📝 Heap profiling guide on Linux

docs/profiling-linux.md

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+# Profiling on Linux
+
+If you're trying to make DevilutionX run faster or use less memory, profiling can be very helpful.
+
+## gperftools
+
+[gperftools] is a library that provides a heap profiler and a CPU profiler.
+
+To install gperftools on Debian and Ubuntu, simply run:
+
+```bash
+sudo apt install libgoogle-perftools-dev
+```
+
+You may also want to install debugging symbols for SDL2:
+
+```bash
+sudo apt install libsdl2-dev-dbgsym
+```
+
+## Heap profiling with gperftools
+
+Heap profiling produces a graph of all heap allocations that are alive between two points
+in a program.
+
+DevilutionX has built-in support for heap allocation via [gperftools].
+
+Then, configure and build DevilutionX with the GPERF option:
+
+```bash
+cmake -S. -Bbuild-gperf -DCMAKE_BUILD_TYPE=RelWithDebInfo -DGPERF=ON -DGPERF_HEAP_FIRST_GAME_ITERATION=ON
+cmake --build build-gperf -j $(nproc)
+```
+
+The `GPERF_HEAP_FIRST_GAME_ITERATION` option will make DevilutionX dump the heap profile of the first game
+iteration.
+
+Start DevilutionX and load a game:
+
+```bash
+build-gperf/devilutionx
+```
+
+Heap profile data will be generated at `main.0001.heap`.
+
+To inspect the profile, run:
+
+```bash
+google-pprof --web build-gperf/devilutionx main.0001.heap
+```
+
+See [gperftools heap profiling documentation] for more information.
+
+[gperftools]: https://github.com/gperftools/gperftools/wiki
+[gperftools heap profiling documentation]: https://gperftools.github.io/gperftools/heapprofile.html