Heap profiling
From the profiling report (+RTS -p) we were able to infer how much different cost centres allocated space, along with a rough estimate of time spent in cost centres in total during the program's lifetime. What if we wanted to see how space usage varies across that lifetime? That would be useful to pinpoint space leaks that manifest themselves only at certain events.
GHC includes a heap profiler, which put simply snapshots heap usage at small fixed intervals and generates a time-dependent report in the form of a .hp file. To enable the heap profiler for an executable, the same -prof flag for GHC is enough. Some limited heap profiling is also supported when compiled without profiling. The same cost centres used for time and allocation profiling are also used for heap profiling, if the heap profile is generated or narrowed down based on cost centres.
To extract a heap report, we need to use some of the -h family of Runtime System options. Those options are as follows:
-h<...
