1. Monitors Chapter Seven Dr. Gheith Abandah1

2. Outline Monitors Software monitors Hardware monitors Dr. Gheith Abandah2

3. Monitors A monitor is a tool used to observe the activities on a system Useful for: – Software optimization – Finding bottlenecks – Tuning – Characterizing workloads Dr. Gheith Abandah3

4. Definitions Event is a change in the system state Trace is a log of events usually including event times Monitors often have overheads Dr. Gheith Abandah4

5. Monitor types Triggers – Event driven: good for infrequent events – Timer driven (sampling): good for frequent events Results displaying – Online – Batch Implementation – Software, hardware, firmware, hybrid Dr. Gheith Abandah5

6. Software monitors Activation mechanism: – Trap instruction – Trace mode; interrupt after every instruction – Timer interrupt (resolution problem) Dr. Gheith Abandah6

7. Hardware monitors Probes Counters Timers Logic analyzers Dr. Gheith Abandah7

8. Comparison Criterion Hardware monitor Software monitor DomainHW events Application and OS events Input rateHighLow Time resolutionHighLow OverheadNoneVaries Dr. Gheith Abandah8