rtprof

A profiling tool is used to identify which functions in some program are consuming the most time in order to identify program areas that would benefit from optimisation. Such a tool can also be used to generate a call graph of some program execution. A call graph is a graphic representation of how the functions in a program call each other, where a graph node represents a function and directed edges connecting these nodes indicate one or more calls from one function to another. Usually with profiling tools, this call graph is in a textual form and consequently difficult to interpret by humans. The graph is made easier to comprehend by using computer graphics to represent it visually.

Existing profiling tools analyse pre-generated profiling data off-line, after the program under measurement has terminated. Often it would be useful to be able to examine the profile of a program while it is still executing. rtprof aims to be a tool capable of profiling a running process and rendering a call graph incorporating the profile interactively.

The profile of the program being measured is incorporated into the visualisation as follows:

• The size of each graph node represents the amount of time spent in that function. This is done proportionately so that two nodes of the same size have accumulated the same quantity of run time over the program's execution.
• The colour of each graph node represents the number of times it has been called. This is also proportionate. A colourmap is used from blue through to purple through to red. For example a node which is blue has been called few times in relation to the total number of function calls made whereas a node which is red has been called many times.
• The colour of each graph edge represents the number of times one function called another. The colour is used in the same way as with graph nodes.
• The transparency of graph nodes and edges indicates the activity of a function. A largely transparent graph node represents a function which has not been called for some time as opposed to a totally opaque graph node which has been active very recently.
• Both graph nodes and edges are rendered with a dark shell around them if they are currently active - in other words if they are part of the call stack.
• Each graph node is annotated to the right with the name of the function it represents.