardware to "spray" them to all available CPUs. You can protect specific CPUs from interrupts as discussed under "Isolating a CPU From Sprayed Interrupts".