Abstract: A method utilizes a virtual flight recorder to harvest a subset of events being collected by an active system tracing facility during operation of a computer system. The virtual flight recorder is “virtual” from the sense that it is not specifically instrumented into a component with which the virtual flight recorder is associated, which eliminates the burden on developers to specifically instrument components of interest, and minimizes the impact on system performance as a result of performance metric collection.

Abstract: A method, apparatus, system, and signal-bearing medium that, in an embodiment, determine a first number of execution cycles used by a calibration program for an event group with a collector inactive, determine a second number of execution cycles used by the calibration program for the event group with the collector active, and calculate a compensation value for the event group based on the difference between the second number and the first number of execution cycles. These determinations and calculations may be repeated for any number of event groups. When performance data is subsequently collected by the collector, collected events that belong to the event groups have their collected execution cycles adjusted based on the calculated compensation values.

Abstract: A method, apparatus, system, and signal-bearing medium that, in an embodiment, retrieve event data from a processor for sampling intervals, where the sampling intervals are evenly distributed, but the control points at which the event data is retrieved are unevenly distributed. The processor executes instructions for logical partitions, and the event data is associated with events that are detected by the processor during the sampling intervals. In response to an interrupt received from the processor at the control point, a determination is made whether the sample point has been reached. If the sample point has been reached, the event data is retrieved from the processor and an event counter is reset to a value that is calculated to cause the processor to include an identical number of the events in the sampling intervals. The value is calculated based on the event counter at the time control point, the event counter at a time of the sample point, and the number of events in the sampling interval.