Analyzing heap memory usage

System Information

In the QNX System Information perspective, you can monitor the heap usage for a particular process through the Malloc Information view. Using the debugger, you can stop execution at interesting places in the code and see which pointers have new values (addresses). If you then switch to the Memory Information view, you can see if the segments containing those addresses have grown.

This is the best tool to use first because you can switch to this perspective at any time to see the statistics. You don't need to reconfigure, recompile, or relaunch your application, and there's no application overhead because the statistics come from the general-purpose process-level allocator.

Memory Analysis

This tool displays data reported by the debug allocation library (librcheck) as the program runs, providing you with realtime statistics about a process's dynamic memory events and changes in its heap usage.

This tool has an easy setup and imposes less overhead than other analysis tools but requires you to relaunch the application with the tool enabled.

Valgrind Massif

Valgrind Massif is designed for heap analysis. This tool can tell you more than Memory Analysis; for example, it reports the peak in heap usage and provides better backtracing details.

You don't need to recompile the application but you do need to configure Massif through the launch configuration. A drawback to using Valgrind is that it reports the results only when the program terminates, so you can't view memory usage in real time. Also, Massif imposes significantly more overhead than Memory Analysis.

Application Profiler

This tool parses the profiling data generated when an instrumented binary is run. In the launch configuration, you can specify heap memory as the profiling metric to make the IDE display the program's heap usage by function.

Profiling has a higher setup cost than other analysis strategies because you must compile the project with the correct flags and relaunch it. The benefit is that the Application Profiler presents the heap data in an easy-to-read format and lets you compare the results from different sessions.

The libc allocator API

If you're comfortable using the libc allocator API, you can read the fields in the _malloc_stats structure to learn the used heap size, number of allocations, block overhead, and more.

To use this API effectively, though, you must know the code well enough to determine suitable places for querying and outputting the heap statistics. Also, you must rebuild and relaunch the application to start outputting them.