You should observe the proportion of the processor's time that is spent servicing interrupts and DPCs. Compare the values of the Processor: % Interrupt Time and Processor: % DPC Time counters to Processor: % Processor Time.
If a busy processor is spending the majority of its time servicing interrupts and DPCs, the processor probably cannot function effectively and a processor bottleneck is likely to develop. Consider upgrading or adding processors to handle the workload.
Alternatively, if the processor has some excess capacity (if Processor: % Processor Time < 85%), or if it is spending a relatively small amount of its time (if Processor: % Interrupt Time and Processor: % DPC Time < 20%) servicing interrupts and DPCs, you probably do not have a problem with interrupts and DPCs.