PERFORMANCE INSTRUMENTATION IN A FINE GRAIN MULTITHREADED MULTICORE PROCESSOR

A method and mechanism for monitoring events in a processing system. A performance monitoring mechanism includes is configured to store a count of events in an event counter. Periodically, the count stored in the event counter is updated to a new count. If the new count equals a predetermined value, an indication that the count equals the predetermined value is conveyed. If the new count does not equal the predetermined value, but is within a given epsilon of the predetermined value and the occurrence of a corresponding event is detected, an indication that the count equals the predetermined value is conveyed. The mechanism is further configured to suppress event counts which correspond to mis-speculations.