Limitations on Collection of Tracing Data

You cannot collect any kind of tracing data from a program that is already running unless the Collector library, libcollector.so, had been preloaded. See Collecting Tracing Data From a Running Program for more information.

Runtime Distortion and Dilation with Tracing

Tracing data dilates the run in proportion to the number of events that are traced. If done with clock-based profiling, the clock data is distorted by the dilation induced by tracing events.