update readme with metrics

Author: FalsePattern

README.MD

@@ -14,11 +14,51 @@ reference implementation.
 - [FalsePatternLib 1.2.0+](https://github.com/FalsePattern/FalsePatternLib)
 - [UniMixins 0.1.11+](https://github.com/LegacyModdingMC/UniMixins)
 
+## Performance
+
+The main performance improvement comes from the fact that the lighting engine is evaluated "lazily", thus it is able to batch more lighting updates
+into a single pass.
+
+Here are some simple to understand values, generated via profiling a pre-set test case:
+
+<details>
+<summary>Test Case</summary>
+
+- World Type: Default
+- World Seed: 123
+- Game Mode: Creative
+- Render Distance: 16
+
+Profiler is started right before clicking Create New World, and stopped after 10 seconds of flying in a straight line in creative mode.
+
+Without Lumi, the active server time spent in lighting engine is 34% of the total active server time (not counting when the server thread is sleeping).
+
+With Lumi, this fraction goes down to 13%, or an approximately 2.5x performance increase over vanilla.
+
+</details>
+
+<details>
+<summary>Flame Graphs</summary>
+
+Horizontal axis is time, vertical axis is the call stack. The blue highlighted parts are calls to the lighting engine update method.
+
+![Flame Graph Without Lumi](docs/Flame_No_Lumi.png)
+
+![Flame Graph With Lumi](docs/Flame_Yes_Lumi.png)
+
+</details>
+
 ## Incompatibilities
 
 - [ArchaicFix](https://github.com/embeddedt/ArchaicFix): Config Change Needed
   - As both mods replace the same parts of code, naturally you will need to set `enablePhosphor` to `false` in the
     ArchaicFix config.
+- [CoreTweaks](https://github.com/makamys/CoreTweaks): Config Change Needed
+  - The `fix_heightmap_range` feature is already implemented in Lumi's lighting engine. Set it to `false` in the
+    CoreTweaks config.
+
+Both of these configs will be automatically modified by Lumi automatically when you launch the game, so you shouldn't even
+need to edit the config files manually.
 
 ## Authors