Runtime Distortion and Dilation with Clock-profiling

Clock-based profiling records data when a SIGPROF signal is delivered to the target. It causes dilation to process that signal, and unwind the call stack. The deeper the call stack, and the more frequent the signals, the greater the dilation. To a limited extent, clock-based profiling shows some distortion, deriving from greater dilation for those parts of the program executing with the deepest stacks.

Where possible, a default value is set not to an exact number of milliseconds, but to slightly more or less than an exact number (for example, 10.007 ms or 0.997 ms) to avoid correlations with the system clock, which can also distort the data. Set custom values the same way on SPARC platforms (not possible on Linux platforms).