This assumes you have installed Eclipse IDE. In Eclipse, navigate to Help > Eclipse Marketplace. In search, type GCMV and install Garbage Collection and Memory Visualizer. Accept the license and select Finish. When prompted, restart Eclipse.
To use the Garbage Collection and Memory Visualizer tool, in Eclipse, select Window > Perspective > Open Perspective > Other. Highlight GCMV (that's the abbreviation for Garbage Collection and Memory Visualizer) and select Open. Then select File > Load File, select a native_stderr.log or native_stdout.log, and select Open. This should produce a view like this.
If No data parsed from sources is displayed, this means the log file being loaded is not a valid log file.