Processing interrupts

Character devices are mostly active at interrupt time so distributing the interrupt handling is important to improve both driver and system performance on multiprocessor systems. Otherwise, interrupts will arrive at the default processor and all activity will take place on that processor. There are two methods for spreading the interrupt processing across CPUs:

• On multiprocessor hardware that handles distributed interrupts, register the driver as using distributed interrupts with the idistributed(D3oddi) function.

• On multiprocessor hardware that does not handle distributed interrupts, move the interrupt processing to an poll(D2oddi) routine that is called by the clock interrupt routine. All CPUs see clock interrupts, so moving processing to the driver's poll time provides better scalability. Careful structuring of locks and data structures will avoid contention for critical resources at clock interrupt time and therefore improve performance.