US Patent 9009368 Interrupt latency performance counters

A system and method for finding the sources of increased interrupt latencies. An interrupt controller includes monitoring logic for measuring and storing latencies for servicing interrupt requests. The interrupt controller determines a measured latency is greater than an associated threshold and in response sends an indication of a long latency. The interrupt controller may send the indication to firmware, a device driver, or other software. The interrupt controller stores associated information with the measured latency for debug purposes. Additionally, the monitoring logic may perform statistical analysis in place of, or in addition to, software.